The effect of variable turbulent intensities on the distribution of zooplankton in the shallow, large Lake Balaton (Hungary)

Abstract

The influence of current velocity on zooplankton organisms is manifold. Moderate current velocity is beneficial for zooplankton, but through various mechanisms too high a current velocity can have detrimental effects. We examined how current velocity acts on zooplankton in Lake Balaton at different levels and found a highly significant, negative relation between current velocity and the density of zooplankton assemblages. Of the studied assemblages, Daphnia galeata × cucullata and Eudiaptomus gracilis exhibited the greatest sensitivity to the degree of current velocity. During calm weather, when the water surface was calm too, nocturnal migration was observed for both Daphnia galeata × cucullata and Eudiaptomus gracilis. We demonstrated that the vertical migration of these two species started before the storm as the usual nocturnal migration, but during the storm the regular pattern was confused.

Keywords

• Balaton
• vertical migration
• current velocity
• zooplankton