The ecology of Cowside Beck, a tributary of the River Skirfare in the Malham area of Yorkshire

Oliver Gilbert, Helen Goldie, David Hodgson, Margaret Marker, Allan Pentecost, Michael Proctor and Douglas Richardson

Dedicated to the memory of Oliver Lathe Gilbert

7th September 1936 - 15th May 2005

Published by

Field Studies Council, Malham Tarn Field Centre, Settle, North Yorkshire BD24 9PU. Tel: 01729-830331 E-mail: fsc.malham@ukonline.co.uk www.field-studies-council.org Copies of this report may be purchased from the Field Centre. This report can also be consulted on the website above.

Contributors The late Oliver L. Gilbert (formerly Department of Landscape, University of Sheffield)

Helen Goldie (Department of Geography, University of Durham) 2 Springwell Road,

Durham DH1 4LR

David Hodgson (The Craven Pothole Club) 9 Craven Terrace, Settle, North Yorkshire BD24 9DF

Margaret Marker (formerly School of Geography and Environmental Science, Oxford

University) 5 Wytham Close, Eynsham, Oxon OX29 4NS Adrian Norris (formerly The Leeds Museum Resource Centre) 17 West Park Drive, Leeds

LSl6 5BL Allan Pentecost School of Health and Life Sciences, Kings College, University of London,

150 Stamford Street, London SE1 9NH Michael C. F. Proctor School of Biosciences, University of Exeter, Hatherly Laboratories,

Prince of Wales Road, Exeter EX4 4PS Douglas T. Richardson (formerly Department of Earth Sciences, University of Leeds) 5

Calton Terrace, Skipton, North Yorkshire BD23 2AY If you would like to be involved in this work please contact: Cowside Beck Research Project at Malham Tarn Field Centre

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Contents

Foreword (Adrian Pickles) 1 Introduction (Oliver Gilbert) 2 Physical background: Geomorphology (Helen Goldie, Margaret Marker) 4 Physical background: Water chemistry (Michael Proctor, Douglas Richardson) 9 Lower Plants

Aquatic bryophytes (Michael Proctor) 12 Lichens (Oliver Gilbert) 15 Freshwater algae (Allan Pentecost) 20

Freshwater invertebrates (Douglas Richardson) 23 Mollusca (Adrian Norris) 25 Cave studies (David Hodgson) 27 Discussion (Oliver Gilbert) 29 Further Research (Michael Proctor, Adrian Pickles) 35 Acknowledgements 36 References 36 Appendices

Appendix 1. Water chemistry (M.C.F. Proctor; D.T. Richardson) 38 Appendix 2. Bryophytes (M.C.F. Proctor) 42 Appendix 3. Algae: diatoms (D.T. Richardson) 43 Appendix 4. Freshwater invertebrates (D.T. Richardson) 45

Colour Plates

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Foreword In 2001 Oliver Gilbert dropped the pebble of an idea into the Research Seminar pool - the idea of a group working collaboratively on Cowside Beck. This is the second report arising from the ripples of Oliver’s pebble. Oliver compiled the first draft of this report; the final version was completed by Michael Proctor and collated by Elizabeth Judson. Oliver saw almost all of this report before he died. He was delighted that so much work had been done and in his last letter to me, written just 6 days before the end, was thinking about the next stage of the work. There can be very few research groups focused on one relatively small geographical area that cut across traditional subject boundaries, across the professional-amateur divide and which engage conservation professionals, land owners and managers with active researchers. The Cowside Beck research project is a rare thing; it should be nurtured, not only for the memory of Oliver Gilbert but for the understanding it can help us develop about a special place, that will serve as an exemplar for others. I hope that the ripples from Oliver’s unassuming inspiration continue to spread in the future. Adrian Pickles Malham Tarn Field Centre

November 2005

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Introduction This project was an outcome of the second Malham Tarn Research Seminar (16-18 November 2001) at which a number of participants from different disciplines decided to collaborate in an interdisciplinary study of the Cowside Beck, the next valley just to the north of the Field Centre. In A Nature Conservation Review, (Ratcliffe 1977), the Malham–Arncliffe group of open water sites including Cowside Beck is listed as Grade 1* and the beck is described as ‘A good example of a torrential upland limestone stream’, in spate, ‘the water level rising by at least 1.5 m.’ It is a part of the Malham/Arncliffe SSSI, and falls within the Craven Limestone Complex Special Area of Conservation. English Nature (1994 a,b) classified Britain’s rivers into six major types based on their geology and vegetation. Twenty-five examples were proposed as a national series of river SSSIs. They included in the section ‘Mountains and Moors’ the Malham /Arncliffe streams which include Cowside Beck and its tributaries; these were the object of our study.

Inevitably the coverage of this report is uneven. A good deal was already known about the freshwater algae (Lund 1961, Pentecost 1981, 1991, 1999), the geology was known in some detail (Shaw 1982; Arthurton, Johnson & Mundy, 1988)), and some information was on record for the lichens (Gilbert 1996, Seaward & Pentecost 2001) and bryophytes (Proctor 1960, Pentecost 1991). For other groups and aspects it was often a matter of starting from scratch. The main fieldwork for the project took place over two field seasons, 2002 and 2003. Some of the participants were already familiar with the site; to others it was new. For those living near Malham, fieldwork could be spread around the year. The contribution of those from farther afield were necessarily limited to shorter intensive visits. Different groups of organisms vary greatly in the ease with which they can be found, identified and recorded. Bryophytes and lichens are conspicuous, and most can be identified in the field, so these surveys can be relatively complete. Algae and cyanobacteria require microscopic examination, but thirty years of recording make the tufa-depositing becks, in particular, among the best-studied streams in the country. Freshwater invertebrates, often present in their larval form, can only be sampled by methods which willy-nilly disturb the limited areas of stream-bed that can be studied; this provides a broad picture but leaves much to be discovered regarding their true diversity and ecology. The cave studies have probably picked up the main points of interest. Perhaps inevitably, the limits of the stream course have been interpreted disparately for different groups of organisms. Thus, most freshwater invertebrates are obligate aquatic species but the mollusc survey covered three true aquatics and 24 others in associated damp habitats. Most of the Cowside catchment supports semi-natural vegetation ranging from calcareous grassland on limestone, through neutral and acid grasslands on drift, to heather-bilberry-cotton-grass communities on peat. The farms in the catchment include some improved grassland but there is little run-off of agricultural chemicals into the streams. Darnbrook Farm lies within the Craven Limestone Grassland Wildlife Enhancement Scheme implemented by English Nature. Most of the watercourses are in a very natural condition; there has been no canalisation, damming, work to improve the trout fishing or significant water abstraction. In places where cattle congregate they disturb the riverbed. A feature of the catchment is that on the south side two tributary streams are among the best examples of tufa depositing watercourses in the country, while on the north side, at the upper levels, the streams are highly acidic and their headwaters include a shallow tarn at 640m surrounded by eroding blanket bog. Other features adding to the diversity are extensive intermittently flowing sections, springs and flushes, gorges, waterfalls, caves, and a gravel fan where Cowside Beck meets the River Skirfare (Fig. 1). The valley contains a major population of Mountain Avens (Dryas octopetala), the most southerly in England.

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Physical Background: Geomorphology

Cowside Beck is a tributary of the River Skirfare (Littondale), which flows into the River Wharfe. It has a catchment of c. 20 sq km with contrasting conditions ranging from peat-covered glacial drift areas on Millstone Grit and Wensleydale Series (formerly termed Yoredales) on Fountains Fell (662 m) and Darnbrook Fell (624 m), to seasonally dry valleys and a few surface streams on limestones in the west and south, rising on the Malham high country plateau (538 m). The karstic nature of much of the total catchment makes it difficult to define its boundaries precisely (as Waltham et al, 1997). The geology of the area has recently been revised, Fig. 3 correlates the new and the old terminologies, and the somewhat different division of the Carboniferous strata in the two Geological Survey sheets covering the area.

The Cowside Beck system and its segments The Upper Cowside valley heads at 400 m in a seasonally dry sector about 875 m in length, it is then fed by intermittent springs. The general alignment here is northeast. The permanent risings appear at 350-375 m altitude downstream of which Upper Cowside stretches for 1.5 km as a small meandering stream with a bed of moss covered limestone boulders and earth banks. Between Thoragill Beck and the confluence with Darnbrook Beck, Upper Cowside swings to align west-east. We have called the part below this confluence Lower Cowside Beck. A little below the confluence the stream enters an 800 m long limestone gorge section, downstream of which Lower Cowside Beck, now a small permanent river with larger boulders in its bed, again trends north-east, for 3 km to the confluence with the Skirfare. In this sector there is a clear valley-in-valley cross section. The overall long-profile (see fig. 2) is well adjusted to the Skirfare at Arncliffe where it is incised into a large depositional gravel fan. A stream ordering exercise identified the importance of the Darnbrook catchment, showing Darnbrook Beck to be a fourth order stream. Lower Cowside Beck remains fourth order after its confluence with Darnbrook Beck since Upper Cowside Beck is third order, thus not affecting order at the confluence.

The entire catchment of Cowside Beck is known to have highly variable discharge; the Darnbrook side is regarded as ‘flashy’, even though it has drift and peat-cover. However, the drift here is not particularly absorbent and neither is saturated peat. Surface flow is affected by underground drainage around and above Darnbrook House, which leaves a long stretch running intermittently. In dry weather Darnbrook Beck now sinks considerably farther upstream than it did in the 1960s showing that the underground drainage is still developing. The same is true for Tennant Gill. The several segments each have a distinctive, although not unvarying, character. Cross-profiles from some segments highlight asymmetry, and it is worth emphasising Lower Cowside’s valley-in-valley profile with impressive limestone scars at Yew Cogar Scar (GR 919706). There is no evidence of glacial drift on the south, limestone side, although here scree is characteristic. On the north side of the Lower Cowside valley there is drift above the break of slope, and areas of cemented scree that locally support steeper slopes. Much of the scree will have been derived from erosion of the limestone under periglacial conditions. Forms of the valley cross profiles and adjustment of the long profile to the Skirfare favour the idea that Cowside Beck did not contain active ice-flow during the most recent glaciation, c. 20 ka ago. Although the area may have been ice-covered, modern thinking considers that most active ice flow was in the dales, and not in the smaller side valleys such as Cowside Beck. Thus the high areas between main valley ice flows may have been fairly inactive in terms of glacial erosion and Cowside Beck could have had inactive ice in it. There is also a possibility that ice flow crossed Lower Cowside Beck at an angle helping to cause the asymmetry (see fig 2.).

Of the two tributary streams into Upper Cowside, Tennant Gill is dry from the farm downwards, whilst Thoragill has minor tufa deposits in its upper waters and is down-cut through drift before it reaches Cowside Beck, with which it is not concordant. Upper Cowside has limestone outcrops in the floors of dry valleys (winterbournes), and there is loess and drift fill in these courses, which is eroding to form steps. The valleys flood after heavy rain and flow from intermittent resurgences and piping from the steps is then active. Below these loessic steps the intermittently occupied streambed varies from stretches dominated by limestone outcrop to those having substantial numbers of loose stones on a stepped limestone base. The loose material varies in size from sub-rounded about 60 cm diameter to small stones and dominates increasingly as the stream becomes permanent and the bed widens towards the confluence with Darnbrook Beck. Small resurgences enter throughout Upper Cowside.

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Fig. 1. Map of Cowside Beck catchment and site locations.

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Fig. 2. Profiles of Cowside Beck System.

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In Darnbrook Beck, above the outcrop of the Middle limestone at 520 m, the small upper rills are lined with gravel from the Millstone Grit. Below the Middle limestone stepped limestones, sandstones and shales of the Wensleydale Series are followed by stepped beds in the Gordale Limestone, in a relatively steep course (see long profile on map). On the main beck certain of the limestone layers create substantial falls, for example at 520 m altitude associated with the Middle Limestone, and in a small ravine at 450 m in massive limestone in the lower part of the Wensleydale Series above the Cock Pits (funnel-shaped karst depressions developed along a fault line). Loose material derived from the drift is also important in the stream bed together with large, emergent limestone boulders. Massive limestones in the Gordale Limestone (Settle BGS Sheet) produce rapids and falls in a tributary from the north side at GR 893712. Downstream where the course levels out there is more gravel but the streambed remains very bouldery with occasional bedrock outcrop and small falls in the Cove Limestone. Near Darnbrook House the bed is dominated by relatively bare, scoured limestone bedrock. Above and below Darnbrook House (GR 889706) the bed is often dry and it is boulder strewn down to the confluence with Upper Cowside Beck. There are many shallow step waterfalls over rock layers across the width of the stream in the upper courses, which become less visible as the watercourse enlarges, but which can still be seen as lines of rapids in the water over stepped horizontal weaknesses in the lower sections of the watercourse. Stepping of the streambed persists throughout Lower Darnbrook and the upper parts of Lower Cowside, reflecting horizontal weaknesses within the Cove and later the Kilnsey Limestones from Cowside Gorge downstream.

The stream network in Upper and Lower Cowside includes karst resurgences in the form of seepages and springs; tufa streams sealed from the bedrock by redeposited limestone and with huge mossy tufa screens; dry valleys; gorge sections and varied scar features. Waterfall Beck is the more impressive of the two tufa stream, the second, Lower Beck is now largely dry. There are seepages on both sides of several of the system’s component streams. In Lower Cowside seepages enter the riverbed from the south side, but from the north side they rise at about 10 to 20 m above the river and have incised small valleys. Some springs rise direct from bedrock, as in the Upper Cowside headwaters, others are stony. There are large input springs particularly in the gorge segment, and again 200 m below Yew Cogar Cave where a resurgence on the south bank adds considerably to the flow. Tracing studies have shown that this water originates partly from the Malham high country and partly from Darnbrook Beck having at some point flowed under Cowside Beck.

Old terms Settle: Sheet 60 (modern) Hawes: Sheet 50 (modern)

Main Limestone

Namurian (Pendlean) Millstone Grit Main Limestone Millstone Grit

Millstone Grit (with Main Limestone)

Yoredale Series Wensleydale

Group (Brigantian)

Underset Limestone Middle Limestone Simonstone Limestone Hardraw Scar Limestone Gayle Limestone Upper Hawes Limestone Girvanella Band Lower Hawes Limestone

Wensleydale Series (Brigantian)

Hawes Limestone (with Girvanella band)

Thorny Force Sandstone Gordale Limestone

Danny Bridge Limestone Great Scar Limestone (D1 & D2)

Garsdale Limestone

Viséan Malham Formation (Asbian & Holkerian)

Cove Limestone

Kilnsey Formation (Holkerian

and Arundian

Kilnsey Limestone

Fig.3. Different names used for the Carboniferous strata in the Malham area, adapted after Arthurton et al, 1988.

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Other inputs include seepages and flushes. The gorge section is narrow and shaded, with scattered ash trees and much outcropping limestone showing shallow stepping over the various horizontal weaknesses within the limestones of the Kilnsey Formation. This imposes a pool–riffle structure. There is little visible outcrop in the streambed in Lower Cowside below the gorge, but stepping, hidden by boulders, is indicated by bars across the stream.

The lower parts of Lower Cowside still have a bouldery bed, and tufa is being deposited on vertical limestone cliff seepages (GR 924713) on the south side. After Brootes Barn (GR 926716) the valley opens out to the Arncliffe fan just before the confluence with the Skirfare, here the streambed is wider, bouldery and has wide beaches.

A noteworthy point on water flow in the whole catchment concerns the southern side, a large area from which inputs of water to Cowside appear to be much less than might be expected and far less than from the northern tributaries. A stream tracing exercise would be needed to confirm where the water goes, but possibilities include underground flow exploiting fractures and faults in the limestone, taking water to the Skirfare via Cote Gill, Sleets Gill Beck, Moss Beck and Kilnsey Crag risings, or southwards into Gordale Beck and the headwaters of the Aire.

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Physical Background: Water Chemistry Two extensive sets of data on water chemistry were collected. Both included pH and water temperature, but other parameters differed so it is possible to present a particularly broad picture of this factor. For methods see section ‘Notes on the measurements’ below. Detailed results can be found in Appendix 1.

The first obvious feature in the water-chemistry measurements is the contrast between the Darnbrook and Cowside Becks. The headwaters of Darnbrook Beck drain from the Millstone Grit and the blanket bog that covers the higher parts of Fountains Fell; they are poor in calcium and other cations, and are acid with a pH in the range 4.2–4.6. They are quickly joined by waters that have percolated through the higher limestone beds in the Wensleydale Series. Most of the headwater streams with any input from the limestones have pH above 7.0. At the time of the measurements Ca concentrations in the Darnbrook were generally below 20 mg/litre over the Wensleydale beds, and only very locally exceeded 40 mg/litre where the stream flows over continuous limestone. By contrast, in the Cowside Beck and its limestone tributaries most measurements were in the range 40–80 mg/litre. The solutes in water draining from the blanket bog come from rain. The dominant cation is sodium (Na+), with smaller (and roughly equal) amounts of calcium (Ca2+) and magnesium (Mg2+), and the dominant anions are chloride (Cl–) and sulphate (SO4

2–). In water which has been in contact with limestone the dominant cation is generally Ca2+, balanced by an equivalent quantity of the bicarbonate anion HCO3

–. Water chemistry is important in the ecology of the streams for two reasons. First, the composition of the water is an important part of the environment for plants, and directly or indirectly, for animals. For aquatic plants the water is the source of mineral nutrients and (when submerged) of CO2 for photosynthesis. Calcium is needed in only rather small amounts as a nutrient, but it plays a very important part in determining pH, and hence the ionic environment in which the other essential elements are taken up. Secondly, the equilibrium in the water between carbon dioxide (CO2), the bicarbonate ion (HCO3

–) and the carbonate ion (CO3

2–) is fundamental in determining whether the water will dissolve solid calcium carbonate (CaCO3) forming fissures or caves in the limestone, or deposit CaCO3 as tufa or marl. Carbon dioxide in solution, bicarbonate and carbonate are linked by the following relationships (square brackets [ ] mean ‘the molar concentration of’):

(1) pH = pK1 + log [HCO3–]/[CO2]

(2) pH = pK2 + log [CO32–]/[HCO3

–]

Fig. 4. Plot of pH against calcium concentration, August 2002. The black triangles identify springhead sites at which water was emerging from deep in the limestone. Sites at which tufa deposition was taking place are indicated by crosses.

