Ponce Coral Reef Surveys - Geology

Ponce Coral Reef Surveys Project 301(h) Program waiver Project Number 2451-074 Record by: Jack Morelock, Wilson Ramirez and Christoph Schmitt Personnel for field program: Jack Morelock, Wilson Ramirez, Christoph Schmitt, Milton Carlo, Gretchen Chiques

Geology of the West Ponce Platform We have previously mapped the sediment pattern on the carbonate platform at Ponce (Figure 1; Acevedo, et al., 1989). Sediment accumulation and subsequent resuspension are functions of sediment sources, wave and current energies, and bathymetry. Since the nature of sediments and the amount of terrigenous sediment available is important to the discussions in this report, a brief summary of the results of our work and the publications by Beach and Trumbull (1981) and Trias (1991) will be presented.

Figure 1. Sediment facies at Ponce

The seaward shelf/slope unit at Ponce is the submerged shelf-edge reef system of living coral which forms the shelf-slope break and extends down the slope. The shelf breaks at 20 to 25 m depth. The reef may be a single or double ridge. The sediments on the reef are consolidated reef rock and thin patches of carbonate sands. Off Isla Ratones, pockets of fine-grained terrigenous sediment are found below 15 m. Figure 2. Sand channel in the Ponce Platform hardground

The carbonate platform sediments are shoreward from the shelf-edge reef system. This is an area of hard carbonate pavement with thin carbonate sands and small patch reefs. The platform hardground has low coral growth under conditions of moderate to strong currents and variable turbidity. Sediments are present in small channels.

The Ponce Basin extends to about 3 km west of Ponce Harbor and grades northward into the nearshore zone. Water depths are 12 to 34 m. The water is generally turbid with Secchi disc readings of less than 5 m. Sediments in the Ponce Basin are poorly sorted terrigenous silts and clays with small amounts of carbonate mud and sand that have been

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carried in from surrounding areas and have accumulated in low-energy, deeper-water conditions. Similar sediments floor the Ponce Submarine Canyon. The northern part of the basin is dominated by dark to olive terrigenous muds. Beach (1975) measured 65 to 70 cm of mud lying over a calcareous sand, showing a change in the depositional environment. He measured sediment accumulation on an artificial reef near Ponce to get an accumulation rate of 4 mm per year for the terrigenous muds. Applying this rate to the accumulated mud blanket shows that it could have been deposited during the last 125 to 150 years. Land stripping for sugar cane, urbanization, and dredging for harbor facilities could account for increased erosion and the development of this mud accumulation.

These fine sediments are resuspended by wave action and ship traffic. The resulting underwater visibility can be less than 1 m. (pers. obs.) The resuspension develops a sediment plume that is transported by currents, carrying fine sediments over the reefs within and west of the basin. The nearshore province sediments are dark, fine-grained sand to fine-grained terrigenous muds. Moderate to strong longshore drift was observed.

Analysis of sediments collected showed that the samples from depths of the five meters were dominantly sands, due to wave action removal of the fine fraction. Deeper parts of the reef had more fine-grained terrigenous sediments. Bajo Tasmanian and Cardona reefs had large amounts of fine-grained terrigenous sediments and poor sediment sorting. Both areas showed finer grain size and more terrigenous sediments at 15 m, suggesting that wave energy removes some of the terrigenous fines at depths above 10 m. Cayo Ratones also showed an increase in fine terrigenous sediments with depth.

Secchi readings during October 2002 gave 10 to 11 m at all sites along the route of the sewer outfall pipeline between Cardona Ridge and the outer shelf ridge. Swell and wind waves created a strong bottom surge during the survey. These resuspended sediments at the LK sites obscuring visibility. The other two sites were equally turbulent, but lacked fine-grained sediments.

Status of the coral reefs 1995 The condition of coral reefs on the southwest Puerto Rico insular margin was discussed in Morelock, et al. (2001). They found greatly reduced coral cover at Ponce relative to other areas. A maximum of 18 species of corals were recorded at 10 m depth. Of these, only seven species were more than 0.5 percent cover (by species) on the eastern reefs. Montastraea cavernosa was dominant at 10 m. This coral is one of the most sediment-resistant species of the scleractinian corals. Figure 3. Coral cover by species at 10 m Ponce.

The total cover of Montastraea cavernosa is not significantly different from values at La Parguera, but the reduction or

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absence of other coral species changes the relative abundance and reinforces the conclusion that Montastraea cavernosa is highly tolerant to a long-term sediment stress condition. No living corals were found below 12 m at Cayo Cardona.

Scope of the work – October 2002 The survey at Ponce was to include the following work. The following scope of work requires that coral survey locations be established at three locations, the leak site, the south face of the Cardona Ridge and the shelf ridge. LEAK SITE (LATITUDE 17 56.05988 LONGITUDE 66 38 34.33817)

Four 45 meter transects would be established at the leak site, emanating from the leak in a cross pattern:

• Transect 1 would extend from the Outfall leak site beginning at the edge of the rubble zone and proceeding in a northeasterly direction.

• Transect 2 would extend from the Outfall leak site beginning at the edge of the rubble zone and proceeding in a southeasterly direction.

• Transect 3 would extend from the Outfall leak site beginning at the edge of the rubble zone and proceeding in a southwesterly direction.

• Transect 4 would extend from the Outfall leak site beginning at the edge of the rubble zone and proceeding in a northwesterly direction.

Note: The “rubble zone” is an area of varying width on either side of the outfall pipeline composed of excavated coralline rock and, in places, armor stone.

Survey sites & survey 2002 Three sites were established:

• Cardona Ridge – 17-57.158 x 66-38.626. The east line had a zero point 10 m due east of the DGPS location and the west line started at 21 m west.

• LK site – 17-56.301 x 66-38.572. The north and east lines had a zero point 33 m due east of the DGPS location and the south and west lines started at 37 m west.

• Shelf Edge Ridge – 17o 55.998 x 066o 38.570. The east line had a zero point 41 m due east of the DGPS location and the west line started at the DGPS position.

All differential GPS positions were at the pipeline within the rubble zone. The leak site was referenced to the inspection chamber and leaks were seen north and south of this structure. At the leak site only the chamber stood above the rubble, but the pipeline was exposed at both of the other sites. Figure 4. Survey sites on the carbonate hardground at Ponce

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Survey methodology At each survey site, we ran the following procedures

• The phototransect with quadrat frames to determine the coral cover by species and total coral cover. This technique is described.

