LITTORAL BENTHOS OF A VICTORIAN LAKE AND ITS OUTLET STREAM - SPATIAL AND TEMPORAL VARIATION

There have been few comparative studies of the fauna in the two major types of freshwater systems, lakes and streams, in the one locality. T his study compared the faunal assemblages at two times of the year (su mmer and winter) on stones in three locations: the littoral zone of tw o shores in Lake Purrumbete (one wave-exposed and one sheltered) and r iffles in the Curdles River, which flows out of the lake. The lake fau na was dominated by crustaceans, gastropods and planarians, whereas th e stream fauna was dominated by insects. The most abundant lake taxa w ere also present, but much less abundant, in the stream. The total num ber of species and individuals and densities of some common species va ried between the three locations and between seasons. However, no cons istent pattern reflecting a difference between the two lake shores was evident. Interpretation of MDS ordinations of the lake fauna was depe ndent on the data standardizations applied, with increased separation of the season-location combinations when species were standardized to equal total abundances; the seasonal difference was always greatest fo r the exposed (cliff) shore. In contrast, MDS on the stream fauna show ed seasonal differences under all standardizations. This was consisten t with the high seasonal turnover of species in the stream compared wi th the lake. These results demonstrate that, even within a local area with similar geology and connected water bodies, lake and stream fauna from the same substratum (stones) can be markedly different. Taxa tha t occurred in both were more abundant in the lake, whereas seasonal di fferences in abundance were much greater in the stream.