Low particulate carbon to nitrogen ratios in marine surface waters of the Arctic

• Autores: Crawford, David W.; Wyatt, Shea N.; Wrohan, Ian A.; Cefarelli, Adrián Oscar; Giesbrecht, Karina E.; Kelly, Brianne; Varela, Diana E.
• Año de publicación: 2015
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: Biología; C:N ratios; Redfield ratios; Particulates; Uptake rates; Phytoplankton; Arctic
• Institución: Universidad Nacional de La Plata

During the Canada Three Oceans and Joint Ocean Ice Study projects in the summers of 2007 and 2008, we measured particulate organic carbon to nitrogen ratios (POC:PON) throughout the euphotic zone in subarctic and arctic waters. Depth-integrated values averaged 2.65 (±0.19) in the Beaufort Sea and Canada Basin (BS-CB domain), and were much lower than both the Redfield ratio (6.6) and the average ratios (3.9 to 5.6) measured across other arctic-subarctic domains. Average uptake ratios of C and N (ρC:ρN) were also lower (0.87±0.14) in BS-CB than in the other four domains (2.10 to 3.51). Decreasing POC:PON ratios were associated with low concentrations of phytoplankton C, reduced abundance of biogenic silica (bSiO2), a smaller relative contribution of the >5 µm fraction to total chlorophyll a and a larger relative contribution of small flagellates (<8 µm) to phytoplankton C. In the subsurface chlorophyll a maximum (SCM) within the BS-CB domain, phytoplankton C represented only ~13% of POC, and therefore low POC:PON may be influenced by the presence of heterotrophic microbes. These ratios are supported by data obtained during other arctic programs in 2006, 2008 and 2009. Previous work has suggested a link between freshening of surface waters and increasing dominance of picophytoplankton and bacterioplankton in the Canada Basin, and the low POC:PON ratios measured during this study may be a consequence of this shift. Our results have ramifications for the conversion between C- and N-based estimates of primary productivity, and for biogeochemical modeling of marine arctic waters.
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