EMILIANIA-HUXLEYI - CHEMICAL-COMPOSITION AND SIZE OF COCCOLITHS FROM ENCLOSURE EXPERIMENTS AND A NORWEGIAN FJORD

Single Emiliania huxleyi (Lohmann) Hay et Mohler, type A, coccoliths harvested from mesocosm enclosures (June 1991) with different nutrient regimes, and the Norwegian fjord, Samnangerfjorden (October 1992), were analyzed with X-ray microanalysis in a Transmission Electron Microscope (TEM). The average molar Ca : C ratios of the free coccoliths varied within a range of 0.65-1.0, dependent on growth condition of E. huxleyi. Free coccoliths sampled from enclosures with high production or density of E. huxleyi, had Ca : C ratios near 1. Coccoliths sampled from Samnangerfjorden, and enclosures with low production or cell density the Ca : C ratios were close to 0.7. The excess of carbon in the coccoliths compared to CaCO3 is probably due to organic matter, mainly carbohydrates. It is concluded that the amount of organic matter associated with coccoliths of E. huxleyi, is dependent on the growth conditions, and carbohydrate may protect the coccoliths from dissolution. A higher Ca : C ratio (0.8 versus 0.7) was determined in the central parts of free coccoliths from slow growing algae. Average content of carbon, oxygen and calcium in single coccoliths was 0.28, 0.87, and 0.67 pg (1.4 : 3.2 : 1 molar ratio) respectively, with an estimated average total weight of 1.8 pg.