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Given that pK1 is roughly 6.4, and pK2 roughly 10.4 (both vary a little with temperature), these equations mean that below pH 6.4 [HCO3

–] must be exceeded by [CO2], that HCO3– predominates between pH 6.4 and

pH 10.4, and above pH 10.4 the predominant ion is CO32–. Each of the equations provides the means to

calculate one of its three variables if we know the other two. For example, from equation (1) the pH in water with 1.0 mmol l-1 HCO3

– (and 0.5µmol l-1 Ca2+) in equilibrium with air (CO2 about 15 µmol l-1) will be about 8.2. We now know both [HCO3

–] and pH, so from equation (2) we can calculate [CO32–] as about 6.3 µmol l-1.

The solubility product of CaCO3 (calcite) is c.1×10-8, so the water will be undersaturated and there will be no tendency to tufa deposition. Fig. 4 shows a set of data collected by MP in August 2002. The dot-dash line to the top left shows the limit set by equilibrium with the concentration of CO2 in the air. In practice this limit is rarely approached in streams because the CO2 concentration in the water is kept high by the respiration of organisms breaking down dead organic material falling into the stream from the banks. The dashed line to the top right is the limit set by the solubility of calcium carbonate. Above it, the water is supersaturated and solid calcium carbonate is precipitated as marl or tufa. Water in the lower left-hand part of the diagram is undersaturated, and can dissolve more CaCO3, so it can potentially further widen fissures and cave passages in the limestone. The essential conditions for formation of tufa are a source of water in which a high concentration of calcium is kept in solution by a high concentration of CO2 (as in the springheads in the lower right-hand part of the diagram), and re-equilibration with the atmosphere when the water emerges at the surface. The water then loses CO2 to the air, its pH rises, and as its composition passes the critical line on the diagram solid CaCO3 begins to be deposited. The process is essentially physical, but the detailed location and form of the deposition can be influenced by the algae and bryophytes in the emerging water. For more detailed discussions of CO2–bicarbonate–carbonate equilibria see Golterman & Clymo (1969) and Stumm & Morgan (1996).

The water analyses All water-sampling sites were located by GPS. Proctor sampled 70 sites during August 2002 measuring pH, conductivity and temperature in the field, and Ca and Mg by atomic-absorption and K and Na by flame-emission spectrophotometry in the laboratory (measurements expressed as mg l-1 of the cation). Richardson measured pH and temperature in the field, and alkalinity, calcium, total hardness (Ca + Mg) and pH on freshly collected samples by titration with EDTA in the laboratory (measurements expressed as equivalent mg l-1 CaCO3). Many of his 36 sites were sampled repeatedly (up to 8 times) throughout 2002 and 2003 so a range of concentrations are given. In addition to the 36 surface sites he analysed samples collected by Hodgson from the underground cave systems. Full results can be found in Appendix 1, a summary of the findings is provided below and in the section on caves. Total hardness (mg CaCO3 l-1)

At the head of Cowside Beck, where intermittent flow is linked to a number of springs active only during periods of wet weather, total hardness is in the range 192-266, these are the highest levels recorded on the main stream. At the first permanent springs it is 167-202, and along the remainder of the beck, down to the confluence with the Skirfare, 138-198. Streams, springs and seepages entering from the south side mostly originate from the karst of the Malham high country; the tufa tributaries have a total hardness of 120-194, slightly lower than the main stream. The highest total hardness recorded (200-300) was found in calcareous seepages some of which support the lime-encrusted alga Chara vulgaris var longibracteata. The main tributary, Darnbrook Beck, originates on the Millstone Grit capped Fountains and Darnbrook Fells which include a small tarn lying among blanket bog. The water of Fountains Fell Tarn and the higher rivulets have a very low hardness in the range <2-8. As these small streams cross the Yoredale Limestone bands they rapidly take up limestone and total hardness reaches 19-25. This is the story of Darnbrook Beck; total hardness increases progressively down-stream as the stream-bed includes more and more limestone until, by the farm, it has risen to 70-136. This is still lower than Cowside Beck, so the influence of the acid headwaters remains apparent throughout.

Electrical conductivity (μS cm-l ) This also highlights the contrast between Cowside and Darnbrook Becks. The conductivity of a natural water is due to the ions in solution. In the acid headwater streams conductivity mainly reflects the cations Na+ and H+ and the anions Cl– and SO4

2–. In the calcareous streams conductivity is almost entirely due to Ca2+ and HCO3

–, and conductivity measurements provide good estimates of Ca concentration (104.5 �S cm-1 = 20 mg l-1 Ca).

Other cations Concentrations of sodium were ~2.5–3.3 mg l-1, and magnesium varied only from 0.36 mg litre-1 (stream draining from Fountains Fell blanket bog), to 1.67 mg l-1 (spring opposite Yew Cogar Scar). Potassium is at very low levels throughout (<0.3 mg l-1).

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pH As already indicated, this has a rather complex relationship with calcium concentration. Broadly, pH rises as Ca increases, but most of this rise takes place over a narrow range below 20 mg l-l Ca. As the Ca concentration rises, pH is limited by the solubility product of CaCO3, and the highest pH values are found at Ca concentrations around 30–40 mg l-1. Concentrations of Ca beyond this can only remain in solution at progressively higher CO2 concentration, and progressively lower pH (Fig. 4). Some remarkably steep gradients of pH can be seen where water emerges from deep springs, and then quickly loses CO2 to the atmosphere, as at the heads of Cowside and the tufa tributaries.

Temperatures of springs In general, actively flowing springs were cold, around 8 oC along Cowside Beck and as low as 6.6 oC on Fountains Fell during summer. This is sufficiently low to enable relic populations of organisms such as flat worms and diatoms to survive well south of their normal range. The temperature of the spring at the head of Waterfall Beck was 10.0 oC; the water here may be from shallower sources. The big spring on the south bank of Cowside Beck (GR 9105 7011; ‘Darnbrook Pot rising’ in Appendix 1)) gave a reading of 10.7 oC (26 Aug. 2002). It is known that water from Darnbrook Pot emerges here; the flow may also include water lost through the bed of the higher parts of Cowside. From measurements of conductivity and temperature it was calculated that this spring accounts for some 3/8 of the total flow below its point of entry, nearly doubling the discharge. General stream temperatures in summer increase from c.11 oC at 610 m on Fountains Fell, to 13-15 oC in Lower Cowside, to c. 19 oC near the confluence with the Skirfare having taken a braided course through the gravel fan.

Tufa This has already been referred to above. It is a soft, porous, calcareous rock characteristically associated with seepages, springs, rapids, and waterfalls in limestone regions. It is local in the British Isles but the two south side tributaries of Cowside Beck, Waterfall Beck and Lower Beck, contain considerable deposits, especially as large, moss covered curtains associated with waterfalls. Conditions leading to the formation of tufa travertine have a large literature (Pentecost 1981, 1992, 2005), of which the outline above is only a brief and simplified summary. Tufa is biologically important as a habitat because it supports a rich mixture of cyanobacteria (‘blue-green algae’) and bryophytes, some species being restricted to this substrate. Thoragill Beck, parts of Darnbrook Beck, and Upper Cowside deposit tufa during periods of low discharge; it forms a soft crust on stones in the stream bed which discourages lichen colonisation.

The water analyses are tabulated in Appendix 1.

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Lower Plants

Bryophytes It is already known that three factors explain much of the biological variation found along a stream course. First there is a strong vertical zonation relating to length of submergence, four overlapping bands can usually be recognised. They have been named (1) Submerged zone (aquatic) which is more or less continually submerged throughout the year; (2) Fluvial mesic zone (amphibious) which is submerged regularly, often for several days at a time, and always after 15 mm of rain over the catchment; (3) Fluvial xeric zone (terrestrial species tolerant of submergence) this is swept by floods once or twice a month, sufficient to restrict higher plant growth and favour cryptogams; (4) Fluvial terrestrial zone (terrestrial) occasionally flooded, supports a higher than usual proportion of species favouring damp habitats. The second important habitat factor is variation down the long profile which affects gradient, to which scouring and bed instability are related, rock type which influences water chemistry, and discharge rates. The third, equally important factor, is the occurrence of special habitats which in the Cowside catchment include springs, waterfalls, gorges, tufa deposits and caves.

Aquatic bryophytes The valley of Cowside Beck and its tributaries, from Stangill Barn and the summit of Fountains Fell to Arncliffe, is very rich in bryophytes, but only a fraction of these are aquatic or regularly associated with running water. Nevertheless bryophytes, mostly mosses, are the dominant aquatic green plants in Cowside Beck and its tributaries. The individual species all have their own particular habitat requirements, and although some are very widespread in the Cowside streams none is universal. For bryophytes, there are particularly big contrasts within the Darnbrook Beck and its tributaries, draining from the grit-capped summit of Fountains Fell and the blanket bog that covers its higher slopes, then flowing over the succession of limestones, shales and sandstones of the Wensleydale (Yoredale) Series (and the glacial drift largely derived from them), before reaching the continuous limestone which forms its bed (and into which it occasionally disappears) down to its confluence with the Cowside Beck below Darnbrook House. The bryophyte cover in Darnbrook Beck is more varied and differs in general character from that of the main stream. Both these things can be attributed in varying degrees to variations in water chemistry, very base-poor and acid in the headwater streams and seldom approaching saturation with calcium bicarbonate even in its lower course. The steepness of the Darnbrook valley adds to the contrast. Cowside Beck itself flows entirely over limestone from its source in intermittent (and some more permanent) springs half-a-kilometre below Stangill Barn to its confluence with the Skirfare at Arncliffe. It is highly calcareous throughout, its bed is less steep, and variation in its bryophyte vegetation is more subtle, but none the less interesting. Its largest tributary after the Darnbrook confluence is the tufa-forming Waterfall Beck, and it is joined by various other risings from the limestone.

As most bryophytes can be recognised in the field they were surveyed by a walk-over survey, lists being made at 60 sites, at each species were awarded frequency values on the scale (a) = abundant, (f) = frequent, (o) = occasional, (r) = rare, (+) = frequency unassessed. Water samples were sometimes taken for pH and/or conductivity measurements. On a less intensive basis the bryophytes of calcareous flushes, mires, tufa and damp limestone were investigated.

The dominant bryophyte species Seven mosses occurred in 40% or more of 60 species lists from different parts of the stream system. These species made up the bulk of the vegetation cover, and dominated the character of the stream vegetation. Brachythecium rivulare (47/60), a very common moss of wet situations, was the most widespread, often forming an irregular zone around and above summer water level; it extends farther above this in damp sheltered places than on the exposed sides of boulders. Of all the species, this ordinary-looking golden green pleurocarpous moss is the nearest to being ubiquitous; it occurs from high on Fountains Fell (but with pH always >6) to all other parts of the system. Cinclidotus fontinaloides (44/60) is almost as common, but more tightly restricted to limestone, where it grows in coarse untidy greenish black tufts and masses in a zone above summer water level but where it is submerged at least by winter floods. It is rare or absent in the higher parts of Darnbrook Beck but almost ubiquitous elsewhere, most prominently in the stretches that flow freely in winter but dry out in summer. Rhynchostegium riparioides (42/60), a common and characteristic moss of neutral or calcareous running waters, is more strictly aquatic than either of the last two, hardly reaching above summer low water level. The ovate leaves of the rather coarse uniform shoots have a strong midrib reaching almost to the apex. Hygrohypnum luridum (38/60) is a more slender plant with smooth rather rigid bluntish leaves curved through about a right angle so that they all point to one side of the stem. It forms tight mats on

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rock surfaces, resistant both to fast-flowing water and to desiccation. Cratoneuron filicinum (32/60) grows in a wide range of moist calcareous habitats, but only occasionally as a true submerged aquatic. Mostly in Cowside it is a streamside species, submerged when water levels are high but exposed in summer, when it forms golden-green semi-erect patches with elegant ‘fir-tree’ branching, and pointed slightly falcate leaves with strong midribs. Palustriella commutata (29/60) is related to C. filicinum but is a coarser green to brownish plant with flat pinnate branching and much more strongly falcate leaves. It requires highly calcareous conditions but is intolerant of drying out, so it is virtually absent from Darnbrook Beck (though present in calcareous seepages away from the stream itself), but can be found throughout the Cowside Beck except in those sections that dry out in summer; it is at its best in and around calcareous springs and tufa seepages. Schistidium rivulare, sensu lato* (24/60) is somewhat similar in its ecology to *Cinclidotus, and of a similar blackish green colour, but it is a much more slender plant with smaller leaves; in fruit, the short capsules with bright red lids and peristome teeth are characteristic. It is highly tolerant of desiccation and probably more resistant to fast-flowing water than Cinclidotus, but loses out where conditions favour larger species. It is common in Darnbrook Beck but more thinly scattered elsewhere.

A few less-frequent species are locally prominent and characteristic. The big thalloid liverwort Marchantia polymorpha (21/60) forms conspicuous patches where shelving slabs or patches of gravel support a carpet of wet moss just above summer water level. Philonotis fontana (17/60), with its patches of erect apple-green shoots, sometimes studded with big capsules like stalked green peas, grows in similar situations; it is a characteristic spring and stream-bank species, seldom seen far from water. Another moss with rather similar habitat preferences is Dichodontium pellucidum (17/60); with us, both these streamside species are commoner in the Darnbrook Beck than elsewhere. Orthotrichum cupulatum (12/60) is primarily a moss of terrestrial habitats where it forms dense desiccation-tolerant cushions on limestone rocks, but it can grow well below winter water level and then produces more diffuse growth rather in the manner of Schistidium rivulare s.l.. It is frequent in the limestone parts of Darnbrook Beck but sparser elsewhere.

Bryophytes and ecological divisions within the stream system (a) The headwaters of Darnbrook Beck Most of the smaller headwater streams drain from the grit cap of Fountains Fell or from the blanket bog that covers the upper slopes. They are base-poor and acid. Measurements in August 2002 gave Ca concentrations between 0.4 and 0.8 mg/litre, and pH 4.25–4.59; the only aquatic bryophyte is the leafy liverwort Scapania undulata, growing in scattered patches on pieces of gritstone in the stream bed. Once below the base of the gritstone, these acid streams are joined by tributaries rising at springs from one or another of the limestones. A tributary which joins the beck from the south, just above the highest fence line and near the bottom corner of the highest plantation had a pH of 7.4 and 16 mg/litre Ca; it rises in a long diffuse seepage starting just below the point where the Pennine Way crosses the outcrop of the Main Limestone (87457145), but it may also receive input from the Underset limestone lower down its course. A much shorter tributary, higher up the beck originates at a strong spring from the Underset Limestone at 87447159, completely surrounded by blanket bog, with 33 mg/litre Ca and pH 7.04. Generally, as soon as there is any significant influence from the limestone, the pH of the stream water rises to 6 or more, even with less than 5 mg/litre Ca. The headwater streams are thus diverse in water chemistry, with a correspondingly diverse but rather fragmentary flora, to which such species as Scapania undulata and Racomitrium aciculare lend a distinctly upland flavour. (b) Middle Darnbrook Beck Between 550 and 500 m (where it crosses the uppermost fence-line and the outcrop of the Middle Limestone) the beck changes from being a diffuse collection of streamlets spread out over the fell side to a well-defined stream in a steep clear-cut valley, bordered by substantial boulders and rock outcrops. The influence of the limestones is pervasive, but a large proportion of the water drains from non-calcareous ground, so that although pH is always above 7 calcium concentrations in the range 10–25 mg/l are the norm. This section embraces only about half-a-kilometre of the course of the main Darnbrook Beck, down to about 88357145 (~ 460–470 m), but several of the tributaries are of similar character. It has a diverse aquatic bryophyte flora in which the bulky calcicole species that dominate much of the rest of the stream system (notably Cinclidotus) are not yet dominant. (c) Lower Darnbrook Beck Below an altitude of ~ 460 m the beck flows over essentially continuous limestone, and its character changes. Limestone influence is still diluted by the large volume of water coming off Fountains and Darnbrook Fells, so calcium concentration varies widely (depending on weather, and the relative contributions of the headwater

* Including S. rivulare (Brid.) Podp. and S. platyphyllum (Mitt.) H. Perss.

