Acute and chronic cobalt toxicity in Dugesia dorotocephala
Date
2011
Authors
Sternenberger, Andrea, author
Ramsdell, Howard, advisor
Legare, Marie, committee member
Strauss, Steven, committee member
Journal Title
Journal ISSN
Volume Title
Abstract
Limited data are available regarding cobalt toxicity for water quality criteria and risk assessment evaluation for freshwater organisms. These experiments were performed to establish median lethal concentrations from short term studies and to identify the most sensitive sublethal effect in a long term study in a flatworm species, Dugesia dorotocephala. Another study was conducted to elucidate the relationship between calcium, magnesium and cobalt toxicity in D. dorotocephala. During 4 and 7 day studies, median lethal concentrations of cobalt increased with total hardness indicating a protective effect. Calcium was shown to be more protective than magnesium in the presence of cobalt. A 60 day study showed fissioning rate, a process essential for maintenance of the D. dorotocephala population, to be the most sensitive endpoint. A lowest observable adverse effect concentration (LOAEC) of 1 mg Co/L (nominal) was incorporated into the calculation of an acute to chronic ratio (ACR), an important metric for risk analysis accounting for sublethal effects that may occur by mechanisms different from lethal ones. A NOAEC (no observable adverse effect concentration) was not determined because significant effects were observed at the lowest cobalt concentrations tested (<1 mg Co/L). Without an exact NOAEC, the ACR values established in this study represent the upper and lower bounds of the acute to chronic ratio for cobalt in D. dorotocephala.