The current status of a sample of english sites of special scientific interest subject to eutrophication

AQUATIC CONSERVATION: MARINE A N D FRESHWATER ECOSYSTEMS, VOL. 5, 191-204 (1995)

The current status of a sample of English Sites of Special Scien tipc Interest subject to eutrophication

LAURENCE CARVALHO* and BRIAN MOSS Department of Environmental and Evolutionary Biology, University of Liverpool, Liverpool L69 3BX. UK

ABSTRACT

Records for 102 Sites of Special Scientific Interest (SSSIs) in England were examined for eutrophic status and for symptoms of eutrophication using criteria established by the Department of the Environment (DOE). Seventy-eight were found to be eutrophic or hyper-eutrophic using total phosphorus criteria. Of the 102 sites, 85 cases (84%) showed symptoms of eutrophication. This had changed overtly the nature conservation interest in 69 cases.

2. The 102 sites were contracted to 96 by listing together eight adjacent SSSIs in the Somerset Levels and treating another split-site SSSI with separate catchments within it as two sites. Within these 96, 17 did not show symptoms of eutrophication and 79 (84%) did. Of the 79 cases, a major cause of the eutrophication in 35 (44%) was sewage effluent with a further five possible cases of effluent problems. The second most important cause (15 sites (19%) and potentially a further six, of the 79 sites) was attributed to the effects of common carp (Cyprinus carpio), and to a lesser extent common bream (Abramis brama), in mobilizing nutrients and increasing turbidity within the water body.

3. Symptoms of deterioration were most frequently recorded in the aquatic plant communities, probably because these are most readily observed. Comparable changes should be expected in animal communities but these are infrequently monitored. There may have been unrecorded changes in some sites that had nonetheless suffered damage. It is likely that detailed studies of sites where there is clear evidence of eutrophication will reveal some deterioration in conservation interest.

4. The primary management required to help restore the conservation interest in the 79 sites involves phosphorus removal from, or diversion of, sewage effluent in at least 30 cases. Of these two- thirds (20) will fall outside the current arrangements being made by the DOE for the application of the Urban Waste Water Treatment Directive. Removal of carp and additional biomanipulative measures are suggested for at least 18 cases (23%) and fishery modifications in a further six, giving a total of 30% of sites where fish are a part of the problem. Further investigation is needed in nearly half of all cases where the situation is not entirely clear.

5. The data available from statutory bodies to assess the trophic states of the sites examined were generally inadequate. Total phosphorus, a key variable in the currently recommended DOE scheme, and widely recognized as very important by the limnological community, is not routinely monitored by the National Rivers Authority (NRA), and methods used for soluble reactive phosphorus are not generally used with a sufficiently low detection limit.

1.

INTRODUCTION

Since the changes in agriculture, population distribution and rural sewerage that followed World War 11, the British Isles have experienced an unprecedented mobilization of nitrogen and phosphorus compounds

*Present address: Environmental Change Research Centre, Department of Geography, University College London, 26 Bedford Way, London WClH OAP, UK

CCC 1052-761 3/95/030191-14 01995 by John Wiley & Sons, Ltd

Received 10 October 1994 Accepted 29 May 1995

192 L. CARVALHO AND B. MOSS

through their urban, semi-natural and natural systems. For the post-war generation, wheat, oil seed rape, nettles, rye-grass, and blanket weed have been the familiar denizens of the countryside. And almost every cranny of moderate diversity that was part of the familiar landscape, even of the cities of immediately post- war Britain, has disappeared or had to be given formal protected status of one sort or another lest it should disappear also. To the above list of indicators of high nutrient availability (eutrophication) came the blue- green algae in 1988.

Blue-green algae (Cyanophyta) were not new as a eutrophication problem. They had caused difficulties in the preparation of domestic drinking water for many years, as witnessed in the annual reports of the London Water Board and its successors. Eutrophication, however, was perceived as an exacerbation of a natural phenomenon but not as a problem because the water industry could cope with its consequences (Collingwood, 1977). In 1980, a report by J. W. G. Lund drew attention to the particular problems of the Norfolk Broadland and Lough Neagh, where the symptoms of eutrophication were reflected, inter a h , in algal blooms, loss of macrophytes, avian botulism, fish kills and declines in other wildlife. The consequences were that eutrophication became recognized as a problem outwith the water industry, which was by that time also acknowledging that it had difficulties with which it could not so easily cope (Hayes and Greene, 1984). However, the report was used in political circles to advance the case that the eutrophication problem was largely confined to the Broads and Lough Neagh. Other examples to which Lund had referred were ignored. What Lund had said, in fact, was ‘We need continued research into eutrophication but, in my view, the Broads and Lough Neagh are the only areas in which action is needed now or in the near future’.

In 1990, Lund and Moss updated the first edition of Lund’s report and pointed out the widespread nature of the phenomenon of eutrophication, its largely anthropological causes, and the importance of perception in its determination as a problem: ‘Because the natural vegetation of almost all land surfaces in the British Isles has been destroyed or altered by man, eutrophication (the process [of increased nutrient loading]) is extremely common. That does not mean that the problems arising from eutrophication are equally widespread. The symptoms of eutrophication are expressed as the increased differential growth of some organisms over others. There is thus no absolute level at which eutrophication presents a problem. Much depends on the perception and needs of the observer. Similarly, there is no single parameter which serves as a yardstick to assess the level of eutrophication at which a problem may be identified’. They noted a greater sensitivity in other countries than in Britain and indeed the OECD was to produce a large report on the subject in 1982, which was largely ignored by regulatory authorities in Britain. In North America and continental Europe, arrangements were then well established to limit phosphorus discharges from sewage treatment works and even to restrict the phosphorus content of laundry detergents either voluntarily or by law.

