Impacts of coral bleaching on coral reef fish community structure

Based at Newcastle University in the School of Marine Science & Technology, this project will explore how strongly coral reef fish communities are dependent on corals by describing what happens over 5-15 years spans at sites which have suffered major bleaching. It will do this first by project scientists gathering new data in collaboration with a number of other institutions in the Western Indian Ocean and Australia. Before and after data on reef fishes at six major locations (Sri Lanka, Maldives, Seychelles, Kenya, Tanzania, Réunion) will then be compared, especially in relation to the major 1998 bleaching event in that region. At the same time in collaboration with the Australian Institute of Marine Science analyse data from many sites gathered through long-term monitoring of the Great Barrier Reef. The investigators will ultimately conduct a combined analysis of the data to gauge large-scale changes occurring across whole regions as a result of substantial bleachin! g events.

Coral bleaching is predicted to increase in frequency in the coming decades, and a recent investigation at one location in Papua New Guinea has indicated that this may have very great impacts on associated fishes and thus the wider reef ecosystem. This study to be funded by the Leverhulme Trust and led by Newcastle University will assess whether or not this holds across two major coral-reef regions of the globe, with clear implications for the future of one of the world’s most biodiverse ecosystems.

Perhaps the most tightly linked and known consequence of global warming at the current time is coral bleaching in tropical seas. As coral reefs are one of the most diverse ecosystems on earth and people in many tropical countries are so dependent on them, mass live coral loss at this scale is likely to have serious implications. Live corals give the reef its structure, providing a matrix of holes as refuges from predation for the diverse assemblage of animals, and they provide a food source to many species. Loss of corals also threatens the very reef framework, because these counteract the erosive processes tending constantly to degrade the structure. Corals also compete for space with algae, the latter often taking over after a bleaching event and supporting a major food web. There is much speculation about the consequences of bleaching for the whole ecosystem; some research indicates that reefs are fragile and the implications of the bleaching are major, while o! ther evidence is more equivocal. Yet to date few studies have looked at large scale effects over periods of time greater than two years. Reefs are however important to fisheries and the tourism industry and there are potential negative indications of bleaching for local livelihoods in the coastal tropics.

We expect to conduct an overall analysis of existing data between and within regions, conduct experiments which build on the pseudocorals manipulation (Williams & Polunin 2001) and use modelling aproaches to expend on the existing empirical base.