Summary
Understanding the sensitivities of Antarctic organisms to metal exposure is essential when developing protective environmental quality criteria for Antarctica. This study takes a community based approach to determine the potential effects of metal contamination on coastal Antarctic zooplankton. Multi-species community toxicity tests were conducted to investigate the sensitivity of the zooplankton assemblage as a whole as well as the sensitivity of key predominant species to aqueous copper, cadmium and zinc. Of the metals tested, copper was found to be the most toxic metal (EC50 of 79µg Cu/L) with cadmium and zinc significantly less toxic (EC50’s of 1417µg Cd/L and 1776 µg Zn/L). It was found that the coastal Antarctic zooplankton communities are more sensitive to copper and less sensitive to cadmium compared with reported studies on temperate zooplankton. Metal toxicity increased with increasing concentration and exposure time in all cases however delayed responses were found in zooplankton exposed to cadmium and zinc when compared to copper. Mortality, particularly in cadmium and zinc treatments was still increasing in tests at 10 days, indicating that a long exposure period is needed when testing for a response in Antarctic zooplankton. An increase in community dissimilarity between treatments and the control at the conclusion of the experiment (day 10) with increasing metal concentrations was observed in most cases. The earlier life stages (copepod nauplii, polychaete trochophores) were found to be more sensitive than adults. Development from nauplii to copepodite in the copepod Ctenocalanus citer was inhibited by exposure to sub-lethal metal concentrations. This study has highlighted the importance of using a community based approach when assessing the impacts of pollution on zooplankton. Results from community tests with longer exposure periods will be useful in revealing the general sensitivities of communities and showing how these sensitivities can vary both spatially and temporally.