The distribution and macrofauna of ponds in stretches of an alpine floodplain differently impacted by hydrological engineering

The purpose of this study was to describe the impact of hydrological engineering on distribution, morphology and macrofaunal community composition of ponds in an alpine floodplain. The study was conducted in 1995 with the study sites being located on the Isar floodplain (Bavaria, Germany). The density of ponds was highest in a bypassed section of the floodplain with a residual flow regime and unrestricted peak floods (up to 40 ponds per river kilometre). In a channelized section and downstream of a reservoir, density was much lower. In 1995, about one third of the ponds were removed by floods or dried out in summer. About the same fraction was generated as a result of flood events. The composition of the macroinvertebrate and vertebrate faunas of 59 ponds was investigated. Cluster analysis classified the ponds into four groups. One of the faunal types was limited to ponds generated by the 1995 floods, where only a few predominantly rheophilic species occurred. The other types represented older successional stages and were inhabited by more species-rich faunas composed mainly of Odonata, Heteroptera and Coleoptera. In the channelized stretch of the Isar floodplain, and downstream of the reservoir only a single pond was generated by the 1995 floods; this caused a lower abundance and diversity of pond types. Copyright © 1999 John Wiley & Sons, Ltd.