• Identification and analysis of the non Scleractinian fauna and flora within the transect quadrats. • Camrecorder video of the transect lines and the hardground environment • Secchi measurements for water turbidity

In addition to these contracted studies, we looked at two other aspects of the environment associated with the pipeline route

• Close-up photographs of coral colonies to characterize “coral health” which is expressed in amount of coral bleaching, coral disease, algal encroachment, color of the colony. These coral were selected within the quadrats and outside but near the line where additional species were seen. The degree of algal encroachment is especially related to the presence of nutrients in the water column.

• Photography and physical examination of the rubble zone to see the extent of colonization of the rubble by coral and other organisms

Coral Cover Surveys Coral cover is an important index of coral reef condition. It is recognized as an important parameter in coral reef quality (Weinberg, 1981; Done, 1992). We define cover as the percentage of a unit area that is occupied by living coral.

Photoquadrats were used to determine coral abundance and condition and to estimate coral cover (Morelock, 1990). In each location, 45 m transects are extended parallel to depth contours. A total of 10 quadrats are placed along each transect at random intervals, with each quadrat (70 x 100 cm; 0.7 m2 area) positioned such that the narrow (70 cm length) side is parallel to the line. Numbered tags are placed next to each coral within the quadrat to assist in identification of the corals.

Figure 4. Photo survey transect line

For each quadrat, one diver records the coral species associated with each number, and notes the condition of the coral. A second diver photographs the quadrat. All quadrats are photographed from a planar perspective at a vertical distance of 1.2 m above the quadrat. This distance is maintained by using a 1.2 m stick. Although variation from true vertical to the surface

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may introduce cover errors, these are slight. Cover is underestimated because the photo is a planar projection of three-dimensional coral. We use digital cameras (Olympus 3040) in underwater housings to obtain a 10 x 7.5 inch 200 dpi digital image.

Figure 5. Photo survey quadrat.

Coral cover is determined for each quadrat using the Deneba Canvas area measuring function. Initially, individual corals are identified on the image and the perimeter of the coral is marked. The individual corals are traced on the image and measured to determine the area in cm2 relative to the area of the image. All data are entered into a spreadsheet in order to calculate percent cover by species and total cover for each quadrat and for the total transect, average colony size, and number of colonies. In this study, "coral cover" is defined as the amount of the total bottom area occupied by living coral colonies within an entire area that includes sand channels and bare areas.

Whenever possible, corals identified within quadrats were recorded to species level. Although the Montastraea annularis group (species complex) have been subdivided into three species as proposed by Knowleton, et al. (1992) many of the surveys used were made before the introduction of new species. Therefore, the cover is designated the Montastraea annularis group and the individual species are not distinguished. Forms or morphotypes of Agaricia agaricites, Porites porites and Meandrina meandrites were not differentiated. In addition, encrusting colonies of Madracis were recorded as Madracis decactis. In this study, we only recognized one species of Stephanocoenia (Stephanocoenia intersepta) and one species of Dichocoenia (Dichocoenia stokesii). The percent cover by all Mycetophyllia species and Diploria species was so low that both are recorded only to genera.

Flora & fauna survey methodology Species diversity and abundance of gorgonians, cnidarians, hydrozoans and sponges were estimated for the transect lines. Total counts were obtained for all. All quadrats were examined in the field and on the quadrat images.

At each site, percent cover in ten randomly placed quadrates along the transects was estimated. In general, all sites were characterized by the dominance of two invertebrate groups, gorgonians and sponges. With the exception of occasional species of Halimeda, macro algae were virtually absent on all sites.

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Video Surveys Video of the transects and general video views over the areas of investigation provides a visual record which can be compared to later surveys, and, if necessary, we can obtain individual stills from the video. EPA is using video transects to measure coral cover on reefs. We had a better record (improved resolution and control of the quadrat photos) using still photography. The video does give an excellent overview of the entire area and has the qualitative value of showing algal abundance and coral vitality from larger scale or perspective.

Coral health and vitality: Photographic analysis of individual coral colonies The Olympus digital cameras (Olympus 3040 in Tetra underwater housing with Nikonos 105 strobe and Olympus 3040 in Ikelite underwater housing with Ikelite strobe) were used to photograph individual coral colonies in the quadrat frames, near the transect lines and in the rubble zone. The photos were taken haphazardly in order to have several photographs of the typical species found in the local area. The digital image is 10 x 7.5 inches with 200 dpi resolution. In the computer, these images can be enlarged to see details of the colony.

Each photo was assessed based on color, signs of bleaching, algal competition, and coral disease (Figure 6). If the coral appeared to be of a normal color, it was scored as a five, if the color was faded or blotchy, it was scored 4 to 1, based on the condition (with 1 being the worst condition). In a similar manner, we scored bleaching conditions, algal competition, and disease.

Figure 6. Examples of black band disease, bleaching, algal mat overgrowth and normal healthy coral

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Data for Cardona Ridge & Shelf Ridge and Leak Site Coral

Coral cover measured in the present survey and in 1993 is presented in Figure 7.

Figure 7. Coral cover by species at 9 – 13 meters on the west Ponce carbonate platform.

The October 2002 surveys were run to either side of the pipeline rubble zone. Coral colony distribution at the three sites is not evenly dispersed. Coral colonies tend to occur in clumps separated by sand and bare rock which may have small colonies of coral. These coral have an area of about 100 cm2 for the Montastraea annularis, Porites asteroides and Diploria. The other species are smaller colonies (Figure 8).

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Figure 8. Coral colonies photographed within a quadrat. Tag 19 marks a Montastraea cavernosa colony.

The cover for the east and west transects at Cardona Ridge were similar, but lower than the results from 1993. This does not seem to represent a general loss of coral on the ridge, but variation in amount of coral cover on what is a hardground (defined as having less than 6% living coral on the surface).

The Outer Ridge results were very similar for the two October 2002 transects and for the comparison to the 1993 survey both in total coral cover and in cover by species. This ridge is also hardground with small clumps of coral and heavy cover by soft coral, gorgonians and sponge.

