Salt lakes of the northern agricultural region, Western Australia

Abstract

A survey of 11 sites covering three large (>10 km long, 6 sites) playa lakes and four pans ( < 1 km 2 , 5 sites) of the Yarra Yarra salt lake system in the Northern Agricultural Region of Western Australia commenced in 2001. These salt lakes are shallow and ephemeral, with inundation being more regular following winter rainfall, but summer inundation also occurred in 2001. Salinity was generally higher in playas (156-368 g l -1 ) than pans (30-284 g l -1 ), but salinity responded noticeably to heavy rainfall events, especially in pans. pH values in the playa lakes (6.68-7.82) were less variable than in the pans (6.81-8.08). The range of dissolved oxygen concentrations was greater in pans (3.7-14.4 mg l -1 ) than in playas (3.9-8.2 mg l -1 ). Cationic concentrations generally followed the pattern of sea water cation dominance. Benthic microbial communities comprised either cohesive to loosely mucilaginous mats, or thin films of diatoms. Five genera of diatom and two species of filamentous cyanobacteria were recorded.

Distribution of modern diatom assemblages among small playas

“…Despite being a conspicuous element of the landscape and under serious threat from well documented land clearance and associated secondary-salinisation issues in the catchment (Henschke 1989;Clarke 2001;Regeneration Technology Pty Ltd 2001;Keighery 2004) only a handful of playas of the Yarra Yarra drainage system have been sampled for their aquatic biology in the past 25 years (see Brock and Lane 1983;Brock and Shiel 1983;Smith 2001;Blinn et al 2004;Pinder et al 2004Pinder et al , 2005Boggs et al 2007b). Systematic survey is likely to have been hindered by the unpredictability of hydroperiod, inaccessibility and socio-economic barriers such as the incompatibility of playas with agricultural land-use practices.…”