Excavating Parrotfish

A school of excavating parrotfish on an East African reef

Parrotfishes are a beautiful, colourful and ubiquitous group of fishes that are present on coral reefs around the world. They’ve received a lot of attention due to their importance in both fisheries, and in how they can help to maintain coral reef health through preventing outbreaks of fleshy macroalgae, that can overgrow and out-compete corals. However, one role that parrotfish are particular important in playing on coral reefs has been somewhat overshadowed. A new study, published in Geology led by Prof Chris Perry, part of the SPACES team, has identified the pivotal role parrotfishes play to build and maintain coral reef islands.

Using survey and sedimentary data the study, coauthored by Paul Kench, Michael O’Leary, Kyle Morgan, and Fraser Januchowski-Hartley (who is also from the SPACES team), links reef ecology with sediment production and found that parrotfish produced more than 85% of the new sand-grade sediment on the reefs surrounding reef islands in the Maldives. Parrotfish have large and well-developed “beaks” that they use to scrape turf algae and benthic organisms off the surface of coral reefs. In the process they also remove some of the rock and coral substrate that underlies the algae, which is ground up while the edible content is digested, and later excreted as sand. This sand is often then transported by waves and currents to the shore, where it maintains the islands.

While this study concentrated on reef islands in the Maldives, it is highly likely that similar processes are at work along the East African coast, particularly at sites such as Vamizi Island in Mozambique, and Mombasa Marine Park in Kenya. By producing sand-grade sediment, healthy and abundant parrotfish communities can maintain beaches where tourism, recreation and cultural activities take place, providing an important and often overlooked ecosystem service.

Beach market in East Africa

Beach market in East Africa

The paper is ‘Linking reef ecology to island building: Parrotfish identified as major producers of island-building sediment in the Maldives’ by C.T. Perry, P.S. Kench, M.J. O’Leary, K.M. Morgan and F. Januchowski-Hartley is published in Geology.

Press release from the University of Exeter

 



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