Data Sheet 1_Microbial community dynamics mediate rapid biomass loss and phosphorus recycling in pelagic Sargassum.pdf

To improve the current understanding of Sargassum biomass dynamics and the contribution of this productive algal bloom to carbon and nutrient fluxes between the Atlantic and the Caribbean, we characterized the growth and decomposition rates of this pelagic alga, nutrient release rates during litter decay, and the bacterial microbiome at several stages of this decay.

The analysis revealed no exceptional growth under increased nutrient availability but a rapid biomass mineralization with a litter half-life of 16 days, comparable to phytoplankton. This fast decomposition triggers swift nutrient release, notably phosphorus, which fuels coastal eutrophication and may help explain oxygen depletion and toxic gas emission during massive beaching events. A microbial succession involving chemoheterotrophic and nitrogen-fixing bacteria predicts functions involved in the biomineralization of nitrogen and phosphorus-containing compounds that may facilitate such efficient phosphorus mineralization, supporting similar patterns in marine debris to terrestrial plant litter, where nutrients drive stage-specific patterns in microbial community succession during litter decomposition.