Characterising the effects of multiple stressors in estuarine environments using pelagic and benthic copepod bioassays

Abstract

Population growth around coastal areas increases anthropogenic stressors in urban estuaries. Robust test methods are needed to evaluate the impacts of these pollutants on exposed ecosystems. The main objective of this thesis was to develop and validate toxicity tests in a native pelagic copepod, and use it with the previously validated benthic copepod Quinquelaophonte sp. The species Gladioferens pectinatus was selected based on life history traits such as wide distribution along coastal areas, ability to be cultured in the lab, high reproductive rates and a short life-cycle and sensitivity to toxicants. Acute (48 hr) and chronic(6 days) copepod bioassays were developed using survival, naupliar development ratio and reproductive success endpoints. The tests were validated using common pollutants; copper(trace metal), phenanthrene (polycyclic aromatic hydrocarbon) and chlorpyrifos (pesticide). The naupliar development was the most sensitive endpoint. Field validation was conducted in combination with the benthic harpacticoid copepod Quinquelaophonte sp bioassay using urban sediment samples from the Ahuriri Estuary in Napier. Gladioferens pectinatus was further validated as a model species to characterize genotoxicity effects using the single cell electrophoresis technique (referred as comet assay). Significant differences between the integrity of DNA in the negative and positive controls and in the field samples suggested G.pectinatus as a good model for an early warning genotoxicity signal. Both test models were also used to generate effects-based information to assess the efficacy of a remediation programme in one of New Zealand’s busiest ports. Sediment and elutriate tests were conducted using sediment samples from locations along a gradient of contaminants in the port. TBT-spiked sediment bioassays were conducted to characterise the toxicity of TBT alone. The acute toxicity bioassay showed that the remediation improved sediment quality, but the chronic responses were not significantly different. The combination of the benthic and pelagic copepod bioassays provided a robust approach to assist in the development of reliable water and sediment quality guidelines. The results suggest that the bioassays can be used as a powerful tool to complement risk assessment processes of estuarine waters and sediment by providing effects-based information and ecologically meaningful measures to improve regulatory processes in New Zealand.