The effects of entrainment on plankton at Koeberg nuclear power station

The plankton community entrained in seawater used for cooling at Koeberg Nuclear Power Station was studied to determine the effects of short-term exposure to heat, chlorine and physical stress on plankton survival and productivity. Field-based studies conducted between September 1985 and February 1988 revealed that phytoplankton biomass, measured as chlorophyll a, was reduced by an average of 55,33 per cent following entrainment, and average productivity was depressed by 38,29 per cent, mainly as a result of chlorination. Zooplankton mortality averaged 17,48 per cent for all species and 21,88 per cent for copepods, the dominant group. Plankton entrainment at Koeberg was not considered to be particularly detrimental to the marine environment because of the localized area affected, the rapid dispersion of heat and chlorine, the rapid regeneration times of phytoplankton and some zooplankton, the low abundance of commercially important species, and the potential for recruitment from the surrounding productive Benguela upwelling region. A review of entrainment effects at overseas power stations is incorporated in the discussion.