Small dams profoundly alter the spatial and temporal composition of zooplankton communities in running waters

Abstract

We analyzed the influence of a small dam on the temporal and spatial properties of zooplankton communities by comparing the zooplankton composition established prior to the dam's construction to that during 5 years after its construction. The dammed water of a small dam, even just by 1m, induced spatial changes in the zooplankton communities similar to those induced by a large dam. Changes in the number of taxa and zooplankton densities were observed a few months after the construction of the dam. In particular, in the number of planktonic rotifers such as Keratella cochlearis, Filinia longiseta, Polyarthra longiremis, Trichocerca similis and the larval stages of copepods considerably increased, along with the density of the littoral taxa of rotifers and crustaceans. Cladocerans appeared in the impoundment after the construction of the dam and their abundance increased in the second year after the dam was built. The abundance of all systematic groups of zooplankton increased in subsequent years after the construction of the dam. The small dam had a great effect on the spatial and temporal composition of the zooplankton communities in the stream studied, related to an abrupt change in the physical conditions from those typical of flowing water to those typical of limnetic basins. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.