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streams, tributaries, and resurgences from the limestone) from around 10–40 mg/litre, but is almost always below levels that are normal in Cowside Beck. The most obvious bryological consequence of this is the rarity of Palustriella commutata in the beck itself, although this species occurs in calcareous seepages a little distance from the stream. Otherwise the bryophyte cover has much in common with ecologically comparable parts of Cowside Beck; the greater frequency of several smaller species (e.g. Racomitrium aciculare, Dichodontium pellucidum, Orthotrichum cupulatum, Amblystegium fluviatile) probably has more to with the steeper, more broken nature of the stream bed than with water chemistry. This limestone section of the Darnbrook Beck is quite varied, with bouldery and slabby, and steeper and gentler reaches. Some species grow along the stream margin or in the moss carpet on slabs sloping into quieter stretches of the beck, (e.g. Philonotis fontana, Cratoneuron filicinum, Didymodon nicholsonii). Some stretches of the beck flow throughout the year, while others dry out more or less completely in summer – most conspicuously the lowest kilometre, overlying the Cove Limestone above and below Darnbrook House. The last section between the road and the confluence is surprisingly bare, with only an open cover, mainly of Cinclidotus, Schistidium rivulare s.l. and Hygrohypnum luridum, perhaps because it is too exposed and too torrent-swept in winter to support the luxuriant masses of Cinclidotus that are a striking feature of the intermittently dry stretches higher up. (d) Cowside Beck headwaters The uppermost springs at the head of Cowside Beck (SD 88776913) are seasonal, flowing in wet periods in winter, but dry for much of the year, so that for the first 100 metres or so there is no continuously defined stream bed in the grassy valley floor. Even when a continuous stream bed is established, it is another 70 metres (and just below a rising on the east bank) before there is a stream of any real permanence. In all of this intermittent section, the dominant moss is Cinclidotus fontinaloides, with smaller amounts of Schistidium rivulare s.l., Hygrohypnum luridum and Brachythecium rivulare. Once there is a permanently-flowing stream the bryophyte vegetation settles down to a rather uniform pattern which continues with minor variations (and occasional breaks) for most of the length of the beck down to its confluence with the Skirfare; calcium concentration is generally 50–80 mg/litre throughout. Below summer water level the dominant moss is Rhynchostegium riparioides. Above this, Brachythecium rivulare forms a rather irregular zone, most prominent and extending highest in relation to water level in moist, sheltered situations, but seldom altogether absent. Hygrohypnum luridum is locally prominent at similar levels, often carpeting the more current-swept and exposed rock surfaces. At higher levels again, Cinclidotus fontinaloides is seldom absent from the sides and tops of boulders, dry and exposed for much of the year but submerged at times of high water, often accompanied by Schistidium rivulare s.l.. Here and there, the highly calcicole Palustriella commutata is prominent in the moss cover at about summer water level, occasionally growing extensively in a characteristic submerged form on the bed of shallow sections of the Beck. In dry periods in summer the beck disappears underground in a deep pool at 89616992 (between the confluences with the Thoragill and Darnbrook Becks) to reappear where it is joined by a strong right-bank tributary at 89756999, but Rhynchostegium riparioides remains abundant in pools among the boulders of the dry stream bed, so this stretch probably never dries out completely. (e) Cowside Beck: Darnbrook confluence to Yew Cogar Cave After a flattish bouldery stretch of some 300 m, much of this section the beck occupies a shallow gorge, its rocky sides and bed with steep faces, big boulders, and shelving slabs. The beck is still dominated by the same large mosses as elsewhere, but mossy slabs sloping gently down into the water provide a habitat in which Cratoneuron filicinum, Philonotis fontana, Dichodontium pellucidum and Marchantia polymorpha are often prominent and Didymodon nicholsonii locally frequent, recalling similar places on Darnbrook Beck. Fissidens rufulus is also rather frequent on flat rocks close to and below summer water level. The gorge is bryologically one of the richest parts of the Cowside valley, but this is reflected in the bryophyte flora of the beck only to a rather limited degree.

(f) Lower Cowside Beck: below Yew Cogar Cave The final 3 km of the beck generally has a bouldery bed, with a channel slightly incised into the waterborne deposits of the valley floor, and a bryophyte cover of the general pattern outlined in paragraph (d) above. Commonly, there is a lot of bare rock surface, presumably because the boulders of the stream bed are tumbled and swept downstream at times of spate, keeping the surfaces scoured clean, particularly in the faster-flowing sections of the channel. A big fast-running spring on the south bank at 91057011 is marked by vigorous growth of Fontinalis antipyretica, a common mainly lowland aquatic moss otherwise only thinly scattered in Cowside, and the combination of calcareous springs with shallow reaches of the beck below Yew Cogar Scar is probably responsible for the local prominence of Palustriella commutata.

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(g) Tufa-forming tributaries: Waterfall Beck and Lower Beck Waterfall Beck rises in springs at the head of a shallow valley on the high limestone some 430 m above sea level. The point where the water emerges depends on season and the preceding weather. On 6 Aug. 2002 the highest active spring (at c. 90896934) contained 74 mg/litre calcium, with a pH of 7.05. The upper parts of the stream recall the headwaters of Cowside Beck, with a profusion of Cinclidotus fontinaloides, accompanied by Brachythecium rivulare, and by Palustriella commutata and Rhynchostegium riparioides from the point at which a continuous flow of water is established and seasonal desiccation is no longer a hazard. A quarter of a kilometre from its source (and at c. 390 m altitude) the stream cascades over a magnificent tufa screen into the Cowside valley. The tufa screen, and a smaller one lower down, is dominated by Palustriella commutata and Rhynchostegium riparioides, with smaller amounts of Cratoneuron filicinum and Didymodon spp. The stream below this is still highly calcareous, but the calcium concentration the same day was only 54 mg/litre and pH had risen to 8.10 – predictable consequences of the precipitation of calcium carbonate between the two points. Compared with the Cowside Beck, the lower part of Waterfall Beck stands out for the prominence of Palustriella commutata and Cratoneuron filicinum, and the frequent occurrence of Philonotis calcarea and Pellia endiviifolia. Most of the valley of Lower Beck, some 400 m to the east, is now dry, water emerging only close to the floor of the Cowside valley. However, older one-inch and 1:50 000 maps mark a stream starting at almost 380 m, and the 1:25 000 map shows an (apparently intermittent) stream up to c. 330 m, so it was probably once more like Waterfall Beck. What there is of a stream has a bryophyte flora similar to (but more limited than) the Waterfall Beck.

Bryophytes of damp habitats away from flowing water (a) Calcareous flushes and mires These are constantly wet and often border the stream, and their vegetation sometimes merges into that of shelving parts of the stream bank. However, they lack the common aquatic species of the streams, and have a different and characteristic flora of their own, in which Campylium stellatum, Palustriella commutata var. falcata, Scorpidium scorpioides and Drepanocladus cossonii are characteristic and often dominant, with smaller amounts of such species as Bryum pseudotriquetrum, Aneura pinguis, Preissia quadrata and locally where calcareous water is emerging, Philonotis calcarea. These communities correspond to the Carex dioica-Pinguicula vulgaris mire (M10) of Rodwell (1991), and are a typical habitat for Primula farinosa, Pinguicula vulgaris, Carex dioica and other small sedges, and Selaginella selaginoides.

(i) Damp limestone and tufa surfaces These diverse habitats carry a rich flora, and there is not space to deal with them in detail here. There are a number of notable species, of which the most striking is Orthothecium rufescens, a beautiful copper-tinged pleurocarpous moss scattered on moist shady limestone outcrops on the steep south bank of Cowside Beck for several hundred metres either side of the footbridge below Darnbrook House. Elsewhere in Britain it is mainly a plant of base-rich cliffs in the mountains. The big tufa screens are generally dominated by Palustriella commutata and Rhynchostegium riparioides, but tufa and damp limestone rocks also provide the habitats for a suite of small acrocarpous mosses. A common and characteristic species associated with damp limestone rocks and small tufa seepages is Hymenostylium recurvirostrum, which forms small dense dark-green cushions or sometimes larger hummocks on stony ground. A similar species, with more obtuse leaves, Gymnostomum aeruginosum, is less common and perhaps more strictly associated with rock. Several other small acrocarps are particularly associated with tufa, of which the commonest, Didymodon tophaceus, also occurs widely in other moist base-rich situations. Eucladium verticillatum, a very characteristic tufa species forming dense lime-encrusted cushions, occurs in Cowside but it not common here. Liverworts frequent on damp limestone include Aneura pinguis, Jungermannia atrovirens, Leiocolea alpestris and Preissia quadrata. Full species lists from Cowside and Darnbrook Becks are given in Appendix 2.

Lichens The lichen flora of Cowside Beck and its tributaries were thoroughly investigated by a walk-over survey and by transects. As with bryophytes, lichens are mostly terrestrial, but specialist aquatic species do occur along with those typical of damp habitats. During summer 2003 water levels were very low providing ideal conditions for survey work. According to the nature of the stream course the lichen flora varies from being absent, through poor to moderate, with a few rich sites. Three ‘hot spots’ were identified, one on Cowside Beck and two in upper Darnbrook. The watercourses elegantly illustrate what makes good and bad habitat for aquatic lichens. Although equivalent to the bryophytes in diversity, the cover (and biomass) of lichens is far lower (Figs 5, 6).

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The lichen flora of the Malham Tarn area has been studied almost continuously since Arthur Wade ran the first of his lichen courses there in 1955. It was not until recently however, that the records were published (Seaward & Pentecost 2001) when those recorded from an area within 5 km of the Field Centre were listed together with a comment on their ecology and frequency. Site information was not provided so it is impossible to discover from the publication which species occur in the Cowside system. Seven lichens new to the Malham list were found during this project bringing the total taxa for the Malham area to over 350.

Cowside Beck For most of their length Upper and Lower Cowside have a bed composed of limestone boulders lying between earth banks. The boulders are almost completely covered with aggressive aquatic bryophytes supplemented for half the year by a dense growth of filamentous green algae. There is little opportunity for lichens in this community as little light penetrates the cryptogam cover. Occasional Leptogium plicatile, Thelidium decipiens and a few common aquatic Verrucaria spp. are present on those parts of the larger boulders kept free of bryophytes by the current. Lichen cover is around 1%. During summer the intermittently flowing headwaters above the permanent springs look like a stony cart track running down the valley. The stones are characterised by Verrucaria aethiobola, an aquatic species that can withstand drying out, and V. praetermissa found on their moist underside. Lichens characteristic of damp limestone are regularly present such as Aspicilia contorta, Caloplaca citrina, Leptogium plicatile and Thelidium papulare. Lichen cover may reach 25%. A dozen or so permanent headwater springs issue from small caves which are stable habitats not subject to trampling by cattle, and the semi-shade discourages bryophytes and algae. The water is highly alkaline with a pH well over 7 and a total hardness of 130-198 mgs CaCO3 l-1. The larger stones in these springs carry greenish colonies of V. rheitrophila and dark ones of V. elaeomelaena. Both can spend their entire lives totally submerged; they are nationally scarce with the latter the rarest. The most exciting length of Cowside Beck for lichens is the 600m gorge below the Darnbrook confluence. Here the bed of the stream is outcropping limestone, its course flanked by shelving beds of limestone. Bryophytes and algae still dominate but there is bare limestone where the flow is fastest and on prominences subject to mild scouring during floods. Around 20 fluvial lichens are present zoned in relation to height above water level. At the upper levels certain lichens such as Agonimia tristicula, Lempholemma polyanthes, Peltigera spp. and Psoroma luridum overgrow the moss. A particular rarity, collected several times, is Staurothele bacilligera. For a long time it was known only from a single record on Ingleborough where it was discovered in 1964. It is now known also from the Northern Pennines and NW Scotland; this is a new Craven site for it. Other species of note in the gorge are Psorotichia schraderi, Staurothele guestphalica and S. hymenogonia. Many of these are small, immersed in the limestone, and have to be collected so they can be identified under a microscope. Fig. 4 represents a 3.75 m long transect across the bed of the gorge extending from 1 m out into the stream to nearly 3 m up the shelving limestone bank; it was divided into fifteen 25 x 25 cm units for recording purposes. It shows bryophytes dominant and the only group present in the submerged zone; lichens appear with a low cover in the mesic fluvial zone and increase in diversity in the xeric fluvial. As habitat conditions become less stressed species successively replace each other forming a series of over-lapping bands. Some have a wide tolerance (Thelidium decipiens, Cinclidotus fontinaloides); with others it is much narrower (Psorotichia schraderi, Rhynchostegium riparioides). The Tufa tributaries The beds of these two streams are covered in tufa that is being actively deposited by the strongly alkaline water (pH 7.7-8.1). Tufa is too soft and crumbly to support lichens so the group is absent from the curtains and the stream beds. However a non tufa-depositing seepage near the bottom of Waterfall Beck supported submerged colonies of the calcareous aquatic Placynthium tantaleum new to the Malham area. On the valley sides of Waterfall Beck, high above the level of the present stream, there are lumps of old tufa in the scree suggesting the possible collapse of a former tufa dam or screen. This old, well-weathered, hardened tufa supports lichens such as Hymenelia epulotica, Polyblastia deminuta and Solorina saccata but they are not aquatics.

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Fig 5. Belt transect 3.75m long, from deep water to high flood level, illustrating lichen and bryophyte zonation on shelving limestone bedding planes in the Cowside Beck Gorge.

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Fig 6. Belt transect 60cm high illustrating lichen zonation on a vertical limestone face at the entrance to the Darnbrook ravine. No bryophytes were present.

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Darnbrook Beck The lowest section of this major tributary runs over Carboniferous limestone to a point just above the Cock Pits. This length dries up in summer and its lichen flora is similar to the seasonally dry section of Upper Cowside. In a number of places permanent seepage drains from limestone bedding planes flanking the stream. These niches support true aquatic lichen communities with Pyrenocollema monense, Staurothele bacilligera and Verrucaria elaeomelaena. A further feature of this reach is the presence of communities associated with bird perches. The larger, more prominent and stable boulders in the stream-bed regularly have guano deposited on them by birds working the stream for insects. This eutrophication encourages a community of nutrient-loving lichens to develop which are found nowhere else on the fell. They include abundant Phaeophyscia orbicularis supported by Candelariella vitellina, Lecanora albescens, Physcia adscendens, P. caesia, P. tenella and the yellow Xanthoria parietina. Above the Cock Pits, where it traverses the Wensleydale Series, the stream has an unstable stony bed scoured by the traction load in times of flood so is still unsuitable for lichens. At two sites, however, limestone lichens are richly developed, one is in the vicinity of a short limestone ravine at 450 m, the other a small waterfall and steep section formed where the beck flows over the Middle Limestone at 520 m. The ravine is carved in massive limestone in the lower part of the Wensleydale Series. It provides a range of conditions from sunless and sheltered in the ravine to well-illuminated at its south-facing mouth. Sheltered faces are covered with Bacidia fuscovirens, Belonia nidarosiensis, Gyalecta jenensis and Opegrapha saxatilis. The lichens on well-lit limestone are zoned in relation to length of submergence (Fig. 6). This figure illustrated how the zonation is terminated at the base of the mesic fluvial zone by silt deposition and at the top by a declining influence of the stream at around 60 cm; this can be regarded as the top of the xeric terrestrial zone. About 40 lichens can be found in the vicinity of the ravine the majority being in well-lit sites. There are six jelly lichens including Collema cristatum, C. fuscovirens, Lempholemma polyanthes, and Leptogium gelatinosum. Pyrenocarpous lichens are well represented notable species being Dermatocarpon miniatum, Polyblastia albida, P. dermatodes, Thelidium fontigenum, and T. papulare. Two lichenicolous fungi are present, Toninia verrucarioides overgrowing Placynthium nigrum and Roselliniopsis tartaricola on Acarospora glaucocarpa. This is only the second British record of the latter; it seems to be something of a Craven speciality as the first record was from Ribblehead. The waterfall formed by the Middle Limestone is a steep jumble of large boulders of impure limestone about 10 m high. These provide a range of niches varying from aquatic through fluvial to merely damp. A number of the lichens of the Cowside system were seen only here, for example, Diploschistes muscorum, Farnoldia jurana, Myxobilimbia lobulata, Peltigera didactyla and Placynthium subradiatum. In the 1960’s there were some large patches of Peltigera leucophlebia in grassland by the fall, they were not relocated though P. membranacea and P. lactucifolia were present. This is a good site to see Acarospora glaucocarpa, Dermatocarpon miniatum, Hymenelia prevostii and Petractis clausa. Millstone Grit tributaries Above the Middle Limestone, Darnbrook Beck branches into a number of small rills flowing over drift and peat. Their water has a low pH and low calcium (pH 4.3-4.6; Ca 0.4-1.2 mg/l). Rushes often form a canopy over the watercourses which flow in shady tunnels, their beds are lined with loose shale and gravel; these two factors render them unsuitable for lichens for most of their length. Where light conditions are better such as at bends, path crossings or by small waterfalls lichens come in if there are stable sandstone boulders embedded in the stream bed or banks. Species tolerant of constant submergence by 2-3 cm of water during average flow include Verrucaria aquatilis, V. funckii and V. rheitrophila. Slightly higher is a V. margacea/V. praetermissa zone. On the sides of stones around water level Bacidia inundata, Baeomyces rufus, Hymenelia lacustris (rare), Porpidia soredizoides, Rhizocarpon lavatum, Trapelia coarctata and T. involuta are sparingly present. These calcifuge lichens are scattered but occasionally reach a cover of 50% and form communities. The headwaters of Tennant Gill support the same assemblage of common acidophilous lichens.