Finally, Lund and Moss noted that although the rates of nutrient loading from conventional sources had probably not greatly increased in the 10-year period since Lund’s first report, perception of the problem by the conservation movement and the general public was increasing. A longer list of sites with eutrophication problems was given, but was described as open-ended, whilst it was pointed out that of the whole collection of waterways in the British Isles: ‘It is arguable that, to a lesser or greater degree, all have experienced some eutrophication compared with their pristine state, and that concern will be progressively shown by the public that they be improved as EEC thinking reaches the British press’.

Meanwhile, in Britain, a particularly warm and calm summer in 1989 had led by then to the surface aggregation of visual blue-green algal populations at the surfaces of lakes and to the death of domestic dogs and sheep drinking the water at Rutland Water in Leicestershire. The illness, attributed also to ingestion of blue-green algae, of army cadets on exercise at Rudyard Lake in Staffordshire heightened the public awareness. The newly formed National Rivers Authority took the issue as a flagship problem and produced a report (NRA, 1990) that has spawned a plethora of warning notices against the risks of blue-green algae, on many lowland lakes in Britain. In its report, the NRA placed emphasis on the proximate causes (e.g.

SSSIs SUBJECT TO EUTROPHICATION 193

hydrographic conditions and weather) of surface-bloom formation and perhaps played down the role of increased nutrient loadings in generating populations capable of forming serious blooms. This issue, however, has not gone away but has been re-emphasized by the general concern for the consequences of modern intensive agriculture (Shoard, 1980), the EC Directives on Urban Waste Water Treatment (European Communities, 1991a) and Nitrates (European Communities, 1991b), and the Sixteenth Report of the Royal Commission on Environmental Pollution (1992), which considered water quality.

The EC Directives have required the UK Government to identify sites that are eutrophic or may become so. The recommendations of the Royal Commission include the routine use of nitrate and phosphate monitoring in determining the states of rivers, and also the need to take into account conservation issues of eutrophication in the setting by the NRA of statutory quality objectives. The Commission noted the widespread occurrence of eutrophic and hyper-eutrophic reservoirs and lakes, of rivers with excessive siltation and weed growth, and the deleterious effects of eutrophication on nutrient-poor waters of conservation value. It expressed the view that this was an undesirable situation. Public concerns about the state of the countryside have also been reflected in measures for Environmentally Sensitive Areas that must result in some reductions in nutrient loading, and the detergent industry has been quietly converting a significant proportion of its products to non-phosphate alternatives.

A tide of awareness of eutrophication issues has now reached Britain and will not recede though there are indications that the wise lesson of Canute may not have been learned at senior government levels. Representatives of the Department of the Environment, in giving evidence to the House of Lords Sub-committee F during consideration of the draft Directive on Urban Waste Water Treatment, refer to Lund and Moss (1990) in such a way as to suggest that eutrophication problems are really still confined to a very few areas. This was not the sense of the report. It thus seems apposite to assemble the evidence of eutrophication damage, particularly to those sites of conservation value that apparently are protected.

There are several ways of doing this. One is to collect data and classify waters according to some conventional scheme, such as that of the OECD (1982), in which bands of total phosphorus and chlorophyll a concentrations are used to define categories labelled ultra-oligotrophic, oligotrophic, mesotrophic, eutrophic and hypertrophic. This has the problem that the data may be inadequate or lacking, that the categories are arbitrary and include only two variables, whilst eutrophication affects the entire multivariate aquatic system, and that different schemes give somewhat different classifications. Such schemes cannot distinguish water bodies having naturally high phosphorus concentrations from those that have such concentrations for anthropogenic reasons. They fail also to reveal sites of formerly very low nutrient concentrations that have experienced low absolute, but high relative, changes in concentrations that may have endangered their conservation status. These are common failings of such spatial state schemes; they cannot detect long-term change easily and mask processes that are environmentally important.

An alternative is a state-changed or value-changed scheme that compares present state (reflected in an unlimited number of variables) with some baseline or target state appropriate to a particular site and based either on its state at some time in the past or on a state which reflects a wise use of the catchment. It is likely that such schemes will become increasingly used because they are not only more informative but they give guidance on the potential for management or restoration of a particular site. Such a scheme has been developed and tested (Moss et al., in press). The results of the testing are discussed later in this paper.

There is a third alternative, in the interim period whilst a state-changed scheme acceptable to a wide range of organizations, and appropriate to the present needs of English Nature and other national conservation organizations is evolved. This is a site by site examination of whatever evidence is available to assess the state and degree of change of sites of particular importance. Such an examination can also reveal gaps in monitoring and recording and lead to a more systematic approach in the future. Such a survey, of a prescribed list of Sites of Special Scientific Interest, is the subject of this paper.


