Monitoring aquatic invertebrates and waterbirds at Toolibin and Walbyring Lakes in the Western Australian wheatbelt

La Trobe University Faculty of Science, Technology and Engineering Murray Darling Freshwater Research Centre

MDFRC item.

Toolibin and Walbyring Lakes are adjacent wetlands in the Western Australian wheatbelt, a region with widespread secondary salinization. Salinity of water in Toolibin has increased in recent years and a Recovery Plan is being implemented to reduce salt loads; Walbyring is also threatened by salinization. As part of a monitoring program to evaluate success of recovery actions, waterbirds and aquatic invertebrates were sampled at both wetlands in December 1999. Toolibin Lake had the richer waterbird community, while Walbyring Lake contained more invertebrate species. Results suggested that gross changes in wetland communities can be detected by monitoring based on an annual waterbird survey and a pair of invertebrate samples collected with 110 µm and 250 µm-mesh pondnets. Comparison of waterbird data from Toolibin in 1996 with earlier surveys showed increases in salinity to 1996 affected occurrence of only a few species. Comparison of invertebrate data from both wetlands in 1996 with surveys in 1992 provided little evidence that increased salinities affected invertebrates, other than water mites. It is suggested that the freshwater fauna of the wheatbelt is comparatively salt-tolerant and substantial changes in community composition will be seen only when salinities exceed 10 000 mg L-1.