The effects of climate change on the world’s oceans have not been kind to coral reefs. Facing a range of threats from multiple fronts, including a diverse array of predators, pathogens and people and, now, the looming specter of rising ocean acidity driven by higher carbon dioxide emissions, the future outlook of corals is looking rather grim: recent surveys suggest that almost 20 percent of the planet’s reefs have been destroyed in the past few decades and that another 50 percent are teetering on the brink of collapse.
The Intergovernmental Panel on Climate Change (IPCC) released a report last month forecasting “more frequent coral bleaching events and widespread mortality” with average global temperature rises of 1 to 3 degrees celsius. In an effort to counter this potential mass die-off, countries like Palau have started establishing the national networks of marine protected areas (MPAs) to protect their reefs from excessive predation and bleaching. Others have gone a step further by enlisting the help of one of the reefs’ most ubiquitous denizens, the parrot fish.
Named for their voluminous dentition which lends them the appearance of a parrot-like beak, parrot fishes are voracious herbivores that rasp algae from corals and other rocky substrates with their hard beaks. Researchers in the Exuma Cays Land and Sea Park in the Bahamas, one of the areas hardest hit by anthropogenic disturbances and increasing ocean acidity, observed that parrot fishes gave the coral reefs an opportunity to regenerate by grazing away the algae blooms smothering the individual polyps.
Video documentation of the sea floor taken by Daniel Brumbaugh, senior conservation scientist at the Center for Biodiversity and Conservation at the American Museum of Natural History in New York City, and his colleagues showed that more baby coral were able to settle inside the park than outside because of the protection granted by the parrot fish.
While Brumbaugh is quick to point out that this phenomenon doesn’t apply to all marine reserves throughout the world, he cites the finding’s significance as a critical step in understanding how we can help coral reefs return. He also explains that the reefs may benefit from the parrot fish halo effect by becoming more resilient to future threats. “If we’re going to have recovery of reefs in the Caribbean and elsewhere, we need baby corals to come back,” Brumbaugh adds. “This is an approach that helps baby corals come back.”
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