Microbial community composition and polysaccharide processing potential in the South Pacific Gyre

The South Pacific Gyre (SPG) covers 10% of the ocean's surface and is considered a marine biological desert. However, recent investigations have shown that primary production occurs throughout the deep euphotic zone and that it fuels the regeneration of nutrients and the recycling of organic matter. We set out to investigate the SPG's microbial communities' heterotrophic capability to utilize polysaccharides, an important marine organic matter component. Using fluorescently labeled polysaccharides (FLA-PS), we analyzed the initial step of organic matter degradation by measuring external hydrolysis rates and the substrates' direct uptake. The presented dataset contains the microbial diversity and abundance results generated during the FLA-PS incubations performed with six polysaccharides (laminarin, xylan, chondroitin sulfate, arabinogalactan, fucoidan, and pullulan) over 18 days. Microbial composition changes and direct uptake (selfish-uptake) were measured in the epipelagic and bathypelagic waters (75 m, 160 m, 1250 m, and 2800 m) in the central gyre, and in the epipelagic (75 m) at two stations adjacent to the gyre. The SPG's microbial community showed remarkably high extracellular enzyme activities, and a considerable fraction of the microorganisms were capable of the direct uptake (selfish-uptake) of the FLA-PS. Interestingly, a wide variety of bacteria are capable of cycling HMW organic matter using distinct polysaccharide processing mechanisms in the SPG. This research shows that the SPG features not only organisms capable of existing on the fine edge of minimal substrate concentrations but also those capable of taking advantage of abrupt changes in physical conditions and substrate availability