These hardgrounds have only a limited amount of coral cover, supplied by only a few species as shown in Table 1. Table 1. Cover on the hardground environment

Coral species Cover by species for the 1993 & 2002 surveys Coral species in the quadrats covering 1.0 to 0.1 percent of the surface Montastraea cavernosa 1.0 Agaricia agaricites 0.5 Montastraea annularis 0.3 Porites asteroides 0.2 Siderastrea siderea 0.2 Diploria strigosa 0.1 Diploria clivosa 0.1 Coral species in the quadrats less than 0.05 percent of surface Madracis decactis Dichocoenia stokesii Isophyllia sinuosa Scolymia Individual coral found outside the quadrats Montastraea annularis – this coral was measured in 1993, occurs as larger, individual colonies Meandrina meandrites Porites porites Stephanocoenia intersepta Diploria labyrinthiformis

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The nature of the hardground can be seen in Figure 9.

Figure 9. Surface of the hardground – typical of the outer ridge and Cardona Ridge. The Montastraea cavernosa in the foreground has a diameter of about 15 cm.

The average coral cover was 2.6 percent of the surface covered with living coral, and this was only seven species of coral (Table 2). Eight other coral species were found during the surveys – the coral can be seen in the plates for coral health analysis. Table 2. Coral cover on the west Ponce carbonate platform. Surveys locations run in 1993 at Cardona Ridge and the Shelf Ridge are now part of the pipeline rubble zone.

location dept

h (m

)

tota

l cor

al c

over

Mon

tast

raea

ann

ular

is

Mon

tast

raea

cav

erno

sa

Agar

icia

aga

ricite

s

Porit

es a

ster

oide

s

Side

rast

rea

side

rea

Dip

loria

stri

gosa

Dip

loria

cliv

osa

Mad

raci

s de

cact

is

Dic

hoco

enia

sto

kesi

i

latitude longitude mon

th-y

ear

Cardona Ridge '93 8 4.0 1.0 1.4 1.5 0.1 0.1 t 17-57.11 66-38.66 Jan-93Cardona Ridge east 9 1.9 0.6 0.5 0.5 0.2 0.1 0.1 17-57.158 66-38.626 Oct-02Cardona Ridge west 9 1.3 0.6 0.5 0.1 0.0 0.1 17-57.158 66-38.626 Oct-02all Cardona Ridge 1.6 0.6 0.5 0.3 0.1 0.1 0.1 LKt1N 13 2.0 1.4 0.0 0.6 17-56.301 66-38.572 Oct-02LKt2E 13 0.7 0.4 0.0 0.2 0.0 17-56.301 66-38.572 Oct-02LKt3S 13 0.3 0.3 17-56.301 66-38.572 Oct-02LKt4W 13 0.3 0.2 0.1 17-56.301 66-38.572 Oct-02all LK transects 0.8 0.6 0.0 0.1 0.2 0.0 Outer Ridge '93 10 2.3 0.2 1.2 0.2 0.1 0.5 0.2 17-56.01 66-38.5 Jan-93Outer Ridge east 9 2.2 0.9 0.1 0.3 0.1 0.8 0.1 0.0 0.0 17-55.998 66-38.570 Oct-02Outer Ridge west 9 2.1 0.1 0.6 0.1 0.6 0.2 0.6 0.0 0.0 17-55.998 66-38.570 Oct-02all Outer Ridge 2.1 0.1 0.7 0.1 0.4 0.2 0.4 0.3

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Coral cover on the lower surface (13 m) to either side of the leak site had an average cover of 0.8 percent living coral. Only three species (Montastraea cavernosa, Siderastrea siderea and Diploria clivosa) were present as more than 0.1 percent cover. Only three other species were present (Agaricia agaricites, Dichocoenia stokesii and Isophyllia sinuosa). Besides the greater depth, this part of the hardground platform had finer sediments which were suspended by wave action to produce greater water turbidity near the bottom. Juvenile recruitment was seen on all transect lines.

Flora and Fauna In general, all sites were characterized by the dominance of two invertebrate groups: gorgonians and sponges (Table 3; Figure 10). The species composition of the gorgonians, notably the presence of species like Muricea, Eunicea and Pterogorgia is indicative of an environment with strong hydrodynamics and low topographic relief with potential strong sediment transport regimes (Figure 11). Sponges also showed growth pattern (e.g. more encrusting vs. erect) that was indicative of strong hydrodynamics. Table 3. Pooled abundances of major groups

LK N LK S LK E LK W SR E SR W CR E CR WGorgonians 0.66 0.03 1.08 0.82 1.65 1.07 8.67 7.29

Sponges 0.94 0.14 0.85 1.05 1.18 1.52 3.87 2.27

Crustose Coralline Algae 0.07 1.47 0 0 0 0 0 0

Pooled species abundances

02468

10

LKN

LKS

LKE

LKW

SRE

SRW

CRE

CRW

survey sites

%co

ver Gorgonians

SpongesCCA

Figure 10. Pooled species abundances for the transects

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Figure 11. Rock knob with soft flora & fauna near transect LK1N. The soft flora & fauna are generally restricted to rock attachment substrate.

The most abundant gorgonian species were members of the genus Pseudopterogorgia, whereas Ampimedon compressa and Iotrocha birotula dominated the sponge fauna on most sites (Table 4).

The transects CR east and CR west had by far the highest abundance of both Gorgonians and Sponges. Sites SR-E and SR-W had slightly higher cover than the four sites at LK. However, the height of gorgonians was substantially larger at sites at SR than at the LK sites. The four sites at LK had the lowest abundance and the smallest sizes of species. Within the transects around the leak area, LK-N and LK-S had the lowest abundance of species with LK-S standing out as the site where sponges and gorgonians were close to absent.

The low cover at LK north and LK south can partially be explained by the substrate type, which only in these two sites essentially consisted of unconsolidated rubble. This makes it very difficult for sessile organism to colonize. It is probably for this reason that these sites were the only ones where Crustose Coralline Algae (CCA) were found covering part of the rubble. As slow growing species, they normally cannot compete against macro algae or algal turfs. The fact that they occur in this environment is due to the inability of sessile species to colonize the rubble. Site LK-S had less rubble than LK-N but nonetheless substantially lower abundances of gorgonians and sponges.

