Assessment of the processes controlling the seasonal variations of dissolved inorganic carbon in the North Sea

We used a seasonal North Sea data set comprising dissolved inorganic carbon (DIC), partial pressure of CO2 (pCO2), and inorganic nutrients to assess the abiotic and biological processes governing the monthly variations of DIC. During winter, advection and air–sea exchange of CO2 control and increase the DIC content in the surface and deeper layers of the northern and central North Sea, with the atmosphere supplying CO2 on the order of 0.2 mol C m22 month21 to these areas. From February to July, net community production (NCP) controls the seasonal variations of DIC in the surface waters of the entire North Sea, with a net uptake ranging from 0.5 to 1.4 mol C m 22 month 21 . During the August–December period, NCP controls the seasonal variations of DIC in the southern North Sea, with a net release ranging from 0.5 to 0.8 mol C m 22 month 21 . Similarly, during the April–August period in the deeper layer of the northern North Sea, the NCP was the main factor controlling DIC concentrations, with a net release ranging from 0.5 to 5.5 mol C m22 month21. In the surface layer of the North Sea, NCP on the basis of DIC was 4.3 6 0.4 mol C m22 yr21, whereas, NCP on the basis of nitrate was 1.6 6 0.2 mol C m22 yr21. Under nutrient-depleted conditions, preferential recycling (extracellular) of nutrients and intracellular mechanisms occurred and were responsible for the non-Redfield uptake of DIC versus nitrate and phosphate.

[1]  J. G. Field,et al.  The Ecological Role of Water-Column Microbes in the Sea* , 1983 .

[2]  F. A. Richards,et al.  The influence of organisms on the composition of sea-water , 1963 .

[3]  B. Delille,et al.  Budgeting sinks and sources of CO2 in the coastal ocean: Diversity of ecosystems counts , 2005 .

[4]  Nicolas Gruber,et al.  The Oceanic Sink for Anthropogenic CO2 , 2004, Science.

[5]  H. G. Gade,et al.  Net community production and oxygen fluxes in the Nordic Seas based on O2 budget calculations , 1999 .

[6]  Wade R. McGillis,et al.  A cubic relationship between air‐sea CO2 exchange and wind speed , 1999 .

[7]  S. Kempe,et al.  Sinks and sources of CO2 in coastal seas - The North Sea , 1991 .

[8]  J. Gattuso,et al.  Planktonic and whole system metabolism in a nutrient-rich estuary (the Scheldt estuary) , 2005 .

[9]  P. C. Reid,et al.  Phytoplankton of the North Sea and its dynamics: A review , 1990 .

[10]  G. Leeuw,et al.  Atmospheric input of nitrogen into the North Sea: ANICE project overview , 2001 .

[11]  J. Gattuso,et al.  CARBON AND CARBONATE METABOLISM IN COASTAL AQUATIC ECOSYSTEMS , 1998 .

[12]  Christiane Lancelot,et al.  Phaeocystis blooms in the global ocean and their controlling mechanisms: a review , 2005 .

[13]  T. Pohlmann,et al.  The ICES-boxes approach in relation to results of a North Sea circulation model , 1997 .

[14]  H. Thomas,et al.  New production enhanced by nutrient supply from non-Redfield remineralisation of freshly produced organic material , 2000 .

[15]  A. Borges,et al.  Controls of the surface water partial pressure of CO2 in the North Sea , 2005 .

[16]  M. Droop.  SOME THOUGHTS ON NUTRIENT LIMITATION IN ALGAE 1 , 1973 .

[17]  A. Watson,et al.  In situ evaluation of air‐sea gas exchange parameterizations using novel conservative and volatile tracers , 2000 .

[18]  K. Banse.  Uptake of inorganic carbon and nitrate by marine plankton and the Redfield Ratio , 1994 .

[19]  John J. Walsh,et al.  Importance of continental margins in the marine biogeochemical cycling of carbon and nitrogen , 1991, Nature.

[20]  U. Brockmann,et al.  Cycling of nutrient elements in the North Sea , 1990 .

[21]  C. Lorenzen,et al.  Fluorometric Determination of Chlorophyll , 1965 .

[22]  R. Wanninkhof.  Relationship between wind speed and gas exchange over the ocean , 1992 .

[23]  V. Ittekkot,et al.  Preferential recycling of nutrients—the ocean's way to increase new production and to pass nutrient limitation? , 1999 .

[24]  C. Heip,et al.  Carbon‐nitrogen coupling and algal‐bacterial interactions during an experimental bloom: Modeling a 13C tracer experiment , 2004 .

[25]  J. Young,et al.  Coccolithophores : from molecular processes to global impact , 2004 .

[26]  Yann Bozec,et al.  Enhanced Open Ocean Storage of CO2 from Shelf Sea Pumping , 2004, Science.

[27]  B. Schneider,et al.  The seasonal cycle of carbon dioxide in Baltic Sea surface waters , 1999 .

[28]  I. Joint,et al.  Phytoplankton biomass and production in the southern North Sea , 1993 .

[29]  T. Tyrrell,et al.  Emiliania huxleyi: bloom observations and the conditions that induce them , 2004 .

[30]  H. Haas,et al.  Organic carbon in shelf seas: sinks or sources, processes and products , 2002 .

[31]  Leif G. Anderson,et al.  Uptake of atmospheric carbon dioxide in Arctic shelf seas: evaluation of the relative importance of processes that influence pCO2 in water transported over the Bering–Chukchi Sea shelf , 2005 .

[32]  Jan O. Backhaus,et al.  Simulations of the north sea circulation, its variability, and its implementation as hydrodynamical forcing in ERSEM , 1995 .

[33]  Y. Bozec,et al.  The continental shelf pump for CO2 in the North Sea - evidence from summer observation , 2005 .

[34]  L. Anderson,et al.  The dynamics of the carbon cycle in the surface water of the Norwegian Sea , 2005 .

[35]  Christopher B. Field,et al.  The global carbon cycle: integrating humans, climate and the natural world. , 2004 .

[36]  Andreas J. Andersson,et al.  Past and present of sediment and carbon biogeochemical cycling models , 2004 .

[37]  G. Radach,et al.  Nutrient dynamics in the North Sea: Fluxes and budgets in the water column derived from ERSEM , 1995 .

[38]  A. Borges.  Do we have enough pieces of the jigsaw to integrate CO2 fluxes in the coastal ocean? , 2005 .

[39]  Chuanmin Hu,et al.  The importance of continental margins in the global carbon cycle , 2005 .

[40]  H. Odum.  Primary Production in Flowing Waters1 , 1956 .

[41]  Manfred Ehrhardt,et al.  Methods of seawater analysis , 1999 .

[42]  J. Goering,et al.  UPTAKE OF NEW AND REGENERATED FORMS OF NITROGEN IN PRIMARY PRODUCTIVITY1 , 1967 .

[43]  B. Delille,et al.  Whole-system metabolism and CO2 fluxes in a Mediterranean Bay dominated by seagrass beds (Palma Bay, NW Mediterranean) , 2004 .

[44]  A. Borges,et al.  The Carbon budget of the North Sea , 2004 .

[45]  C. Copin-Montégut,et al.  Processes controlling annual variations in the partial pressure of CO2 in surface waters of the central northwestern Mediterranean Sea (Dyfamed site) , 2002 .