Bellingham Bay, a shallow, urbanized embayment in north Puget Sound, is experiencing increasing seasonal hypoxia. But, rates of sedimentary geochemical processes that might contribute to this change are not well quantified. This project explored the relationships between sedimentary biogeochemical processes, nutrient fluxes, and oxygen consumption in Bellingham Bay. Working with the Washington State Department of Ecology, we sampled 25 stations throughout the bay, and measured fluxes of dissolved oxygen, dissolved inorganic nitrogen, dissolved inorganic phosphorus, silicate, and dissolved inorganic carbon between sediment and overlying water. We observed decreases in the fluxes of DO, DIC, and DIN with station depth, suggesting that more organic carbon and nitrogen loading is occurring near shore. DIN:DIC and DIP:DIC flux ratios were generally less than those predicted by the Redfield ratio, suggesting that the sediment is a net sink of nitrogen and phosphorus in this coastal embayment. We also found that DO:DIC flux ratio was generally less than the expected 1:1 ratio, indicating production and storage of reduced species such as sulfide, through microbial anaerobic respiration. Further, comparison with water column oxygen consumption rates indicates that total oxygen consumption by the sediment roughly equals oxygen consumption by the water column. These findings suggest that the benthos may play at least two roles in regulating seasonal hypoxia and eutrophication: (1) as a sink for nutrients, which could have some mitigating effect on eutrophication, and (2) as a consumer of water column dissolved oxygen, which could exacerbate seasonal hypoxia. These findings are a crucial step towards linking sedimentary biogeochemical processes with eutrophication and hypoxia in Bellingham Bay.