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La Trobe University Faculty of Science, Technology and Engineering Murray Darling Freshwater Research CentreMDFRC item.Lake Torrens, a large (similar to 6000 km(2)), episodic, saline playa lake in arid central Australia, filled for the first recorded time in March 1989. This unique event followed unprecedently heavy rain over its catchment. Water remained in the lake until early 1990. Salinities remained low (< 40 g l(-1)) until November 1989, then increased rapidly to > 200 g l(-1) before the water evaporated completely. Na and Cl probably dominated the ions. Twenty-nine taxa of aquatic animals were recorded. Crustaceans dominated and of these Parartemia minuta (anostracan), Daphniopsis queenslandensis and Moina baylyi (cladocerans), and several species of ostracods were the most important. Other significant taxa included Tanytarsus barbitarsis (chironomid), Brachionus plicatilis (rotifer) and Craterocephalus eyresii (fish). The fauna was dominated by widespread forms that are either part of a distinct assemblage found widely in central Australian salt lakes (especially P, minuta, D. queenslandensis, M. baylyi and Trigonocypris subglobusus [ostracod]), or cosmopolitan forms (B. plicatilis), or forms found widely in Australian salt lakes (e.g. Diacypris compacta, Tanytarsus barbitarsis). However, possibly three new species also occurred: a new species of a new genus of mytilocypridinid, Branchinella nov.sp. and Heterocypris is nov. sp. Their occurrence is anomolous. It is suggested that further work will show that they too are widely distributed. Both genera of the latter two taxa are typical of temporary waters and specimens may have been washed in from nearby water-bodies. Sixty-four species of bird were recorded when the lake contained water, many breeding. The breeding of the banded stilt (Cladorhynchus leucocephalus) was notable; breeding of this species had been unknown in South Australia since 1930. A large population built up until breeding was stopped by predation from the silver gull (Larus novaehollandiae). When dry, the lake has a depauperate but well-defined and regionally restricted 'terrestrial' fauna (scorpions, spiders, beetles, ants).

La Trobe University Faculty of Science, Technology and Engineering Murray Darling Freshwater Research CentreMDFRC item.Lake Gregory is a large semi-permanent lake system in arid north-western Australia. Its catchment extends intohumid areas and as a result the lake has dried only twice in the last 25 years. Although the system is mostly fresh,parts of it become saline as they dry.We identified aquatic invertebrates and undertook chemical analysis of watersamples from several sites at Lake Gregory in 1989, when the main water-body was saline, and in 1991 and 1993,after the system had flooded and was fresh. During the period 1989–1993, salinities varied from 0.1hto 82h, andionic composition ranged from strong sodium chloride dominance, in saline water and fresh water of the easternpart of the system, to bicarbonate dominance in fresh water of the western area. At least 174 invertebrate specieswere recorded, including two mollusc species that were never collected live. This species richness is much higherthan that recorded from other Australian arid zone lakes, probably owing to long periods of inundation with freshwater. The fauna was dominated by insects (42 per cent of total species richness), crustaceans (27 per cent) androtifers (22 per cent). Most species (160) were restricted to fresh water; only 12 species were found in salinewater. Only one ostracod occurred in saline conditions, although ostracods are a dominant group in Australiansaline lakes. Among species restricted to fresh water, the proportion of rotifer and protozoan fauna that occurred inbicarbonate-dominated water was greater than the proportion of insect, crustacean and hydracarine fauna that didso.

Murray-Darling Freshwater Research CentreMDFRC item.General ecological expectations about the relationship between latitude and species richness are that at low latitudes (the tropics) species richness is greater than at higher latitudes (temperate and polar regions). Recent work suggests that this may not be the case for several habitat types and biological groups in Australia. Results are conflicting: on present evidence (admittedly sparse) it appears that in Australian tropical fresh waters species richness is generally depressed in zooplankton and littoral microfaunal communities, but not in macroinvertebrate communities in typical streams and in fish communities (and perhaps also in amphibian and reptile communities). The situation is indeterminate for tropical phytoplankton and macrophyte communities.