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Table 4. Soft flora and fauna on the transect lines.

transects LK N LK S LK E LK W SR E SR W CR E CR W Species Erythropodium caribaeorum 0.12 0 0.17 0.07 0.55 0.15 3.5 2.15 Plexaura homomalla 0 0 0 0 0 0.02 0 0 Plexaura flexuosa 0 0 0 0.09 0.05 0.09 0 0 Pseudoplexaura sp. 0.02 0.01 0.54 0.28 0.05 0.06 0.05 0.05 Eunicea sp. 0.03 0 0.07 0.16 0.12 0.03 0.09 0.11 Plexaurella sp. 0 0 0.03 0 0 0 0 0.04 Muricea sp. 0.2 0 0.09 0.12 0.26 0.25 0.52 0.25 Pseudopterogorgia americana 0.06 0 0.09 0.02 0.38 0.33 2.9 2.65 Pseudopterogorgia acerosa 0.04 0 0 0 0 0 0.1 0.2 Pseudopterogorgia bipinnata 0.17 0 0.03 0.05 0.18 0.03 0.33 0.16 Pterogorgia sp. 0 0.02 0.03 0 0 0 0 0 Gorgonia ventalina 0.01 0 0.03 0.02 0.06 0.11 0.83 0.33 Gorgonia mariae 0.01 0 0 0.01 0 0 0 0 Amphimedon compressa 0.11 0.06 0.16 0.15 0.27 0.22 0.46 0.37 Aplysina fulva 0.06 0.02 0.05 0.03 0.05 0 0.42 0 Ircinia strobilina 0 0 0 0 0 0.2 0.16 0 Ircinia felix 0.05 0.03 0.5 0.07 0.05 0.5 0 0 Callyspongia vaginalis 0 0 0.04 0 0.06 0.4 0 0 Iotrocha birotula 0.02 0.03 0.02 0.38 0.13 0.09 0.58 0.5 Cinachyra sp. 0 0 0 0 0 0 0.3 0 Calyx podatypa 0 0 0 0 0.12 0 0 0 Holopsamma helwigi 0 0 0 0 0 0 0.48 0.45 Tedania ignis 0 0 0 0 0.18 0.07 0.5 0.55 Strongilacidon sp. 0 0 0 0 0 0 0.09 0.05 Clathria sp. 0 0 0 0 0 0 0.15 0.31 Halisarca sp. 0.42 0 0.06 0 0 0 0 0.04 Mycale laevis 0.02 0 0 0 0.05 0 0.28 0 Chondrilla nucula 0 0 0.02 0 0.1 0 0 0 Raphidophlus juniperinus 0.04 0 0 0.04 0.05 0 0.15 0 Cliona langae 0.04 0 0 0 0 0 0 0 Xestospongia muta 0 0 0 0.38 0.2 0.03 0.3 0 Eudistoma sp. 0 0 0 0 0 0 0.04 0 Clavelina puerto Ricensis 0 0 0 0 0.02 0.01 0.12 0.05 Udotea sp. 0 0.19 0 0 0 0 0 0 Caulerpa sp 0 0 0 0.02 0 0 0 0 Halimeda copiosa 0 0 0 0.11 0.3 0 0.15 0.02 Palythoa grandis 0 0 0 0 0.15 0.4 0 0.5 Millepora alcicornis 0.03 0 0.05 0 0.09 0.19 0 0 red algae unident. 0 0 0 0.3 0 0.2 0 0 CCA 0.07 1.47 0 0 0 0 0 0 Spirobranchus giganteus 0 0 0 0.02 0 0 0 Rubble w algal turf 100 83.5 0 0 0 9.6 0 0 Hardground w algal turf 0 9.5 81 64.4 96.3 89.5 88.5 68.5 Sand 0 7 19 35.6 3.7 0.9 11.5 31.5

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Statistical analysis of changes 1993 to 2002 Data for the leak site

Modified table 2.

location dept

h (m

)

tota

l cor

al c

over

Mon

tast

raea

ann

ular

is

Mon

tast

raea

cav

erno

sa

Agar

icia

aga

ricite

s

Porit

es a

ster

oide

s

Side

rast

rea

side

rea

Dip

loria

stri

gosa

Dip

loria

cliv

osa

Mad

raci

s de

cact

is

Dic

hoco

enia

sto

kesi

i

Cardona Ridge '93 8 4.0 1.0 1.4 1.5 0.1 0.1 t

Cardona Ridge east 9 1.9 0.6 0.5 0.5 0.2 0.1 0.1

Cardona Ridge west 9 1.3 0.6 0.5 0.1 0.0 0.1

LKt1N 13 2.0 1.4 0.0 0.6

LKt2E 13 0.7 0.4 0.0 0.2 0.0

LKt3S 13 0.3 0.3

LKt4W 13 0.3 0.2 0.1

Outer Ridge '93 10 2.3 0.2 1.2 0.2 0.1 0.5 0.2 Outer Ridge east 9 2.2 0.9 0.1 0.3 0.1 0.8 0.1 0.0 0.0 Outer Ridge west 9 2.1 0.1 0.6 0.1 0.6 0.2 0.6 0.0 0.0

Statistical comparisons between transects from the same site. These statistical tests were designed to establish the differences or similarities between neighboring transects located at the same site. The cover by species obtained from each quadrant was transformed to normalize the data using the arcsine of the species cover. Variability in the cover of coral species present was compared between the two east-west transects at the CR and SR sites and the four north-south, east-west transects at the LK site to determine if significant differences were present (Table 5). The statistical analysis used to perform this test was a one-way factorial ANOVA (Analysis of Variance). Only three significant tests (at 95% significance level) were obtained, one per site. These results suggest that most coral species do not change in a significant way between adjacent transects, and that the differences in coral cover magnitude observed in the graphs are caused by natural variations of coral populations. Since the analysis reflects high similarities between adjacent transects, it is reasonable and safe to pool the data from the different transects at each site and use it together as a representation for the whole site.

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Table 5. Coral Species Cover Comparisons WITHIN sites (one-way ANOVA).

