Recent research shows that not only are herbivorous fish—like parrotfish and surgeonfish—critical to coral reef health, but that Caribbean reefs are suffering because herbivorous species have been overfished:
Can fish save coral reefs from dying? UC Santa Barbara researchers have found one case where fish have helped coral reefs to recover from cyclones and predators.
Coral reefs worldwide are increasingly disturbed by environmental events that are causing their decline, yet some coral reefs recover. UCSB researchers have discovered that the health of coral reefs in the South Pacific island of Moorea, in French Polynesia, may be due to protection by parrotfish and surgeonfish that eat algae, along with the protection of reefs that shelter juvenile fish.
The findings are published in a recent issue of the journal PLoS ONE. The UCSB research team is part of the Moorea Coral Reef Long-Term Ecological Research (MCR LTER) project, funded by the National Science Foundation.
In many cases, especially in the case of severely damaged reefs in the Caribbean, coral reefs that suffer large losses of live coral often become overgrown with algae and never return to a state where the reefs are again largely covered by live coral. In contrast, the reefs surrounding Moorea experienced large losses of live coral in the past –– most recently in the early 1980′s –– and have returned each time to a system dominated by healthy, live corals.
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A major reason the reefs in the Caribbean do not recover after serious disturbances is because these reefs lack healthy populations of parrotfishes and surgeonfishes, due to the effects of overfishing, explained Adam. “Without these species to help crop the algae down, these reefs quickly become overgrown with algae, a situation that makes it very hard for corals to re-establish themselves,” he said.
Managers have tried to reverse the trend of overfishing through the creation of Marine Protected Areas (MPAs), where fishing is severely restricted or prohibited. “Our results suggest that this strategy may not be enough to reverse the trend of coral reefs becoming algal reefs,” said Brooks. “Our new and very novel results suggest that it also is vital to protect the fringing reefs that serve as nursery grounds. Without these nursery grounds, populations of parrotfishes and surgeonfishes can’t respond to increasing amounts of algae on the reefs by outputting more baby herbivores.”
Read more in this report from ScienceDaily. You can also read the full scientific article Herbivory, Connectivity, and Ecosystem Resilience: Response of a Coral Reef to a Large-Scale Perturbation, at PLoS ONE.
[Photo: Sharife]
Green sea turtles (Chelonia mydas) may have an important part to play by grazing on algae on reefs as well.