Salinity-structured and particle-associated variations in bacterial communities and enzymatic activities in the coastal North Atlantic

Undergraduates: Karylle Abella, John Paul Balmonte Carol Arnosti

Faculty Advisor: Carol Arnosti
Department: Chemistry

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Marine microbes secrete enzymes to initiate the degradation of organic matter, but the extent to which compositional differences of bacterial communities correspond with differences in enzymatic potential are poorly understood. The manner in which these relationships vary along salinity gradients and with particle association is understudied, despite important implications for river-to-ocean transfer of organic carbon. We build on a previous study that investigated microbial enzymatic activities (EEA) across different salinities and organic matter sources between the South Atlantic Bight and Mid-Atlantic Bight: at the mouth of Chesapeake Bay (CBM), Cape Lookout Nearshore (CLN), and Cape Hatteras Offshore (CHO). To investigate the relationship between bacterial community composition (BCC) and enzymatic potential, we coupled 16S rRNA gene sequencing analyses with previously measured EEA. Our results demonstrate that salinity differences underlie patterns of dissimilarity in both bulk and particle-associated communities at all sites, and these patterns parallel substantial variations in EEA at CBM (freshwater-influenced) versus CLN and CHO (marine), in bulk seawater as well as on particles. Additionally, taxonomic analyses reveal the enrichment of specific taxa on particles; these taxa differ at CBM versus CLN and CHO. Congruence in BCC differences and EEA suggest a link between structure and function¿¿¿a relationship evident along salinity gradients and with particle-association.