The effects of power plant condenser cooling water entrainment on the amphipod. Gammarus sp.

The abundant Hudson River amphipod Gammarus sp. was examined for viability before and during entrainment in the Indian Point cooling water system. The mean per cent survivial of Gammarus sp. sampled during ΔT's of 7.1–8.3°C and ambient temperatures of 24.9–26.0°C was 98.5 and 97.4 per cent for the two intake stations and 90.1 and 96.8 per cent for the discharge canal stations D-1 and D-2 respectively. A statistically significant (α = 0.05) difference was detected between the survival of Gammarus sp. at the intake stations and discharge station D-1. located near the upper end of the discharge canal. Entrained Gammarus sp. experience increased initial and latent mortalities during periods of condenser chlorination. Comparison of the abundances of entrained Gammarus sp. during day and night sampling periods reveals a significantly higher occurrence during darkness. Temperature bioassays indicate that the thermal tolerance of Gammarus sp. is dependent on exposure time and ambient temperature. The temperature resulting in a 50 per cent mortality of Gammarus sp. for 30 min exposure times increased approximately 11 C as ambient temperatures increased from 2.5 to 25.8°C. Consequently, Gammarus sp. was capable of surviving ΔT's of greater magnitude as the ambient temperature to which they were acclimated decreased. Temperature bioassays indicated that Gammarus sp. should be able to tolerate all projected time-temperature exposure combinations encountered during entrainment through the cooling water system.