Time-related mortality responses of striped bass ( morone saxatilis) ichthyoplankton after exposure to simulated power plant chlorination conditions

Abstract

Time related mortality responses of striped bass eggs and prolarvae were evaluated after exposure to interacting total residual chlorine (TRC), ΔT and exposure time representing condenser entrainment and effluent discharge conditions. Mortality observations were conducted at unequal time intervals for 36 h after exposure to the test conditions. A non-linear least square regression model was separately fit to the cumulative mortality data for both eggs and prolarvae. Analysis of the immediate mortality response (death at time 0) of both eggs and prolarvae showed no significant effects of ΔT or interactions between ΔT and the other variables; however, only a few hours after exposure ΔT does have a significant effect on the mortality response. Significant two-way interactions between life stage and exposure time ( P < 0.001) as well as life stage and TRC ( P < 0.003) were found. Analysis of maximum percent cumulative mortality using an arcsine transformation showed no significant interactions among factors affecting latent mortality responses of either life stage. Significant latent mortality effects (mortality after time 0) were due to life stage, exposure time, TRC and ΔT. Cumulative percent mortality increased for both life stages as each test condition increased; prolarvae experienced greater mortality than eggs at all levels. Time of peak mortality for prolarvae occurred later with lower levels of treatment. The mortality peak was sharper in prolarvae than in eggs.