The Effect of perturbations on phytoplankton assemblages in a deep reservoir (Vouglans, France)

Disturbances, such as rainfall and hydrological management of Vouglans reservoir, seem to influence the establishment of the ecological system inside this man-made lake. In this paper, the main effect of these disturbances are changes in the z mix :z eu ratio, with a shift in the composition and phytoplankton dynamics, and consequently in the Shannon’s diversity. The seasonal changes found in the surface layers of Vouglans reservoir were typical for mesotrophic and temperate lakes, but some perturbations induced the ‘reversion’ to an earlier stage in the expected successional pattern during the stratification period. This early-state displayed an intensive proliferation of the filamentous u…