Can sound science help the reefs?

To achieve all this, a diverse group of biologists have teamed up to form the Coral Chorus project, led by Aran Mooney, Amy Apprill and Joel Llopiz. Together, they bring their respective areas of expertise: Aran a bio-acoustician and sensory ecologist, Amy a coral microbiologist, and Joel a larval fish ecologist. To keep all the moving parts of this four-year National Science Foundation (NSF) project on the go, a throng of postdoctoral researchers, students and volunteers have helped in the field and back at the lab sorting samples and analysing data, simultaneously moving the project along while gaining invaluable scientific training and experience. This interdisciplinary attitude to environmental research is undeniably valuable, a comprehensive, creative and open-minded approach that will, for the sum of its parts, produce a more complete and holistic view of what shapes these reefscapes and helps them to function. The setting for this project is the southern coast of St. John in the Virgin Islands National Park. St. John, one of the US Virgin Islands tucked in among the coral reefs of the Caribbean, is an ideal location for this ecological endeavour. A marine park is in place, where it is not permitted to anchor from anything larger than a small dinghy, and there is very limited infrastructure or human habitation on the southern shore of the island. This means higher levels of protection and less input into the ocean from human activities on land, where lush forest stands guard over the bays. The marine environment here is much quieter than at most other Caribbean destinations and it supports a rich scientific history, providing some very useful background data to build on. In fact, one of Coral Chorus’s research sites, Tektite, was the location of the underwater habitat of the same name where, in the late 1960s, divers and researchers lived underwater for days to weeks at a time, observing marine life and studying human physiology. Sylvia Earle was one of these intrepid aquanauts.

Vocalisations are known to many of us who dive on both temperate and coral reefs. It is often quite obvious that the fish are barking at us, letting us know to keep our distance. It is also apparent that their barking serves as communication between members of the same species or other animals sharing habitats. It is even known to be a form of contact calling, used to maintain some level of shoaling (for instance, at night with sweepers). What is really exciting, however, is when species gather en masse to spawn and engage in dense vocalising bouts, males advertising their wares to females and competing vigorously with other males. One such site has been identified on a ledge south-west of St. John, where thousands of red hinds Epinephelus guttatus, a small grouper, gather in these noisy spawning aggregations. Many other groupers are known for this acoustic behaviour and even the famed Atlantic cod Gadus morhua from the North Atlantic is such an example. Further identifying these types of important spawning sites shaped by sound, and subsequently where and when to offer protection, is imperative to the replenishment of reefs. Of course, all these vocalisations are also adding to the soundscape of each reef.