Little sea creatures, baby coral and fish, can identify the good reefs from bad ones, thanks to their olfactory organs. When a reef is degraded by seaweed, sea animals turn away from the stench of the seaweed. But they are drawn to healthy reefs that give off the right chemical signals. It’s the first evidence that corals react over long distances to “smells” in the water.

Corals and fish

How abandoned coral reefs could be repopulated

Results of the study show that controlling seaweed is crucial to repopulating reefs. Once seaweed takes over a coral reef, simply stopping fishing in the area might not be sufficient to help decayed reefs recover. The study was conducted in Fiji by researchers at the Georgia Institute of Technology, Atlanta. Findings of the research were published in the journal Science.

Researchers, led by Dr Danielle Dixson, chose marine protected areas containing healthy coral reefs off the coast of Fiji. They made use of this area because it was immediately adjacent to heavily fished areas full of seaweed, creating a nice experimental setting. Scientists took water from these healthy and weedy areas to the lab. They placed the fish in a special chamber, offering the little creatures the choice between the two.

All the young fish from 15 different species chose the water from healthy reefs. They spent about 80% of their time on this side of the special chamber. That didn’t surprise many because even baby fish have tails and a nose. But researchers were surprised to see baby corals behaving in the same fashion. The three species of coral larvae swam, wagging their little hairs, into the better smelling water.

Baby coral able to assess chemical signals on a large-scale

Scientists then contaminated water from the healthy reefs with the smell of seaweeds. They found that the fish and coral would avoid the contaminated water as much as water from bad reefs. But when they mixed aroma of healthy corals with bad water, it attracted the little creatures. Scientists found that coral has the ability to assess the smell on a large-scale, when they are floating around, reports BBC.

Of course, baby corals can’t fight well against the water current. But they drift through different reefs, and they go down when they find good chemical signals. If seaweed producing bad smells, a previously abandoned reef could slowly be turned around.