Coral Species CR east v. west SR east vs. west LK t1 vs. t2 vs. t3 vs. t4

Montastraea cavernosa not-significant test not-significant test not-significant test

Agaricia agaricites not-significant test no-tsignificant test not-significant test

Porites asteroides significant test not-significant test not-significant test

Siderastrea siderea not-significant test not-significant test not-significant test

Diploria strigosa not-significant test not-significant test not-significant test

Diploria clivosa not-significant test significant test not-significant test

Madracis decactis not-significant test not-significant test not-significant test

Dichocoenia stokesii not-significant test not-significant test significant test

The specific results (tables) of the ANOVA analysis are included in the Appendix.

Statistical comparisons between sites. Coral species diversity was compared among all sites studied (CR, SR, and LK). For this comparison the Shannon-Weaver Diversity Index (H') and Evenness Index (J') were used. Diversity indices can be useful in the identification high diversity or low diversity areas. Comparisons between low and high diversity areas can help us to better define environmental factors that affect coral populations. The majority of diversity measures are generally aimed at species diversity and based on the principal of discretely countable units. Ecologists use the concept of diversity to characterize species abundance relationships in communities. (What is a community?) There are many ways of describing diversity. Essentially, it has two components:

• species richness, or the number of species, and • evenness, or how abundance data are distributed among the species concerned.

One problem with counting the number of species as a measure of diversity is that rare and common species are treated alike. Community 1 may have 50 individuals of species A and 50 individuals of species B, whereas community 2 may have 99 individuals of species A and 1 individual of species B. The first community is intuitively more diverse than the second, yet both have the same number of species. The Shanon-Wiener (also called Shannon-Weaver) index (H') includes both species number and evenness, where a greater number of species increases diversity, as does a more equitable distribution of individuals among species. For this reason, the Shannon-Weaver index (Shannon and Weaver 1949) is widely used for diversity studies. The number obtained varies from 0 for communities with only a single taxon to high values for communities with many taxa, (entropy). Where there is absolute diversity the Shannon-Weiner Diversity Index is equal to1.00. The index considers both the number of species and the distribution of individuals among species. For a given number of species, the largest value of H’ results when every individual belongs to a different species allowing in this way for a relative measure of diversity. The value of H' itself doesn't mean much, but when comparing H' between habitats, it measures the diversity of one habitat in comparison to another.

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H’ is a more reliable measure as sampling size increases, so the addition of the calculation of evenness (J’) is often applied. Evenness (J’) is a measure of the similarity of different species. When there are similar proportions of all species then evenness is one, but when the distribution is very dissimilar (some rare and some common species), then the value decreases. In other words, J' can have a maximum of 1 (unity) but lower values indicate a less evenly distributed coral fauna.

H' max is the maximum diversity possible on a given reef based on the total number of species observed, and would occur only if all species were represented by the same total number and size of individuals [H' max = natural lognumber of species].

For this analysis, a modified form of the Shannon-Weaver diversity index, which uses number of species and cover (i.e. size) frequency data determined from photoquadrats (H'c) by the following equation:

H'c= -SUM(Pi*lnPi) Pi= Ci/C = cover of corals belonging to the ith species/total cover The test measures the order (or disorder) observed within the studied system. The order is characterized by the number of individuals observed for each species.

The evenness index (J') was calculated for H'c using H'max= ln (# species) by the equation: J'=H'/H' max Table 6. Shannon-Weaver diversity index (H’c) for coral species in all sites

Coral Species CR site SR site LK site Montastraea annularis - 0.1450 - Montastraea cavernosa 0.3569 0.3662 0.2158 Agaricia agaricites 0.3675 0.1450 - Porites asteroides 0.3384 0.3159 Siderastrea siderea 0.1973 0.2239 0.2599 Diploria strigosa - 0.3159 Diploria clivosa 0.1973 0.2780 0.3466 Madracis decactis 0.1973 - - Porites porites - - - Dichocoenia stokesii - - -

0

0.1

0.2

0.3

0.4

H'c LK site

SR site

CR site

Figure 12. Shannon-Weaver diversity index (H’c) for coral species in all sites

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Table 7. Analysis of Variance (ANOVA) comparing the Shannon-Weaver diversity index (H’c) for coral species at all sites

DF: Sum Squares: Mean Square: F-test:2 .069 .034 1.78521 .404 .019 p = .192423 .473

Source:Between groupsWithin groupsTotal

Model II estimate of between component variance = .002

Comparison: Mean Diff.: Fisher PLSD: Scheffe F-test: Dunnett t:

CR vs. SR -.017 .144 .03 .244

CR vs. LK .104 .144 1.126 1.501

SR vs. LK .121 .144 1.521 1.744

Table 6 and Figure 12 show the Shannon-Weaver diversity index (H’c) for the coral cover for the species present in the Ponce sites surveyed during October of 2002. H’c in the Cardona Ridge (CR) site ranged from 0.1973 to 0.3675; from 0.1450 to 0.3662 in the Self Ridge (SR) site; and from 0.2158 to 0.3466 in the Leak (LK) site. Ranges of the Shannon-Weaver diversity index at the CR and SR sites show more similarities in coral cover order (lower index) relative to the LK site with higher disorder (higher index). Only three coral species were common to all three sites: Montastraea cavernosa, Siderastrea siderea, and Diploria clivosa. Montastraea cavernosa has similar H’c in the CR and SR sites showing a higher index (coral cover disorder) relative to a lower index in the LK site (coral cover order). Shannon-Weaver diversity index for Siderastrea siderea varied from low at CR (coral cover order) to high at LK (disorder). The H’c of Dpc is lowest at the CR site, indicating high order in the cover, and highest at the LK site indicating species cover disorder. The data show that not only the LK site has much fewer species of coral present than the other two sites (i.e. different coral species distribution), but also has a higher Shannon-Weaver diversity index, in most cases, relative to the other sites (coral cover disorder in the system).