Fountains Fell Tarn This shallow, highly acidic tarn (pH 3.5; hardness <2-8) lies in a hollow among eroding blanket bog. Its shore line is composed of heavily leached, flat pieces of coarse grit-stone. These support a <1 % lichen cover which means that many stones are bare. They comprise Lecidea plana, Porpidia crustulata, P. tuberculosa and Trapelia coarctata, the former is a first record for the Malham area. These species, which are lichens of damp rock rather than true aquatics, are not obviously zoned in relation to the water margin.

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Calcareous flushes and mires A number of these were examined in Upper Cowside and on the south side of the gorge. They occupy gentle slopes on the flood plain beyond the reach of most floods so are stable. The open vegetation of Carex spp. allows light to reach the soil surface. The main habitat for lichens are low rounded or lopsided limestone boulders projecting 5 to 25 cm out of the wet soil. These carry a good lichen cover that is zoned in relation to height above soil level. A few of the species such as Staurothele hymenogonia were not seen elsewhere. Underhangs on lopsided boulders support the Gyalectetum jenensis community composed of Gyalecta jenensis, Acrocordia conoidea, Clauzadea metzleri, Petractis clausa and Opegrapha calcarea.

Freshwater algae

This area was already one of the best-worked stream systems in the region, indeed the Malham district is one of the most intensively studied areas for algae in the British Isles (Pentecost 1999). The Darnbrook-Cowside system was surveyed in some detail by the Wests, father and son (West & West 1899). Much of the West’s work appears to have been concentrated in the lower reaches of Cowside Beck from Darnbrook Farm to Arncliffe. Here they recorded a total of 22 taxa (8 cyanobacteria, 10 Chlorophyta, 4 diatoms) several of which were national rarities (Cosmarium dovrense) or recorded in Britain for the first time (Homoeothrix janthina, Rivularia biasolettiana). Nothing appears to have been added until the extensive diatom studies at Malham Tarn conducted by Round (1960). One of Round’s sites was ‘Cowside Top Springs’ where he recorded a rich diatom flora totalling 33 species and varieties including Cymbella silesiaca and Luticola mutica. Further work on the freshwater algae, with special reference to the cyanobacteria was conducted by one of us (AP) beginning in 1972 and lasting up to the present time. Investigations centred on Waterfall Beck and much of this work is summarised in three papers (Pentecost 1978, 1981, 1991). A survey in 1990 produced a list of 99 algae that included 23 cyanobacteria, 19 chlorophytes, 50 diatoms, two xanthophytes and one rhodophyte (Batrachospermum moniliforme). A large proportion of these algae were associated with bryophytes. The following account summarises the above papers.

Waterfall and Lower Becks This pair of becks are very similar, being calcareous, nutrient poor, well oxygenated, tufa depositing hill streams. Due to easier access most work has been done on Waterfall Beck (Pentecost 1991) the algae of which he described with reference to five major floristic units (Fig. 7). (1) Mats of the moss Palustriella commutata which support a particularly diverse algal flora dominated by diatoms consisting of loosely attached ones (Achnanthes minutissima, Navicula tripunctata) and strongly adpressed species. (2) Rhynchostegium riparioides, another mat-forming aquatic moss, had a much lower species diversity but Achnanthes lanceolata, Cocconeis placentula and Meridion circulare were more abundant. (3) A well known (Fritsch 1929, Butcher 1946, Pentecost 1982) calcite encrusted rock and tufa community (Fig. 8) composed mainly of cyanobacteria Gongrosira incrustans (green alga), Phormidium incrustatum, Schizothrix calcicola and Homoeothrix crustacea. (4) Rock colonised by endoliths such as Gongrosira incrustans Hyella fontana, Phormidium favosum and Leptolynghia (Schizothrix) perforans, these penetrate up to 1.3 mm into the rock and make a significant contribution to algal biomass covering about 16% of the bed of Waterfall Beck (Pentecost 1992). (5) Oedogonium australe (green algae) was the most abundant alga overall forming extensive mats when discharge was low.

Transects across the stream showed that the abundance and distribution of species was determined by length of submergence (Pentecost 1982). Deeper more turbulent water had Schizothrix calcicola and several species of diatom, particularly Achnanthes minutissima, A. microcephala, Cymbella ventricosa, Diatoma hiemale and Rhoicosphenia curvata. The only green alga present was Gongrosira incrustans. Permanently wet rock flanking the deeper water, supported a community dominated by filamentous cyanobacteria (Phormidium, Schizothrix) which had a greater species diversity than stands subject to frequent drying out, these were dominated by coccoid cyanobacteria such as Gloeocapsa spp. An unusual feature of the flora is the regular appearance in spring of Chrysonebula holmesii (coccoid chrysophyte), a very rare alga first described from Gordale Beck and almost endemic to the Malham area. It produces great quantities of mucilage resulting in the formation of easily visible patches of thick white jelly which are a common sight in these two becks. The growth has disappeared almost entirely by late summer.

The most conspicuous tufa-forming species, is Rivularia haematites that occurs as dark olive-brown buttons on stones in tufa streams (Fig. 7). This species does not often occur on tufa-screens, it is found on the bed of streams close to the water surface. If cut open the hemispherical buttons are seen to have a concentric structure, colonies may live for 15-25 years. A tufa-forming rarity is the desmid Oocardium stratum.

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Fig. 7. Diagramatic section across a tufa deposit, illustrating the habits of the flora and fauna (Pentecost 1982).

Fig.8. Diagramatic section through calcareous biofilm showing in (a) spongy structure with scattered algal colonies and filiaments and (b) a dense, nodular deposit dominated by colonial algae. Bar lines indicate 2mm (Pentecost 1982).

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The 2002 to 2004 survey This concentrated largely on diatoms taken from algal mats, bryophytes, foam, etc in the various streams, springs, flushes and wet rock faces. The results from DR’s collections are presented in Appendix 3; voucher specimens have been retained. Casual records of other algal groups were made from most stream courses and from Fountains Fell Tarn.

Cowside Beck During spring and summer, particularly during times of low flow, this stream supports dense, aggressively competitive mats of filamentous green algae (blanket weed) which together with bryophytes form a canopy that shades the river bed discouraging lichen growth. Taxa involved are numerous and include Cladophora glomerata, Microspora, Oedogonium, Ulothrix zonata and Vaucheria, and in more sheltered water Mougeotia, Spirogyra porticalis and Zygnema. Springs remain largely free of blanket weed and here smaller and more delicate algae can be found belonging to genera such as Batrachospermum, Chaetophora and Draparnaldia. These springs are home to several cold water diatoms e.g. Caloneis alpestris, Diatoma hymale, Didymosphenia geminata and Meridion circulare.

Darnbrook Beck This is similar to Cowside but the steeper gradient and the fact that much of the stream course dries out in summer reduces the quantity and diversity of algae. In upper Darnbrook, diatoms are widely distributed in moss cushions. Samples of the moss Schistidium rivulare s.l. investigated by A.P. yielded an abundance of Meridion circulare, with smaller numbers of Achnanthes minutissima, Diatoma mesodon, Gomphonema acuminatum, Cocconeis placentula, Caloneis bacillum, Cymbella minuta, C. silesiaca, Fragilaria capucina and Navicula radiosa. Most of these taxa are calcicoles and limited to limestone streams. One of the most striking algae up Darnbrook is Haematococcus pluvialis whose blood-red resting cells cover hollows in the limestone where water collects. During favourable periods the flagellate stage develops forming deep-red suspensions containing up to 230,000 cells per ml. A damp ledge in the ravine above the Cock Pits produced the first British record of Gloeobotrys coenococcoides which suggests that there is still much to be discovered.

Fountains Fell Tarn This shallow dystrophic water body was sampled several times but not thoroughly surveyed. The algal flora is rich in desmids such as Cosmarium formulosum, Cylindrocystis sp., Mesotaenium sp. (abundant) and Staurastrum sp. Filamentous green algae were common and in November 2002 included Microspora stagnorum, not previously recorded from the Malham area. A sample of phytoplankton taken in March 2004 produced only Amphidinium elenkenii, Chlorogonium baculiforme and Chromulina cf. nitens in small numbers. This rather sparse phytoplankton, occurring at 630 m, probably contains some further specialists and would repay further study.

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Freshwater Invertebrates For this study Cowside and Darnbrook Becks were arbitrarily divided into upper and lower sections along eastings SD91 and SD89 respectively, these divisions do not correspond to any obvious habitat boundaries. Collections were made from a further eight stream segments most of which correspond to ecological units. Sampling was carried out using kick netting, stone turning, agitating moss in a tray, and sweeping bankside vegetation. Aquatic higher plants are virtually absent, but Monkey flower (Mimulus guttatus) is present in two springs on Cowside. A map showing recording areas and a table with full details of the freshwater invertebrates recorded and their distribution within the twelve units is provided as Appendix 4.

Clear, swift, cold, freshwater streams with a mossy, boulder covered limestone bed are particularly rich in freshwater shrimps, mayflies, stoneflies and caddis. These form the main biomass of the ecosystem and support, at a higher level, fish and birds such as the dipper (Cinclus cinclus). The results show the invertebrate groups to consist of widespread generalists and narrow specialists confined to specific habitat niches for example, sand and gravel deposits (Caenis rivulorum), cold springs (Crenobia alpina), backwater pools (Gerris thoracus), or altitude (Agapus articus). Apart from sampling Fountains Fell Tarn the acid Millstone Grit tributaries were not surveyed or their invertebrates might have been as distinctive as their bryophytes and lichens. Also given more time the spectacular tufa tributaries deserve a thorough survey being some of the best examples of their kind in Britain and likely to support unusual invertebrate communities. Crustacea The freshwater shrimp (Gammarus pulex) is widespread and present in large numbers. Its absence from Fountains Fell Tarn and the highest Millstone Grit rivulets is due to their low calcium levels. The species is unusual in breeding during the winter. The white-clawed crayfish (Astacus pallipes) was searched for but not found, it is not known if it has ever been present in the catchment. Tricladida (flatworms) Despite a careful examination of spring heads and flushes Crenobia alpina (Fig. 9) was found only in one spring and three flushes in Upper Cowside. It is restricted to running water and can breed only at temperatures below 12oC so is regarded as a glacial relic. Over the year the temperature of these springs varies from 7.8 to 12.0oC. Its apparent absence from other cold springs in the catchment is unusual though a cave population exists in Robinson’s Pot. Ephemeroptera (mayflies) Mayfly nymphs are frequent in clear running water and Cowside Beck is no exception. The dominant species are Baetis muticus, B. rhodani, Ecdyonurus torrentis and Ephemerella ignita, with Heptagenia lateralis, H. sulphurea, Paraleptophlebia submarginata and Rithrogenia semicolorata common. In contrast to the above generalists many mayfly nymphs are structurally adapted for existence in particular habitat niches so have a restricted distribution. For example Caenis rivulorum larvae (Fig. 9) were only found associated with the sand and gravel fan just above Arncliffe while Ameletus inopinatus, a montane species, was present in substantial numbers in upper Darnbrook; this is the first record from the headwaters of the River Wharfe. The presence of a few species were established by being swept from streamside vegetation as adults e.g. Ephemerella notata.

Plecoptera (stoneflies) As with mayflies the adults are short-lived and take no food so most records are of nymphs, which live from one to three years. Anyone turning stones in the catchment will be surprised at the abundance of Dinocras cephalotes (Fig. 9) one of Britain’s largest stoneflies, it is followed in frequency by Amphinemoura sulcicollis, Isoperla grammatica, Leuctra hippopus, L. inermis, Protonemura meyeri and Siphonoperla torrentium. Appendix 4 shows that a number of stoneflies are restricted to upper Darnbrook Beck, these include Leuctra moselyi which was found only in this site during a survey in the 1950s (Henson 1963).

Hemiptera–Heteroptera (water bugs) Three species of water bug, all of which live on the surface of the water, are present. The water cricket (Velia caprai) is common on pools in streams. The water boatman (Gerris thoracus) only turned up in a backwater pool of Darnbrook Beck, it is more a species of still water. The high altitude, acid-loving species Arctocorisa carinata, was recorded from Fountains Fell Tarn, which is confirmation of an old record (Henson 1963). Its British distribution is upland lakes in the N. England and Scotland.

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Trichoptera (caddis flies) Caddis flies are well known because their larvae usually live in protective cases that they make of objects collected from their habitat. The adults are moth-like insects, their four wings being thickly covered by hairs. A good number of species (13), both as adults and larvae were recorded from the catchment (Appendix 4, Table 1). Almost ubiquitous are Philopotamus montanus, Plectrocnemia conspersa and Rhyacophila dorsalis (Fig. 9). A number of species were only found in lower Cowside Beck, while Halesus radiata was only in Thoragill Beck. The star find was Melamophylax mucoreus, an inhabitant of upland stony streams and known from only one lake in the British Isles, Malham Tarn. It was recorded from Darnbrook Beck in the 1950’s (Henson 1963); this time it showed up in Thoragill Beck.

Diptera (true flies) The larvae of Chironomidae (non-biting midges) were common throughout the system; Simuliidae (black-flies) were relatively uncommon.

Coleoptera (water beetles) Only truly aquatic species were investigated. These had a scattered distribution due to specialised habitat requirements. Agabus bipustulatus and A. guttatus were found occasionally in backwaters and slow flowing sections of Darnbrook Beck, while Helophorus grandis, Oreodytes davisii and O. sanmarkii occur among aquatic mosses in Cowside. Agabus articus (Fig. 9) was only in Fountains Fell Tarn, from where previous records of this montane species had been made (Henson 1963).

[Vertebrates: Pisces (fish) Brown trout occur throughout the length of Cowside Beck, lower Cowside containing some large specimens. Bullheads (Cottus gobio) are present in Lower Cowside.]

(a) (b) (c) (d)

(e)

(f)

Fig.9. A selection of freshwater invertebrates recorded: (a) stonefly larva Dinocras cephalotes, (b) mayfly larva Caenis rivulosum, (c) caddisfly larva Rhyacophilia dorsalis, (d) flat worm Crenobia alpine, (e) water beetle Aganus articus, (f) river limpet Ancylus fluviatilis.

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Mollusca To date 87 species are known to occur within the area managed by the National Trust, which covers Darnbrook Beck, parts of Cowside Beck, and Malham Tarn, so it can be seen that the potential for a large molluscan fauna exists. The mollusca recorded for this project were found strictly within the springs and the streams comprising Cowside and Darnbrook Becks, and their various tributaries. These are very fast flowing, high-altitude, mountain limestone streams which, because of their nature, are very poor in freshwater mollusca with only three truly aquatic species present. However, a large number of calcareous springs and seepages occur which feed the flow of these streams and conditions in these are more amenable. Calcareous springs were examined from Thoragill Beck to just above Arncliffe between September 2003 and August 2004; 33 species of mollusca were recorded from within the confined parameters of the survey. Fifteen of these can be considered streamside species (see below), the other 17, listed at the end, have a wider ecological amplitude. Of the aquatic species only two occurred in any numbers within the rocky, fast-flowing, rivers, these being the wandering snail (Lymnaea peregra) and the river limpet (Ancylus fluviatilis) (Fig. 8.) Jenkin’s snail (Potamopyrgus antipodarum) also occurred, but rarely and only in very small numbers. The recorder was unable to locate any specimens of pea-shell (Pisidium), due to the lack of suitable silt-rich habitats within the stream systems. I would expect at least two species to occur within the habitats surveyed. Those species associated specifically with the margins of streams are listed below, with notes on their habitats. They are typical of the zone covering aquatic moss cushions to high-level flood debris. Of species from the drier habitats Vitrea subrimata, from an Upper Cowside spring, is strictly a subterranean, arctic relict, normally found under deep-set stones in or at the base of limestone scree. Several of the species are more normally found in disturbed habitats, such as roadside banks or disturbed woodland. The shortage of suitable alternative habitats has the effect of leaving some species, such as Arianta arbustorum, no alternative but to live in the flood plains of the river system, this species was not located in any other habitat in the area. The scarcity of thick-stemmed plants such as marsh thistle, and the total lack, in most of the springs, of other molluscan traps such as twigs, makes it very difficult to locate many of the smaller species such as Punctum pygmeum, Columella and the Vertigo species, without using destructive sampling methods. Potamopyrgus antipodarum Scarce, found in small numbers in Cowside Beck Galba truncatula Common in the most of the calcareous springs and stream side marshes Lymnaea (Radix) peregra Common in calcareous springs and in some sections of the various streams Ancylus fluviatilis Often difficult to locate but generally common within the main streams Carychium (Carychium) minimum Scarce in calcareous springs, usually under stones Succinea putris Widespread in the more luxuriant vegetated areas Oxyloma (Oxyloma) elegans elegans

= O. pfeifferi Common in the calcareous springs Columella edentula Scarce in calcareous marshes, probably under recorded Vertigo (Vertigo) antivertigo

Common under twigs in the marshes off Monks Road, should occur elsewhere in the calcareous marshes

Vertigo (Vertigo) substriata Probably common in most of the calcareous springs Vertigo (Vertigo) pygmaea Widespread, but rarely common Punctum (Punctum) pygmaeum Rare, its small size makes if very difficult to locate in most types of habitat Euconulus (Euconulus) trochiformis

(= E. alderi) Fairly common, can be found on the open wet soil and amongst plants Nesovitrea (Perpolita) hammonis Common in most of the calcareous springs

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Deroceras (Deroceras) laeve Common in marshy areas by the stream as well as in the calcareous springs. Trichia plebeia Scarce; in wet mossy areas by springs.