PROCEDURE

Surveys by English Nature staff in 1991 and 1992 indicated that over 120 inland water SSSIs appeared to be showing visible signs of deterioration, thought to be caused by eutrophication, in their nature conservation interest. This list of sites (which includes 90 lake, pond, and reservoir sites, 17 wetland and ditch systems, three canals, and 16 rivers) was solely based on staff impressions. The present study was initiated to provide a more detailed picture of most of these sites and included 79 standing waters (ponds, lakes, reservoirs), 17 ditch systems, three canals and three running waters. In particular it had the following aims:

(a) To assess the current state of these sites, particularly in terms of total phosphorus and chlorophyll a concentrations and other features suggested by the DOE (1993), who have recently proposed criteria for the identification of areas subject to eutrophication, as required by the EC Directive on Urban Waste Water Treatment.

(b) To assess, using quantitative and qualitative criteria, whether these sites are being affected by eutrophication.

(c) To identify the causes of eutrophication. (d) To assess whether the conservation interest is under threat. (e) To set, if possible, an appropriate water quality objective (in a general sense, not in that presently being

(f) To identify the most appropriate management needed to achieve restoration. (g) To identify those sites for which action is a priority, either because more information is needed to

establish the cause of deterioration, or where there is a clear indication of eutrophication and remedial action is urgently required.

discussed as a potential statutory measure) for restoration of each site.

The DOE criteria, referred to above, are based on a review of standing fresh waters carried out by the OECD (1982) which suggested that the most useful variables are total phosphorus concentration and chlorophyll a concentration. For example, a water body is said to have a greater than 50% probability of being ‘eutrophic’ where the annual average total phosphorus concentration is greater than 50 pg L- *. The corresponding figure for peak chlorophyll a concentration is 30 pg L-I. As these concentrations are based on an average of cases they can only be used as indicators of possible problems and do not represent absolute limits. For this reason non-quantitative criteria may be more useful, particularly in identifying sites which are not clearly eutrophic, but which may be highly sensitive to nutrient inputs. The following qualitative criteria have been proposed by the DOE (1 993):

(i) Dissolved oxygen. Excessive super-saturation of surface layers and decreased saturation in deeper stratified layers (hypolimnia).

(ii) Effects on fauna. Adverse changes in diversity and abundance of invertebrates and fish fauna which can be attributed to the effects of nutrient enrichment.

(iii) Effects on macroflora. Substantial adverse changes in macrophyte abundance and diversity. (iv) Effects on microflora. Exceptional increases in plankton, floating or attached algal biomass leading

to blooms, scums, or discoloration.

The selection of Sensitive Areas (Eutrophication) using these criteria is governed solely by their being subject to eutrophication, whether or not a sewage discharge is involved. However, under the provisions of the Urban Waste Water Treatment Directive, phosphate need only be removed at sewage treatment works serving populations greater than 10 000 population or the equivalent of this if other sources of phosphorus are treated at the works. The UK Government has determined that where this is not the case, sites will not be designated as Sensitive Areas. Large numbers of already eutrophicated or highly sensitive water bodies will thus be excluded from the lists published by the DOE, on grounds of technicality.


PRESENTATION OF DATA

This paper covers a total of 102 Sites of Special Scientific Interest (SSSIs) listed by English Nature staff. For each site the available data and the status of each site are summarized by region. Data were collected from English Nature files, the Public Register of the NRA, British Waterways, the water supply companies, and in some cases by original sampling.

Table 1 lists the trophic categories of the SSSIs examined according to the DOE criteria for total phosphorus concentration. It also shows the number and percentage of the total with symptoms of eutrophication (also according to DOE guidelines). These comprised 84% of all sites. Table 2 summarizes each individual site. Detailed information on each site is given in Carvalho and Moss (1994). There are 96 listings in this table because the eight SSSIs in the Somerset Levels have been grouped as they essentially comprise one system. Conversely Betton Pool and Bomere, although in a single SSSI, are in distinct catchments and have been considered separately. The following definitions apply to Table 2:

Aquatic conservation interest when notified ‘Low’-the site is not notified for its aquatic interest; ‘Medium’-notable interest is for wetland areas adjacent to the open water or for species not directly affected by eutrophication, such as birds; ‘High’-site is noted for aquatic species that are sensitive to eutrophication, such as submerged aquatic plants, benthic invertebrates, and fish. Present aquatic conservation interest: ‘No change observed’ equals no change that could be attributable to eutrophication; ‘Reduced’ means changes in aquatic community attributable to eutrophication. Records, however, were sometimes scanty and symptoms may have gone unrecorded in many cases. Primary causes: Obvious causes have been listed; there may have been additional small sources of nutrient loading. Action needed to maintainlrestore conservation interest: All sites may potentially be damaged by eutrophication in the future. Recommendations include existing action, immediately proposed action and measures in some cases simply to monitor the situation.

Table 1. The trophic categories of the SSSIs examined, based on the OECD total phosphorus concentration (pg L-’) criteria, and the number of sites examined which show symptoms of eutrophication (using DOE guidelines). Figures in brackets indicate percentage of

SSSIs examined showing symptoms, for each OECD category.

