Trajectories of tropical marine communities under high temperature and eutrophication conditions.

In recent decades, concerns have been raised that coral reefs are shifting from coral-dominated states to systems dominated by macroalgae. Meanwhile there is growing evidence that other benthic groups are increasing in abundance on coral reefs, in particular sponges and benthic cyanobacterial mats (BCMs, dense mats of diverse microbial consortia dominated by cyanobacteria). Given global trends in increased water temperatures and eutrophication due to coastal development and runoff, BCMs and sponges may be more resilient to environmental change than corals, or even macroalgae, leading to possible shifts of dominance. The overall aim of this project is to understand how tropical marine species communities respond to past and current environmental change and identify possible shifts in dominance of benthic groups related to temperature and eutrophication gradients. Using a multifaceted approach including photogrammetry, genomics, and water quality analysis, I will study current and past benthic distribution patterns and dynamics of whole communities through three main components: Marine lakes: discrete marine communities replicated over space, under similar degrees of eutrophication while each lake differs in temperature, representing natural states of future climate change scenarios; Coral Reefs: natural eutrophication gradient, caused by runoff and other human activities, while maintaining similar temperatures among sites; Sediment cores: window into past biodiversity dynamics, as paleolimnology provides a useful approach to study how diversity has shifted over time and under what circumstances. Through our field-validated data, we will identify feedbacks and conditions that can set the stage for large community fluctuations under future scenarios predicted for climate change.