Restoration of a Cayman Reef

Jack Morelock and Walter Jaap




On 12 January, 1996, a cruise ship accidentally struck portions of Soto's Reef off George Town, Grand Cayman Island, British West Indies. The incident was the result of a winter storm that dislodged the ship's anchor. The vessel was restricted in maneuvering because of other vessels in the anchorage and strong offshore winds. The ship's hull struck portions of the reef mass, dislodging and crushing reef formations as it maneuvered out of the harbor. A survey by the Cayman Islands Department of the Environment (DOE) quantified the damage at approximately 7,500 ft2, 967 m2 (based on aerial photogrammetry). The damage was in the depth range of 15 to 50 ft (4.6 to 15.2 m). Damages included abrasion from the ground tackle, dislodged coral formations , and a large crushed area where the hull came down hard on the reef.

Soto's Reef, one of the better known dive sites on Grand Cayman, lies within the Cayman Islands Coral Reef Park. The area is visited by thousands of divers and snorkelers annually, because the relatively shallow depth (less than 30 ft.; 10 m) provides an excellent dive site for novices to view coral reef marine life.

Reef Restoration Program

After a reconnaissance of the grounding site, the consultants met with the DOE to propose and develop a restoration plan that included removing rubble, salvaging and transplanting dislodged corals, and moving large coral formations back onto the reef.

The goals established were:

Work began in late January, within weeks of the incident. To facilitate an orderly restoration and record keeping, the area of damage was divided into three work zones.






















































Rubble was removed from the reef surface and put into piles on the sand surface below the reef. Coral was collected separate from the rock rubble and placed in crates to be used later in the reconstruction.

Approximately 15 large reef boulders, more than 50 medium sized boulders, and about 100 small boulders were moved back onto the cleared reef platform using lift bags . These reef boulders and smaller pieces of limestone that were salvaged were used to construct three-dimensional relief in areas where the vessel's hull had flattened the reef profile.

After the boulders and coral were removed, winter storm surges cleaned the sediments from the bare reef surface. Without this we would have had to use air lifts.

The movement of large blocks was accomplished using the buoyant force of air within lift bags to raise the mass and move it to a position that we deemed most appropriate. Some structures were moved into position in the large scarred areas. Very large structures were turned to their upright orientation, but were not moved.

The most time-consuming effort was re-attaching salvaged coral colonies back onto the reef or to the boulders. The base of the coral and the substrate was cleaned with a wire brush. We used an underwater epoxy material (Liquid Rock 500) with an applicator that mixes and dispenses the epoxy . In wave surge areas, we used a pneumatic drill to drill a 1/4 inch hole in the bottom of the coral and the substrate, (one to two inches deep). Stainless steel rod was used with epoxy to serve as an anchor to keep the coral in place. Epoxy was applied to the base of the coral and or the reef substrate, and the coral was pressed onto the substrate. The coral cover in undamaged areas was estimated at 20 to 30 percent living coral (surveys reported here give more information) and in the restoration, we tried to achieve 15-20% cover in critical areas.

The coral on restored areas had a very realistic reef appearance. All areas of re-attachment were tested by hand, and any coral that could be broken off was glued again.

Restoration Monitoring Program

This project was the largest attempt ever made to restore a reef immediately following a vessel grounding and monitoring the results is important for future considerations. The monitoring project was intended to answer the following questions:

Status and trends monitoring is the best way to determine the success of any restoration. This approach should provide answers to the questions previously posed. Monitoring coral reefs through time is a proven method to document the dynamics of community structure. In this case, monitoring will evaluate the success of transplanting corals, building structures, and replacing the large masses that were dislodged by the accident

Monitoring Methods

Damage and restoration in zones one and two is characterized as spatially separated patches. Zone three was a large relatively uniform scarified area; most of the damage occurred in zone three. We divided the monitoring into tasks relating to specific restoration.

Coral health and vitality: Photographic analysis of individual coral colonies

A 35 mm Nikonos camera, with a 35 mm lens, Ikelite M-50 strobe (50 Watt seconds of power), and the Nikonos "close-up" accessory lens were used to photograph corals in the areas where the transplanting occurred and in adjacent undamaged areas (zones one, two, and three). The photos were taken haphazardly in order to have several photographs of the typical species found in the local area. The photograph print size is four by six inches (152 cm2) and the actual coverage area of the coral in the photo was reduced by a magnification ratio of 0.93 based on a reference scale in a photograph. Thus the coverage in a photo was approximately 141 cm2. Corals were the principal focus of this photographic sampling.

