According to a study based in Fiji, fish and baby corals in the Pacific Ocean are capable of smelling the difference between a good reef and a bad reef. When searching for a new home, these animals detect the chemical cues that are present when a reef is littered with seaweed and avoid them, flocking to much healthier habitats instead.
When offered a choice between two water samples in a lab, the animals were repulsed by the smell of seaweed that invades reefs that have been depleted, but were drawn to the smell of a healthy coral reef. While these findings aren’t exactly surprising, this is the first time that corals have been shown to react to chemical “smells” in water over long distances.
These findings suggest that controlling seaweed is key to repopulating depleted reefs. Once a coral reef has decayed and become depleted, seaweed takes over. While this may stop people from fishing in the area, without removing the seaweed, it’s not enough to bring the coral back.
“If you’re setting up a marine protected area to seed recruitment into a degraded habitat, that recruitment may not happen if young fish and coral are not recognizing the degraded area as habitat,” said Doctor Danielle Dixson from the Georgia Institute of Technology, the first author of the study.
“This is the first time that we’ve seen coral’s ability to assess this on a large scale, when they’re floating around,” said Professor Mark Hay, the study’s senior author. “They can’t do much against a current. So what we think is going on is that they’re drifting through these different reefs, and if it smells good, they go down. It’s a very strongly selected behavior. Over aeons, there’s been good reefs and bad reefs and if you settle on the bad ones, you die.”
“Having the right conditions is important. These animals are programmed to look for the places that they’re going to be most successful in,” said Professor Steve Widdicombe, head of science in Marine Life Support Systems at the Plymouth Marine Laboratory. “It was very interesting to see this idea that if we’re going to bring these habitats back, just leaving them alone might not be enough. We might have to make some active steps.”
Read more about the story at Discovery.