The study, which was published this week in the journal Proceedings of the Royal Society B, shows that the odor coming from dead coral reefs may bar small fish from sensing the telltale chemical signs of nearby predators.
Healthy coral reefs are usually the home of thousands of fish species. But when the reefs go sick and die the entire ecosystem is threatened to perish. Coral gardens worldwide are now under a lot of pressure from warming oceans which can trigger a devastating phenomenon that wipes dozens of them every year: coral bleaching.
Coral bleaching happens when corals are under so much stress that they eject the algae living in them and turn completely white as if they were “bleached.” While some reefs may recover from bleaching, repetitive events may turn coral reefs into large graveyards.
But dead coral skeletons are not only a depressing sight. According to the new study, they may also have a huge impact on the marine life. Scientists at James Cook University in Queensland, Australia, and Uppsala University, in Sweden, found that damselfish have a poor ability to spot hungry predators in the proximity of dead corals.
Lead author of the study Prof. Mark McCormick explained that baby fish can sense chemical cues released by the bodies of wounded fish to identify new predators in the area. Next, the fish match the alarm signals with visual and olfactory data on predators learning how to avoid them in the future.
But when corals die, the sense of smell of small fish seems to be altered. And so does their learning mechanism. Study authors said that the smell of a wounded companion paired with other info about the predator help young fish stay away from new predators. This, however, happens only in regions with live corals. When dead corals are present, the fish’ learning ability drops dramatically.
On the other hand, a fish species that can only live on dead corals had no troubles in detecting new predators, researchers noted. But most species were not as lucky. Dr. Oona Lönnstedt, another researcher involved in the study, noted that coral degradation could not only hinder the process of avoiding predators but also force many species to go extinct.
Dr. Oona Lönnstedt, another researcher involved in the study, noted that coral degradation could not only hinder the process of avoiding predators but also force many species to go extinct.
“Many reef fish need specific habitats that only healthy coral reefs can provide,”
Dr. Lönnstedt said.
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