Abstract
Various physical, chemical and biological parameters were followed over a two week period prior to the blooming of the coccolithophorid Emiliania huxleyi (Lohmann) Hay et Mohler in Bj0rnafjorden (western Norway). Total inorganic carbon concentrations and pCO2 profiles showed low values at the surface, due to freshwater influence. Such low values may be of competitive advantage for phytoplankton like coccolithophorids capable of utilising bicarbonate besides CO2 as an inorganic carbon source for growth. Low nutrient concentrations in the surface limited dense bloom formation here. Subsurface bloom formation was restricted because of the poor incident irradiance conditions. The assimilation number was low (varying between 3.16 and 15.88 mg C mg chi a −1 day−1, mean 7.82 mg C mg chi a −1 day−1). Calcification rate of E. huxleyi increased gradually over the sampling period, but did not exceed 11 % of total inorganic carbon assimilation by the end of the survey. In general the phytoplankton population consisted of various spring diatoms, dinoflagellates and Euglenophyceae; E. huxleyi was not abundant, but increased in numbers (surface values) from 32000 to close to 175000 cells per litre by the end of the period, which can be regarded as a non-bloom condition. The turnover of the phytoplankton biomass was high; 66.1 % (s.d. 38.1, n = 7) of the phytoplankton primary production was grazed on a daily basis; predominantly by copepods. In addition 21.8 % (s.d. 8.8) of the phytoplankton primary production was mineralised by bacteria. Only 10 % (s.d. 40.8 %) of primary production resulted in an actual increase in phytoplankton standing stock.
