Mortality and LC50 values for several stages of the marine copepod Tigriopus brevicornis (Müller) exposed to the metals arsenic and cadmium and the pesticides atrazine, carbofuran, dichlorvos, and malathion.

The toxicity of three insecticides (carbofuran, dichlorvos, malathion), an herbicide (atrazine), and two metals (arsenic and cadmium) to ovigerous females, copepodids, and nauplii of Tigriopus brevicornis was determined by 96-h semistatic (or static-renewal) bioassays. Freshly prepared aqueous stock solutions of these pesticides and metals were diluted to appropriate concentrations. Mortalities were recorded and test solutions were changed completely each day up to 96 h. The rate of mortality was analyzed for linear regressions, and LC50 values were determined by probit analysis. LC50 values for ovigerous T. brevicornis females were 153.2 micrograms liter-1 for atrazine, 59.9 micrograms liter-1 for carbofuran, 47.9 micrograms liter-1 for cadmium, 27.5 micrograms liter-1 for arsenic, 24.3 micrograms liter-1 for malathion, and 4.6 micrograms liter-1 for dichlorvos. Comparison of the overall toxicities of these pesticides and metals indicated that dichlorvos was the most toxic substance to T. brevicornis, followed by malathion, arsenic, cadmium, carbofuran, and atrazine. Available LC50 data indicate that marine copepods are more sensitive to pollutants than Daphnia magna, Acartia tonsa, and Tisbe battagliai, or as sensitive as the mysid Mysidopsis bahia.