Photosynthèse phytoplanctonique: Réponse à un stimulus simple, imitant les variations rapides de la lumière engendrées par les vagues

Abstract

Experiments were conducted in order to assess the response of marine phytoplankton production to a simplified stimulus modelling rapid light fluctuations induced by sea surface waves. Studies were carried out in the St Lawrence Estuary, during three clear and absolutely calm days. The photosynthesis of artificially incubated samples was generally depressed in fluctuating light, when compared with that in constant light of the same average intensity. There is, however, a daily trend of increased energy utilization in varying light, at saturating intensities, while some unpredictable instances of higher photosynthesis were observed in fluctuating light, especially at low intensities. Results are interpreted in terms of changes in carboxylation pathways, and might be a function of the average fluctuating light intensity and of the sun adaptation by the phytoplankton. It follows that the use of fixed light ‘imitated in situ’ incubators should be viewed with some caution.