Invasive macroalgae shape chemical and microbial waterscapes on coral reefs

On coral reefs, the tight coupling between microorganisms and metabolites drives reef biogeochemical processes and mediates ecological interactions. In the wake of the widespread shift from coral to macroalgal dominance, deciphering the unseen diversity of microbes and chemicals and their spatial distribution is paramount to understand the consequences of benthic community changes on coral reef ecosystem function and resilience. This study demonstrates that macroalgal assemblages modify the multiomic signature of reef boundary layers. It reveals a spatial structuration of planktonic microbial communities and identifies specific classes of compounds characterizing two invasive macroalgal species and their surrounding waters. Results support that macroalgae release chemicals which select for specific planktonic microbial communities, thereby creating a detrimental environment for corals.