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.
"We wanted to know why Moorea's reefs seem to act differently than other reefs," said Tom Adam, first author, research associate with MCR LTER, and postdoctoral fellow at UCSB's Marine Science Institute. "Specifically, we wanted to know what ecological factors might be responsible for the dramatic patterns of recovery observed in Moorea."The research team was surprised by its findings. The biomass of herbivores on the reef –– fish and other animals that eat plants like algae –– increased dramatically following the loss of live coral. "What was surprising to us was that the numbers of these species also increased dramatically," said Andrew Brooks, co-author, deputy program director of MCR LTER, and associate project scientist with MSI. "We were not simply seeing a case of bigger, fatter fishes –– we were seeing many more parrotfishes and surgeonfishes, all of whom happened to be bigger and fatter. We wanted to know where these new fishes were coming from."
"We discovered that these fringing reefs act as a nursery ground for baby fishes, most notably herbivorous fishes," said Brooks. "With more food available in the form of algae, the survivorship of these baby parrotfishes and surgeonfishes increased, providing more individuals to help control the algae on the fore reef. In effect, the large numbers of parrotfishes and surgeonfishes are acting like thousands of fishy lawnmowers, keeping the algae cropped down to levels low enough that there is still space for new baby corals to settle onto the reef and begin to grow."
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."
In short, the research team found that by using MPAs, managers can help protect adult fish, producing bigger, fatter fish. "But if you don't protect the nursery habitat –– the babies produced by these bigger fish, or by fish in other, nearby areas –– you can't increase the overall numbers of the important algae-eating fish on the reef," said Brooks.
According to the scientists, it appears that Moorea's reefs may recover. "One final bit of good news is that we are seeing tens of thousands of baby corals, some less than a half-inch in diameter, on the fore reefs surrounding Moorea," said Brooks.
MCR researchers will follow the coral reef recovery process over the next decade or more, in search of additional information that can aid managers of the world's coral reefs.
Additional co-authors are Russell J. Schmitt and Sally J. Holbrook of UCSB's Marine Science Institute and the Department of Ecology, Evolution, and Marine Biology; Peter J. Edmunds and Robert C. Carpenter of California State University, Northridge; and Giacomo Bernardi, of UC Santa Cruz.
Gail Gallessich | EurekAlert!
Managing an endangered river across the US-Mexico border
18.07.2016 | International Institute for Applied Systems Analysis (IIASA)
The European pet trade is jeopardising the survival of rare reptile species
13.07.2016 | Helmholtz-Zentrum für Umweltforschung - UFZ
Munich Physicists have developed a novel electron microscope that can visualize electromagnetic fields oscillating at frequencies of billions of cycles per second.
Temporally varying electromagnetic fields are the driving force behind the whole of electronics. Their polarities can change at mind-bogglingly fast rates, and...
Breakup of continents with two speed: Continents initially stretch very slowly along the future splitting zone, but then move apart very quickly before the onset of rupture. The final speed can be up to 20 times faster than in the first, slow extension phase.phases
Present-day continents were shaped hundreds of millions of years ago as the supercontinent Pangaea broke apart. Derived from Pangaea’s main fragments Gondwana...
Scaffolding and specialised workers help with the delivery – Heidelberg biochemists gain new insights into biogenesis
A type of scaffolding on which specialised workers ply their trade helps in the manufacturing process of the two subunits from which the ribosome – the protein...
Scientists at the Helmholtz Zentrum München have developed a new mass spectrometry imaging method which, for the first time, makes it possible to analyze hundreds of metabolites in fixed tissue samples. Their findings, published in the journal Nature Protocols, explain the new access to metabolic information, which will offer previously unexploited potential for tissue-based research and molecular diagnostics.
In biomedical research, working with tissue samples is indispensable because it permits insights into the biological reality of patients, for example, in...
Chemists at the University of Basel have succeeded in using computer simulations to elucidate transient structures in proteins. In the journal Angewandte Chemie, the researchers set out how computer simulations of details at the atomic level can be used to understand proteins’ modes of action.
Using computational chemistry, it is possible to characterize the motion of individual atoms of a molecule. Today, the latest simulation techniques allow...
15.07.2016 | Event News
15.07.2016 | Event News
11.07.2016 | Event News
22.07.2016 | Information Technology
22.07.2016 | Physics and Astronomy
22.07.2016 | Life Sciences