Healthy Sound, Healthy Coral
Fish are known to be essential for coral reefs to function as a healthy ecosystem. Unfortunately, when corals start dying, fish are not attracted to them as much as before. But I bet you didn’t know that one of the factors influencing this attraction is the sound of the reefs. This is where researchers from the University of Exeter found a way to draw fish back to degrading corals using loudspeakers.
Healthy corals have very loud and noisy biological soundscapes, created by the sounds from all the inhabitants that live within them, such as shrimps snapping their claws and fish grunting. When young fish are trying to locate an area to settle down, these soundscapes are a crucial input into their decision-making. Reef fish populations are sustained by recruiting juvenile fish that spend time in the open ocean searching for a suitable home to establish themselves. Using their senses, they determine which reefs are the best, but degraded corals neither smell nor sound attractive compared to healthy ones. Once reefs start to degenerate, they are like ghost towns, completely silent and no-one wants to live in a haunted house. That is why the novel “acoustic enrichment” management tool has been explored to see if it can help reverse the deterioration of coral reefs.
Using loudspeakers to broadcast healthy coral soundscapes on the Great Barrier Reef in Australia, scientists found that this conservation tactic has potential. Underwater speakers were placed in patches of dead coral and recordings were played of a flourishing reef. To make sure it wasn’t a coincidence, they placed dummy speakers (with no sound) to see if this affected the abundance of marine life. However, it was indeed found that fish were more likely to gather and stay on reefs with the playback of healthy coral sounds. In fact, the fish community development due to acoustic enrichment doubled fish numbers overall and caused a 50% rise in species richness. Different fish groups play varying environmental roles on reefs so maintaining species richness is important in creating a healthy ecosystem.
This is extremely promising for corals that are critical for marine life. Using this method, as well as active habitat restoration and conservation measures, will help rebuild fish communities and recover habitats!
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