A study of Lake Wyara, an episodically filled saline lake in southwest Queensland, Australia

Abstract

Abstract. Lake Wyara lies on a tertiary fault, but is much modified geomorphologically by wind and subsequent wave action from the west, so that the eastern shore is smoothed and lined by beaches at various levels, but there is no lunette. When full and overflowing, which has occurred 4-5 times in the last 108 years, it is 3400 ha in area and ca 6m in depth. Most overflows are due to floodwaters from the adjacent Paroo catchment entering the lake via its outflow and then returning again back to the river. During 1987-96, it completely filled and dried once, salinity varying from 2.8 to 350 g L -1. Water was clear, alkaline and strongly dominated by Na and Cl-ions. Macrophytes grew abundantly offshore at lower to moderate salinities, fish were few in variety and limited to low salinities, and waterbirds were usually both diverse and numerous. During the 10 years of study, only 13 zooplankter species and 23 species of littoral inverbebrates (with 3 ostracods common to both lists) were encountered; most lived at lower salinities (<30 g L -1) and none was found >60 g L -1. Dominants were mainly crustaceans and included Boeckella triarticulata and Daphnia angulata when hyposaline, and Daphniopsis queenslandensis, Moina baylyi, Diacypris spp., and Mytilocypris splendida at higher salinities. Insects were generally limited to hyposaline conditions, but Micronecta sp., and Tanytarsus barbitarsis were euryhaline. Overall, the invertebrate fauna is depauperate by comparison with saline lakes elsewhere in Australia, but similar to that in other large saline lakes in the semi-arid and arid zones of central and eastern Australia. This is related to the lake's episode nature which provides an unreliable and unpredictable habitat and therefore not encouraging speciation and also to a relatively homogenous habitat throughout the lake due to strong wind action smoothing shorelines vertically and horizontally.

The biology of the saline lakes of central and eastern inland of Australia: a review with special reference to their biogeographical affinities

“…Lake waters are dominated by Na and Cl ions (Na >> Mg > Ca > K and Cl >> SO 4 > HCO 3 ) due to long accumulation of marine aerosols (Herczeg et al, 2001), though in a few hypsosaline lakes in the Paroo SO 4 and occasionally Ca dominate (Williams and Kokkinn, 1988;Williams et al, 1998;Timms, 1993Timms, , 1998a. Lake Buchanan has unusual water chemistry in that Ca % Mg due to local catchment influences (Chivas et al, 1986).…”

“…Lake Torrens lies in a graben with basal lacustrine sediments of Cainozoic age (Twidale & Campbell, 1993), Lake Eyre has been present in some form since the middle Jurassic but its present basin was created by epeirogenic earth movements in the last 30,000 years (Kotwicki, 2000). Lake Wyara lies on a Tertiary fault (Timms, 1998a), and Lake Buchanan lies along a fault line in an intermontane basin and dates back in some form to the early Tertiary (Chivas et al, 1986). Presently, these lakes are shallow ( < 2 m deep) playas, though episodic fillings raise their levels to flood surrounding country and are marked by stranded beaches.…”

“…Lake Torrens has the most parsimonious filling regime, having significant water only once since white settlement (early 1800s) (Williams et al, 1998). At the other extreme Lake Wyara more often than not has water and dries only in severe El Niñ o events (Timms, 1998a). Lake Eyre has some water every 2-3 years but major fillings are much longer apart (e.g.…”

“…Pleistocene floodings were extensive and are well documented for Lake Eyre (Kotwicki, 1986). Most of the lake basins are modified by wind action, with Lake Wyara having the most smoothed eastern shore and much degraded lunette dune (recognisable only on satellite images; present form and augering suggest it lacks younger lunettes homologous with those of surrounding lakes- Timms, 1998a).…”

“…In 1993, I showed that the fauna of saline lakes in the Paroo was almost as diverse as in more climatically benign western Victoria (Timms, 1993) and later (Timms, 1998a(Timms, , 2002 suggested that much of the simplicity of the fauna of large inland lakes was associated with habitat homeogeneity, rather than it being explained by episodicity limiting diversification in arid-zone lakes.…”