Dissolved Organic Matter as a Potential Nutrient Source from the Kuroshio Current to the Subtropical Gyre

Dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) are important components of dissolved organic matter (DOM) in the marine environment. While DOC serves as the major energy source to sustain microbial metabolism, DON can serve as a supplemental source of nitrogen when inorganic forms are scarce. Recent global models suggest that accumulated DON at the ocean margins must be an alternative source of nutrients that is laterally transported to the subtropical gyres. Prior studies that have identified periodic net accumulation of DOM in marine environments suggest that microbial communities become limited by nutrient availability but also that the accumulated DOM can become bioavailable when introduced to a new community. This study seeks to investigate the bioavailability of DOM transported from the Kuroshio Current into the subtropical gyre when exposed to various microbial communities. Using water collected in August 2024, we conducted a series of dark incubation experiments comparing the effects of mixing of surface and subsurface water within and between water masses. Samples were collected to measure changes in DOC and DON, accompanied by inorganic nutrient concentrations, bacterial abundance, DOM and 16S community compositions, as well as dissolved oxygen consumption rates over time. Conclusions from these experiments are forthcoming but are expected to highlight (1) the metabolic potential of the microbial community composition in determining the bioavailability of DOM and (2) the rates of remineralization and nutrient regeneration during lateral transport from the Kuroshio Current to the subtropical gyre. 

Presentation Preference: Poster

Primary Presenter: YuChen Yen, National Taiwan University (r12241405@gmail.com)

Authors:

Brandon Stephens, National Taiwan University  (bstephens@ntu.edu.tw)