Build-up and decline of organic matter during PeECE III
1Leibniz Institute for Marine Sciences (IFM-GEOMAR), Düsternbrooker Weg 20, 24105 Kiel, Germany
2Bjerknes Centre for Climate Research, Univ. of Bergen, Allégaten 55, 5007 Bergen, Norway
3Geophysical Institute, Univ. of Bergen, Allégaten 70, 5007 Bergen, Norway
4University of Bergen, Department of Biology, Box 7800, 5020 Bergen, Norway
Abstract. Increasing atmospheric carbon dioxide (CO2) concentrations due to anthropogenic fossil fuel combustion currently change the ocean's chemistry. Increasing oceanic [CO2] and subsequent decreasing seawater pH have the potential to significantly impact marine life. Here we describe and analyze the build-up and decline of a natural phytoplankton bloom initiated during the 2005 mesocosm Pelagic Ecosystem CO2 Enrichment study (PeECE III). We show that processes of inorganic carbon uptake in mixed surface waters and organic carbon export to depth were significantly enhanced at elevated CO2, while ammonium regeneration in deep waters was substantially reduced. This has important implications for our understanding of pelagic ecosystem functioning and future carbon cycling.