PATTERNS OF CARBON AND NITROGEN UPTAKE DURING BLOOMS OF EMILIANIA-HUXLEYI IN 2 NORWEGIAN FJORDS

Blooms of the coccolithophorid Emiliania huxleyi were monitored in two land-locked fjords, Fauskangerpollen and Nordasvannet (Western Norway ), in May 1993. The chemical composition of particulate matter, size-f ractionated photosynthesis, calcification, nitrogen uptake rates and t he patterns of macromolecular synthesis were examined during the peak and decline of E. huxleyi blooms. The temporal evolution of the bloom in Fauskangerpollen was defined by a gradual decrease in cell abundanc e and cell-specific calcification rates, and by increasing numbers of empty coccospheres and the ratio detached coccoliths/living cells. A l arge proportion of the nitrogen required for microplankton growth was supplied by ammonium and dissolved organic compounds such as urea and, as a consequence, the f-ratios were low (similar to 0.2). In general, nitrogen uptake patterns were consistent with ambient concentrations of nitrogenous species. The photosynthetic carbon metabolism of E. hux leyi-dominated phytoplankton assemblages was characterized by high car bon allocation into lipids and relatively low carbon incorporation int o protein as compared with diatom-dominated assemblages. Consequently, the organic C/nitrogen uptake ratio determined stoichiometrically was significantly higher (up to 10.8) when coccolithophorids were dominan t than in diatom-based or mixed-phytoplankton assemblages These carbon incorporation patterns were reflected in differences in the chemical composition of particulate matter.