The effects of thermal, chemical and radiological stressors on embryonic development in lake whitefish (Coregonus clupeaformis)

Abstract

Power generation relying on once-through cooling has the potential to release thermal, chemical and radiological stressors into the environment. These discharges may impact development in aquatic species that spawn near cooling water releases. This thesis explores the impacts that stressors associated with industrial cooling water discharges can have on lake whitefish (Coregonus clupeaformis) embryonic development. In-situ incubation in custom designed chambers was used to examine development in thermally impacted areas near a nuclear power plant in Lake Huron. Temperatures at sites near cooling water discharges were significantly warmer and more variable compared to off-site reference locations but were below lethal levels. However, an accelerated development and potential earlier hatch was predicted at these sites based on temperature modelling and morphometric measurements on retrieved embryos. Chemical (morpholine and sodium hypochlorite) and radiological effects were examined in laboratory reared embryos following both chronic and acute exposures. Embryos became more resistant to radiation as development progressed, while mortality from morpholine exposure was greatest close to hatch. Embryos were minimally impacted by incubation in sodium hypochlorite. Both a synergistic and protective effect were observed in percent mortality when stressors were examined in combination. Low dose sublethal exposure to morpholine and ionizing radiation resulted in changes in hatch timing and stimulation in growth. Overall, this work helps to advance the understanding of how thermal, chemical and radiation exposure impacts embryonic survival and development, and evaluates potential effects of exposure at environmental levels on lake whitefish.