Regardless of the differences in H’c between the CR, SR sites and the LK site the ANOVA analyses (Table 7) revealed a not-significant variance in the H’c indices between the three sites at 95 % confidence. However, the probability obtained for the ANOVA test (p=.1924) is low indicating that the variance between the sites is high and very close to being significant (p=.05). The Dunnett t-test and Scheffe F-test (Table 7) also show the similarity between the CR, SR sites versus the LK site. Table 8. Evenness index (J’) for coral species in all sites

Coral Species CR site SR site LK site Montastraea annularis - 0.0660 - Montastraea cavernosa 0.1834 0.1667 0.1204 Agaricia agaricites 0.1889 0.0660 - Porites asteroides 0.1739 0.1438 - Siderastrea siderea 0.1014 0.1019 0.1451 Diploria strigosa - 0.1438 - Diploria clivosa 0.1014 0.1265 0.1934 Madracis decactis 0.1014 - - Porites porites - - - Dichocoenia stokesii - - -

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0

0.05

0.1

0.15

0.2

J' LK site

SR site

CR site

Figure 13. Evenness index (J’) for coral species in all sites

Table 9. Evenness index (J’) for coral species in all sites



Model II estimate of between component variance = 8.978E-5

Comparison: Mean Diff.: Fisher PLSD: Scheffe F-test: Dunnett t:

CR vs. SR .004 .075 .008 .125

CR vs. LK .049 .075 .932 1.365

SR vs. LK .044 .075 .77 1.241

Table 8 and Figure 13 show the Evenness Index (J’) for the coral species present in the Ponce sites surveyed during October of 2002. Coral species J’ index in the CR site ranged from 0.1014 to 0.1889; from 0.0660 to 0.1667 in the SR site; and from 0.1204 to 0.1934 in the LK site. Large differences were not found in the range of Evenness indexes among the LK, CR, and SR sites. They are all low in the evenness distribution of coral fauna. However, differences were present when individual species are considered. Only three coral species were present t the three sites: Montastraea cavernosa, Siderastrea siderea, and Diploria clivosa. Montastraea cavernosa has a lower J’ index or less evenly distributed coral fauna t the LK site relative to the CR and SR sites. For Siderastrea siderea and Diploria clivosa, the Evenness Index is lower t CR and SR, relative to LK. These data suggest that the species have a more evenly distributed fauna than at the LK site. The J’ index supports the conclusions obtained from the H’c index indicating similarities between CR and SR sites and differences between these two sites and the LK site.

Regardless of the differences in J’ between the CR, SR sites and the LK site, the ANOVA analysis (Table 9) revealed a not-significant variance in the J’ indices among the three sites at 95 % confidence. However, the probability obtained for the ANOVA test (p=.3389) is low, indicating that the variance among the sites is high, and very close to being significant (p=.05). The Dunnett t-test and Scheffe F-test (Table 5) also show the similarities between the CR, SR sites vs. the LK site. The magnitude of the

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variability in the evenness index for all the sites is lower (p=.3389) than the variability in H’c between the sites, indicating more similarities in the evenness of the coral populations and less similarities in the coral cover.

Statistical analysis of changes between 1993 and 2002 in the Cardona (CR) and Shelf Ridge (SR) Reefs

Coral species Shannon-Weaver Diversity Statistics (H') and Evenness Indices (J') were compared for the Cardona Ridge and Outer Shelf Ridge sites for the years 1993 and 2002 to determine if significant changes have occurred in the populations of coral species present in these reefs during the last nine years. Positive or negative changes in the coral cover can give insights to changes in the environment that could have affected these coral populations. Table 10. Shannon-Weaver diversity index (H’c) for coral species in CR and SR sites at 1993 and 2002

Coral Species CR 1993 CR 2002 SR 1993 SR 2002

Montastraea annularis 0.3417 - 0.2124 0.1450 Montastraea cavernosa 0.3662 0.3569 0.3394 0.3662 Agaricia agaricites 0.3677 0.3675 0.2124 0.1450 Porites asteroides 0.0890 0.3384 0.1363 0.3159 Siderastrea siderea 0.0890 0.1973 0.3318 0.2239 Diploria strigosa - - - 0.3159 Diploria clivosa - 0.1973 - 0.2780 Madracis decactis - 0.1973 - - Porites porites 0.1450 - - - Dichocoenia stokesii - - - -

0

0.1

0.2

0.3

0.4

H'cSR 2002

SR 1993

CR 2002

CR 1993

Figure 14. Shannon-Weaver diversity index (H’c) for coral species in CR and SR sites at 1993 and 2002

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Table 11. ANOVA analysis of the Shannon-Weaver diversity index (H’c) for coral species in the CR site between 1993 and 2002

DF: Sum Squares: Mean Square: F-test:1 .003 .003 .13218 .447 .025 p = .720619 .451


Model II estimate of between component variance = -.002Comparison: Mean Diff.: Fisher PLSD: Scheffe F-test: Dunnett t:

1993 vs. 2002 -.026 .148 .132 .363

Changes were detected in the coral population and the H’c index of the Cardona Ridge site from 1993 to 2002 (Table 10 and Figure 14). The Montastraea annularis and Porites porites species are not present in the transects measured during October, 2002. They also were not detected by visual inspection of the area, suggesting that they disappeared as part of the reef species composition at Cardona Ridge. The coral cover of Porites asteroides and Siderastrea siderea increased in disorder from 1993 to 2002 (higher H’c index). Species that are known to be tolerant of adverse environments ( Diploria clivosa and Madracis decactis) were absent in 1992 but are present in 2002. The analysis of coral cover distribution suggests that the Cardona Ridge has been negatively affected since 1993.

Regardless of these changes in species composition and H’c index, the ANOVA analysis suggests that these changes are part of the normal variability of the reef system since the probability obtained for the variance test (Table 11) was reasonably high (p=.7206).

In the case of the Outer Shelf Ridge, the changes in the coral cover do not seem to follow any trend (Table 10 and Figure 14). Coral cover disorder (H’c) decreased for three of the species present (Montastraea annularis, Agaricia agaricites, and Siderastrea siderea) and increased for two of them (Montastraea cavernosa and Porites asteroides). These changes in cover order/disorder of specific corals are not related to the corals species documented tolerance to adverse conditions. Two new species were present in the 2002 surveys that were not detected in the area during the 1993 surveys (Diploria strigosa and Diploria clivosa). Overall the statistical analyses do not indicate positive or negative trends in the coral species populations and the changes seem to be caused by natural random reef variations. Table 12. ANOVA analysis of the of the Shannon-Weaver diversity index (H’c) for coral species in the SR site between 1993 and 2002



Model II estimate of between component variance = .001Comparison: Mean Diff.: Fisher PLSD: Scheffe F-test: Dunnett t:

1993 vs. 2002 -.08 .136 1.639 1.28

This conclusion is supported by the ANOVA analysis of changes in H’c between 1993 and 2002. The not-significant result (p= .2247) suggests that the changes between 1993 and 2002 are part of the normal changes in coral cover of a coral community.