Each photo was assessed based on color, signs of bleaching, algal competition, and coral disease. 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 ( 1 being the worst condition). In a similar manner, we scored bleaching conditions, algal competition, and disease. Sponge-coral competition was not seen in any of the photographs.

A transparent overlay with ten random points was superimposed over each photograph. The overlay had a border that defined the perimeter of the photograph and ten random points were positioned within the overlay border.

We tabulated the attributes in the photograph lying directly under the points. The number of points superimposed on an attribute divided by the total number of points multiplied by 100 is the percent contribution for that particular attribute. We computed the means and the standard deviation for each attribute by control and transplant site. We included coral, bleached corals, diseased corals, algae, sponges, and other (other includes bare rock, poorly illuminated areas in the photos, and micro-caverns). Results were compared statistically and graphically.

The statistical approach is that there is no difference in the survival and health of the transplanted corals compared to the adjacent populations. We used univariate, non-parametric tests and multivariate trend analyses to evaluate the status.

Evaluating coral cover using photo and video analytical methods

Coral cover is an important index of recovery. It is recognized as an important parameter in coral reef quality. Cover is the percentage of a unit area that is occupied by living coral. The corals that were transplanted replaced the corals lost due to the accident. By comparing the values of cover in the three damaged areas with adjacent undamaged areas, we can compare damaged versus non-damaged and evaluate recovery.

The transect sampling technique has been employed for a number of years. It is rapid, providing cover by species or the cumulative contribution by all species. Photographic assessment is rated as a good method to evaluate coral reef status. The method utilizes a 35 mm Nikonos camera with a 28 mm lens mounted on a vertical apparatus that has a fixed distance of 1.2 m from the reef surface. At this distance, each photo covers an area of 0.7 m2. We used 200 ISO print type color film and four by six inch prints. Following development, we measured the planar area (two-dimensional) of the living coral. The photograph is scanned into the computer and planimetry (digitizing the outline of the coral polygon using Jandel Sigma Scantm) defines the perimeter of the coral. Data are imported to a spreadsheet for statistical and graphic analyses.

Stability of large reef boulders that were moved

Approximately 15 large (greater than two meters in diameter) and more than 50 medium-sized boulders were lifted and moved from the sediment beds back onto the reef. The stability of the living coral surfaces that were shaded or partially buried were monitored by visual inspection and were documented with video recordings.

Recruitment of corals on the damaged area

Each of the monitoring stations (photo quadrat) was visually and photographically studied for settlement of juvenile corals. Settled corals are small, inconspicuous, and enigmatic to identify. We identified the juvenile corals to the best taxonomic resolution based on our experience and ability (species, genera, and family).

Field Operations

During our initial dives, we marked potential sampling stations with flagging tape. At the same time, we made general notes on the reconstruction and a video record of the three restored areas. We also took test photos and a video transect on the control station and across the large rubble pile. Following discussions with the DOE principals, we installed permanent sampling stations in the respective zones (restored and controls) that were located by GPS. Installation included drilling a hole in the reef framework and cementing a reference stake in the hole. The stake serves as an index mounting for the camera system (photo-quadrats) and a reference marker for the recruitment study.

Photo-quadrat stations were established in the three damage zones ( Zone One, Zone Two, Zone Three ), with nearby control stations for comparison. Each quadrat consisted of two photographs covering a planar area of 0.65 m2 taken 180o from each other and about 70 cm between the two photograph edges; the photo-quadrat composite area was 1.3 m2. Identification of coral species was made in the field, and that information was transferred to the prints when they were digitized. More than 600 coral colonies were measured from the 15 double photo quadrat stations in this study.

Sets of two companion stakes were installed in the restored and undamaged areas as terminal points for the video transects. The transects pass or bisect across the area of the photo stations. A tape measure was laid between the reference markers, and an 8 mm video camera was used to record a path along the tape measure. This provides a record for an area that is approximately 0.5 m wide for the length of the transect.

Results

Coral vitality

Table: Point-count analysis 1997

The sites are designated as Control (C) or Restored (R) and are shown on the zone maps.
The values are mean percent of cover

Mean coral cover in the photographs ranged from 38.9 percent to 58.5 percent.

Site Coral Algae Sponge Bleached
coral		 Diseased
coral		 Other
1C 39.0 36.0 7.4 0 0 17.7
1R 40.1 42.7 0 7.9 0 9.3
2C 58.5 23.6 0 7.5 0 10.3
2R 42.6 37.2 0 11.5 0 8.7
3C 41.1 29.6 7.1 7.1 0 15.1
3R 39.9 31.9 7.2 10.8 0 10.3

With the exception of zone two, the corals in the control and restored areas were very similar in all categories. The zone two control photographs exhibited a relatively higher percentage of coral and lower percentage algae compared to zones one and three. Perhaps the explanation is that the control for this area was in somewhat shallower depths and the corals generally were larger.

