Dissolved organic carbon and nitrogen cycling along the west Antarctic Peninsula during summer

Abstract

The cycling of dissolved organic matter in the productive west Antarctic Peninsula (WAP) region is not well understood. For this study, dissolved organic carbon (DOC) and nitrogen (DON) concentrations and other biogeochemical measurements were collected along the WAP shelf during austral summer 2017. Concentrations of both DOC and DON in the upper ocean were lower than in lower latitudes (38.13–48.00 μmol C L−1, 2.90–10.52 μmol N L−1). DOC is produced along with particulate organic carbon during primary production, and is subsequently consumed by bacteria. DON shows high variability and is more likely the product of bacterial activity only in the surface waters. The N-isotopic composition of nitrate and particulate nitrogen showed intense nitrification, especially along the coast, and supports the findings of intense upper ocean cycling of organic matter of both particulate and dissolved forms. Export of DOM from the productive surface layer was negligible in the shelf waters of the WAP. Samples from glacial melt areas showed increased DON concentrations (7.88–10.52 μmol N L−1) so we conclude that increasing warming and continuing melting of Antarctic glaciers may lead to higher concentrations of dissolved organic matter but also higher bacterial activity with more intense upper-ocean carbon and nitrogen cycling.