Molluscs with a wider ecological amplitude: Cochlicopa lubrica, Carychium (Saraphia) tridentatum, Pyramidula rupestris, Clausilia bidentata, Discus (Discus) rotundatus rotundatus, Vitrea subrimata, Vitrea contracta, Euconulus (Euconulus) fulvus, Oxychilus (Oxychilus) cellarius, Oxychilus (Ortizius) alliarius, Deroceras (Deroceras) reticulatum, Arion (Arion) ater, Arion (Kobeltia) distinctus, Arion (Microarion) intermedius, Trichia (Trichia) hispida, Trichia (Trichia) striolata striolata, Arianta arbustorum arbustorum. Sub-fossil molluscs from tufa in Lower Beck are listed by Keen (1989). For a full tabulation of the freshwater invertebrates recorded in 2001–2003 see Appendix 4.

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Cave Studies Six caves in the area resurge into Cowside Beck. Few cavers visit these systems so they are in a largely natural condition and contain fine calcite formations. Elements of an underground fauna had been reported in the past so a more detailed search was carried out for this project. The cave entrances are shown on the Map (fig 1), they are:

Cherry Tree Hole, SD881704, length 1.25 km, contains two streams. Darnbrook Pot, SD885710, depth 71m, contains a main stream passage 350m long. Robinson’s Pot, SD899706, length 2.5 km, contains four streams. Thoragill Cave, SD889702, a small resurgence cave. Loop Cave, SD903700, a small resurgence cave. Yew Cogar Cave, SD908700, length 1.1 km, contains two streams.

The water in or resurging from the caves is alkaline with high total hardness, electrical conductivity and pH. Detailed analysis for Robinson’s Pot are given in Appendix 1 from which it can be seen that its waters are less alkaline than those in the aerated surface waters of Darnbrook Beck with which it runs parallel but deep underground.

The fauna and flora of the six caves was not rich but included the following: Vertebrates A bat detector showed bats using Cherry Tree Hole throughout the year. Results from a logger demonstrated late summer swarming (Fig. 10). Brown Long-eared, Daubenton’s and Natterer’s bats were caught at the site. Large quantities of bat droppings are also present in the main chamber of Darnbrook Pot where a Daubenton’s was seen. A fish was seen at the start of Sump 1 in Robinson’s Pot; it was probably a trout. Insects and spiders During two visits to Cherry Tree Hole flies were caught deep underground. They were identified at the Natural History Museum, London as Heliomiza captiosa, a first record for a Yorkshire Cowl. Larvae and adults of the stonefly Dinocras cephalotes extend throughout the entire Robinson’s Pot system. A web-spinning caddis fly larva (Plectronemia conspersa) occurs in Robinson’s Pot. The Herald moth (Scoliopteryx libatrix) uses Loop Cave for hibernation. Loop Cave is also home to a breeding colony of the spider Meta merianae. This cave threshold spider is fairly widespread in Britain. Crustacea, flatworms and true worms The Freshwater Shrimp, Gammarus pulex, has inhabited the same site in Robinson’s Pot since it was discovered there in 1975 as has the flatworm Crenobia alpina. The latter is a cold water species, the water temperature here averages 8.8o C. The Worm Series, a side passage off the main stream passage in Robinson’s Pot, has mud banks on both sides showing abundant worm casts. They are produced by a large and healthy population of an albino form of the green earthworm Allolobophora chlorotica. This species is common in limestone soils in the Malham area where it has a pink/greenish colour. It can survive and breed for at least 50 weeks totally submerged below aerated water. Unpigmented cave populations are otherwise known only from Ingleborough Cave.

Fig. 10. Results from a bat detector showing late summer swarming at Cherry Tree Hole over three nights in August 2003.

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Fungi A dead, water worn branch of a deciduous tree found in Cherry Tree Hole supported fruits of the Candle-snuff fungus (Xylaria hypoxylon). A sample of foam from the main stream in Robinson’s Pot contained spores of the following Hyphomycetes (aquatic fungi); Articulospora sp. and Tetracladium marchalianum.

Robinson’s Pot was first surveyed for cave life by Hodgson in 1975. At that time it was considerably richer than it is today, for example 30 cavernicolous species were found, including 7 caddis fly larvae compared to just one caddis in the present survey. In 2002 a strong smell of sheep dip was present underground and on investigation it was discovered that water contaminated by sheep dip was entering the system at several places. Its widespread distribution was confirmed using a conductivity meter. It is suspected that this is the reason for the sharp fall in diversity and is perhaps a new factor to be taken into account when analysing cave biodiversity data.

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Discussion The recognition of the Malham-Arncliffe complex, comprising Malham Tarn, the Tarn outflow stream, Gordale Beck and Cowside Beck, as a key open-water site (Grade 1*) in the Nature Conservation Review (Ratcliffe 1977) has already been alluded to. The three upland streams are described as ‘outstanding’ and form a series. The Tarn outflow is the slowest flowing, with little spating, silted pools and appreciable amounts of aquatic higher plants. Gordale Beck is intermediate in character, with Cowside Beck being distinctive for its spates, fast flow, bed lined with unstable boulders, cobbles and stones, and a virtual absence of aquatic higher plants.

In 1989, as a follow-up from their national survey of macrophytes in rivers, the Nature Conservancy Council commissioned a survey of macrophytes in the same three streams using standard methods (Holmes 1983). This resulted in a report covering two 500 m lengths of Upper Cowside, and four 500 m lengths of Lower Cowside. Highly detailed hand-drawn maps backed up by photographs and species lists were prepared. Though more descriptive than interpretive the report types four lengths of Cowside Beck into ‘mesotrophic rivers downstream of oligotrophic catchments’ and two as ‘rivers with impoverished ditch floras’ (NCC 1983). While the Tarn Outflow and Gordale Beck contain silted weedy pools supporting submerged, floating-leaved and emergent macrophytes, the channel of Cowside Beck had only sparse marginal aquatics such as Water Sweet-grass (Glyceria fluitans), Monkey flower (Mimulus guttatus) and occasional Water-cress (Rorippa nasturtium-aquaticum). This is a result of torrential flow and an unstable, stony, stream bed. Invertebrates are usually the best covered group in stream studies, and various books and papers have detailed their distribution in hill streams and lowland rivers (e.g. Hynes 1970, Crothers 1989, Harper 1990) but few provide more than very general comparisons with Cowside Beck. The stream in Ashes Hollow on the Long Mynd (Arnold & Macan 1969), at a comparable range of altutudes, more calcareous in its headwaters but less so lower down, suggests some interesting comparisons and many of the mayflies and stoneflies are common to the two sites. The cold-water flatworm Crenobia alpina is abundant in a headwater spring at 446 m at the Long Mynd site, but absent lower down; with this in mind the high calcareous springs in the Darnbrook headwaters could well repay further investigation. The NCR (Ratcliffe 1977), however, includes notes on the fauna of streams in the Malham-Arncliffe complex that are pertinent and include species not found by us in Cowside. The invertebrate fauna is greatly influenced by the gradient, physical nature, and stability of the stream bed. The absence of silt in Cowside rules out the presence of molluscs such as Pisidium spp. and Sphaerium cornutum, the alder fly (Sialis lutaria) and the mayfly Procloeneon pseudorufulum all present in the Tarn Outflow. Instead, species typical of fast currents and a stony bed dominate in Cowside. Examples are mayfies belonging to the family Ecdyonuridae (Ecdyonurus torrentis, E. ventosum), caddis flies of the family Glossosomatidae (Agapetus fuscipes, Glossosoma conformis), and stoneflies such as Dinocras bipunctata. Headwater species, typical of torrential streams, show a number of anatomical adaptations that help them survive. These include a flattening of the body (Dinocras, Rhithrogena), streamlining and a reduction of projecting structures (Baetis), the presence of suckers (Ancylus fluviatilis) or a broad foot (Lymnaea peregra), development of friction pads (Rithrogena), and the use of silk or sticky secretions (many Trichoptera and Simuliidae larvae). Certain species such as Gammarus pulex show no special adaptations but avoid strong currents by living in moss, gravel or under stones. Several specialised freshwater habitats are present in the Cowside/Darnbrook catchment. These are streams with intermittent flow, springs, tufa and a shallow oligotrophic tarn. There is 800m of winterbourne at the head of Upper Cowside and the lowest 2 km of Darnbrook dries out in the summer. Desiccation episodes eliminate Gammarus, the nymphs of mayflies, stoneflies, caddis flies and many Diptera unless they are near to emergence. The egg stages are more resistant. Hynes (1970) suggests that Platyhelminthes (flatworms), Oligochaeta (true worms), Ostracoda, Copepoda, Hydracarina (water-mites), Chironomidae (midges) and some water beetles are able to survive by burrowing down into the substratum. A 1m x 1m quadrat recorded in the stony bed of the Cowside Beck winterbourne after a long dry spell produces several true worms, the slug Arion ater, Collembola and an adult stonefly (Leuctra inermis) confirming Hynes observations. Of the other specialised habitats, cold water springs were searched for the flatworm Crenobia alpina, this glacial relic was locally present where the water temperature remained below 12oC. A special search should be made for the spring-dwelling species Aptidea muliebris (caddis) and Hydroporus ferrugineus (water beetle). The freshwater invertebrates of the tufa tributaries appear to be depressed, possibly because stones in

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the stream bed are cemented by a cover of tufa providing a rather simple niche structure. Fountains Fell Tarn is too oligotrophic to support species such as Gammarus but two montane insects, the water-beetle Agabus arcticus and the water-bug Arctocorisa carinata, have outlying localities here. The classic texts on the ecology of running waters (Allan 1995, Hynes 1970, Macan 1963) make only a passing mention of bryophytes so there is little with which to compare the information in this paper. The short paper by Tutin (1949) on a Lake-District stream provides some interesting comparisons with the present site. Impoundment of the head waters of the River Tees in 1970 encouraged rapid algal and bryophyte growth in the river below the dam where there was controlled flow (Armitage 1976), this suggests that previously spates had been important in controlling the biomass of these groups. This effect can be observed in the Cowside catchment where the steeper Darnbrook Beck (see profile on Map) has a lower bryophyte cover than Cowside which in places is choked by aquatic mosses. Observation has shown instability of the bed, scour and the ripping off of material during floods to be responsible for a reduction in bryophyte cover. The dominant mosses of the stream channel are seven vigorous mat-forming species that quickly recolonise areas from which they have been stripped by the current. They are arranged in an irregular zonation corresponding to length of submergence with Rhynchostegium riparioides under water for most of the year and at the other extreme Brachythecium rivulare dominant above summer water level. The zonation is visible on boulders in the river and on shelving limestone in Cowside Gorge. There are few associates of any note. Specialised niches along the watercourses show variation from the above pattern. Winterbourne stretches at the head of Upper Cowside and in Lower Darnbrook have Cinclidotus fontinaloides dominant with lesser amounts of Hygrohypnum luridum and Schistidium rivulare s.l., all are resistant both to desiccation and to prolonged submergence. Cold water springs here support no distinctive bryophytes but the tufa tributaries provide suitable ground for small acrocarpous mosses such as Didymodon tophaceus, Eucladium verticillatum, Hymenostylium recurvirostrum and Philonotis calcarea. These grow alongside Palustriella commutata and Cratoneuron filicinum. The base-poor and acidic headwaters of Darnbrook Beck support only the leafy liverwort Scapania undulata and occasional Racomitrium aciculare, these provide an upland flavour. Some of the more unusual species of the stream corridor are found away from flowing water in less stressed marginal habitats such as calcareous flushes and mires, on damp limestone and in associated tufa flushes. From such sites Gymnostomum aeruginosum, Jungermannia atrovirens, Leiocolea alpestris, Orthothecium rufescens, Preissia quadrata and Scorpidium scorpioides were recorded; none are new to the Malham area. The role that bryophytes play in the freshwater ecosystem are to provide essential cover for many invertebrates, some of which, such as Dinocras bipunctata, have a nymphal stage lasting for three years. Bryophytes also afford a habitat for numerous algae, especially diatoms, that can be sampled by squeezing water out of them, certain mosses have a richer attached algal fauna than others. In places, where the dominant mosses grow so thickly in the stream channel that they form a blanket across it they eliminate many lichens, algae and smaller bryophytes by competitive exclusion. It is not thought that they provide a significant food source for grazers. The results of a nation-wide survey of lichens associated with streams on chalk and limestone has recently been published (Gilbert 1996), it included the gorge section of Lower Cowside which is the richest length of the catchment. Most stretches have an impoverished lichen flora due to the dominance of bryophytes, the large stretches of winterbourne, and instability/scour of the stream-bed. Three ‘hot-spots’ lift the lichen flora of Cowside from mediocre to well above the national average. These sites all have appreciable amounts of bryophyte-free outcropping limestone. They are the 600m long gorge in Lower Cowside where limestone bedding planes flank the stream; the limestone ravine and waterfall low in the Wensleydale Series on Darnbrook Beck; and the waterfall flowing down block-scree below the Middle Limestone on the same stream. From these sites rare but characteristic lichens of limestone streams such as Bacidia fuscoviridis, Eiglera flavida, Placynthium subradiatum, Staurothele bacilligera, S. guestphalica and Thelidium fontigenum were recorded. As with the bryophytes these are zoned in relation to length of submergence. The upper zones have a composition that includes nitrophilous lichens such as Xanthoria parietina, Physcia caesia and P. adscendens which shows the habitat is mildly eutrophicated, possibly by the activity of birds. Winterbourne stretches support an impoverished lichen community in which Leptogium plicatile, Thelidium decipiens and Verrucaria aethiobola are able to tolerate the alternation of prolonged dry and wet periods. Active tufa is, as a substratum, too soft and crumbly to carry lichens. Cold springs, where coarse bryophyte

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and algal growth is depressed, hold a submerged community composed of Verrucaria elaeomelaena and V. rheitrophila. Ried (1960) has shown how the former is extremely sensitive to drying out; exposure to 40% relative air humidity for 24 h resulted in considerable damage. The Millstone Grit tributaries hold impoverished communities of common calcifuge lichens (Gilbert & Giavarini 1997). Gilbert (1996) concluded that the richest sites in terms of lichen diversity were quite simply those with the greatest area of exposed limestone. These tend to be rejuvenated stretches in the middle reaches of rivers where wide gently shelving beds of limestone flank the watercourse. Examples are Aysgarth Falls on the River Ure and Ghaistrill’s Strid on the Wharfe. Headwater streams only a few metres wide with earth banks can never rival the overall diversity of these major sites despite the occasional presence of topographically complex features such as a small waterfall and gorge. Lichens hardly interact with the rest of the ecosystem, providing neither food nor shelter for invertebrates. There is observational evidence that the thallus surface is resistant to invasion by many bryophytes and algae. The algae of Cowside Beck and its tributaries have been the subject of detailed studies over many years; the communities occurring in the tufa tributaries are of national importance. The torrential nature of the watercourses results in a periphyton of firmly attached diatoms, red and green algae, and cyanobacteria. Their distribution is determined by light, temperature, substratum, current, scouring, pH and grazing. During periods of low summer flow every substratum in the stream is covered in a fluffy brown carpet of diatoms and dense trailing streamers of filamentous green algae up to a metre long. These may get devastated by floods that leave only a few tough, rope-like strands of Cladophora glomerata visible. From persistent basal parts and from survivors in sheltered niches the periphyton redevelops until razed by the next flood. Filamentous green algae have different tolerances to stream flow with those characteristic of fast currents being dominant in Cowside (Cladophora, Oedogonium, Ulothrix), while Mougeotia and Spirogyra are found only in slack water. Most tolerant of scour are cyanobacteria with endolithic thalli, these dominate the steepest parts of the tufa becks. The tufa screens are notable for developing an extensive, seasonal cover of the stalked diatom Didymosphenia geminata which gives them a feel like velvet. Many of the filamentous Chlorophyceae grow primarily during summer which is believed to be a response to temperature (Hynes 1970). An outstanding example of control by temperature are those diatoms that show optimal growth in cold water springs. In Cowside they include Diatoma hiemale, Meridion circulare and the rhodophyte Lemanea fluviatilis. M. circulare, which requires a temperature below 150C ( Hynes 1970), also occurs in upper Darnbrook as a result of altitude. Diatoms are largely indifferent to light levels which explains how they are able to grow abundantly as epiphytes deep in bryophyte mats and cushions. Batrachospermum moniliforme is intolerant of competition but relatively indifferent to pH as are Lemanea and Stigeoclonium. Most of the common algae in Cowside Beck are typical of alkaline water e.g. Achnanthes spp. Cladophora glomerata, Cocconeis spp. Gongrosira incrustans and all the cyanobacterial communities described from Waterfall Beck. In contrast Fountains Fell Tarn has an acidophilous flora that includes many desmids and Microspora stagnorum. Little is known about the probably substantial effects of grazing on the periphyton biomass. Cyanobacteria are usually avoided but other algae are palatable. Areas cleared of algae can often be seen around snails and freshwater limpets, and Douglas (1958) studying a stony stream in Wales found that the numbers of grazing caddis-fly larvae (Agapetus fuscipes) was negatively correlated with the numbers of Achnanthes. Chara vulgaris var. longibracteata is locally present in Upper and Lower Cowside. This lime-encrusted stonewort occurs in wet habitats chiefly on the flood plain such as calcareous mires; it was recorded once in an oxbow and Ecosurveys (1990) found it in a deep pool. It requires fine material for its rhizoids to anchor into and the bed load of the main beck is mostly too coarse, and its currents too strong, for such a delicate species to survive. On the basis of water chemistry and geomorphology, the watercourses divide into relatively uniform segments which will be discussed in turn: Upper and Lower Cowside Apart from a little Mimulus guttatus (Monkey flower) in lateral springs no riverine higher plants are present in the watercourse which, throughout the year is dominated by seven species of large aquatic mosses. These thickly cap boulders in the stream bed eliminating smaller bryophytes, and many algae and lichens by competitive exclusion. Due to their different tolerances to submergence the seven species cover a wide zone