OECD Category Number of SSSIs Number with symptoms

examined of eutrophication (YO)

Oligotrophica ( < 10) Mesotrophicb (10-50) Eutrophic (50-100) Hypertrophic ( > 100) Unknownc Total

2 13 13 65 9

102

0 (0) 9 (69)

10 (77)

9 (100) 57 (88)

85 (84)

aOEgotrophic sites include Bassenthwaite Lake and Ullswater, but as only orthophosphate-phosphorus concentrations were available, this classification may underestimate their trophic state.

Phosphorus removal has been introduced (by North West Water) at STWs discharging into these sites as a pro-active policy to grotect the rare fish populations (vendace and powan). Mesotrophic: Malham Tarn, Claife Tarns and Mosses, Derwentwater, Esthwaite Water, Thurstonfield Lough, Windermere, Hatfield

Forest Lake, Rainworth Lakes, Foxcote Reservoir, Gordano Valley, Dungeness, The Swale, Whitmoor Common. ‘Unknown: Water quality data unavailable. Laughton Pond, Norbury Meres, Chasewater, Sutton Park, Limpenhowe Meadows, Ludham & Potter Heigham Marshes, Upton Broads & Marshes, Weston Turville Reservoir, Lower Moors.


Table 2. Summary of SSSIs surveyed arranged according to regions formerly used by English Nature. Conservation interest refers specifically to the aquatic interest of the site (symbols, L, low; M, medium; H, high; R, reduced; NC, no change noted; f, fish kill or changes in community attributable to eutrophication. Only certain NRA regions were able to give information on sites where fish kills due to deoxygenation had been observed; many regions said this information is not readily available. In addition, it is not public register information and can be expensive to buy from the NRA. Fish kill information is thus incomplete. Symbols for likely primary causes are: S, sewage or sewage effluent; A, farm stock wastes; STa, septic tank effluent; L, landfill leachate; B, migratory gull roost; ISal, increased salinity; I, internal loading from sediment; C, carp/bream effects; Cx, complex mixture of several sources; ?, possible source; -, no apparent problem. Symbols for action needed to maintain or restore conservation interest: PR, phosphorus (or potentially nitrogen) reduction by diversion, isolation or precipitation (u indicates this is already being undertaken); FM, fish community manipulation (biomanipulation by removal of zooplanktivores, or provision of zooplankton refuges; DA, diversion or treatment of farm stock effluents; BZ. provision of buffer zones of semi-natural vegetation to remove nutrients (includes establishment of wetlands, extension of wetlands or development of river corridors along streams); DL, divert or treat leachate from landfill; SD, re-route storm drain; Mx, water column mixing; AS, avoid or control fish stocking; T, improve septic tank system or effluent; c, flood containment; Sed, sediment removal; Sal, salinity reduction; Mo, continue or establish monitoring programme; FI, further investigation needed. For present total P concentrations, *means that the value is based on a single sample, > means that the value is for soluble reactive P and is

likely considerably to underestimate total P. Potentially achievable objectives are given based on Moss et al. (in press).

Conservation Present Objective National Grid interest at conservation Primary Present Total Total P

Site Reference notification interest causes Action needed P (pg L-I) (pg L-I)

(a) North Eastern Region Hornsea Mere TA190470 Melbourne & Thomton SE799473

Pocklington SE723456 Askham Bog SE570480 Malham Tarn SD894668 Semerwater SD9 13865

(b) North West Region Bassenthwaite NY21 5295

Claife Tarns SD372968

Derwentwater NY260208 Elterwater NY334042 Esthwaite SD361962 Siddick Pond WOO2304 Thurstonfield NY320563

Ullswater NY4 15200 Windermere SD390950 Denaby Ings SE500009 Laughton Pond SK543896

Mickletown Ings SE403275

(c) West Midlands Region

Ings

Lake

(Moss Eccles)

Lough

(Roche Abbey)

M M

R R

FM,BZ 360 60 PR,BZ >>250

SD,BZ loo* PR,BZ 1590*

Mo 125 T 20* 21

H L H M

R R

NC NC

H NC S PRu,Mo >>lo 25

Mo 1 o* H NC

H M H M H

NC R R

NC R

Mo,?PR >>I2 PR 200

PRu,Mo 29 16 BZ,Mo 90*

FI

H H M L

NC R R ?

?S S C -

Mo,?PR >lo 7 PRu,Mo >>20 13 FM,AS 145

FI

H R S SD,AS 620 (The Whinney)

Comber Mere Norbury Meres Oak Mere Petty Pool Quoisley Meres Rostherne Mere Tabley Mere Tatton Mere

SJ587445 SJ559492 SJ574679 SJ620700 SJ549456 SJ744842 SJ723769 SJ755802

M M H M H M H H

NC R

NC R

NC Rf

NC NC

?A ?C

?DA,FI FI Mo

?DA,FI ?DA,FI

PRu,BZ,FI FI FI

360

60 260 405 440 325 235

Continued

- ?A ?A S

?A


Table 2. (continued).


