Biophysical drivers of coral reef community structure across a tropical benthic seascape

Abstract Coral reefs are global biodiversity hotspots, important for ocean health and providing ecosystem services for thousands of species (including humans). Coral benthic communities form the structural basis of these ecosystems, influencing ecological processes and ecosystem functions. For thousands of years, coral benthic communities have been driven by naturally occurring properties of the environment, which we refer to as biophysical drivers. However, as humans increasingly encroach on and alter coastal marine ecosystems, anthropogenic conditions may override biophysical drivers, making it challenging to identify the sources of changes in community composition and consequent ecosystem functioning. Here, we use multivariate analyses to demonstrate that bathymetric slope (surface steepness) and intercardinal bearing, a proxy for wind and wave exposure, are significant drivers of benthic composition across Tetiaroa, French Polynesia, a remote coral atoll where the influences of biophysical conditions have not been previously investigated. Distance-based redundancy analysis concluded that together, these biophysical variables explained 66.02% of the variance in benthic community composition. Determining the most important drivers of benthic community composition in this area of minimal human influence provides baseline data for natural coral reef ecosystems. This information will help us understand and predict coral reef community responses to changing environmental conditions and guide conservation and restoration efforts of this ecologically important atoll.