A 13C labelling study on carbon fluxes in Arctic plankton communities under elevated CO2 levels

[摘要] The effect of CO₂ 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. ¹³C labelled bicarbonatewas added to nine mesocosms with a range in pCO₂ (185 to1420 μatm) to follow the transfer of carbon from dissolvedinorganic carbon (DIC) into phytoplankton, bacterial and zooplanktonconsumers, and export. A nutrient–phytoplankton–zooplankton–detritus modelamended with ¹³C dynamics was constructed and fitted to the data toquantify uptake rates and carbon fluxes in the plankton community. Theplankton community structure was characteristic for a post-bloom situationand retention food web and showed high bacterial production (∼31%of primary production), high abundance of mixotrophic phytoplankton, lowmesozooplankton grazing (∼6% of primary production) and lowexport (∼7% of primary production). Zooplankton grazing andexport of detritus were sensitive to CO₂: grazing decreased and exportincreased with increasing pCO₂. Nutrient addition halfway through theexperiment increased the export, but not the production rates. Althoughmixotrophs showed initially higher production rates with increasing CO₂,the overall production of POC (particulate organic carbon) after nutrient addition decreased withincreasing CO₂. Interestingly, and contrary to the low nutrientsituation, much more material settled down in the sediment traps at lowCO₂. The observed CO₂ related effects potentially alter futureorganic carbon flows and export, with possible consequences for theefficiency of the biological pump.

[学科分类] 地球化学与岩石