How can you tell a healthy reef from an ailing one? According to new research published in Science, if you’re a fish or a young coral, then you can tell by the chemical signals of the surrounding seawater.
As the BBC reports, researchers found that certain chemical signals—the fish equivalent of smells—were enough to either draw in or deter fish and larval corals from particular environments. In experiments in the lab, fish were given the choice between two water samples from Fiji, one taken from a healthy reef, and another taken from a reef that had become choked with seaweed. The fish overwhelmingly chose the water taken from the healthy reefs.
The fact that coral larvae exhibited the same behavior was particularly surprising to the researchers, as young corals aren’t as mobile as young fish.
"They're kind of like bags of snot," author Mark Hay told the BBC. "We didn't think it would happen either."
In addition to testing the water samples, the scientists found that adding the scent of healthy corals to the less appealing water samples could draw fish in.
The researchers hope that their insights could provide a way forward for reef restoration projects looking to entice corals and fish to previously abandoned reefs. A news article in Science about the research reports that some restoration options might include removing seaweed (either by hand or by allowing Parrotfish to eat their way through the weeds) and planting healthy corals in struggling areas to jump-start growth.