Table: Qualitative evaluation of coral vitality 1997

We scored the corals on a gradient of one to five in the photographs for color, bleaching, algal competition, and disease. A score of five was good to excellent, and a score of one was poor.

Site 1C 1R 2C 2R 3C 3R
number of photographs 32 34 33 35 35 37
number of species 13 12 15 7 13 8
color
mean 5 4.7 4.7 4.7 4.9 4.8
std.dev. 0 0.5 0.4 0.6 0.4 0.4
bleaching
mean 4.9 4.8 4.8 4.5 4.9 4.8
std.dev. 0.4 0.4 0.4 0.7 0.3 0.4
algal competition
mean 4.6 4.3 4.8 4.5 4.6 4.6
std.dev. 0.7 1.0 0.4 0.6 0.7 0.6
disease
mean 5 5 5 5 4.9 5
std.dev. 0 0 0 0 0.6 0

The conditions for the corals all scored relatively high, implying good vitality. All areas have statistical equivalency except for zone two control which had significantly higher coral cover than the other zones. The percentage of coral cover was about twenty percent higher in area two compared to the other areas The corals we transplanted are in similar condition to those that were not influenced by the grounding.

Evaluating coral cover using photo analytical methods

Zone 1 had one control station and two restored areas monitored. Cover for the control station and the restored monitor stations (averaged) was low with a loss of 3.2 percent of the 23.1 percent coral cover for the control. The two restored stations had 2.8 percent loss of the 9.4 percent cover that was present in July 1996.

Montastraea annularis was the most common coral in both control and restored areas.

Table: Percent coral cover in Zone 1 1996 to 1998.

values are percent of cover by coral
other species present: P. porites, S. siderea, A. cervicornis, M. decactis, E. fastigiata (less than 0.1%)

control 1 % cover 96 %cover 98 change
in cover		 restored
1 & 2		 % cover 96 % cover 98 change
in cover
M. annularis 16.5 16.0 -0.5 5.1 4.7 -0.4
M. cavernosa 1.3 1.4 +0.1
A. agaricites 3.9 1.7 -2.2 3.1 0.9 -2.2
P. asteroides 1.4 0.8 -0.6 1.2 1.0 -0.2
totals Jul-96 23.1 Jul-96 9.4
Jul-98 19.9 -3.2 Jul-98 6.6 -2.8

Zone 2 also has one control station and two monitor sites in the restored area. The control site showed a 0.4 percent reduction in the 12.2 percent cover that was present in 1996. Most of this loss was a loss of Agaricia agaricites colonies. The monitor sites in the restored area showed a 2.8 percent loss of coral cover from the in the 8.8 percent in July 1996.

Table: Percent coral cover in Zone 2 1996 & 1998.

values are percent of cover by coral
other species present: M. cavernosa, P. porites, F. fragum, C. natans (less than 0.1%)

control 1 % cover 96 %cover 98 change
in cover		 restored
1 & 2		 % cover 96 % cover 98 change
in cover
M. annularis 4.2 1.4 -2.8 3.7 2.6 -1.1
A. agaricites 3.3 0.3 -3.0 3.6 1.6 -2.0
P. asteroides 4.7 9.5 +4.8 1.5 1.8 +0.3
totals Jul-96 12.2 Jul-96 8.8
Jul-98 11.8 -0.4 Jul-98 6.0 -2.8

A winter storm produced major wave forces on the reef restoration area. Several large boulders (greater than 1 m diameter) were moved. Specifically the boulder containing station 7 restored in zone 3 and station 5 in zone 3 were moved. At station 7, the boulder was tilted almost 40 degrees. Quadrat 7b was photographed and evaluated, but quadrat 7a was out of position for the camera stand. Visual examination showed that the glued coral was still largely in position. The boulder of station 5 was turned and no photographs could be taken. The analysis of coral cover was made with quadrats 5a, 5b and 7a excluded.

The July 1998 quadrat survey showed only small changes in coral cover with the restored areas and control areas being relatively stable. Some of the coral colonies in both the restored and control areas continued to diminish in size, especially fragmentation of large Montastraea annularis heads . However some of these and other colonies show growth during the year between surveys. Zone 3 was the most affected by wave action, and many of the coral were moved or turned, but total cover changed only slightly. During each survey, there has been slightly different photo coverage because the stakes have flexibility and the position may not be in perfect register.

