Alternative stable states and phase shifts of coral- to algae- dominated systems has been observed on Caribbean coral reefs with little or no signs of recovery. To better understand the mechanism by which depletion of herbivores leads to a loss of coral, large parrotfish were excluded from coral nursery habitat in two locations on the Belizean Barrier Reef, Glovers Reef and Carrie Bow Cay. Mimicking the removal of large fish by fishing, the authors used ‘parrotfish deterrents’ (PDs) around coral settlement plates and studied herbivory and macroalgae abundance. At both sites algae abundance was found to reduce coral recruitment. Porites coral failed to recruit at medium levels of algae and was more negatively impacted than Agaricia coral. These finding along with other studies suggest that algal abundance is a proximate driver of coral recruitment and thus recovery of Caribbean coral reefs.

Author: Steneck, R.S., S.N. Arnold, and P.J. Mumby
Year: 2014
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Marine Ecology Progress Series 506: 115–127. doi: 10.3354/meps10764