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 (PI C), particulate organic carbon (POC) and organic nitrogen (PON), and t he numbers and type of Emiliania huxleyi coccospheres and detached coc coliths were determined in sea water enclosures with low, intermediate and high phosphate loadings. In the enclosures with the low and the i ntermediate phosphate loadings, intense blooms of E. huxleyi type A de veloped. PIC increased exponentially (mu = 0.3 day-1) and reached maxi ma of 0.3 g C m-3. PIC increased both during night and day. At the pea k of the blooms, E. huxleyi made up 80 and 50 % of total POC in the en closure with the low and the intermediate phosphate loading, respectiv ely. High phosphate loading favoured other phytoplankton species and h ad 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 wit h decreasing net specific growth rate. As long as E. huxleyi numbers i ncreased, all PIC was contained in the small particle size class (< 10 mum). Massive cell lysis, corresponding with the release of large num bers of coccoliths, marked the end of blooming in the enclosures with low and intermediate phosphate loadings. Subsequently in these enclosu res, PIC decreased, probably due to dissolution of detached coccoliths .