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Internal Report 242
O'Connor R, Humphrey CL, Lynch CM & Klessa B
Supervising Scientist Division, 1997
Department of the Environment, Water, Heritage and the Arts
Aquatic macroinvertebrates were sampled from the littoral zone of eleven lentic waterbodies of Magela and Nourlangie Creek catchments over a 3 week period in May 1996. Four of the waterbodies occurred on the project area of the Ranger Uranium Mine (RUM), three of which were contaminated to varying degrees by mine-waste waters. Differences in taxa richness were not marked between waterbodies on the mine lease and control waterbodies, with Gulungul Billabong having the highest average richness (25.4 taxa) and Jabiru lake the lowest (18). However, some differences in the macroinvertebrate community of sites on the RUM lease from others was evident using multivariate ordination techniques. Environmental correlates of the ordination space included various features of aquatic macrophytes. In particular the amount of macrophyte cover at sites was a gradient that appeared particularly important in separating artificial waterbodies from natural billabongs. The absence or low abundance of palaemonid prawns and bithyniid snails from the waterbodies receiving mine waste waters was correlated with the environmental gradient separating these sites from control waterbodies within the Magela system which suggests their numbers were affected by mining activities. Impacts of mining on lentic waterbodies was generally less apparent in 1996 than it was in 1995.