Relations entre la lumière et la photosynthèse du phytoplancton dans un réservoir mésotrophe (Pareloup): Variations saisonnières des paramètres

Abstract

The relationships of vertical profiles of phytoplankton photosynthesis to underwater light were analysed in a series of 48 experiments performed in the mesotrophic reservoir of Pareloup. The light saturated photosynthetic rates (Popt), the initial slope of light saturation curves (α) and the quantum yield at limiting light intensities (Φm) vary over more than one order of magnitude. A strong correlation appears between α and P opt which suggest the possibility of predicting the values of one from those of the other. Both parameters are correlated with chlorophyll concentrations and temperature but these two factors account for only 43 % of the variance of Popt. Changes in the photosynthetic light responses by phytoplankton were observed during summer when the euphotic layer became thermally stratified. These results are discussed with regard to predictive models of phytoplankton production. © Masson, 1988.