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 an d 37 chemical and physical variables in littoral sediments of 76 Tasma nian dystrophic and (ultra-)oligotrophic highland lakes indicate stron g west-east, gradients in pH, calcium concentration, sodium concentrat ion, alkalinity, and gilvin, which are underlain by an oceanic-inland gradient and geological discontinuities. Two major clusters of lakes a re 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 ch anges. Changes in species composition occur gradually across the corri dor separating the two provinces. Highly significant inference models can be constructed for pH and calcium concentration and related variab les, which can be used in palaeolimnological reconstructions in Tasman ian highland lakes.