Fear of Sharks Influences Seaweed Growth on Fijian Coral Reefs


Fishes’ fear of sharks helps shape shallow reef habitats in the Pacific, according to new research by a scientist at Bigelow Laboratory for Ocean Sciences.

The study is the first clear case of sharks altering a coral reef ecosystem through an indirect effect – creating an atmosphere of fear that shifts where herbivores feed and seaweeds grow. Referred to as a trophic cascade, these complex relationships exist throughout nature but the linkages are often hard to identify.

The study, published in Scientific Reports, looked at reefs located along the coast of Fiji. Many of its islands are surrounded by shallow, intertidal reefs that are commonly found in the Pacific. Through environmental monitoring and experiments, the research team found that sharks alter the feeding behavior of algae-eating fish in the ecosystem. This change reverberates down the food chain to affect where seaweed, a chief competitor to corals, grow on the reef.

“Although sharks are charismatic predators that capture the interest of many, we still only have a very basic understanding of their ecological roles in nature,” said Doug Rasher, a senior research scientist at Bigelow Laboratory and lead author of the new paper. “This is the first location where we’ve determined that sharks are not just a passenger in the ecosystem but actually shape the way it looks and functions.”

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