Abstract
Mesocosm experiments and field studies were conducted in Raunefjorden, Bjørnafjorden and Samnangerfjorden in southern Norway during April - May 1992 to assess the production of lipid biomarkers by the coccolithophorid Emiliania huxleyi (Lohmann) Hay et Mohler. The long-chain alkenone distribution was distinctive in having high relative abundances of tetraunsaturated C and C38 alkenones. A diunsaturated C37 alkenoate was tentatively identified for the first time. Total alkenone + alkenoate concentrations increased exponentially at the same rate as E. huxleyi cell numbers and particulate calcite concentrations, indicating that the average ratio of organic to inorganic carbon production in E. huxleyi was roughly constant during the experiments. High biomarker to calcified cell ratios (< 2.5 pg ∂ (alkenones + alkenoates) cell−1) in the later stages of the mesocosm experiments and in natural fjord waters suggested significant numbers of uncalcified E. huxleyi cells. The original Uk37 ratio of Brassell & al. (1986), which includes the abundance of tetraunsaturated alkenones, was highly correlated with temperature for waters 8.5°–14°C in both mesocosms. However, the slopes of the regressions (0.0283 and 0.0101 Uk 37 units per °C, respectively) differed by over a factor of two between the mesocosms. Furthermore, both the Prahl & al. (1988) Uk 37-based temperature calibration and Conte & Eglinton (1993) multivariate temperature calibrations derived for eastern North Atlantic waters were poor estimators of water temperature in the mesocosms and in the fjords. Our data clearly indicate that temperature is not the sole factor controlling the alkenone/temperature relationship, and that one or more additional factors (e.g. genetic andlor physiological) must be involved.