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Table 13. Evenness index (J’) for coral species in CR and SR sites at 1993 and 2002

Coral Species CR 1993 CR 2002 SR 1993 SR 2002

Montastraea annularis 0.1643 - 0.0886 0.0660 Montastraea cavernosa 0.1761 0.1834 0.1416 0.1667 Agaricia agaricites 0.1768 0.1889 0.0886 0.0660 Porites asteroides 0.0428 0.1739 0.0569 0.1438 Siderastrea siderea 0.0428 0.1014 0.1384 0.1019 Diploria strigosa - - - 0.1438 Diploria clivosa - 0.1014 - 0.1265 Madracis decactis - 0.1014 - - Porites porites 0.0697 - - - Dichocoenia stokesii - - - -

0

0.05

0.1

0.15

0.2

J'SR 2002

SR 1993

CR 2002

CR 1993

Figure 15. Evenness index (J’) for coral species in CR and SR sites at 1993 and 2002

Table 13 and Figure 15 show the Evenness Index (J’) for the coral species present in the CR and SR sites surveyed in January, 1993 versus October, 2002. Coral species J’ index in the CR site increased by different levels of magnitude for all species counted in the survey. This indicates an increase in the evenness of the coral cover by species during the last nine years and suggests as stabilization of the reef environment. Two species (Montastraea annularis and Porites porites) present in the 1993 survey were absent in 2002. These two species have been proven to be sensitive to adverse changes in the reef environment. Two species were present in the 2002 surveys but absent in 1993 (Diploria clivosa and Madracis decactis). These species are resistant to stress levels in the reef suggesting deterioration of the reef environment since 1993. Table 14. ANOVA analysis of the Evenness Index (J’) for coral species in the CR site between 1993 and 2002

DF: Sum Squares: Mean Square: F-test:1 .002 .002 .28816 .098 .006 p = .598717 .099


Model II estimate of between component variance = -4.823E-4Comparison: Mean Diff.: Fisher PLSD: Scheffe F-test: Dunnett t:

1993 vs. 2002 -.02 .078 .288 .537

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The analysis on the variations in J’ index between 1993 and 2002 at the CR site (Table 14) indicates that the changes present are part of the normal variations of reef evenness in a coral population since the ANOVA test was not-significant (p=.5987).

The changes in coral species evenness (Table 13 and Figure 15) at the Outer Shelf Ridge seem to be smaller in magnitude relative to the ones present at the Cardona Ridge. Most of the species show very similar J’ indexes between 1993 and 2002 with the exception of Porites asteroides that increased since 1993, suggesting a more even distribution for Porites asteroides. The ANOVA analysis (Table 15) resulted as not-significant, supporting this conclusion. However, the probability obtained in the analysis was low (p=.133), suggesting that the variability in evenness is high and close to being significant. Table 15 ANOVA analysis of the Evenness Index (J’) for coral species in the SR site between 1993 and 2002



Model II estimate of between component variance = .001Comparison: Mean Diff.: Fisher PLSD: Scheffe F-test: Dunnett t:

1993 vs. 2002 -.043 .058 2.598 1.612

Coral health analysis About 60 close-up photographs of coral were available. These were observed and analyzed for color, signs of bleaching, algal competition, and coral disease. Twenty-two of these photographs were selected from the three sites surveyed October 2002 to include in Plates 1 – 3. At least one of each species found on the hardground platform is included in the plates. At all three sites, the coral was relatively free of algal overgrowth. Perhaps 10 percent of the colonies showed some overgrowth and/or loss of surface area. Visual observations during the field program agreed with this. There was no apparent difference in the condition of the coral from the three different sites: Cardona Ridge, Leak Site, Outer Ridge. No coral bleaching was seen and no diseased corals were observed in October. Only one occurrence of the sponge Cliona was seen (Figure 17). The character of the coral in plates 1 – 3 is discussed in Table 16. Figure 17. Cliona has killed large areas of coral in the clear waters of La Parguera, Desecheo and Mona; but in turbid waters like Mayagüez and Ponce, it is very rare.

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Table 16. Analysis of the coral health for the October 2000 sites

Coral figure

Alg

al o

verg

row

th

Col

or

Col

ony

loss

comments

Agaricia agaricites 4 3 5 Color loss does not seem to be bleaching, cause undetermined. Algal overgrowth only at edges

Agaricia agaricites 5 5 5 Excellent condition Agaricia agaricites 5 5 5 Excellent condition, algae at edges has not advanced Colpophyllia natans 5 5 3 Remaining coral is in good condition, but progressive loss of

colony, cause unknown Dichocoenia stokesii 5 5 5 Diploria clivosa 5 5 3 Remaining coral is in good condition, but progressive loss of

colony, cause unknown Diploria strigosa 5 5 5 Diploria labyrinthiformis 4 4 5 Algae is covering part of the colony, coral has under saturated

color Isophyllia sinuosa 5 5 5 Madracis decactis 5 5 5 This coral is often found in low light environments Meandrina meandrites 5 5 5 Montastraea annularis 5 5 5 Very little Montastraea annularis at these sites; usually the

dominant coral on Caribbean reefs, but reduced drastically in high sediment influx environments

Montastraea cavernosa 5 5 5 This is the most common species at the sites Montastraea cavernosa 4 4 5 Algal overgrowth at edges, color slightly under saturated Montastraea cavernosa 5 5 5 Mycetophyllia 5 4 5 Light areas may be fish bites Porites asteroides 5 5 5 This species is very active in colonizing the survey sites and the

rubble zone Porites asteroides 5 5 5 Porites porites 5 5 5 Siderastrea siderea 3 5 5 Algal overgrowth extend over colony Siderastrea siderea 5 5 5 Small colonies of this species are very common at all sites Siderastrea siderea 5 5 5

Transect photographs from the 1993 surveys of Cardona Ridge and the Outer ridge were used to examine the health of corals in the area 10 years ago (Plate 4; Table 17).