Site Reference notification interest causes Action needed P (pg L-I) (pg L-I)

The Mere, Mere

Bittell Resrs Upton Warren

Pools

Westwood Gt Pool Bomere Betton Pool Colemere Fenemere Marton Pool,

Chirbury Crosemere W hitemere Aqualate Mere

Betley Mere Black Mere

(Black Firs & Cranberry Bog)

Cop Mere Maer Pool Alvecote Pools

Chasewater Sutton Park

(d) East Region

Southill Lake Grafham Water

Woodwalton Fen Abberton Res’r

Cornmill Stream /Old R. Lea

Glemsford Pits Hanningfield Res Hatfield Forest L. Tring Res’rs

Blackbrook Res’r Eyebrook Res’r

SJ574679

SPOl8750 SO935672

SO880633 SJ500080 SJ510078 SJ433332 SJ445228 SJ295027

SJ434304 SJ414330 SJ747482

SJ747482 SJ748503

SJ802297 SJ789384 SK249050

SK039080 SP098974

TL141428 TLl50680

TL230840 TL970180

TL380013

TL840464 TQ730980 TL538202 TQ730980

SK458 174 SP854955

H

H M

H H H H H H

M H M

M H

M H H

H H

M M

H M

H

H M M M

H M

Rf

Rf R

NC NC NC NC R

NC

NC NC R

NC R

R R

?NC

NC R

Rf R

NC NC

R

R R R Rf

NC NC

S

? ?C

- - - - C -

- -

S A C

STa,A -

S ?

s , c

- ?S?C

C S

S?A S

S

S?C C C S

PRu,Mo

FI FI

Mo Mo Mo Mo FM FI

FI FI

PR,T, FM,FI

FI T,DA,FI

PR,FI FI

PR,AS, FI

Mo FI

FM PRu (in pre-res’r lagoon) PR,BZ PR (in

pre-res’r lagoon)

PR

235 (Little Mere)

~ 1 9 0 >595

(Moors) >260

(Sailing) >> 105

65 115 400 485

~ 6 3

215 1455

~ 3 8 5

506 >300*

315 430* 320

(Pretty Pigs) 95 (Gillmans)

65* 300

>805 440

685*

PR by C,FM 115* FM 35* FM 35* PR 475

(by diversion) ? FI >120 S ?PR ~ 5 0

Continued

198 L. CARVALHO A N D B. MOSS

Table 2. (continued)

Site National Grid

Reference

Rutland Water

Alderfen Broad Ant Broads and

Marshes

Bure Broads and Marshes

Kenninghall & Banham Fens/ Quidenham Mere

Limpenhoe Meadows Ludham & Potter

Heigham Marshes Upper Thurne

Broads

Upton Broads & Marshes Yare Broads &

Marshes Pitsford Res’r Attenborough Gravel

Chesterfield Canal Pits

Rainworth Lakes

(e) South Region Foxcote Res’r Weston Turville Coate Water

(0 South West Region Blagdon Lake Chew Valley Lake Gordano Valley Loe Pool Slapton Ley South Milton Ley Lodmoor Radipole Lake Great Pool, Tresco Lower Moors,

St Mary’s Porth Hellick Pool,

St Mary’s Somerset Levels

(8 SSSIS)

SIC928070

TG355 195 TG362213

TG318164

TM041875

TG39903 1 TG4 10 170

TG4 1521 5

H

H

SP780708 SK522341

SK72282 1

SK583583 -8K762944

SP711364 SP862096 SU188820

ST520595 ST570600 ST435730 SW647250 SX82644 1 8x685422 SY688813 SY672805 SV894146 SC912106

SV924108

H

Conservation Present Objective interest at conservation Primary Present Total Total P

notification interest causes Action needed P (pg L-I) (pg L-l)

M R S PRu (in 55

H Rf S Sed,FM 289-1 174 H R S Sed, PRu, FM 180 78

(Barton Broad)

H R S PRu, more 163 55

M R ?S?C FM 135*

pre-res’r lagoon)

PR,FM (Hoveton Great BD)

H R c x BZ,FI H R cx BZ,FI

H Rf B,ISal Sal 98 38 (Hickling

Broad) R c x BZ FI

R S PR 836

M R S PR 110 M R S PR (by 435*

H R ?S ?PR,FI 1000* isolation)

H R C FM 40*

M R S PR,FI 40 M R ?S?C FI H R C FI 75*

M M H H H M M M M M

NC Rf

NC R R

?NC R

NC NC ?R

S,A PR,DA cx ?PR,Mx - Mo S PR

S,A PR,BZ,?FM ?A DA,Mo L DL S PR - Mo L DL

285* 72 >>90 66

>>I45 101 >>510 105 >290

30*

150* 250* 105*

H NC ?L,?STa FI 155*

Rf S,STa PR ~ 6 4 0 (R. Parrett)


Table 2. (continued).


Site Reference notification interest causes Action needed P (pg L-l) (pg L-I)

(g) South East Region Brent Res’r Ingrebourne Marshes Dungeness The Swale Walland Marsh Bookham Commons

(Isle of Wight Pond)

Godstone Ponds Hedgecourt Lake Puttenham

Common-The Tarn 8t Cutmill Pond

Thursley Common (Hammer Ponds)

Whitmoor Common

TQ217873 TQ539835 TR050180 TR000670 TQ960240 TQ 126652

TQ353516 TQ355403 su9 12457

SU915410

SU990531

M M M M H M

H H H

?H

H

R R R R Rf R

R R R

NC

R

? sc A ?

