| Summary: | Bacterial degradation activity strongly controls the export flux of organic matter in the ocean. Bioreactive compounds like polysaccharides are preferentially consumed by marine bacteria, since they provide an excellent yield of carbon and energy for heterotrophic metabolism. Included in sinking particles, polysaccharides contribute substantially to the export of organic carbon, and impact sinking processes through the enhancement of marine snow formation. However, there are still few studies describing the fluxes of polysaccharide-derived carbon to marine heterotrophic bacterioplankton. Here, we stepwise pursue the pathway of bacterial polysaccharide degradation, presenting data on extracellular glucosidase activity, glucose uptake rates, and bacterial biomass production, as well as related impacts on polysaccharide concentration and composition from field and laboratory experiments. Since ocean acidification is currently shown to be a profound perturbation of marine systems, affecting processes in biogeochemical cycles, experimental simulations were an integral aspect of our studies. Results are included to discuss the importance of bacterial polysaccharide degradation for the efficiency of carbon export, the diagenetic alteration of sinking particles, and the properties of extracellular polymeric substances today and in the future ocean.
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