“They Can Smell Marine Protected Areas.” New Research Shows How Coral Larvae and Juvenile Fish Sniff Out Healthy Reefs

by Carolyn Sotka

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Coral Spawning.  Photo by Jim Maragos

In much the same way that dogs can detect cancer just by a change in a person’s scent, new research shows that baby corals and fish use smells to find the best and most suitable habitat. Once thought to be passive drifters after spawning, Georgia Tech chemical ecologists Dr. Mark Hay and Dr. Danielle Dixson found that baby coral have a highly evolved ability to move towards healthier reefs and away from unhealthy ones. Fifteen species of juvenile fish were also found to mimic this preference.

The study, conducted in Fiji, compared a marine protected area (MPA) to a nearby-fished area. The MPA, aka healthy reef, was dominated by coral cover while the fished area, aka unhealthy reef, was dominated by seaweed. In both the lab and the field, the team used the chemical signatures of these two areas and subjected corals and fish to a choice. In short, where do you want to live?

Their findings were remarkable and published in a recent edition of Science Magazine. Coral larvae were four to five times more likely to swim towards the MPA than the fished areas. Young fish swam towards the MPA waters four to eight times more than the fished areas.

This is a very important adaptive skill for corals, because once they settle they are unable to move again. So in the absence of herbivores that cull the seaweed, settling in a poor or unhealthy environment dominated by seaweeds is detrimental to coral survival.

Coral reefs are in fast decline around the world, and this study provides insight into the restoration of degraded reefs and a new understanding for management. Using chemical and other behavioral cues in management can help improve ecosystem functioning by focusing on key species and select habitat engineering to improve settlement, biodiversity and the health of reefs.

To learn more about the Hay & Dixson study check out this video.

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