Piontek, J., Händel, N., Sperling, Martin, Riebesell, Ulf and Engel, Anja (2010) Effects of rising seawater CO2 on the bacterial turnover of organic matter in temperate marine systems. [Talk] In: EPOCA, BIOACID, UKOARP Annual Meeting 2010. , 27.09.-30.09.2010, Bremerhaven, Germany .

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Abstract

The bacterial turnover of organic matter is the major CO2-regenerating process in the ocean. About 75-95% of freshly produced organic carbon gets remineralized within the surface ocean, the zone that is most strongly affected by ocean acidification. Thus, rates of organic matter turnover changing in response to elevated seawater pCO2 would comprise a high feedback potential to climate change. Bacterial activity in the ocean is mainly fuelled by labile organic matter, a fraction of the chemically complex organic matter pool that provides high carbon, nitrogen and energy yields to bacterioplankton metabolism and growth. We investigated the impact of ocean acidification on the bacterial processing of polysaccharides and proteins, two important components of bioreactive organic matter, at a full marine site (Gulf of Biscay, North Atlantic) and in a brackish coastal ecosystem (Baltic Sea). During in situ studies and experimental simulations of present-day and future-ocean seawater pCO2, we determined rates of bacterial extracellular enzyme activities and of glucose and amino acid uptake, as well as bacterial biomass production using fluorescent and radioactive labelled
substrate analogues. Furthermore, concentration and composition of organic matter were determined by different analytical tools. Our results reveal that the bacterial turnover of organic matter is sensitive to future changes in seawater pCO2. Effects of ocean acidification on enzymatic processes in coincidence with effects on the organic matter supply to bacterioplankton can potentially alter carbon fluxes in the future ocean and may feed back to
rising pCO2 in the atmosphere

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