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from constantly submerged (Rhynchostegium riparioides) to just above summer water level (Brachythecium rivulare). Floods locally rip this cover away depositing a thick zone of bryophyte debris either side of the beck but bare patches of rock thus created soon become recolonised. This dense, usually constantly wet carpet of bryophytes stretching from bank to bank across much of Upper and Lower Cowside is joined in spring and summer by extensive patches of filamentous green algae. At least seven genera are involved; it would be a useful project to work on their ecology, seasonality, niche preferences, etc as at their height they cover a third of the beck cutting out even more light from the stream bed and discouraging the development of smaller algae such as Batrachospermum moniliforme and Draparnaldia sp. This mixed bryophyte and algal blanket, often up to 2 cm deep, provides a major habitat for a number of aquatic organisms a several being national rarities. Water squeezed from them is rich in calcicolous diatoms with the moss Palustriella commutata supporting a particularly diverse algal flora including Achnanthes minutissima and Navicula tripunctata while the structurally similar moss Rhynchostegium riparioides has a much lower species diversity but Achnanthes lanceolata, Cocconeis placentula and Meridion circulare are more abundant. Among the filamentous algae, genera without an external mucilaginous sheath support far higher numbers of epiphytic diatoms. Many invertebrates live in this bryophyte/algal community and were sampled by agitating moss in a tray. A number are generalists such as the freshwater shrimp (Gammarus pulex), and stonefly and mayfly nymphs, but three specialist water beetles – Helophorus grandis, Oreodytes davisii and O. sanmarkii – are limited to this habitat. Permanent flow enables populations of brown trout and bullheads to flourish but no white-clawed (native) crayfish have ever been reported despite their presence in many Dales rivers. Darnbrook Beck below the Middle Limestone This stretch is 3 km long. The lower 2.2 km flows over continuous beds of Carboniferous limestone and dries up completely each summer. It only exhibits permanent flow for the 0.8 km upstream of the ravine in the Wensleydale Series limestone just above the Cock Pits. Here, sandstones and shales appear in the stream bed. The alternation of wet and dry conditions is harsh and limiting on aquatic organisms. Stream gradient is also an important factor being much steeper than in Cowside leading to greater instability and exposing bed-rock to scouring by the traction load during times of flood. In response to these stringent conditions the biomass of bryophytes, lichens and algae is far lower than in Cowside. There is an open cover of Cinclidotus, Schistidium rivulare s.l. and Hygrohypnum. Much of the bryophyte diversity along this length is found on slabby rock at the edge of the stream particularly where seepage keeps the substrate wet throughout the year. The lichen flora of the stream bed is sparse consisting of Leptogium plicatile, Thelidium decipiens and Verrucaria aethiobola which can withstand alternate wet and dry spells. Two ‘hot spots’ for lichens occur on this stretch both related to extensive areas of sound, unscoured Wensleydale limestone associated with waterfalls. Here, the high lichen cover is controlled by length of submergence, exposure to spray, light conditions and shelter; for a number of species these are the only sites where they occur in the Cowside catchment. Little work has been carried out on the algae of Darnbrook Beck. Cushions of Schistidium rivulare s.l. yielded an abundance of the diatom Meridion circulare with smaller numbers of a further nine species. All were calcicoles, the acid influence of the headwaters having been neutralised in this stretch. Invertebrates show a reduction in numbers compared to Cowside but upland specialists are present such as the mayfly Amelitus inopinatus and the stonefly Leuctra moselyi. Darnbrook Beck above the Middle Limestone to Fountains Fell Tarn This section is composed of small headwater rivulets draining from the gritstone cap of Fountains Fell and flowing over peat, or acid drift. Rushy vegetation often meets over the channels that are lined with unstable fine material so bryophytes, lichens and algae are scarce. The occasional large piece of well illuminated gritstone at a track crossing, or rapids, may carry the upland leafy liverwort Scapania undulata forming a single species community. Lichens are more abundant, in the rare places where the rivulets emerge from their shady tunnels a community of up to ten aquatic calcifuge lichens can be found. The acid substratum appears able to buffer any alkalinity derived from the high limestones.

Fountains Fell Tarn is an extreme habitat in terms of its pH at 3.5, hardness at < 2-8, and simple shore-line formed of heavily leached Millstone grit flags lying over redistributed peat from the surrounding blanket bogs. It is by no means unique, a further 17 shallow dystrophic water bodies occur on the 610 m plateau between Fountains Fell and Wild Boar Fell. Little is known of their ecology. This one is too acid for more than a 1 % cover of common lichens and bryophytes to develop along the shore line. The planktonic flora is rich in desmids in contrast to alkaline parts of the catchment where diatoms dominate; the blanket weed

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contains an unusual species. Invertebrates have not been sampled intensively but include the montane water beetle Agabus arcticus collected here in 1963 and 2003. Investigating the ecology of these ‘Pennine Tarns’ would make a valuable conservation exercise. Cowside Gorge This 600 m long limestone gorge is bryologically and lichenologically one of the richest parts of the catchment. This is a result of continuous stream flow and the banks and bed being composed of shelving limestone, rather than unstable earth or boulders. This varied habitat of rock ribs, vertical faces, horizontal ledges, backwaters, pools and gravel deposits, are all largely free from rock scour. While aggressive pleurocarpous mosses are still prominent there are plenty of niches for smaller, less competitive acrocarpous species such as Didymodon nicholsonii, Fissidens rufulus and Philonotis fontana. The bryological survey was more strictly confined to the stream course than the lichen one or several additional species of damp rock would have been recorded. The small amounts of ‘bare’ limestone that are constantly present, often on prominent ridges, are colonised by a variety of lichens which produce a mosaic community with the bryophytes (Fig. 4). Some rare aquatic lichens are present that have not previously been recorded from the Malham area such as Staurothele bacilligera and S. guestphalica. As an illustration of how lichens and bryophytes are coexisting in the gorge several lichens are overgrowing the moss matching them for growth rate. Apart from the cave investigations other groups were hardly studied in the gorge.

Spring heads There are around 20 permanent springs associated with Cowside Beck; all are strongly calcareous with pH around 7.0, and discharge cold water. They proved unexpectedly interesting in part because the bed of the small ‘caves’ from which they issue are undisturbed by farm stock and the semi-shade depresses aggressive bryophytes and blanket weed. They provide ideal conditions for species of low competitive ability such as the aquatic lichens Verrucaria elaeomelaena and V. rheitrophila, the filamentous algae Batrachospermum moniliforme and Draparnaldia spp., and bryophytes like Jungermannia atrovirens and Philonotis calcarea. A population of the water beetle Limnius violkmari was only seen in a spring. Their constantly low temperature enables a number of cold water diatoms and the flat worm Crenobia alpina to survive. The tufa tributaries These are the paramount habitat of the catchment and of national importance. Waterfall Beck and Lower Beck, are highly calcareous, nutrient poor, well oxygenated, tufa depositing streams both containing a series of magnificent mossy tufa screens varying from 1 m to 10 m high. The beds of both streams are sealed from the underlying limestone by tufa deposits so flow is permanent. Of the many watercourses in Craven, only these two together with Cote Gill, Howgill near Kilnsey and Gordale Beck are tufa depositing; all rise on the Malham high ground. A hundred species of algae and cyanobacteria have been recorded from Waterfall Beck including some that are rare on a world scale e.g. Chrysonebula holmesii. The communities they form comprise five floristic units, their complexity and relationships are shown in Fig. 7. Though the tufa deposits are largely moss covered the bryophytes are typically those present in elsewhere in Cowside Beck, they become tufa encrusted and help build the screens. Only the cushion forming Didymodon tophaceus and Eucladium verticillatum favour tufa deposits. Active tufa is too soft and unstable to form a substrate for lichens, none were seen in either beck though a non-tufa depositing seepage adjacent to Waterfall Beck held a colony of Placynthium tantalium growing directly on limestone, a new record for the area. Invertebrates were not collected from these tributaries. The fauna and flora of the six caves in the area are in a largely unspoilt condition. The larger caves produced the longest lists. Bats are the most important group present, three species using Cherry Tree Hole and Darnbrook Pot for daily roosting and winter hibernacula. Other cave biota are uncommon. Chapman (1993) has identified five cave communities to which species can be assigned. The ‘wall association’ includes the Herald moth, the dipteran Heliomiza captiosa, other visiting insects, and the predator spider Meta merianae. The ‘terrestrial mud bank community’ is represented by the albino population of the earthworm Allolobophora chlorotica in Robinson’s Pot, it feeds off organic matter and bacteria. ‘Freshwater stream communities’ include in washed surface-stream species such as Gammarus pulex, stonefly larvae (Dinoceras cephalotes), caddis fly larvae (Plectronemia conspersa) and trout, all as self-maintaining populations. ‘Batellites’ have lives revolving round the presence of bats, exploiting droppings and carcasses. These have not been surveyed but are almost certainly present and should include the bat tick (Ixodes vespertilionis), Diptera, snails, millipedes and fungi. The fifth community ‘Pool-surface associations’ is little studied, it involves springtails (Collembola) and fungi.

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Cavernicolous biota are present in far lower numbers than were reported in a survey carried out in Robinson’s Pot in 1976. The reason may be toxic sheep dip that is entering the system at several points. This new factor should be taken into account when analysing cave biodiversity. An important finding has been that even in catchments that are in a natural condition watercourses are not uniformly suitable for all groups. Lichens were virtually absent in Upper and Lower Cowside and the tufa tributaries, and were rare in areas of intermittent flow; only one species of bryophyte was typical of the acid rivulets; algae were outstanding in the tufa streams; springs were good for lichens, algae, and glacial relics. In areas of intermittent flow all groups were seriously depressed. Not enough is yet known about the invertebrates to compare stream sections or identify hot-spots, but enough examples of niche specialisation were encountered to show that freshwater invertebrates are far from uniformly distributed. To give one example from many, nymphs of the mayfly Caenis rivulorum were only found associated with the Arncliffe sand and gravel fan. The torrential headwaters of the Dale’s rivers provide the richest habitat along their entire course for cryptogamic plants.

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Further Research The preceding pages exemplify the amount and diversity of information that can be amassed about a site in a relatively short time by a group of committed and knowledgeable people, amateur and professional, working together. We hope they will provide useful background and, in some fields at least, a baseline against which future observations can be compared. Obviously much remains to be done. Our knowledge of many groups of organisms here is tantalisingly incomplete even at the inventory level, and even in such relatively well-worked groups as the bryophytes and algae. But there are also big gaps in our understanding of life histories and ecological relationships within the Cowside catchment, and it is here that attention should particularly be concentrated. Answers to questions often prompt yet more questions, and the research questions we ask in 2005 may be very different from the questions we would have thought to ask fifty years ago. We need to know much more about physical aspects of the streams themselves, and their changes of water level and flow, both around the seasons and following individual rainfall events. How variable are pH and concentrations of the major ions in the headwater streams and upper course of Darnbrook Beck (and its lower tributaries draining from Darnbrook Fell), and how do these variations bear on the organisms living in the streams? How much of the drainage is on the surface, and how much is underground in the limestone, and where does it go? Parts of both Darnbrook and Cowside becks are seasonal, drying out in summer and in periods of low rainfall. The bryophytes and lichens in these stretches (most conspicuously the big moss Cinclidotus fontinaloides) must be tolerant of both long submergence and long desiccation, but how long, and what intensity of desiccation will they survive? Parallel questions can be asked for other organisms. Insect larvae and other invertebrates can respond to the stream-bed drying out by moving down to levels where water is still present, but which of them can do this and what are their limits? What are the effects on the bryophyte and lichen cover, and aquatic invertebrate populations, of movement of the stones in the stream-bed when the beck is in spate? In looking to the future of research in the Cowside catchment, two cautions are in order. First, much of the catchment, although in a nicely ‘semi natural’ state, is enclosed farmland. Any research should observe proper courtesy to those who live and work on the land, and respect their wishes and needs. Second, some of the most characteristic and attractive features of the Cowside Beck system are of limited extent, and fragile. A lot of past work has concentrated on the two tufa streams, ‘Waterfall Beck’ and ‘Lower Beck’; the tufa deposits in these are vulnerable. There are many interesting and important questions, crying out for answers, in the open high ground of the Darnbrook headwaters, and along the main courses of the two streams, which can be tackled with minimal risk of damage to the site. Malham Tarn Field Centre was established nearly 60 years ago. In its early days it was natural for research to be concentrated on inventory of species, and their broad environmental relationships. Since that time we have become increasingly aware of process and change– of the dynamics of ecosystems, the flow of energy and the cycling of inorganic nutrients within them, and the constant flux of their plant and animal populations. There is still much basic understanding and knowledge that should be developed. A landscape like Cowside is not a static picture, but rather a play being enacted on a stage which itself is slowly changing. The responses of land owners and managers to the changing economic and social climate, influenced by national and European policies, are already changing farming practice in the valley. Public concern with global warming in recent years has reminded us of what we knew already from the peat record in Malham Tarn Moss (Pigott & Pigott, 1959); that climate is not constant. These two interlinked themes – local management and global change - may well be the major preoccupations of future research on our site.

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Acknowledgements We thank Alan A. Heaton, without whose co-operation the invertebrate survey would not have been possible, Mike Samworth who collected and identified plankton from Fountains Fell Tarn, and the Geography Department at Durham University for drawing the detailed map. Mr J. Hall at Darnbrook Farm, Mr W. Cowperthwaite at Tennant Gill , Mr R Harrison at Home Farm, Mr S Towler at Middle House, Mr M. Campbell at Castle Farm and Mr R Miller at the Falcon Hotel, Arncliffe generously allowed us access to their land. The National Trust and the Field Studies Council at Malham Tarn have been supportive throughout the project in particular the assistance of Adrian Pickles, Martin Davies, Elizabeth Judson and Rhys Davies all helped the project to function. The photograph on the front cover is by permission of Robin Sutton.

References ARMITAGE, P.D. 1976. A quantitative study of the invertebrate fauna of the River Tees below Cow Green Reservoir. Freshwater Biology 6: 229-240. ARNOLD, F.N & MACAN, T.T. 1969. Studies on the fauna of a Shropshire hill-stream. Field Studies 3: 159-

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Settle. Memoirs of the British Geological Survey, Sheet 60 (England and Wales) HMSO, London BUTCHER, R.W. 1946. Studies in the ecology of rivers V1. The algal growth in certain highly calcareous

streams. Journal of Ecology 33: 268-283. CHAPMAN. P. 1993. Caves and Cave Life. Harper Collins, London CROTHERS, J.H. 1989. Student investigations on the fauna or an Exmoor stream. Field Studies 7: 311-336. DOUGLAS, B 1958. The Ecology of the attached diatoms and other algae in a small stony stream. Journal of

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165-196. GILBERT, O.L. 1996. The lichen vegetation of chalk and limestone streams in Britain. Lichenologist 28:

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Lichenologist 29: 347-367. GOLTERMAN, H.L. & CLYMO, R.S. 1969. Methods for Chemical Analysis in Fresh Waters. IBP

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Literary Society: Scientific Section. 9: ii, 15-91. HYNES, H.B.N. 1961. The invertebrate fauna of a Welsh mountain stream. Archiv für Hydrobiologie 57:

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Journal of Conchology 33: 173-178. LUND, J.W.G. 1961. The algae of the Malham Tarn district. Field Studies 1: 85-119. MACAN, T.T. 1963. Freshwater ecology. Longmans, London. MALHAM TARN RESEARCH SEMINAR 2001. Past, Present, Future. Monitoring and Managing Change

at Malham Tarn. Pp.37. Malham Tarn Field Centre: Settle. PENTECOST, A. 1978. Blue-green algae and freshwater carbonate deposits. Proceedings of the Royal

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PENTECOST, A. 2005 Travertine. Springer 452pp. PIGOTT, M.E. & PIGOTT, C.D. 1959. Stratigraphy and pollen analysis of Malham Tarn and Tarn Moss.

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Appendix 1a. Field measurements and water samples from Darnbrook and Cowside becks. M.C.F. Proctor, 3–6 and 24–27 Aug. 2002. The samples are listed from headwaters downstream in order of grid reference eastings, Darnbrook Beck first, then Cowside Beck.

