Changes in the waterbirds and other biota of Lake Yumberarra , an episodic arid zone wetland

Lake Yumberarra is a small freshwater lake (151 ha) in the Currawinya National Park in southwestern Queensland. During 1995-2003 it held water much of the time in two fillingdrying cycles, one initiated by riverine flood water and the second by local runoff. Water in both was clear, alkaline and generally fresh, but became saline as it dried. Zooplankton comprised 27 crustaceans and a few rotifers with the copepod Boeckella triarticulata dominant. Numbers were greatest soon after filling and in each spring and least towards drying. At least 44 taxa of macroinvertebrates inhabited the littoral zone, with hemipterans and chironomids dominant. Waterplants, chiefly Myriophyllum verrucosum, grew abundantly in the first half of each filling cycle. A limited fish fauna inhabited the lake, with carp present only in the first cycle. The lake was used extensively by 59 species of waterbirds, with four foraging groups dominant at different times probably reflecting fluctuating abundance of their food resources. Breeding in the lake was not widespread, nor was the lake used much by migratory waders, unlike some other wetlands in the Paroo. Its unusually high species richness and bird densities means the lake is important for feeding and maintaining waterbird diversity in an arid landscape.