JPR Advance Access originally published online on February 5, 2007
Journal of Plankton Research 2007 29(4):359-367; doi:10.1093/plankt/fbm021
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Colony size, cell number, carbon and nitrogen contents of Phaeocystis pouchetii from western Norway

1 Skidaway Institute of Oceanography, 10 Ocean Science Circle, Savannah, GA 31411, USA 2 UNIFOB, Department of Biology, University of Bergen, PO Box 7800, N-5020 Bergen, Norway 3 Department of Marine Biology, Centre for Ecological and Evolutionary Studies, University of Groningen, PO Box 14, 9750 AA Haren, The Netherlands
* Corresponding author: peter.verity{at}skio.usg.edu
Received on November 30, 2006; accepted on January 30, 2007
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Phaeocystis pouchetii is an ecologically important colony-forming marine phytoplankton species in northern hemisphere cold waters. It plays a central role in the processing of biogeochemically important elements in the upper ocean during spring blooms. Here, we report highly significant quantitative relationships among colony size, cell number and particulate carbon and nitrogen contents of field populations of P. pouchetii, which provide the means to quantitatively convert its biological expression into units of biogeochemical significance. Populations were sampled from mesocosms incubated in situ in western Norway and either fertilized with nitrate and phosphate or left unamended. Phaeocystis colony blooms developed in both scenarios, but were much greater in fertilized treatments. Colonies from the latter treatments were larger, contained higher concentrations of cells and more particulate carbon and nitrogen than those in the unfertilized mesocosm. Considering all data, log cell number increased linearly with log colony volume with a slope of 0.54. Log carbon and nitrogen increased with log colony volume, with respective slopes of 0.92 and 1.22, indicating a significant component of non-cellular carbon and nitrogen within the colonies. Carbon and nitrogen contents of colonies were linearly related, and fertilized colonies contained more nitrogen relative to carbon than unfertilized colonies. These equations are particularly applicable to contemporary studies of P. pouchetii because they represent colonies growing in environments that mimic a continuum from natural to eutrophicated ecosystems.
Department of Geophysics, Stanford University, 379 Panama Mall, Stanford, CA 94305-221, USA