Table: Percent coral cover in Zone 3 1996 to 1998.

values are percent of cover by coral
other species present: Mycetophyllia sps, M. mirabilis, E. fastigiata, D. strigosa, S. siderea, M. cavernosa, P. porites, A. cervicornis, I. sinuosa (less than 0.1%)

control
3 sites		 % cover 96 %cover 98 change
in cover		 restored
6 sites		 % cover 96 % cover 98 change
in cover
M. annularis 19.7 15.0 -4.7 4.8 3.8 -1.0
A. agaricites 4.0 3.0 -1.0 2.8 2.0 -0.8
P. asteroides 0.8 0.4 -0.4 1.0 1.3 +0.3
totals Jul-96 24.5 Jul-96 8.6
Jul-98 18.4 -6.1 Jul-98 7.1 -1.5

Restored stations have less cover than the control stations. The results indicate that the coral cover is twofold greater in the control stations in area one; it is relatively similar in area two stations; and there is approximately a threefold difference in the control and restored stations (mean value) for area three. These results are not unexpected. We did not attempt to locate lush areas in the restored areas for sampling stations. Also, no coral was cropped from outside areas - only coral recovered in the damage zones was used in the restoration.

The principal species on the reef and those used in the restoration were: Montastraea annularis, Agaricia agaricites, and Porites astreoides.

The measurements of total cover, diversity, and evenness are shown the next Table. The species and diversity values imply that these areas have low species richness and that the relative abundance is biased toward a few species (low evenness). The values of diversity and evenness were consistently lower in the restored areas compared to the control areas.

Table: Summary of cover and species diversity

zone control
coral cover		 restored
coral cover		 H'c - control
diversity		 H'c - restored
diversity		 J'c - control
eveness		 J'c - restored
eveness
one 23.3 11.0 0.7 0.5 0.2 0.2
two 12.9 10.3 0.5 0.5 0.2 0.2
three 26.6 9.3 0.8 0.7 0.2 0.2

Photo-quadrats also provide the ability to track individual corals and to follow recruitment. We could also use the outlines of coral from each survey site over time to show the change in individual coral at all sites.

Classification of the cover documents the similarity and dissimilarities of stations and time. Losses of coral cover, increases in coral cover, and import of species by fragmentation have all contributed to the change. The table presents a matrix of similarity values of pooled coral cover data for control and restored stations. The marked changes between 1997 and 1998 are documented in the very similar coefficient values: control coefficient value was 57.5 andf the restored value was 58,8. The coefficient values for the 1996 - 1997 comparison was 82.8 for the control areas and 82.9 for restored areas. It is reasonable to say that the changes are consistent in the control and restored areas.

Table: Bray Curtis Similarity Coefficient Matrix

R = Restored areas pooled; C = Controled areas pooled
date is month - year

R 7-96
C 7-96 78.8 C 7-96
R 12-96 91.0 68.8 R 12-96
C 12-96 68.6 90.7 64.4 C 12.96
R 7-97 83.0 64.9 90.6 60.5 R 7-97
C 7-97 79.8 82.9 81.2 80.7 75.9 C 7-97
R 7-98 49.2 38.5 54.7 42.8 58.8 49.1 R 7-98
C 7-98 50.2 54.1 56.7 61.4 54.9 57.5 68.1

Stability of Large Reef Boulders that Were Moved

These were examined visually and are present in the video. We did not see evidence that structures had moved or broken on the first monitor survey. However after the winter storm our visit in July 1998 had changes in zone three. Two large restoration structures were impacted. the first was toppled and the photo station marker that was used to index the camera apparatus was missing. It appeared that the large boulder to which it was attached had rolled into a moderate-sized canyon and the station marker that was on the surface is now facing the sea floor. In the second case, a large structure shifted, and the photo reference marker is tilted to the side - no longer in a vertical alignment.

In the first situation, most of the adjacent area has been severely disturbed, but in the second, the transplanted corals are still attached. The fact that so few of the corals were dislodged is evidence that the epoxy has good strength.

Coral Recruitment

Coral recruitment was measured with a 0.0625 m2 quadrat that was randomly placed on the sea floor, and all coral recruits less than 3 cm maximum dimension within or under the quadrat frame were inventoried. The number of quadrats sampled was 60 (3.75 m2). Where possible species of the juvenile corals was determined; however, because they are often very difficult to differentiate as juveniles, some were only identified to genus.

In addition to measurements at the restoration site, we selected a reef that is seldom visited by divers (in a Preserve)to compare recruitment. This was designated New Reef.

In comparing the results of 1997 with 1998, the control areas had a slight reduction in recruitment, the restored areas had a slight increase and the New Reef had a slight decrease. These results show that natural recovery from recruitment is occurring.