Epiphyton dynamics during an induced succession in a large shallow lake: wind disturbance and zooplankton grazing act as main structuring forces

Abstract

We investigated the main structuring forces driving epiphytic algae dynamics with wind disturbances and zooplankton grazing acting as potential stressors by inducing a natural 60-day epiphyton summer succession. We cleaned macrophytes in the subtropical shallow Mangueira Lake, southern Brazil, using soft sponges and sampled them randomly at short-term intervals. Simultaneously, we sampled and classified zooplankton from the littoral zone according to their particle ingestion size. Disturbance by wind was the main factor driving the epiphyton succession. Tightly attached diatoms were well adapted to the system’s high mean wind velocity (15 m s−1), whereas low wind velocity (<7 m s−1) reduced community diversity. Summer storms (46.7 mm of precipitation; 29.5 m s−1 wind velocity) caused phosphorus input and favored prostrate diatoms. Epiphyton was very productive (8028.8 mg C m−2 h−1), consistent with a heterogeneous community. Small rotifers and ciliates were abundant in the water column during the study. Our data indicate that rotifers as well as other zooplankton grazed on epiphyton, due to the positive correlation between algal diversity and rotifer abundance as well as between diatom and zooplankton biomasses, whereas Copepods and Cladocerans followed large motile diatoms in abundance. We conclude that epiphyton is an important food source for zooplankton in Mangueira Lake.