Population-level ecological risk assessment of planar polychlorinated aromatic hydrocarbons in great cormorant (Phalacrocorax carbo) around Tokyo Bay, Japan.

Assessment of population-level ecological risk posed by planar polychlorinated aromatic hydrocarbons (p-PCAHs; including polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, and dioxintike polychlorinated biphenyls) in sediment of Tokyo Bay (Japan) and rivers via fish ingestion to the great cormorant (Phalacrocorax carbo) population was conducted by means of a probabilistic approach. Population decline risk was used as an indicator of population-level effects and compared with other indicators of effects. The increment of egg mortality risk posed by current p-PCAH levels was estimated to be 11.7%. This risk was interpreted in terms of both the increase of the risk of population decline in a 10-year period on a recently abundant cormorant population, and the reduction in population growth rate (r). Population decline risks of 20% and below were estimated to be 16% for the reference population and 32% for the exposed population, whereas the reduction in r was estimated to be 10%. The risk expressed in terms of population viability is a more susceptible measure and a more easily understandable indicator than both egg mortality risk as an individual-level risk and the reduction in r. Translating the effects due to pollutants into the risk on population viability will make ecological risk assessment more conductive to risk management.