Physicochemical attributes were measured and aquatic macroinvertebrates were collected from six wetlands near Perth, Western Australia at three weekly intervals over a 13 month period from August 1988 to September 1989 . The six wetlands encompassed a range of depths, pH, concuctivities, nutrient concentrations and colours . Temporal changes in the macroinvertebrate communities appeared to be related to seasonal changes in the physical and chemical characteristics of the wetlands . Community composition differed more between the less enriched wetlands then the higly enriched wetlands where communities were generally similar . High species richness was associated with seasonal drying . High macroinvertebrate abundance appeared to be associated with the presence of either green algal or cyanobacterial blooms in the enriched wetlands . The highest macroinvertebrate biomass was recorded in wetlands with both cyanobacterial blooms and abundant macrophytes present .
Different forms of the hydriid mussel Alathyriajacksoni occur in riverine habitats of the Murray-Darling river system, south-eastern Australia. Electrophoretic data for three enzymes (glucose phosphate isomerase, malate dehydrogenase and malic enzyme) support the assumption that these are morphological variants of one species. Shells from the Murray in South Australia are elongate-oval, with the dorsal margin extended posteriorly as a blade or 'wing', whereas shells from Victoria and New South Wales have a dorsal arch and a postero-ventral inflection. The variation appears to be associated with water velocity. The arched shells have comparatively large, strong adductor muscles; the posterior adductors are elongate and both anterior and posterior adductors are displaced ventrally. These internal modifications are reflected in changing shell shape as size increases. The changes apparently enhance the mussel's ability to maintain an anchorage in a strong current, but lessen the effectiveness of its valve seal. An incidental observation is that the related species A. condola Iredale, known from the Murrumbidgee and Lachlan rivers, may also occur in the middle reaches of the Murray.
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