Western Antarctic Peninsula plankton raw sequence reads

The Southern Ocean in the vicinity of Antarctica is a region characterized by seasonally-driven marine phytoplankton blooms that are often dominated by microalgal species which produce large amounts of dimethylsulfoniopropionate (DMSP) - which has multiple physiological and ecological roles. After its release from phytoplankton, DMSP is consumed by marine bacteria to access the sulfur and carbon for biomass production, or is broken apart by algal and/or bacterial enzymes, releasing dimethylsulfide (DMS). It is thought that the presence of DMSP can influence the diversity of microbial assemblages in seawater due to the tight coupling of many processes involving DMSP that are mediated by marine planktonic bacteria, archaea, and microbial eukaryotes. Just as the DMSP cycle may influence the structure and composition of microbial assemblages, it is probable that the types of microorganisms present in a parcel of seawater at a given time or location will affect the magnitude (and direction) of DMSP cycling. This two-way interaction may depend on several factors, including the genomic potential of the microbes in the community, the frequency of DMSP genes within the microbial assemblage, as well as the broader functional and biological diversity of the microorganisms in a particular environment. Given the almost universal presence of DMSP in seawater, understanding its cycling can help us quantify and reproduce bacterial-protistan interactions in various oceanic regions. The major goals of the project are to examine: (1) the extent to which the cycling of DMSP in Southern Ocean waters influences the composition and diversity of bacterial and protistan assemblages; (2) conversely, whether the composition and diversity of Southern Ocean protistan and bacterial assemblages influence the magnitude and rates of DMSP cycling; (3) the expression of DMSP degradation genes by marine bacteria seasonally and in response to additions of DMSP; and, to synthesize these results by quantifying (4) the microbial networks resulting from the presence of DMSP-producers and DMSP-consumers along with their predators in SO waters. We will conduct continuous growth experiments with DMSP-amended natural samples during field sampling of different microbial communities present in summer and fall seasons. Data from the molecular (such as 16S/18S tag sequences, DMSP-cycle gene transcripts) and biogeochemical (such as biogenic sulfur cycling, bacterial production, microbial biomass) investigations will be integrated via network analysis.