Effect of phytoplankton settling quality on microbenthic fauna

The aims of this study were to evaluate how climate-driven changes in phytoplankton communities may affect benthic biodiversity and ecosystem functions. In a 4-weeks experiment, we investigated how microeukaryotic and bacterial communities responded to different OM quality inputs from two common phytoplankton species in the Baltic Sea, the diatom Skeletonema marinoi and filamentous cyanobacteria Nodularia spumigena. Metabarcoding analyses on 16S and 18S rRNA were conducted upon experiment termination, revealing subtle but significant changes in diversity and community composition of microeukaryotes in response to settling OM quality. Sediment bacterial communities were less affected, although we observed a clear effect on denitrification gene expression (nirS and nosZ), which was positively correlated with increasing proportions of cyanobacteria. Altogether, these results suggest that future changes in OM input to the seafloor may have important implications on both the composition and function of microbenthic communities.