First impressions matter, even to fish and coral. Reefs in the Pacific Ocean are being subjected to a smell test according to a new study. Coral and fish can smell if the reef has gone bad. The study is helping explain why some reef conservation efforts are failing.

The fish use chemical clues to avoid reefs that are littered with seaweed. Instead, they migrate over to the healthy reefs to take up residence. Danielle Dixson, an assistant professor of biology at the Georgia Institute of Technology led the study. Researchers honed in on Fiji’s ‘Coral Coast’ as their study ground.

Talk about a tough life. Where did you do your study? Oh, Fiji. The Coral Coast is actually the perfect ground to study the ‘smell test’ effect. Dixson commented on the demarcation of good and bad zones in the reefs. “The reefs in Fiji have such a stark contrast between the healthy areas and the degraded areas.”

The team set up shop along the southern end of Fiji’s main island, Viti Levu. From there, they studied multiple Marine Protected Areas. They collected samples from both the healthy, protected areas, and the collapsing, non-protected areas.

Researchers set up a tank with a plume of water from a good reef, and one from a bad. Given the choice, the fish specimens preferred to swim in the healthy plumes. That held true of fish that had adapted to swimming in degraded reefs. Coral acted the same way before they settled in to become hard polyps.

Common seaweed, known as Sargrassum polycystum, also kept fish and baby coral away. Seaweed normally moves in and blooms, taking over a once thriving reef.

What the study, published in the journal Science, shows is that removing seaweed may be the best conservation tool. It might be able to turn the tide of a degrading reef into a flourishing one.

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