Cx,?S C

A,C C C

?C

C

FI PR,FM BZ,?DA BZ,FI BZ,FI

FM,As,FI

FM,FI FM RM

AS

FM

>>720 >>3930

40* 36*

590* 165*

255* 60* 85*

110

35*

(v)

(vi)

Present total phosphorus concentration: If total phosphorus concentrations were not available, orthophosphate-phosphorus (P04-P) concentrations, if available, are given. Water quality objective: This has been based on calculated, hindcasted baseline values (Moss et al., in press) in the few cases where these were available. The values reflect land use in the catchment determined by the natural character of the catchment climate, topography, geology and soils and the availability of suitable technology for phosphorus removal at sewage treatment works.

RESULTS AND DISCUSSION

Incidence of problems

The survey covered 102 sites (Table 1). These included about 120 individual water bodies but the statistics given in the tables are largely by SSSI rather than water body and hence are conservative in indicating the numbers of water bodies damaged by eutrophication. In examining English Nature files, considerable concerns were noted about eutrophication problems in other sorts of habitat including fully terrestrial sites, rivers, estuaries and other coastal habitats and wetlands. For example, in checks made at only two regional offices, problems were noted in six coastal grazing marsh sites in Essex, three estuarine SSSIs, and several moor and moss sites in Yorkshire. Together with data mostly on standing waters and ditches, this suggests that eutrophication is recorded as an extremely widespread problem in England. Of the 102 sites, some of which may have been naturally nutrient rich, 78 (76%) were eutrophic or hyper-eutrophic according to total phosphorus criteria established by the DOE, and 85 (84%) showed symptoms of eutrophication problems (Table 3).

Availability of data

Considerable problems were encountered in gaining adequate data from statutory sources for total phosphorus, the main water quality variable used in the DOE scheme. This was because total P is not


Table 3. The primary causes of change in the 79 SSSIs identified in Table 2 as showing symptoms of eutrophication. Percentages are given in parentheses. These add up to more than 100 because a given site

may be affected by more than one cause.

Causes(s) Number of SSSIs affected

Main sewage eMuent Possible main sewage effluent Fish community Possible fish community problem Farm animal wastes Possible farm animal wastes Septic tanks Possible septic tank problems Landfill effluent Possible landfill effluent problems Migratory gull roostP Sediment release Complex of reasons, none clearly predominant Unknown with no obvious possibility

'Hickling Broad (but probably now diminishing as a problem (Bales el a/., 1993)).

routinely monitored by the NRA except at a few sites, mainly in East Anglia and the Cumbrian Lake District. Soluble reactive phosphorus was sometimes measured, but using methods that gave a lower detection limit of 50 pg L-I. This is appropriate for the analysis of sewage and industrial effluents, for which it was designed, but quite inadequate for lake monitoring where detection limits of < 5 pg L- are essential and easily attainable by standard methods. Data were sometimes obtained from the scientific literature and often by original analyses to fill the gaps in the statutory record.

Assessments were made also using the qualitative criteria listed by the DOE and indicated in the Introduction. Generally these were from English Nature files and the literature and were mainly notes of increases in phytoplankton populations or sometimes declining macrophyte communities. Data on dissolved oxygen or fauna, both listed for use as criteria by the DOE, were scanty or, more usually, completely absent.

There are problems in using the total phosphorus criterion in that some lakes are likely to have long been naturally nitrogen limited and may show high total phosphorus concentrations without necessarily having severe eutrophication symptoms (Moss et al., 1994). Some of the deeper West Midland meres are in this category, but they are few. A larger number of other lakes may be anthropogenically nitrogen limited because of artificially high inputs of phosphorus, but these will show high total phosphorus concentrations and will not be misclassified. Yet other lakes, which are very shallow and dominated by macrophytes, may have large total phosphorus concentrations but low algal crops (Scheffer et al., 1993). The phytoplankton crops may be nitrogen limited at some times of year and grazer limited at others, and their total phosphorus concentrations may suggest a far worse state than is the case. The classification proposed by the DOE is unable to cope with these subtleties of ecology.

Moss et al. (in press) have applied their state-changed approaches to a tranche of British lakes, most of them different from those surveyed here. More than half the British lakes examined were found to have more than doubled their total phosphorus or total nitrogen concentrations, compared with individual baseline states that represent their water quality under land use dependent on natural constraints, and with no sewage effluent discharge. A widespread occurrence of significant eutrophication symptoms is thus independently confirmed.

SSSIs SUBJECT TO EUTROPHICATION 20 1

Causes of problems

Table 3 shows the primary causes of the changes in the 79 sites that have been established as showing symptoms of eutrophication. Thirty-five (44%) of the problem sites involve sewage effluent discharge and this may also be implicated in up to a further five sites. In 31 cases it was impossible to identify the sources precisely or there were several potential contributors. Properly detailed studies of most sites have never been made. Several of these ‘unknown’ sites may involve the production of eutrophication symptoms by the fish community, a feature clearly identified in 15 (19%) of the 79 sites. The problem arises partly through mobilization of phosphorus from the bottom sediments by carp (Cyprinus carpio) feeding (Lamarra, 1975). In these cases, external nutrient loads appeared to be low and unlikely to lead to the severe symptoms observed and associated with large populations of stocked carp. The problem seems to be exacerbated by the presence of substantial bream (Abrarnis brarna) populations (Giles, 1992; Breukelaar et al., 1994) which feed in the sediment and also remove zooplankton grazers from the plankton in their first year of life. Other coarse fish such as roach (Rutilus rutilus) have similar impacts on the zooplankton. The incidence of the problem associated with carp was surprising and conceivably could be behind about a third of the total caseload. However, there is no doubt that carp angling has become extremely popular, leading to much stocking with this fish. The different traditions of anglers and fishery officers on the one hand and conservationists on the other, and the general lack of appreciation of the top-down effects that fish have in structuring the ecosystems of shallow lakes, have contributed to a generally much too liberal attitude to stocking practices.