Sample no. and date

Site National Grid ref. (GPS)

Cond. /µS cm-

1

Temp. /°C

pH Ca2+

/mg l-1Mg2+

/mg l-1Na+

/mg l-1K+

/mg l-1

66 5/8 Fountains Fell: stream in blanket bog 8720 7176 37 10.1 4.42 0.66 0.68 3.0 0.1 67 5/8 Fountains Fell: lower down same stream 8723 7173 39 9.7 4.59 0.76 0.68 3.0 0.1 68 5/8 Fountains Fell: next headwater stream 87307167 48 11.7 4.27 0.41 0.36 2.6 0.0 4/8 Fountains Fell: lower down same stream 8743 7166 - - 4.44 60 3/8 Fountains Fell: lower down, above confluence 8745 7169 33 12.2 6.58 4.4 0.44 2.6 0.0 4/8 Fountains Fell: stream on drift ? over Main Limestone 8746 7166 37 11.0 4.25 5/8 Fountains Fell: confluence, S branch 8748 7165 37 - 4.42 5/8 Fountains: confluence, N branch 8748 7165 35 13.9 4.51 71 5/8 Fountains: tributary to N 37 12.2 4.58 1.2 0.49 2.7 0.0 69 5/8 Fountains: below 3-fold confluence 8750 7169 65 11.3 6.95 9.0 0.73 2.9 0.0 59 3/8 Fountains: main beck below 3-fold confluence 8754 7161 26 11.2 6.42 3.8 0.47 2.6 0.1 4/8 Fountains Fell: stream below (69) 8756 7165 62 11.5 7.22 Fountains Fell: stream below (69) 8757 7163 62 11.3 7.20 72 5/8 Fountains Fell: spring (? from Underset Lst) at head of

tributary 8744 7159 180 6.6 7.04 33 1.39 3.2 0.1

70 5/8 Same tributary nr confluence with main stream [c. 8750 7165]

171 7.9 7.90 30 1.39 3.2 0.1

58 3/8 Fountains Fell: ~ 100m below source of stream rising under Main Limestone

8745 7145 - - - 15.6 0.83 2.6 0.1

3/8 Lower down same stream 8757 7148 98 10.0 7.41 3/8 Same nr confluence with main stream 8784 7163 85 11.6 7.43 57 3/8 Darnbrook: fence line above Middle Limestone 8789 7167 41 12.9 7.15 6.8 0.50 2.6 0.0 3/8 DarnbrookBeck, small tributary 8800 7163 73 12.8 - 3/8 Darnbrook Beck, below confluence 8803 7164 49 14.1 7.39 3/8 DarnbrookBeck, tributary 8811 7165 65 12.7 - Darnbrook Beck, aboveconfluence 51 13.3 7.47 3/8 Darnbrook, on sandstone band 8822 7153 58 14.4 7.47 56 3/8 Darnbrook, prominent flat slabs 8831 7146 60 14.5 7.65 10.2 0.59 2.5 0.0 3/8 Darnbrook Beck, bottom of gorge 8850 7138 58 14.3 7.52 55 3/8 Darnbrook Beck, near Cock Pits 8859 7128 59 14.3 7.62 10.5 0.58 2.5 0.1 24/8 Darnbrook Beck, roughly level with Cock Pits (cf. 55) [c. 8859

7128] 85 12.5 -

………3/8

Stream (1) flowing to Cock Pits 8832 7124 54 12.4 7.28

61 3/8 Stream (2) flowing to Cock Pits 8833 7121 60 11.0 7.14 9.2 0.63 2.6 0.1 23 24/8 Darnbrook Beck: above small waterfall/gorge 8874 7118 98 13.6 8.02 18.4 0.90 2.8 0.0 24/8 Darnbrook Beck: bouldery reach 8894 7108 173 14.8 8.12 24 25/8 Darnbrook Beck: bouldery reach 8901 7113 - - - 56 1.20 2.8 0.2 24/8 Darnbrook: top of tufa-depositing stretch 8908 7112 240 15.2 8.19 22 24/8 Darnbrook Beck: tributary 8920 7117 65 13.7 7.78 15.0 0.49 2.5 0.0 Darnbrook: main stream above confluence 267 15.7 8.35 Main stream below confluence 177 14.0 8.27 21 24/8 Darnbrook: tributary below lowest plantation 8929 7114 139 14.1 8.20 26 0.94 3.1 0.1 Darnbrook: main stream above confluence 128 15.0 8.12 Darnbrook: main stream below confluence 132 14.5 8.10 20 24/8 OLGs Lower Darnbrook Site 1 (gauge) 8943 7101 194 15.7 8.20 39 1.03 2.9 0.2 24/8 Darnbrook: tufa seepage from drift 8954 7057 380 16.0 7.95 19 24/8 Darnbrook Beck: pool just before dry stretch of stream

bed above farm 8957 7094 192 15.8 8.52 38 1.03 3.1 0.1

62 4/8 Cowside: uppermost active spring 8876 6912 436 8.5 7.11 83 0.85 2.7 0.1 63 4/8 Cowside: lateral springhead 8893 6920 394 7.8 7.05 77 0.81 2.8 0.1 64 4/8 Cowside: rising in side valley 8916 6934 393 7.8 7.08 74 0.81 2.8 0.2 4/8 Cowside: same tributary at confluence 8912 6938 392 8.4 7.47 Cowside Beck above confluence 400 9.7 7.26 65 Cowside Beck below confluence 393 9.3 7.36 77 0.83 2.9 0.2 73 6/8 Thoragill Beck at road bridge 8914 7009 372 14.7 8.28 68 0.87 2.7 0.0 74 6/8 Cowside Beck: footbridge below Darnbrook Farm 8992 7008 391 11.7 8.10 79 0.89 3.1 0.2 25 26/8 Cowside, bouldery reach above gorge 9025 7004 345 13.3 - 70 0.90 3.3 0.1 26/8 Cowside, slabby stretch nr gorge head 9045 7000 339 13.7 - 26/8 Cowside, slabby stretch in gorge 9066 7004 334 14.2 - 26.8 Waterfall Beck at confluence 9081 7004 235 15.4 - Cowside Beck upstream 333 14.2 - Cowside Beck downstream 323 14.5 - 26/8 Cowside Beck above Yew Cogar Cave [c. 9081

7004] 332 15.3 -

Cowside Beck below Yew Cogar Cave 330 15.3 - 26.8 Waterfall Beck at fence line 9082 6994 243 15.5 - 75 6/8 Waterfall Beck, below tufa screens 9086 6970 274 14.2 8.10 54 0.92 2.9 0.3 76 6/8 Waterfall Beck, below big tufa screen 9086 6961 326 12.9 7.91 60 0.99 2.8 0.2 77 6/8 Waterfall Beck, top of waterfall 9086 6958 348 12.2 8.06 67 1.00 2.9 0.1 78 6/8 Rising at head of Waterfall Beck 9089 6934 371 10.0 7.05 74 0.91 2.9 0.0 28 26/8 Just downstream of Darnbrook Pot rising 9105 7011 245 10.7 - 48 0.90 3.0 0.1 Cowside Beck just upstream of last 322 14.7 -

27 26/8 Cowside Beck, bouldery stretch nearby 9117 7015 292 13.2 - 62 1.01 3.3 0.3 26 26/8 Near bottom of Lower Beck 9120 7013 241 15.0 - 46 0.84 3.1 0.1 29 26/8 Cochlearia spring on S bank downstream of Lower Beck 9146 7023 345 8.7 - 64 1.56 3.1 0.2 30 27/8 Spring at gully head on N bank 9155 7052 408 9.0 - 75 1.67 3.4 0.3 31 27/8 Bouldery stretch by Yew Cogar Scar 9178 7066 304 17.1 - 59 0.99 3.3 0.2 32 27/8 Arncliffe, opposite tearoom 9296 7192 298 19.5 - 56 0.99 3.3 0.1

38

Note on the cation measurements In the scientific literature on water chemistry, cation concentrations have been expressed in various different ways. In the water-supply industry, and in analytical work relating to public water supplies, calcium and magnesium concentrations have traditionally been measured in terms of ‘hardness’, in recent years often expressed in terms of the equivalent concentration of CaCO3 in mg l-1. These units may also be appropriate in, e.g., cave studies, where the interest centres on the solution or deposition of solid CaCO3 as limestone or speleothems. In natural waters, cation concentrations have generally been expressed in either mg l-1 of the particular cation (1 mg l-1 Ca2+ corresponds to 2.5 mg l-1 CaCO3), or moles or (more often) ‘equivalents’ litre-1. Concentration in mol l-1 is the concentration in g l-1 divided by the atomic weight of the cation. Concentration in equiv l-1 is concentration in g l-1 divided by (atomic weight/valency) of the cation: it corresponds to the molar concentration of ionic charge, and is useful in computing the balance of cations and anions. In calcareous waters draining from pure limestones such as those around Malham, electrical conductivity is mostly due to Ca2+ and HCO3

- ions, and calcium concentration can be estimated with good accuracy from conductivity measurements. A conductivity of 104.5 μS cm-1 at 25 °C corresponds to a calcium concentration of 20 mg l-1, 1.0 mequiv l-1 or 0.5 mmol l-

1 (Fig. A1.1)

5004003002001000

80

60

40

20

0

Conductivity /μSiemens cm-1

Ca2+

/mg

litre

-1

Fig. A1.1. Calcium concentration plotted against electrical conductivity (corrected to 25 °C). The dotted line shows the expected relationship if conductivity is assumed to be entirely due to Ca2+ and HCO3

–. Over most of the range (with pH >6.5) this is substantially the case; there is a good linear fit and calcium concentration be calculated from conductivity with an accuracy of ±5% or better. The small ‘hook’ shown by the points at the bottom end of the graph reflects sites on the blanket bog on Fountains Fell, with a pH ~4.5 and a substantial part of the total conductivity contributed by H+ ions.

Fig. A1.2. Darnbrook Beck (above) and Cowside Beck (below), showing locations of water-sampling points used by D T Richardson.

39

Appendix 1b. Water analysis data. D.T. Richardson

/mg CaCO3 l-1

Hardness

Site Site no Grid reference

Date

Total Alkaline Non-alk.

Ca Mg

pH Temp. /°C

Mg/Ca NAH/TH

3 8876 6911 11/10/2002 225 220 5 221 4 7.21 7.5 0.018 0.022 3 24/01/2003 266 262 4 264 2 7.2 7 0.007 0.015 5 8884 6920 20/06/2002 261 259 2 258 3 6.88 8 0.011 0.008 5 24/01/2003 184 178 6 180 4 7.6 7.2 0.022 0.033 5 23/08/2003 231 228 3 229 2 7.03 7.5 0.009 0.013

Cowside Beck; headwater springs

5 27/09/2003 192 186 6 186 6 7.2 8 0.032 0.031 7 8888 6924 11/05/2002 180 174 6 174 6 6.84 8 0.034 0.033 7 20/06/2002 202 198 4 200 2 7.42 9 0.01 0.02 7 24/05/2003 167 162 5 164 3 7.8 7.8 0.018 0.03

Cowside Beck; first permanent flow

7 27/09/2003 194 188 6 188 6 6.9 8.2 0.032 0.031 SP-1 8980 7000 29/03/2002 156 148 4 152 2 7.8 15 0.013 0.026 SP-1 04/04/2002 154 146 8 150 4 8.17 13 0.027 0.052

Cowside Beck

SP-1 08/03/2002 150 142 8 148 2 7.1 7.5 0.013 0.053 SP-2 9020 7005 29/03/2002 154 146 8 150 4 8.18 10.3 0.027 0.052 SP-2 04/04/2002 152 146 6 148 4 8.15 13 0.027 0.039 SP-2 22/04/2002 172 167 5 168 4 7.22 12 0.024 0.029

Cowside Beck

SP-2 30/05/2002 122 118 4 118 4 7.28 n/d 0.034 0.033 SP-2 14/09/2003 150 144 6 146 4 8 16.1 0.027 0.04

- 9135 7019 29/03/2002 140 132 8 135 5 7.97 9.2 0.037 0.055 Cowside Beck - 14/09/2003 146 138 8 140 6 8.2 14.8 0.043 0.055

SP-3 9300 7194 17/02/2002 147 136 11 142 5 7.85 7 0.035 0.075 SP-3 29/03/2002 138 130 8 134 4 8.14 10.2 0.03 0.058 SP-3 04/04/2002 145 136 9 142 3 7.64 13 0.021 0.062 SP-3 20/06/2002 176 172 4 172 4 7.97 12 0.023 0.023 SP-3 16/07/2002 182 180 2 177 5 8.02 20 0.028 0.011

Cowside Beck

SP-3 01/10/2002 198 196 2 190 8 7.31 11 0.042 0.01 8 8916 6934 29/03/2002 165 158 7 162 3 7.45 8 0.018 0.042 8 11/05/2002 164 158 6 162 2 7.4 9 0.012 0.036 8 20/06/2002 190 186 4 186 4 7.42 9 0.021 0.021 8 24/01/2003 167 162 5 164 3 7.3 7.8 0.018 0.03 8 08/03/2003 148 140 8 146 2 7.2 7.6 0.014 0.054 8 23/08/2003 190 178 12 184 6 7.27 9 0.033 0.063

Cowside Beck; spring

8 27/09/2003 190 184 6 186 4 7 8 0.021 0.031 9 8908 6936 29/03/2002 165 158 7 162 3 7.45 8 0.018 0.042 9 24/01/2003 184 178 6 180 4 7.6 7.2 0.022 0.033 9 08/03/2003 166 156 10 162 4 7 7.6 0.025 0.06

Cherry Tree Hole resurgence

9 23/08/2003 162 144 18 156 6 7.06 9 0.038 0.111 10 8915 7011 20/12/2001 176 168 8 172 4 n/d 4.4 0.023 0.045 10 17/02/2002 156 144 12 152 4 8.08 7.5 0.026 0.077 10 29/03/2002 143 135 8 138 5 8.03 12 0.036 0.056 10 04/04/2002 154 146 8 150 4 8.23 12 0.027 0.052 10 20/06/2002 147 142 5 143 4 7.54 15 0.028 0.034 10 16/07/2002 174 170 4 170 4 7.82 20 0.023 0.023 10 04/07/2003 152 142 10 146 6 8.19 13.5 0.041 0.066

Thoragill Beck 1

10 14/09/2003 180 172 8 176 4 8.1 16.3 0.023 0.044 11 8912 7009 29/03/2002 176 164 12 172 4 7.98 11 0.023 0.068 11 20/06/2002 208 202 6 204 4 7.84 16 0.02 0.029 11 16/07/2003 194 190 4 190 4 7.36 20 0.021 0.02 11 04/07/2003 204 196 8 198 6 8.1 14 0.03 0.039

Thoragill Beck; tributary

11 14/09/2003 204 198 6 202 2 7.8 15.7 0.01 0.029 15 9105 7011 29/03/2002 130 122 8 124 6 7.73 7.1 0.048 0.061 15 01/10/2002 202 200 2 198 4 7.02 10 0.02 0.01

Cowside; Darnbrook Pot rising

15 14/09/2003 144 140 4 138 6 6.8 10.3 0.028 0.043 16 9082 6996 29/03/2002 120 114 6 117 3 7.88 9 0.026 0.05 16 01/10/2002 132 130 2 128 4 8.1 12 0.031 0.015

Waterfall Beck; rises at 434 m O.D.

16 14/09/2003 120 114 6 116 4 7.9 16.1 0.034 0.05 17 9124 7009 29/03/2002 130 122 8 124 6 7.7 7.7 0.048 0.061 17 22/04/2002 126 122 4 122 4 7.7 11.3 0.032 0.032 17 01/10/2002 196 194 2 190 6 7.8 9 0.031 0.01

Lower Beck; rises at 381 m O.D.

17 14/09/2003 128 124 4 120 8 7.8 15.1 0.067 0.031 18 9148 7024 29/03/2002 142 134 8 136 6 7.71 8.3 0.044 0.056 Cowside Beck; spring 18 01/10/2002 192 185 7 184 8 7.85 9 0.043 0.036 19 9161 7050 30/05/2002 134 130 4 130 4 7.95 9 0.031 0.03 Cowside Beck; spring

(north side) 19 01/10/2002 222 216 6 212 10 8.05 13 0.047 0.027 20 9219 7100 30/05/2002 180 178 2 174 6 7.17 11 0.034 0.011 21 9218 7100 30/05/2002 180 178 2 174 6 6.95 9 0.034 0.011

Cowside Beck; springs

22 9242 7122 30/05/2002 180 178 2 174 6 6.5 10 0.034 0.011

40

/mg CaCO3 l-1

Hardness

Site Site no Grid reference

Date

Total

Ca Mg

pH Temp. /°C

Mg/Ca NAH/TH

Alkaline Non-alk.