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Table 17. Analysis of the coral health for the 1993 survey sites – 1 = very poor 5 = very good

Coral figure

Alg

al

over

grow

th

Col

or

Col

ony

loss

comments

Agaricia agaricites 5 5 5 Colpophyllia natans 5 5 5 Excellent condition Colpophyllia natans 5 5 5 Montastraea cavernosa 4 5 5 Slight algal incursion from one edge Montastraea cavernosa 5 5 5 Porites asteroides 5 3 5 Color loss, may be bleaching Siderastrea siderea 5 5 5

Coral in the present environment and in that of 1993 show no apparent difference in condition. Personal observation is that conditions are about the same as described by Acevedo, et al. (1989). The remaining coral on the platform seem to have made an adjustment to the sediment influx (Figure 18).

Figure 18. Relation of coral cover to terrigenous sediment influx – low cover at Baja Tasmanian, Cardona and Ratones reefs.

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Discussion of the rubble zone at all sites At each site, the rubble zone was located so that we could position our transects. The rubble zone at the outer ridge and at Cardona ridge had large boulders (Figures 19, 20, 21 – plate 5) and the pipe was partly exposed (Figure 22 – plate 5). The rubble fill at the leak site was much smaller (gravel to cobble size) and uniformly spread (Figure 23 – plate 5). Only the inspection chamber was exposed (Figure 24 – plate 5). The leaks were seen within a couple of meters north and south of the chamber (Figure 25 – plate 5).

The most striking feature in the rubble zone was the high rate of coral recruitment (plate 6). The most common coral recruits were Porites asteroides and Siderastrea siderea, but Diploria clivosa, Agaricia agaricites and Montastraea cavernosa were also present. The boulder area had a heavy growth of new soft coral and gorgonians (Figure 26).

Figure 26. Soft flora and fauna growth on the rubble boulders.

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Conclusions The area of investigation is not a coral reef environment. Coral cover at all sites on the platform was less than four percent. Individual clumps of coral form knobs on the surface, but even these have low percentages of living coral (Figure 27).

Figure 27. Outer Shelf Ridge. Knob on the hardground surface is covered with Palythoa.

Results from the coral cover transects are very similar for the 1993 and 2002 surveys. Although the surveys were not conducted in the same locations (original surveys were in what is now the rubble zone), the transects in October 2002 are similar to the 1993 survey. Both the species present and the percent of cover are about the same at the Outer Ridge Site. At the Cardona Ridge, the species making up the cover are the same group, but total cover was 4% in 1993 and only 1.6% in 2002. This difference is probably caused by the patchy distribution of coral colonies on the hardground, and the clumping of the colonies that do occur. Only three significant tests (at 95% significance level) were obtained, one per site. These results suggest that most coral species do not change in a significant way between adjacent transects and that the differences in coral cover magnitude observed in the graphs are caused by natural variations of coral populations.

No Montastraea annularis were present in the 2002 survey, but several colonies were seen near the transect lines. The other principal components of the cover, Montastraea cavernosa and Agaricia agaricites were encountered in less percentage in the 2002 surveys. Colonies of the three species were in good condition, showing no decline due to increased adverse conditions.

Coral cover at the leak site was lower that on the two ridges. Two factors probably contributed to this: • greater depth (13 m compared to 9 m) • higher turbidity on bottom.

Both Montastraea annularis and Agaricia agaricites were not encountered in the transects and were very rare in the near-transect area.

Coral health conditions showed – good color, no bleaching, very little algal overgrowth, no disease and low general Cliona incursion. Comparison of the 1993 and the 2002 photos of coral showed colonies in about the same general condition.

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Juvenile recruitment is considered to be an important aspect of continuing survival of reef environments. Recruitment at the three sites seemed to be normal as compared to the better reef areas in Puerto Rico. Coral recruitment (Porites asteroides, Siderastrea siderea, Diploria) is good in the hardground, also good in the rubble zone, despite low coral cover.

Effluent from the leak seems to be diffusing upward, with no appreciable effect on the coral or other flora and fauna. There has not been an increase in algal abundance like that seen at Mayagüez in the Sea Grant Reef Study.

Secchi disk measurements were made on all three days. The values were 10-11 meters at all sites. Bottom visibility was much less at the leak site than the two ridges. Wave action was suspending fine sediment present at this site, but not at the ridges.

References 1. Acevedo, Roberto, Jack Morelock, and R. A. Olivieri. 1989. Modification of coral reef zonation

by terrigenous sediment stress. Palaios 4: 92-100.

2. Beach, David K. 1975. "Sedimentation on the Western Island Caja de Muertos Insular Shelf, Puerto Rico." master's thesis, University of Puerto Rico RUM.

3. Beach, David K., and James V. A. Trumbull. 1981. Marine Geologic Map of the Puerto Rico Insular Shelf, Isla Caja de Muertos Area, U.S. Geological Survey, Washington, D.C..

4. Done, Terence J. 1992. Constancy and change in some Great Barrier Reef coral communities: 1980-1990. Amer. Zool. 32: 655-62.

5. Knowlton, Nancy, Ernesto Weil, Lee A. Weight, and Hector M. Guzman. 1992. Sibling species in Montastraea annularis, coral bleaching, and the coral climate record. Science 255: 330-333.

6. Morelock, Jack. 1990. Interpretation of coral reef cover and survey techniques. annual meeting American Assoc. Petroleum Geologists, Abstr.

7. Morelock, Jack, Wilson Ramirez, Andy Bruckner and Milton Carlo. 2001. Status of coral reefs, southwest Puerto Rico. Caribbean Journal of Science, Online Special Publication 4: 57 p.

8. Shannon, C. E. and W. Weaver. 1949. The mathematical theory of communication. University of Illinois Press, Urbana

9. Trias, Juan L. 1991. Marine Geologic Map of the Puerto Rico Insular Shelf, Guanica to Ponce Area, U.S. Geological Survey, Washington, D.C..

10. Weinberg, Steven. 1981. A comparison of coral reef survey methods. Bijdragen Tot De Dierkunde 51, no. 2: 199-218.

Appendices Coral transect photo sets – 10 images each transect plus close-up photographs

Coral colony and Flora and fauna photographs

PDF version of report

Video transects and general scenes with log

Flora & Fauna counts

Coral cover statistics

Daily work logs

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Documents

Ponce Coral Reef Surveys - Geology