Mortality and LC50Values for Several Stages of the Marine CopepodTigriopus 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 ofTigriopus brevicorniswas 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 LC50values were determined by probit analysis. LC50values for ovigerousT. brevicornisfemales were 153.2 μg liter−1for atrazine, 59.9 μg liter−1for carbofuran, 47.9 μg liter−1for cadmium, 27.5 μg liter−1for arsenic, 24.3 μg liter−1for malathion, and 4.6 μg liter−1for dichlorvos. Comparison of the overall toxicities of these pesticides and metals indicated that dichlorvos was the most toxic substance toT. brevicornis, followed by malathion, arsenic, cadmium, carbofuran, and atrazine. Available LC50data indicate that marine copepods are more sensitive to pollutants thanDaphnia magna, Acartia tonsa, andTisbe battagliai, or as sensitive as the mysidMysidopsis bahia.