A 13 C labelling study on carbon fluxes in Arctic plankton communities under elevated CO 2 levels

• Published in: Biogeosciences
• Main Authors: A. de Kluijver, K. Soetaert, J. Czerny, K. G. Schulz, T. Boxhammer, U. Riebesell, J. J. Middelburg
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2013
• Subjects: Ecology; QH540-549.5; Life; QH501-531; Geology; QE1-996.5; Arctic; Svalbard; Ny-Ålesund; Ny Ålesund; Ocean acidification; Phytoplankton; Zooplankton
• Online Access: https://doi.org/10.5194/bg-10-1425-2013; https://doaj.org/article/952e3e9ff901433cb84c0b004f7b5109

The effect of CO 2 on carbon fluxes (production, consumption, and export) in Arctic plankton communities was investigated during the 2010 EPOCA (European project on Ocean Acidification) mesocosm study off Ny Ålesund, Svalbard. 13 C labelled bicarbonate was added to nine mesocosms with a range in p CO 2 (185 to 1420 μatm) to follow the transfer of carbon from dissolved inorganic carbon (DIC) into phytoplankton, bacterial and zooplankton consumers, and export. A nutrient–phytoplankton–zooplankton–detritus model amended with 13 C dynamics was constructed and fitted to the data to quantify uptake rates and carbon fluxes in the plankton community. The plankton community structure was characteristic for a post-bloom situation and retention food web and showed high bacterial production (∼31% of primary production), high abundance of mixotrophic phytoplankton, low mesozooplankton grazing (∼6% of primary production) and low export (∼7% of primary production). Zooplankton grazing and export of detritus were sensitive to CO 2 : grazing decreased and export increased with increasing p CO 2 . Nutrient addition halfway through the experiment increased the export, but not the production rates. Although mixotrophs showed initially higher production rates with increasing CO 2 , the overall production of POC (particulate organic carbon) after nutrient addition decreased with increasing CO 2 . Interestingly, and contrary to the low nutrient situation, much more material settled down in the sediment traps at low CO 2 . The observed CO 2 related effects potentially alter future organic carbon flows and export, with possible consequences for the efficiency of the biological pump.