Fish communities as an indicator of coral reef degradation in the East Central Red Sea

Coral reefs are priority habitats which are vulnerable to natural and anthropogenic disturbances. These can cause phase shifts from pristine coral habitat to degraded algal-dominated states. As a result, changes in the... [ view full abstract ]

Coral reefs are priority habitats which are vulnerable to natural and anthropogenic disturbances. These can cause phase shifts from pristine coral habitat to degraded algal-dominated states. As a result, changes in the distribution and abundance of associated species may become apparent. In the Eastern Red Sea, human-induced reef degradation is likely to increase with planned development along the Saudi Arabian coast and with the changing climate. The present study therefore investigates the ecological effects of coral-algal phase shifts in reef-associated fish communities, along gradients of habitat degradation. Six inshore reef areas, each showing within-reef gradients in benthic cover, from coral to algal dominance, were studied. Communities were assessed via visual census in areas dominated by: hard coral, co-dominance of coral and turf algae, and macroalgal canopies. Water quality parameters (temperature, salinity, chlorophyll a content and nutrient concentrations) were quantified and related to the biological patterns. We hypothesise changes in fish community composition, with reduced diversity and abundances of organisms in degraded habitats; as well as potential shifts in the dominance of species and functional groups. The present study aims to identify the ecological tipping point at which increased algal dominance induces a change in fish community composition and propose potential bioindicators of habitat degradation. The findings will have critical implications for the management and conservation of understudied Red Sea coastal systems.