Oculina Bank

Andrew Shepard, NURC; Sandra Brooke, ORCA & Myra Brouwer, SAFMC

Oculina coral head on sandy bottom (Photo: NURC-UNCW).The Oculina Bank extends 170 km along the shelf edge from Fort Pierce to Daytona, Florida, from 30 to 70 km offshore at depths of 60-100 m.  Over the past thousand or more years, the ivory tree coral, Oculina varicosa, has built up coral mounds or bioherms. The 90 km stretch of pinnacles, mounds, and ridges (5-35 m above bottom and 100-300 m in width) from Fort Pierce to Cape Canaveral is known as the Oculina Bank.  In 1984, the area was first designated as the Oculina Bank Habitat Area of Particular Concern (OHAPC) and closed to  bottom fishing.  The OHAPC was significantly expanded in 1994 and the original OHAPC became the Oculina Experimental Closed Area. Unfortunately by then, over 90% of the Bank that used to be covered with live coral mounds had been damaged. (learn more about the management history of the Oculina Bank).

Biodiversity of intact, living Oculina bioherms is similar to that of shallow tropical coral reefs.  The productive and diverse Oculina reefs support dense and diverse populations of fishes (>70 species), and are important breeding grounds for commercially important populations of gag and scamp grouper, nursery grounds for juvenile snowy grouper and speckled hind, and feeding grounds many reef and pelagic fish species. The HAPC's location at the southern end of the South Atlantic Bight (SAB), directly under the Gulf Stream, makes it a potentially important source of fish recruitment for the entire SAB.

Fishes among OculinaOne of the most important ecological services that the Oculina Bank may provide is as spawning site for reef fish, including several grouper species.  This mission was specifically schedule in the springtime (although weather can be difficult this time of year), in the hope of seeing evidence of reproductive behaviors. Divers and robots, however, are limited in ability to census on deep, rough pinnacles, where we expect to find fish aggregations. The ship will deploy a bio-observatory, built by John Reed of Harbor Branch Oceanographic Institution, a tripod equipped with an acoustic hydrophone and still camera. Technical divers will follow up the deployment and carefully place the tripod so it is imaging a high relief pinnacle. The sounds and images will be archived in a data logger. The observatory will be recovered in six weeks.

A lone Oculina colony tangled in fishing gear and surrounded by coral rubble and sediment (Photo: NURC-UNCW).The remaining intact areas of Oculina colonies, which are located at the southern end of the OHAPC, produce large numbers of free-swimming coral larvae every summer (Booke and Young, 2003). It could be that these larvae are transported to the damaged regions of the OHAPC by the prevailing northerly current. However, there is little evidence of new corals settling onto the coral rubble left behind from illegal trawling. It is possible that the coral fragments do not provide sufficiently elevated or stable substrate for new corals to seetle on, but it is also unclear to what extent illegal trawling has affected survival of newly established colonies. Concern over whether Oculina coral can successfully re-colonize an area recently promted NOAA Fisheries to designateOculina varicosa as a "Species of Concern."

Restoration experiments
Reefblock structure with several small Oculina colonies (photo: S. Brooke).We began coral colonization experiments in 1996 by deploying 56 'reefblocks' (1 m3 cement block structures) in the Oculina Experimental Closed Area from Jeff's Reef in the south to Sebastian Pinnacles to the north. In 2000, we deployed the first series of experimental reefballs (concrete domes 1 m diameter x 0.7 m high) in groups of 5, 10 or 20. This experiment was designed to determine whether the size of the module clusters affected the recruitment of corals and fish. At the same time, we also scattered 450 small round discs (30 cm diameter) in groups of 25 a little distance to the east and west of the reefballs. These discs all had coral transplants (harvested from a wreck outside the Oculina reserve). The idea was to see whether they could be used to 're-seed' the damaged area using small pieces of coral. In 2001, we put an additional experiment in place. This time we deployed 120 reefballs a little further south of the previous experiment. Half of the reefballs had complex internal structure placed inside to provide microhabitat for small fish, and the others were left empty. As in 2000, we also placed sets of reefdisks (450) to the east and west of the reefball experiment.

Reefdisks just prior to deployment showing coral fragments attached to the PVC pipe (Photo: S. Brooke).Over the past several years, we have been able to peek at these structures (taking advantage of other research missions being done in the area) and found that transplanted coral fragments have survived, and new coral colonies have established on the older reefblocks. We have also seen a greater abundance and diversity of reef fish associated with the reefballs than the surrounding coral rubble (Brooke et al. 2006, Koenig et al. In press). While these preliminary observations are encouraging, we need to conduct a thorough survey to find out whether the restoration modules are having an effect on coral recruitment and fish population recovery in the Oculina Closed Area.

Survey approach
Assessing the restoration modules is not easy.  It requires one to maneuver around the clusters of modules without disturbing them, and be sufficiently close to take images of small coral colonies and observe cryptic and small fish. This kind of dexterity can only be obtained from human divers. The Oculina habitat is not an easy one to work in; it is deeper than normal scuba diving depth and the current conditions and visibility are unpredictable. The AUV and ROV from Mission Leg 2 will pinpoint the location of the modules, and on Leg 3, we will utilize teams of highly trained technical divers from the National Undersea Research Center (NURC) to carry out the surveys. The divers will use SCUBA with Trimix, Enriched Air Nitrox (EANx) and Oxygen. 

The divers will use video and digital photography to document coral colony size and density, and fish abundance and diversity at each artificial structure (or set of structures). They will then tag each surveyed module with a numbered plastic tag for identification purposes.

experimental reefballs deployed in 2001, showing the coral transplant and the internal structure (Photo: S. Brooke)Expected results
We expect to find that coral transplants on the restoration modules have survived and grown. We also expect to see small coral colonies throughout the modules which will indicate successful corals settlement. We do not however, expect similar coral colonization on the rubble around the modules. We will determine the success of the modules in enhancing habitat recovery by compating coral settlement on the modules with settlement on surrounding rubble. We also expect higher abundance and diversity of fish around the reefball clusters than on the surrounding rubble, with the greatest diversity among those containing complex internal structures. Overall, we expect that the placement of artificial structures will attract coral colonization and the return of fish communities in severely damaged areas of the OHAPC.

The first time we saw the extensive damage done to the Oculina coral reefs, it was a watershed moment for many of us. It is not enough to document how an incredible natural resource is being lost, perhaps forever. This knowledge has to be shared among many: the scientific community, resource managers who are charged with implementing regulations, teachers and students who will be the next stewards of these resources and with all those who care about the public good and enhancing the world for our children. 

This web site's daily logs and career interviews will be seen by hundreds of classrooms we hope to engage during our cruises. With help from SAFMC, the NOAA Coral Reef Conservation Program, and Harbor Branch Oceanographic Institution, we will host a professional development workshop for science and math teachers from across the East Florida region and multiple grade levels.