Summary
Stressors associated with climate change, and contaminants resulting from the activities of humans, are affecting organisms and ecosystems worldwide. Until recently, the impacts of these stressors on marine ecosystems have largely been examined in isolation. However, with predicted climate change, it is essential that the interactions between these stressors are known, so that the risks of contamination under present and future climate change scenarios can be determined. High latitudinal species may be more susceptible to contamination and climate change than equivalent species in temperate and tropical areas. Detoxification of contaminants by polar species is likely to be slower due to slow metabolisms in colder climates. Organisms in polar regions also have characteristically small temperature tolerances through adaptation to relatively stable and low oceanic temperatures. Therefore, any increase in ocean temperature associated with climate change is likely to be particularly detrimental to marine ecosystems in these areas. Despite this, very little is known of how climate change stressors and contamination will affect Antarctic and subantarctic species, nor how these stressors will interact with each other in marine ecosystems worldwide. Despite being relatively untouched, the subantarctic has endured many decades of human habitation leading to the accumulation of wastes and contamination in some areas. In addition, climate change in subantarctic marine environments is evident. On Australia’s subantarctic Macquarie Island, temperature and rainfall are increasing. Not only will this create thermal and osmotic stresses, increased rainfall will potentially increase mobilisation of contaminants from the land into the intertidal zone. Near-shore marine assemblages are particularly at risk, due to both fuel spills associated with shipping, which often occur close to land, and to run-off of contaminants from terrestrial systems. The effects of multiple stressors were investigated on intertidal marine invertebrates from a range of taxonomic groups collected from subantarctic Macquarie Island. Test species included the bivalve Gaimardia trapesina, the flatworm Procerodes ohlini, the sea cucumber Pseudopsolus macquariensis and an harpacticoid copepod. Copper was chosen as a representative contaminant as it highly toxic to biota and is common at contaminated sites in polar environments. Replicate tests were run on each species to enable determination of point estimates such as median lethal concentrations (LC50s). Metal concentrations in test solutions were determined by Inductively-Coupled Plasma Optical Emission Spectrometer (ICP-OES). Once sensitivity to copper alone was determined, multi-stressor tests were conducted by exposing test organisms to a range of copper concentrations, and to several salinities and temperatures relevant to predicted climate change scenarios. Interactions between stressors were determined by comparing LC50s for each stressor combination, and by ANOVA. Sensitivity to copper was found to be amplified by increased temperature and reduced salinity. Concurrent with other regions of the world, this indicates that the interactive effect of contamination and climate change stressors will have major impacts on subantarctic marine invertebrates and ecosystems.