Diel changes in the biochemical composition of the particulate matter coupled with several parameters in the hypereutrophic Villerest reservoir (Roanne,France)

The diel changes of the biochemical composition of particulate matter was studied in Villerest reservoir (located on the Loire river, near the city of Roanne, France) during July 92. Several biomass and metabolic indicators (proteins, carbohydrates, lipids, chlorophyll a and primary production) were assessed bihourly over 2 days.Since the P/C is largely recognized as a good integrator of the metabolic functions of the cells, we examined its distribution pattern concomitantly with aforementioned parameters. The results demonstrated enhanced P/C ratios clearly indicating that nutrients were sufficiently available for growth. In addition, this index showed a diel significant variation with levels higher in the night than in the day. Moreover, these results suggest that phytoplankton species during the night used the day-synthesized carbohydrates to insure the cell metabolic functioning.