Meeting Abstract

S1-7  Saturday, Jan. 4 11:00 - 11:30  Antarctic Microbial Interactions Revealed by Continuous Flow Incubation and Variable Rates of DMSP Supply COUNTWAY, PD*; MATRAI, PA; Bigelow Laboratory for Ocean Sciences, East Boothbay, Maine; Bigelow Laboratory for Ocean Sciences, East Boothbay, Maine

Interactions between bacteria and protists drive ecosystem processes and contribute to the overall diversity, structure, and function of marine plankton communities. These interactions occur through direct cell-to-cell contact or via cell metabolites that provide biochemical and ecological linkages among diverse groups of organisms. One metabolite, the phytoplankton-derived compatible solute dimethylsulfoniopropionate (DMSP), may play a key role in structuring Antarctic microbial assemblages. A series of experiments were performed to investigate microbial interactions related to DMSP cycling during the austral summer (2017) and fall (2018) at Palmer Station (Anvers Island, Antarctica). The diversity, structure, and function of Antarctic plankton communities were investigated through seawater incubation experiments conducted in both continuous and batch modes. Incubation bottles containing natural microbial assemblages were supplied with nutrient- and DMSP-amended filtered seawater with two different supply rates. Batch treatments served as controls for the continuous cultivation. Overall, the supply of DMSP was depleted very quickly, likely via bacterial DMSP demethylation and lyase pathways, with evidence for a wide variety of DMSP genes in coastal Antarctic waters. The summer microbial assemblage was characterized by relatively low levels of bacterial diversity while substantially higher levels of bacterial diversity were detected during the fall. Evidence suggests that the supply rate of DMSP influenced the structure of microbial assemblages for both bacteria and protists. This experimental design opens the door to quantify additional protist-bacteria interactions in aquatic environments.