Sensitivity and response time of three common Antarctic marine copepods to metal exposure

Understanding the sensitivity of Antarctic marine organisms to metals is essential in order to manage environmental contamination risks. To date toxicity studies conducted on Antarctic marine species are limited. This study is the first to examine the acute effects of copper and cadmium on three common coastal Antarctic copepods: the calanoids Paralabidocera antarctica and Stephos longipes, and the cyclopoid Oncaea curvata. These copepods responded slowly to metal exposure (4–7 d) emphasising that the exposure period of 48–96 h commonly used in toxicity tests with temperate and tropical species is not appropriate for polar organisms. We found that a longer 7 d exposure period was the minimum duration appropriate for Antarctic copepods. Although sensitivity to metal exposure varied between species, copper was more toxic than cadmium in all three species. P. antarctica was the most sensitive with 7 d LC50 values for copper and cadmium of 20 μg L⁻¹ and 237 μg L⁻¹ respectively. Sensitivities to copper were similar for both O. curvata (LC50 = 64 μg L⁻¹) and S. longipes (LC50 = 56 μg L⁻¹), while O. curvata was more sensitive to cadmium (LC50 = 901 μg L⁻¹) than S. longipes (LC50 = 1250 μg L⁻¹). In comparison to copepods from lower latitudes, Antarctic copepods were more sensitive to copper and of similar sensitivity or less sensitive to cadmium. This study highlights the need for longer exposure periods in toxicity tests with slow responding Antarctic biota in order to generate relevant sensitivity data for inclusion in site-specific environmental quality guidelines for Antarctica.