25 8680 7125 20/12/2001 8 0 8 4 4 n/d n/d 1 1 25 09/10/2002 <4 0 <4 n/d n/d 4.25 7.6 - 1 25 23/08/2003 <4 0 <4 n/d n/d 4.36 n/d - 1 25 28/09/2003 2 0 2 n/d n/d 3.5 12 - 1

Fountains Fell Tarn

26 8665 7124 28/09/2003 <2 0 <2 n/d n/d 3.7 13 - 1 27 8720 7176 05/08/2002 4.45 0 4.45 1.65 2.8 4.42 10.1 1.7 1 28 8723 7173 05/08/2002 4.7 0 4.7 1.9 2.8 4.59 9.7 1.47 1 29 8730 7167 05/08/2002 2.5 0 2.5 1.02 1.48 4.27 11.7 0.98 1 30 8750 7169 05/08/2002 25.5 n/d n/d 22.5 3 6.95 11.3 0.133 -

Darnbrook headwaters (Fountains Fell)

31 8750 7169 03/08/2002 19 n/d n/d 17 2 7.15 12.9 0.118 - 32 8843 7121 19/02/2003 32 24 8 26 6 7.3 1.7 0.23 0.25 Darnbrook; stream above

old mine level 32 12/09/2003 44 38 6 38 6 7.2 11.1 0.158 0.136 33 8850 7138 09/04/2002 88 80 8 78 10 n/d n/d 0.128 0.091 Darnbrook Beck 33 22/04/2002 74 71 3 66 8 7.52 n/d 0.121 0.04 34 87907087 04/04/2002 83 78 5 82 1 8.16 13 0.012 0.06 34 08/06/2002 83 80 3 78 5 7.81 14 0.064 0.036 34 16/07/2002 111 108 3 104 7 8.13 21 0.067 27 34 14/06/2003 108 106 2 102 6 8.5 21 0.059 0.019 34 13/09/2003 104 98 6 98 6 8.3 16 0.061 0.058

Darnbrook Beck

34 11/03/2003 134 132 2 128 6 7.97 n/d 0.047 0.015 35 8990 7060 17/02/2002 74 66 8 66 8 7.79 5 0.121 0.108 35 29/03/2002 104 98 6 100 4 8.05 13 0.04 0.058 35 08/06/2002 83 80 3 78 5 7.61 14 0.064 0.036 35 12/06/2002 70 66 4 68 2 7.58 15 0.029 0.057 35 19/02/2003 94 84 10 86 8 8.1 1 0.093 0.011 35 28/02/2003 136 126 10 128 8 7.8 6 0.062 0.073

Darnbrook Beck

35 14/03/2003 74 68 6 72 2 8 7 0.028 0.081 36 8932 7119 29/03/2002 73 66 7 67 6 7.84 13 0.089 0.096 Darnbrook Beck; tributary 36 16/07/2002 84 80 4 79 5 7.91 17 0.063 0.048

41

Appendix 2a. Bryophyte lists: UpperCowside Beck (above confluence) and lower Darnbrook Beck (below road): August 2002 and July 2003. M.C.F. Proctor

Grid reference 8887

6913 8884 6921

8890 6924

8891 6923

8897 6298

8906 6934

8915 6937

8915 6943

8925 6948

8933 6959

8939 6969

8946 6979

8961 6992

8961 6996

8968 6999

8979 7002

8988 7003

8992 7008

8996 7017

8994 7037

8774 7018

CBh CBh CBh CBh CBh CBh CBh CBh CBh CBh CBh CBh CBh CBh CBh CBh CBh CBh DBl DBl TG Date 15/7 15/7 15/7 15/7 17/7 17/7 17/7 17/7 17/7 17/7 17/7 17/7 17/7 17/7 17/7 17/7 17/7 6/8 17/7 17/7 14/7 Cond. /μSiemens cm-1 [436] - - 394 - - 393 - - - - - - - - - - 391 - - - Cinclidotus fontinaloides (d) (d) (d) (a) (va) (va) (f) (f) (f) (f) (f) (r) (a) (a) (o) (f) (+) (a) (a) Schistidium rivulare (o) (la) (la) (+) (a) (a) Brachythecium rivulare (o) (a) (a) (a) (ld) (a) (a) (f) (a) (la) (la) (f) (f) (f) (a) (f) (+) (o) Bryum capillare (+) Dichodont.pellucidum (r) (o) Didymodon tophaceus (r) Didymodon sp. (o) Hygrohypnum luridum (o) (o) (la) (o) (f) (r) (la) (la) (o) (f) (la) (f) Orthotrichum cupulatum (f) (f) Marchantia polymorpha (r) (+) (f) Bryum pseudotriquetrum (o) Philonotis fontana (o) (r) (f) Cratoneuron filicinum (f) (f) (a) (r) (o) (o) (f) (o) (o) (f) (f) (+) (f) Jungermannia sp. (o) (o) Palustriella commutata (o) (o) (ld) (o) (o) (o) (r) (o) (la) (r) (la) (va) (+) Rhynchostegium riparioides (o) (f) (a) (ld) (a) (va) (d) (ld) (va) (d) (va) (va) (+) (a) Calliergonella cuspidata (r) (o) (o) Plagiomnium sp. (r) Fissidens rufulus (r) Didymodon rigidulus (f) Fontinalis antipyretica (o) Aneura pinguis (o) Pellia endiviifolia (o) Thamnobryum alopecurum (r)

CBh = upper Cowside Beck; DBl = lower Darnbrook Beck (below road); TG = Tennant Gill Appendix 2b. Bryophyte lists: Lower Cowside Beck (from Darnbrook confluence) and tributaries, August 2002 and July 2003. M.C.F. Proctor

Grid reference 9025

7004 9045 7000

9062 7005

9066 7004

9117 7015

9178 7066

9199 7094

9217 7094

9233 7110

9245 7125

9254 7131

9089 6934

9086 6958

9086 6961

9086 6966

9086 6970

9082 6994

9120 7013

CB CBg CBg CBg CB CB CB CB CB CB CB WB WB WB WB WB WB LB Date 26/8 26/8 26/8 26/8 26/8 26/8 18/7 18/7 18/7 18/7 18/7 6/8 6/8 6/8 6/8 6/8 26/8 26/8 Cond. /μSiemens cm-1 345 339 - 334 322 304 - - - - - 371 348 326 - 274 243 241 Cinclidotus fontinaloides (f) (a) (a) (va) (a) (va) (o) (a) (f) (la) (la) (va) (r) (+) (lf) Racomitrium aciculare (o) Schistidium rivulare s.l. (f) (f) (o) (o) (o) (o) (o) Brachythecium plumosum (o) (r) Brachythecium rivulare (la) (a) (a) (a) (f) (f) (f) (f) (f) (f) (f) (a) (+) (o) Bryum capillare (r) Dichodont.pellucidum (r) (f) (la) (r) (o) Didymodon tophaceus (r) (r) Didymodon sp. (r) (o) Hygrohypnum luridum (a) (la) (a) (a) (a) (a) (la) (a) (a) (o) (f) (a) Orthotrichum cupulatum (o) (+) Marchantia polymorpha (f) (f) (o) (o) (r) (o) (o) Conocephalum conicum (+) (+) Bryum pallens (o) (r) Bryum pseudotriquetrum (o) (o) (o) (o) (o) (f) (f) Philonotis fontana (f) (f) (o) Philonotis calcarea (o) (r) (o) (o) (la) Cratoneuron filicinum (f) (f) (f) (f) (o) (o) (o) (va) (o) (f) (a) (f) (a) Jungermannia sp. (o) (r) Palustriella commutata (a) (la) (a) (la) (a) (la) (a) (va) (a) (d) (d) (d) (d) (d) Rhynchostegium riparioides (d) (f) (a) (a) (a) (a) (la) (a) (a) (a) (a) (f) (a) (f) (o) (o) Calliergonella cuspidata (f) Plagiomnium sp. (r) Fissidens rufulus (lf) Didymodon rigidus (o) Funaria hygrometrica (r) Fontinalis antipyretica (o) (o) (o) Pellia endiviifolia (+) (o) (o) (f)

CB = Cowside Beck; CBg = Cowside Beck (gorge); WB = Waterfall Beck; LB = Lower Beck

42

Appendix 2c. Bryophyte lists: Darnbrook Beck (excl. acid headwaters and dry part above and below Darnbrook House) August 2002 and July 2003. M.C.F. Proctor.

Grid reference 8744

7159 8745 7161

8750 7169

8756 7165

8757 7163

8766 7165

8783 7165

8784 7163

8811 7165

8825 7149

8842 7145

8850 7138

8859 7128

8865 7126

8872 7120

8881 7117

8892 7104

8901 7113

8916 7112

8926 7114

8944 7103

DBu DBu DBu DBu DBu DBu DBu DBu DBm DBm DBm DBm DBm DBl DBl DBl DBl DBl DBl DBl DBl Date 5/8 14/7 5/8 5/8 5/8 14/7 14/7 14/7 3/8 16/7 16/7 3/8 3/8 16/7 16/7 16/7 16/7 25/8 25/8 25/8 25/8 Cond. /μSiemens cm-1 180 - 171 62 62 - - - 51 - - 58 59 - - - pH 7.04 - 7.90 7.22 7.20 - - - 7.47 - - 7.52 7.62 - - - - - - - Scapania undulata (o) (f) (f) (+) Polytrichum commune (o) Cinclidotus fontinaloides (f) (+) (+) (lf) (f) (o) (o) (a) (a) (f) Amblystegium fluviatile (+) (la) (f) (o) Racomitrium aciculare (a) (o) (o) (lf) (+) (+) (o) Schistidium rivulare (a) (+) (a) (va) (+) (ld) (va) (va) (a) (a) (o) Brachythecium plumosum (a) (+) (la) (o) (o) (lf) Brachythecium rivulare (o) (la) (+) (a) (f) (+) (+) (la) (la) (la) (va) (a) (f) (a) (a) Bryum capillare (+) Dichodontium pellucidum (+) (o) (+) (+) (o) (o) (f) (a) (la) (f) Didymodon tophaceus (o) Didymodon sp. (o) (o) (o) Bryoerythr. recurvirostrum (o) Hygrohypnum luridum (a) (a) (d) (+) (a) (ld) (+) (f) (la) (f) (o) (a) (ld) (a) Orthotrichum cupulatum (la) (f) (+) (f) (f) (f) (f) (la) Marchantia polymorpha (f) (+) (la) (f) (f) (f) (la) (a) (la) (la) (a) Bryum pallens (o) Bryum pseudotriquetrum (o) (+) (f) (f) (f) (f) Philonotis fontana (o) (+) (la) (la) (f) (f) (la) (va) (a) (f) (a) Philonotis calcarea (f) Cratoneuron filicinum (+) (+) (o) (f) (o) (f) Jungermannia sp. (+) (o) Chiloscyphus polyanthus (a) (a) Palustriella commutata (+) (a) Rhynchosteg. riparioides (a) (ld) (o) (f) (r) (o) (a) (ld) (a) Pellia endiviifolia (lf) Calliergonella cuspidata (la) Rhizomnium punctatum (r) Fontinalis antiptretica (o)

DBu = upper Darnbrook Beck (above fence line); DBm = middle Darnbrook Beck; DBl = lower Darnbrook Beck (below Cock-pits).

Appendix 3. Diatoms recorded from the Cowside Beck catchment in 2002 and 2003. D.T. Richardson

Cowside WB Lower B. Darnbrook Thoragill

8888 8950 9088 8878 9242 9288 9153 9045 9081 9127 9121 8910 8910 8954 8955 8944 8910 8918 8914 8912 Grid ref. SD 6924 6982 7006 6914 7122 7169 7052 7001 7003 6980 7010 7110 7110 7096 7097 7104 7017 7006 7010 7010 Habitat* R SF S SP SP CF WRF WRF S S S SF S TS CF CF S S S S Date 20/6 20/4 1/10 22/4 30/5 20/6 30/5 1/10 1/10 22/4 1/10 24/8 24/8 24/8 24/8 24/8 20/6 4/7 4/7 24/6 Amphora ovalis (Kütz.) Kütz. (+) (+) (+) (+) Cocconeis pediculus Ehr. (+) (+) (+) (+) (+) (+) (+) (+) (+) (+) (+) (+) (+) (+) (+) Cocconeis placentula (Ehr.) Hust. (+) (+) (+) (+) Cymbella cistula (Ehr.) Kirch. (+) (+) (+) (+) (+) (+) (+) (+) Cymbella cymbiformis Ag. (+) (+) (+) Diatoma hyemale (Roth) Kirch. (+) (+) Diatoma tenue Ag. (+) (+) (+) Diatoma vulgare Bory (+) (+) Didymosphenia geminata (Lyngb.) (+) (+) (+) (+) (+) (+) (+) (+) Diploneis elliptica (Kütz.) Cleve (+) Diploneis ovalis (Hilse) Cleve (+) (+) (+) (+) (+) (+) Encyonema minutum (Hilse) (+) (+) (+) (+) Epithemia argus (Ehr.) Kütz. (+) Eunotia arcus Ehr. (+) (+) (+) (+) (+) (+) Eunotia sp. (+) Fragilaria crotonensis Kitton (+) Fragilariforma virescens (Ralfs) (+) Frustulia rhomboides (Ehr.)De Toni (+) (+) (+) (+) (+) Gomphoneis olivaceum (Horne) (+) (+) (+) (+) (+) Gomphonema acuminatum Ehr. (+) (+) Gomphonema clavatum Fricke (+) Gyrosigma attenuatum (Kütz.) Rab. (+) Melosira varians Ag. (+) Meridion circulare (Grev.) Ag. (+) (+) (+) (+) (+) (+) (+) (+) (+) (+) (+) Navicula radiosa Kütz. (+) (+) (+) (+) (+) (+) (+) (+) (+) (+) (+) (+) Nitzschia linearis W. Smith (+) (+) (+) (+) Pinnularia viridis (Nitz.) Ehr. (+) (+) (+) Rhopalodia gibba (Ehr.) O. Müller (+) (+) (+) (+) (+) Synedra rumpens Kütz. (+) Synedra ulna (Nitz,) Ehr. (+) (+) (+) (+) (+) (+) (+) Synedra ulna var. oxyrhynchus (Kütz.) (+) Tabellaria flocculosa (Roth) Kütz (+)

*Abbreviations: WB = Waterfall Beck; CF = calcareous flush; R = resurgence; SP = spring; SF = stream foam; TS = tufa spring; WRF = wet rock face.

43

Fig. A3.1. Diatoms recorded from the Cowside Beck catchment in 2002 and 2003; see table in Appendix 3. 1 Amphora ovalis; 2 Cocconeis pediculus; 3 Cocconeis placentula; 4 Cymbella cistula; 5 Diatoma hymale; 6 Diatoma tenue; 7 Diatoma vulgare; 8 Didymosphenia geminata; 9 Diploneis elliptica; 10 Diploneis ovalis; 11 Encyonema minutum; 12 Epithemia argus; 13 Eunotia arcus; 14 Fragilaria crotonensis; 15 Fragilariforma virescens; 16 Frustulia rhomboides; 17 Gomphoneis olivaceum; 18 Gomphonema acuminatum; 19 Gomphonema clavatum; 20 Gyrosigma attenuatum; 21 Melosira varians; 22 Meridion circulare; 23 Navicula radiosa; 24 Nitzschia linearis; 25 Pinnularia viridis; 26 Rhopalodia gibba; 27 Synedra rumpens; 28 Synedra ulna; 29 Tabellaria flocculosa.

44

Appendix 4. Freshwater invertebrates, 2001-2003. For the purposes of this list Cowside Beck is divided into upper and lower sections by the eastings grid line 391, and Darnbrook beck into upper and lower sections by the eastings line 389. L = larva and A = adult recorded. D.T. Richardson

Site Cowside Beck Darnbrook Beck upper lower upper lower

DarnbrookBeck tributaries

Thoragill Beck

Thoragill tributary

Waterfall Beck

wer Beck ring 891693 ountains Fell Tarn

Site no. 1 2 3 4 5 6 7 8 9 10 11 12

AMPHIPODA Gammarus pulex (L.) (+) (+) (+) (+) (+) (+) (+) (+) (+) (+) (+)

TRICLADIDA Crenobia alpina (Dana) (+)

EPHEMEROPTERA Ameletus inopinatus Eaton L Baetis muticus (L.) LA LA L LA L L LA LA L L Baetis rhodani (Pictet) L L LA L L L L L L Baetis scambus Eaton L Caenis rivulorum Eaton L Ecdyonurus torrentis Kimmins L L L L L L L L Ephemerella ignita (Poda) L L LA L Ephemerella notata (Eaton) A Heptagenia lateralis (Curtis) L LA L L Heptagenia sulphurea (Müller) L L L L Paraleptophlebia submarginata (Steph.)

L L L L

Rithrogenia semicolorata (Curtis) L L L L L

PLECOPTERA Amphinemoura sulcicollis (Stephens) L L A L L Brachyptera risi (Morton) LA L L Dinocras cephalotes (Curtis) L L L L L L L L L Isoperla grammatica (Poda) LA LA L LA L A L Leuctra geniculata (Stephens) L Leuctra hippopus (Kempny) L L L A L L Leuctra inermis Kempny A LA A A L Leuctra moselyi Morton A Nemoura cinerea (Retzius) L A Perlodes microcephala (Pictet) L Protonemoura meyeri (Pictet) LA LA LA A Protonemoura praecox (Morton) A A LA Siphonoperla torrentium (Pictet L LA L LA

HEMIPTERA-HETEROPTERA Arctocorisa carinata (Sahlberg) (+) Gerris thoracus Schummel (+) Velia caprai Tamanini (+) (+) (+)

TRICHOPTERA Agapetus fuscipes Curtis A Allogamus auricollis (Pictet) A Beraea mauris (Curtis) A A Drusus annulatus Stephens A Halesus radiatus (Curtis) A L Hydropsyche instabilis (Curtis) L Hydropsyche siltalai Döhler L Lepidostoma hirtum (Fabricius) L Melamophylax mucoreus (Hagen) A Philopotamus montanus (Donovan) A LA A A Plectronemia conspersa (Curtis) L L L L L L L Polycentropus flavomaculatus (Pictet) A Potamophylax latipennis (Curtis) L L Rhyacophila dorsalis (Curtis) L L L L A

DIPTERA Chironomidae L L L L L L L Simuliidae L L

COLEOPTERA Agabus arcticus (Paykull) A Agabus bipustulatus (L.) A Agabus guttatus (Olivier) A Helodidae sp. L L L Helophorus grandis Illiger A Limnius volkmari (Panzer) A A Oreodytes davisii (Curtis) A A A Oreodytes sanmarkii (Sahlberg) A A A

MOLLUSCA Ancylus fluviatilis (Müller) (+) (+) (+) (+) Lymnaea peregra (Müller) (+) (+) (+)

45