Distribution of benthic diatom assemblages in Tasmanian highland lakes and their possible use as indicators of environmental changes

Classification and gradient analyses of littoral diatom assemblages and 37 chemical and physical variables in littoral sediments of 76 Tasmanian dystrophic and (ultra-)oligotrophic highland lakes indicate strong west-east, gradients in pH, calcium concentration, sodium concentration, alkalinity, and gilvin, which are underlain by an oceanic-inland gradient and geological discontinuities. Two major clusters of lakes are recognised, concordant with the recognition on chemical and optical criteria of western and eastern limnological provinces and coinciding with a steep gradient in mean annual rainfall and major geological changes. Changes in species composition occur gradually across the corridor separating the two provinces. Highly significant inference models can be constructed for pH and calcium concentration and related variables, which can be used in palaeolimnological reconstructions in Tasmanian highland lakes.