Effects of metal contaminants on the development of the common Antarctic sea urchin Sterechinus neumayeri and comparisons of sensitivity with tropical and temperate echinoids

Abstract

A toxicity test was developed to examine the effects of metal contaminants on the sen- sitive early life history stages of the common Antarctic echinoid Sterechinus neumayeri (Meissner). Embryos and larvae of the sea urchin were exposed to the metals copper, cadmium, zinc and lead, and the effects of each metal on development to hatched blastulae after 6 to 8 d, and to 2-arm plutei after 20 to 23 d were monitored. These metals are common in Antarctic marine environments and are often found at elevated levels at sites subject to anthropogenic inputs. For all metals tested, the long- term test to the 2-arm pluteus stage was more sensitive than the short-term test. Copper was the metal most toxic to developing embryos and larvae of S. neumayeri with EC50s of 11.4 µg l -1 and 1.4 µg l -1 following 6 to 8 d and 20 to 23 d exposure respectively. Exposure to cadmium at concentra- tions greater than 2 mg l -1 caused a significant decrease in the proportion of embryos developing nor- mally to hatched blastulae (EC50 = 6.9 mg l -1 ) and concentrations greater than 0.2 mg l -1 , caused a decrease in normal 2-arm plutei. EC50 values calculated for zinc were 2230 and 326.8 µg l -1 for the short- and long-term tests respectively. Lead had no effect on development of embryos following 7 d exposure at all concentrations tested (up to 3.2 mg l -1 ). As the concentration of Cu shown to inhibit development of S. neumayeri is similar to levels found at impacted sites in Antarctic nearshore envi- ronments, results of this study indicate that this metal may have an impact on the development of S. neumayeri. The sensitivity of S. neumayeri to copper and cadmium in tests based on development to hatched blastulae (6 to 8 d) are generally comparable to results of tests on echinoids from tropical and temperate regions that use development to 2-arm plutei (2 to 4 d) as the end-point. However, the Antarctic species is more sensitive to copper and cadmium than the tropical and temperate species if the tests are continued to the same stage of development, the pluteus larva (20 to 23 d for the Antarc- tic species). Comparing the tolerance of a key developmental stage common to all planktotrophic sea urchins may be more ecologically relevant than simply comparing exposure over a fixed period of time, because for an embryo to survive to adulthood it must successfully complete all development stages. This is the first reported evidence that Antarctic species could be more sensitive to contami- nants than species from warmer regions.