Macroinvertebrate community structure and water quality variation in an effluent impacted wetlands (Lake Coleman), Victoria, Australia

Abstract

Temporal and spatial variation in water quality and macroinvertebrate community structure were assessed in Lake Coleman, a shallow wetland adjacent to the Gippsland Lakes, Victoria, Australia. Littoral water quality and macroinvertebrate samples were collected annually in spring for 3 years following the cessation of a 30 year discharge of a treated effluent to the wetland. The discharged effluent contained highly coloured pulp and paper wastewaters as well as domestic and industrial effluents. Temporal changes in wetland water quality were related to the cessation of effluent discharge which resulted in reduced water colour and nutrient concentrations at discharge sites. Water quality was also affected by the inundation of the wetland by floodwaters in 1993 which lowered salinities across the wetland and also increased colour and nutrient concentrations at non-outfall sampling sites. Lake Coleman littoral macroinvertebrate species richness was lower than that reported for an adjacent, relatively unimpacted wetland, but was up to 3 times higher than in another local wetland impacted by sewage discharge. Macroinvertebrate community structure was variab;e over time and displayed no consistent pattern between sites. Changes in macroinvertebrates species richness and densities were associated with wetland flooding. Further monitoring is required to assess long term changes to wetland macroinvertebrate community structure resulting from current management strategies.