STANDING STOCKS OF PIC, POC, PON AND EMILIANIA-HUXLEYI COCCOSPHERES AND LITHS IN SEA-WATER ENCLOSURES WITH DIFFERENT PHOSPHATE LOADINGS

Time series of the standing stocks of particulate inorganic carbon (PIC), particulate organic carbon (POC) and organic nitrogen (PON), and the numbers and type of Emiliania huxleyi coccospheres and detached coccoliths were determined in sea water enclosures with low, intermediate and high phosphate loadings. In the enclosures with the low and the intermediate phosphate loadings, intense blooms of E. huxleyi type A developed. PIC increased exponentially (mu = 0.3 day-1) and reached maxima of 0.3 g C m-3. PIC increased both during night and day. At the peak of the blooms, E. huxleyi made up 80 and 50 % of total POC in the enclosure with the low and the intermediate phosphate loading, respectively. High phosphate loading favoured other phytoplankton species and had negative effects on the abundance of E. huxleyi (10% of total POC) and the PIC standing stock (mu = 0.2 day-1; maximum 0.09 g C m-3). PIC per E. huxleyi cell differed between the enclosures and increased with decreasing net specific growth rate. As long as E. huxleyi numbers increased, all PIC was contained in the small particle size class (< 10 mum). Massive cell lysis, corresponding with the release of large numbers of coccoliths, marked the end of blooming in the enclosures with low and intermediate phosphate loadings. Subsequently in these enclosures, PIC decreased, probably due to dissolution of detached coccoliths.