Biological monitoring of eutrophication changes, other than for algae, has generally been minimal and has centred on aquatic plants, which correspondingly appear to be the group most affected by eutrophication. However, eutrophication affects the whole system, and it is inconceivable that where changes occur in the primary producers, there will not also be changes in the invertebrate, fish and feeding or breeding bird communities.

Required management

Indications of the primary management needed to restore some of the conservation value to sites now showing undesirable symptoms of eutrophication are given in Table 4. External nutrient control involving phosphorus removal or eMuent diversion is needed in 30 (38%) and potentially 34 sites (43%) and is being carried out already in a few of these. Thirteen of the 30 sites are known to receive sewage eMuent from at least one treatment works serving a population equivalent of 10000 or more and will thus fall under the aegis of the Urban Waste Water Treatment Directive. Phosphate removal can thus be anticipated at these large works for the following sites: Windermere proposed SSSI*, Alvecote Pools, Graham Water* + , Cornmill Stream and Old River Lea, Glemsford Pits, Tring Reservoirs, Rutland Water*+, Bure Broads and Marshes*, Yare Broads and Marshes, Pitsford Reservoir+, Attenborough Gravel Pits, and Ingrebourne Marshes. At sites labelled*, phosphorus stripping has already been installed, at least at some of the relevant works, whilst three of these sites (+) have iron dosing carried out at the reservoir, though this is not necessarily entirely in the conservation interest. Many of these sites, however, also receive effluent from STWs serving a population equivalent of less than 10000 and thus may not be greatly improved by the modification only of the larger works in the catchment.

This leaves 17 of the effluent-affected sites receiving effluent solely from works serving less than 10000 population equivalents and thus not under the aegis of the Urban Waste Water Treatment Directive. Thus, more than half of the sites affected by sewage effluent and intended to be protected by the spirit of the Directive will be excluded. In a written reply to a Parliamentary question on May 18 1994, the Minister of State for Environment and the Countryside, Robert Atkins, declared a list of only 33 Sensitive Areas (Eutrophication) and indicated that at least 20 other possible sites needed further monitoring. Most sites on


Table 4. The primary management needed in the 79 SSSIs identified as showing symptoms of eutrophication. Percentages add up to more than 100 because several measures may be needed at a single site.

Solution(s) Number of SSSIs affected(%)

Sewage effluent diversion or phosphorus removal (including 30 (38)

Possible need for effluent diversion or P removal 4 (5) Fish community manipulation 18 (23) Possible need for fish community manipulation 1 (1) Need for control over fish stocking 6 (8) Buffer zones, wetland enhancement 12 (15) Diversion of stock wastes 2 3) Possible need for diversion of stock wastes 5 (6) Improvement in septic tank function 3 4) Re-route storm drain 1 (1) Flood containment 1 (1) Sediment removal 2 (3) Diversion of landfill leachate 2 (3) Salinity reductiona 1 (1) Continue or establish monitoring Much further investigation needed 35 (44)

nine sites where already being carried out)

16 (20)

aSalinity reduction needed to develop grazing zooplankton populations: Hickling Broad (Upper Thurne Broads & Marshes).

the declared list are large rivers and only nine (Bassenthwaite Lake, Lake Windermere, Hanningfield Reservoir, R. Bure, R. Ant, Grafham Water, Foxcote Reservoir, Pitsford Reservoir, and Rutland Water) are included in the list of sites discussed in this paper. Four of these sites already have phosphorus removal treatment installed, the remainder are drinking water reservoirs. This suggests that the Government’s motivation in applying the Directive is focused more on water supply than conservation. The list of sites needing further monitoring includes two that are common with the list discussed here (River Yare/Wensum and Loe Pool). There are no sites in either government list that are presently near-pristine and which would benefit from prevention. When some other EC countries are designating all of their water bodies as potentially sensitive to eutrophication (the most logically defensible position), the official reaction to the opportunities offered by the Urban Waste Water Treatment Directive can be described as seriously flawed.

Where manipulation of the fish community is indicated in Table 4, what is meant is that common carp, at least, should be removed. Other biomanipulative measures such as protection of newly growing plants from bird grazing, may also then be needed to restore the conservation interest fully. There is an urgent need for the conservation bodies to evolve, with the NRA, a policy on fish stocking that takes into account wider aspirations than the opportunity to catch large, aggressive fish by a group of specialist anglers. The whole issue of fish interactions within their ecosystem also needs extended research, for good predictive data are few. Much fisheries research in the past has concentrated on growth rates with the hidden agenda of increasing the sizes of the fish in a context where the rest of the environment was seen as secondary or background. Such essentially agricultural approaches are not appropriate to the management of whole ecosystems for nature conservation.

