Biogeosciences Discuss., 10, 11255-11282, 2013
www.biogeosciences-discuss.net/10/11255/2013/
doi:10.5194/bgd-10-11255-2013
© Author(s) 2013. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Biogeosciences (BG). A final paper in BG is not foreseen.
Temperature and phytoplankton cell size regulate carbon uptake and carbon overconsumption in the ocean
S. E. Craig1, H. Thomas1, C. T. Jones1, W. K. W. Li2, B. J. W. Greenan2, E. H. Shadwick3, and W. J. Burt1
1Department of Oceanography, Dalhousie University, 1355 Oxford Street, P.O. Box 15000, Halifax, Nova Scotia, B3H 4R2, Canada
2Bedford Institute of Oceanography, Department of Fisheries and Oceans, Dartmouth, Nova Scotia, B2Y 4A2, Canada
3Antarctic Climate & Ecosystems Cooperative Research Centre, University of Tasmania, Hobart, Tasmania, Australia

Abstract. Phytoplankton plays a critical role in the uptake of atmospheric carbon dioxide by the ocean, and is comprised of a spectrum of cell sizes that are strongly associated with different oceanographic conditions. Studies suggest that the ocean will become increasingly stratified in response to a warming climate, limiting nutrient exchange to the upper sunlit ocean and favouring small cells able to grow in warmer, nutrient poor conditions. Here we show that, in a temperate shelf sea, a summertime population of numerically abundant small cells accounts for approximately 20% of annual carbon uptake. These small cells are not well represented by chlorophyll a – the ubiquitously used proxy of phytoplankton biomass – but rather, are strongly correlated with surface water temperature. Given the persistent near-zero nutrient concentrations during the summer, it appears that small cells drive carbon overconsumption, and suggest that their role in carbon fixation will become increasingly important in a warming ocean.

Citation: Craig, S. E., Thomas, H., Jones, C. T., Li, W. K. W., Greenan, B. J. W., Shadwick, E. H., and Burt, W. J.: Temperature and phytoplankton cell size regulate carbon uptake and carbon overconsumption in the ocean, Biogeosciences Discuss., 10, 11255-11282, doi:10.5194/bgd-10-11255-2013, 2013.
 
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