Temporal population dynamics of the phantom midge Chaoborus crystallinus and its influence on the zooplankton community

The predatory larvae of the phantom midge Chaoborus are considered a key factor for zooplankton community structure in freshwater ecosystems. This study analysed C. crystallinus population dynamics and its influence on the zooplankton community structure in ponds by means of different methods of multivariate statistics based on data collected from 19 mesocosm studies over a period of 14 years. Usually, there were three Chaoborus generations per year in the evaluated studies. According to redundancy analysis the population structure of C. crystallinus varied significantly between years and seasons (within a year). Ordination analysis indicated that C. crystallinus had a significant long-term impact on the zooplankton community structure but this impact was weak when compared to time-related factors. The fourth larval stage had the greatest influence on the zooplankton community. C. crystallinus promoted high densities of rotifers and reduced the abundance of small crustaceans (copepods and small cladocerans). The abundance of large cladocerans such as daphnids was unaffected by the number of C. crystallinus larvae. There was no indication that the predatory impact of C. crystallinus on zooplankton substantially influenced phytoplankton. This study provides new findings to a better understanding of impacts on the pelagic food web related to Chaoborus predation.