Seasonal zooplankton patterns in a shallow oligotrophic lake: Loch Rusky (Scotland)

Abstract

The zooplankton taxa and their seasonal distribution are describeb for Loch Rusky, a shallow oligotrophic lake in the central region of Scotland. 15 species were indentified : 11 Rotifera, 2 Cladocera and 2 Copepoda. Only 5 species Polyathra remata, Keratella cochlearis, Filinia terminalis, Trichocerca sp. and Eudiaptomus gracilis occurred In sufficient numbers to facilitate a description of their seasonal pattern. The annual zooplankton variation was dominated by rotifers for most of the year, but copepods (E. gracilis, Cyclops sp.) only were dominant in the epilimnion during summer. It is presumed that this pattern was the result of the rotifers faster rate of reproduction and higher grazing efficiency under oligotrophic conditions, as well as the decrease of larger zooplankton by the continuous programme of fish stocking in the lake.