Contrasting end-summer distribution of organic carbon along the Gerlache Strait, Northern Antarctic Peninsula: Bio-physical interactions. (March 2018)

• Record Type: Journal Article
• Authors: da Cunha, Leticia C.; Hamacher, Claudia; Farias, Cassia de O.; Kerr, Rodrigo; Mendes, Carlos Rafael B.; Mata, Mauricio M.
• Is Part Of: Deep sea research. Volume 149(2018)
• Page Start: 206
• Page End: 217
• Publication Date: 2018-03
• Subjects: Carbon export -- Biological carbon pump -- Intra-season variability -- High-salinity shelf water -- Recalcitrant carbon; Oceanography -- Periodicals; Ocean bottom -- Periodicals; Marine biology -- Periodicals; 551.46
• DOI: 10.1016/j.dsr2.2018.03.003
• Languages: English
• ISSNs: 0967-0645

Abstract

Abstract: Dissolvedorganic carbon (DOC) was determined at the Gerlache Strait, a coastal area off the Northern Antarctic Peninsula, in the austral summers of 2015 and 2016 during NAUTILUS I and II cruises, respectively. Hydrographic conditions in the area were very different between the study years. Despite that, the surface mixed layer displayed higher DOC concentrations compared to intermediate and deeper waters, as a result of the strong water column stratification, for both years. DOC accumulation on the surface is significantly related to the net community production (NCP), and stronger when the nitrate surface deficit (ΔNO3 - ) is higher (2016). The presence of a surface/subsurface thermal front at the central Gerlache Strait likely promotes the export of surface-produced organic carbon to deeper layers. A weak correlation between DOC and apparent oxygen utilization (AOU) suggests that the degradationof organic carbon in the deeper water column has a small role in oxygen consumption (less than 10%). This "recalcitrant" DOC characteristic below the surface layers observed in this study is similar to that found twenty years ago in the same area (FRUELA campaign, early Summer 1995). The Gerlache Strait allows, as an adequate regional scale study, assessments on the efficiency of the export and distribution of organic carbon in deep water masses in view of the observed trends of freshening, cooling, and lightening in the Antarctic Peninsula shelf waters. Highlights: Different hydrographic conditions during summer affect organic carbon distributions. A summer thermal front may promote export of organic carbon to the deepest portion of the Gerlache Strait. Less stable surface mixed layer conditions favor higher biological activity and organic carbon accumulation. Consumption of deep organic carbon (dissolved and particulate) corresponds to ~ 6.5 – 7.8% of the apparent oxygen utilization in the water column.