Issues of monitoring

There is, in general, a lack of systematic monitoring of sites for symptoms of eutrophication by either the NRA or English Nature. This may be remedied in the future as the NRA brings standing waters more centrally into its hitherto largely fluvial monitoring programme. There is no single species that can be used


unequivocally to monitor eutrophication, and so the recording of community change is, and will continue to be, a difficult task. The setting of appropriate standards for restoring conservation interest at each site is theoretically possible but requires a detailed knowledge of the community structure prior to damage. In general, data of appropriate detail are not available. However, the scheme proposed by Moss et al. (in press) potentially offers a method of setting realistic water quality objectives for individual sites in a landscape that will remain agricultural, and in a technological environment that no longer inevitably means discharging high-phosphate concentration sewage effluent. Against the setting of such baseline standards, a long-term detailed familiarity with a site in all its aspects by local staff is likely to produce the most reliable evidence of changes, whilst monitoring water transparency might provide a ready indicator at site level backed by chlorophyll a and total phosphorus or total nitrogen analyses carried out in a suitable laboratory. The trophic ranking scheme developed by the former Nature Conservancy Council (Palmer et al., 1992) offers a way of quantifying plant changes, though it becomes less sensitive in lakes of medium to high fertility than it is in the most infertile sites.

General issues

It is becoming increasingly clear that eutrophication has become a severe problem for nature conservation as well as for public amenity and water supply and that present systems of directing land and water planning and management are inadequate to cope. The difficulties are that the symptoms of eutrophication are only proximate problems and that the ultimate solution to the problem of eutrophication must involve integral management of the landscape. An important step forward was made in 1974 when the Water Authorities were organized on a catchment basis. The NRA still retains that structure, but it has little say in the management of land. Hence, like the conservation organizations, it is unable to deal with many problems of the waters for which it is responsible. There is, in addition, a danger that in the formulation of arrangements for the proposed Environmental Agency in which it is intended to combine the functions of the NRA, the Pollution Inspectorate and the waste management agencies of local authorities, the local authority political boundaries used by the latter organizations will be adopted (Touche Ross & Co, 1994). This may have advantages on organizational grounds but will be entirely retrogressive in terms of wise management of resources.

Would not the land and waterscape be much better managed by a series of unitary bodies organized on a natural catchment basis and responsible for water resources, agricultural advice and grant award, urban waste disposal, pollution control, planning, countryside management and nature conservation collectively within their catchments? There might be perhaps about 30 to 50 such bodies responsible for the whole of Britain as a compromise between the potential abuse of power that comes with size and the need for the gamekeepers to be of a minimum size to cope with increasingly heavy poachers. It would require some properly thought out, environmentally based legislation to form and guide such bodies, but their loyalties would be to the balanced management of the resources of their catchments rather than to the individual sectional interests that frequently confront each other at present. The management of eutrophication problems is just one of many issues that would benefit greatly from such a fundamental approach.

ACKNOWLEDGEMENTS

We are grateful to English Nature for commissioning this investigation. Views expressed, however, are those of the authors and not necessarily those of English Nature.

REFERENCES

Bales, M., Moss, B., Phillips, G. L., Irvine, K. and Stansfield, J. 1993. ‘The changing ecosystem of a shallow, brackish lake, Hickling Broad, Norfolk, U.K. I1 Long-term trends in water chemistry and ecology and their implications for restoration of the lake’, Freshwater Biology, 9, 141-165.

204 I.. CARVALHO AND €3. MOSS

Breukelaar, A. W., Lammens, E. H. R. R., Klein Breteler, J. G. P. and Tatrai, I . 1994. ’Effects of benthivorous bream (Abramis brama) and carp (Cyprinus carpio) on sediment resuspension and concentrations of nutrients and chlorophyll a’, Freshwater Biology, 32, 113-121.

Carvalho, L. and Moss, B. 1994. Environmental Audit of Lakes Subject to Enrichment, Final Report of English Nature Contract F72-06-3 1, English Nature, Peterborough.

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Department of the Environment, Ministry of Agriculture, Fisheries and Food, and Welsh Office 1993. Methodology for Identifying Sensitive Areas (Urban Waste Water Treatment Directive) and Methodology for Designating Vulnerable Zones (Nitrates Directive) in England and Wales, Consultation Paper, March 1993. DOE, London.

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Anglia’, Water Pollution Control, 1984, 42-51. Lamarra, V. A. 1975. ‘Digestive activities of carp as a major contributor to the nutrient loading of lakes’,

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Moss, B., McGowan, S. and Carvalho, L. 1994, ‘Determination of phytoplankton crops by top-down and bottom-up mechanisms in a group of English lakes, the West Midland meres’, Limnology and Oceanography, 39, 1020-1029.

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Palmer, M. A., Bell, S . L. and Butterfield, I. 1992. ‘A botanical classification of standing waters in Britain: applications for conservation and monitoring’, Aquatic Conservation: Marine and Freshwater Ecosystems, 2, 125-144.

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Shoard, M. 1980. The Theft of the Countryside, Temple Smith, London. Touche Ross & CO 1994. Options for the Geographical and Managerial Structure of the Proposed Environment Agency,

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Documents

The current status of a sample of english sites of special scientific interest subject to eutrophication