The impact of pesticides on the benthic macroinvertebrates in a rural lake

KELLAR, C.; LONG, S.; BALLESTEROS, M.L; GOLDING, L.,; GAGLIARDI, B.; PETTIGROVE, V.

Berlin

Congreso; 6th SETAC World Congress / SETAC Europe 22nd Annual Meeting; 2012

Human activities at the landscape scale are a threat to the ecological integrity of many aquatic ecosystems. It is often difficult to isolate the effects of pollutants from other causative factors, and to identify the primary pollutants causing ecosystem stress. Additionally, pollutants may not be homogenously dispersed, with potentially varying effects on biota living within the same water body; therefore there is a need to have appropriate strategies for management in order to maintain the ecological integrity of the whole ecosystem. The study was undertaken at Lake Hawthorn in northwestern Victoria, Australia. Results from previous surveys of the lake showed that sediments were impacted by a number of pesticides which were also toxic to macroinvertebrates. Pesticides were not dispersed homogeneously throughout the lake. The aims of the study were to a) determine the number of samples that should be collected to ensure that there is an adequate assessment of contaminants present in sediment and water and b) determine if the composition and health of benthic macroinvertebrates are affected by the presence of pesticides. The lake was divided into six sampling locations and between three and five sites selected at each location, where sediment and surface water was collected and a range of chemicals were measured (including metals, a range of pesticides and nutrients). Benthic macroinvertebrates were sampled in a subset of sites at each location for species abundance and diversity and also for changes at the sub-organism level on a number of biochemical biomarkers. Sediments were also assessed for toxic effects on survival, growth and emergence of Chironomus tepperi using a laboratory-based bioassay and impacts on indigenous macroinvertebrates using field-based microcosms. There were elevated concentrations of copper and total petroleum hydrocarbons in sediment at one location within the lake, an urban inlet drain. There were also effects on C. tepperi survival at this location. Furthermore, there were no in situ chironomids collected at this location. Biomarker analyses on the chironomid Tanytarsus semibarbitarsus collected in situ showed that chironomids are responding differently within the lake. Our results show that the pollutants present in Lake Hawthorn vary spatially and that they are toxic to aquatic life. Results on sampling strategically and the usefulness of a multiple lines of evidence approach for aquatic biomonitoring will be discussed.