A comparative study of water level regimes and littoral benthic communities in Scottish lochs

Abstract

There has been little previous research on the impact of fluctuating water levels on the littoral communities of Scottish lochs. In 1980, 27 lochs were visited and the physical characteristics, macrophytes and zoobenthos of selected shores were studied. Long-term water level data were available for most of the lochs and these were used to divide them into three categories with (1) natural, (2) minor (i.e. less than 5 m fluctuation in the year preceding sampling), and (3) major fluctuations (i.e. more than 5 m fluctuation in the year preceding sampling). Examples of the weekly variations in water level changes over a year are given. The biological results were relatively clear. Though most of the shores studied had comparable substrates, the flora and fauna were linked with the type of water regime of the previous years. In the natural lochs and those with minor fluctuations in level, the littoral macrophytes and zoobenthos were usually varied and reasonably abundant, but in the lochs with major fluctuations the flora and fauna were very impoverished and sometimes completely absent. The critical level changes which cause this impoverishment are discussed and ways of ameliorating the problems are suggested.