A Paleo-ecological study of Lake Dobson and Lake Perry (Tasmania)
Vanhoutte, K.; Vyverman, W.; Sabbe, K.; Muylaert, K.; Cocquyt, C. (1998). A Paleo-ecological study of Lake Dobson and Lake Perry (Tasmania). Biol. Jb. Dodonaea 65: 194-195
Beeckman, T.; Caemelbeke, K. (Ed.) (1998). Populations: Natural and manipulated, symposium organized by the Royal Society of Natural Sciences Dodonaea, University of Gent, 29 October 1997. Biologisch Jaarboek (Dodonaea), 65. Koninklijk Natuurwetenschappelijk Genootschap Dodonaea: Gent. 257 pp., more
Evidence from a paleolimnological study of a core from Lake Nicholls (Tasmania, Cameron et al. 1993) indicated that recent changes in diatom composition in this lake might be related to climatological changes. The main objective of the present study was to test this hypothesis through the diatom analysis of cores from two other Tasmanian lakes, L. Dobson and L. Perry. Changes in diatom composition were interpreted using inference models for 'pH', 'g440' and alkalinity, based on the TASDIAT-training set (Vyverrnan et al. 1995, 1996), a data set containing information on the littoral diatom composition of 76 Tasmanian highland lakes. The training set was expanded with five lakes (Judd's Charm, L. Picone, L. Tahune, Lonely Tarn and L. Vera) and 73 taxa, most of which are new records for Tasmania, while some are as yet undescribed. Canonical ordination analyses confirmed the gradient revealed by the TASDIAT-training set, i.e. a strong west-east gradient which is mainly related to a precipitation gradient and a geological and pedological discontinuity (silicious rocks -> Jurassic dolerite). Based on these gradients the Tasmanian highland lakes can be roughly subdivided into three types [eastern, western and corridor lakes (which have intermediate properties)]. In the cores from both lakes, a distinct change in diatom species composition and diversity could be observed throughout the cores. The observed trend, namely a decrease in diatom diversity towards the younger layers, in L. Dobson was very similar to the decrease observed for L. Nicholls by Cameron et al. (1993), while the trend in L. Perry was different, in such that here the diversity increased towards younger layers. However, statistical analysis using the TASDIAT transfer model for the selected environmental variables 'HCO3-', 'pH' and 'g440' (gilvin) indicated that the observed changes in species composition could not significantly be related to changes in these variables. This may either indicate the observed changes in species composition are not primarily related to changes in 'pH', 'HCO3-' or 'g440'. In addition, the observed differences between L. Dobson/L. Nicholls and L. Perry might indicate that local environmental conditions (e.g. fire) might have an important influence on the diatom flora of highland lakes. Based on the current results it is not possible to evaluate the hypothesis of Cameron et al. (1993). Further research will therefore include the (1) further refinement of the inference model and the construction of models for other variables (such as 'Ca2+'), (2) the collection of more autecological information on the taxa present and (3) the analysis of additional cores from Tasmanian lakes.
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