Coral restoration in The Abacos, The Bahamas: An ecosystem approach

Background/Question/Methods

The coral reefs around Castaway Cay, Bahamas have been negatively affected by a number of natural and anthropogenic stresses. This decline is evident in the area’s low coral cover, scarcity or absence of key reef building corals, and lack of ecologically and economically important species. The ecosystem’s inability to recover from these impacts suggests that they have undergone a phase shift to an algal dominated state. The goals of this project were to (1) determine baseline health of six patch reefs surrounding Castaway Cay through fish and benthic surveys, (2) investigate whether the introduction of Diadema antillarum on certain patch reefs would decrease algal cover and increase coral diversity and abundance and (3) use coral transplanting to accelerate coral repopulation.

Annual species diversity surveys were conducted at each of six patch reef locations. Data were collected along eight transects at each reef site and broken pieces of unattached coral were identified and collected. Urchins were collected from donor sites with higher abundance and translocated to Glass Bottom Reef. Collected coral was trimmed and reattached to the ocean floor using a marine grade epoxy. Transponder and visual tags were used to mark individuals for annual monitoring. Over 1000 D. antillarum have been translocated and 113 pieces of reef building coral (Acoropora palmata and Acoropora cervicornis) have been transplanted onto Glass Bottom Reef.

Results/Conclusions

Yearly monitoring of reef sites from 2008-2011 showed that fish and benthic communities remained fairly stable. An increase in of crustose coralline algae and decrease in turf algae could be attributed to the grazing by D. antillarum and would support the idea of introducing the keystone grazer to reef sites for increased coral reef health. Of the corals transplanted 73% have been resighted and 67% of these corals have shown positive growth and appear to be healthy. In 2010, corallivorous snails (Coralliophila abbreviate) were discovered invading the transplanted corals on Glass Bottom Reef and efforts were made to remove the snails in 2010 and 2011.

Results show that the techniques are successful at promoting transplanted coral growth and do not impact the species diversity on the reefs. Data suggests that increasing the number of key grazers on the reef could promote healthy habitat for new coral. Additional research is needed to understand the impact corallivorous snails have on corals in the Bahamas.