A PHOTOTAXIS INHIBITION ASSAY USING BARNACLE LARVAE

The effects of sublethal concentrations of phenol and cadmium on the p hototactic responses of the stage II nauplii of the barnacle Balanus a mphitrite were investigated. Increased toxicant concentrations caused a reduction in phototactic responses. Balanus amphitrite nauplii expos ed to nominal phenol concentrations of 100 ppm and higher for 1-12 h f ailed to exhibit phototactic responses, while longer exposure times of 24 and 48 h reduced the lowest observable effect concentration (LOECs ) to 80 and 60 ppm, respectively. For cadmium, the LOECs, based on nom inal concentrations, for B. amphitrite following 1, 6, 12, 24, and 48 h exposures were 20, 4.5, 4.0, 1, and 0.75 ppm, respectively. The LOEC s can be significantly reduced by increasing the duration of exposure to the toxicants. A good relationship exists between the phototactic r esponse and toxicant concentration as well as exposure time. Results o f this study indicate that the toxicant-induced reduction in phototact ic responses of barnacle larvae can be used in a sensitive, rapid scre ening test for ecotoxicological assessments. (C) 1997 by John Wiley & Sons, Inc.