Using Fish as a Sentinel in Risk Management of Contaminated Sediments.

Sediments polluted by historical emissions from anthropogenic point sources are common in industrialized parts of the world and pose a potential threat to the function of aquatic ecosystems. Gradient studies using fish as a bioindicator are an option to assess the ecological impact of locally polluted areas. This study investigates the remaining effects of historical emissions on sediments outside ten Swedish pulp and paper mills using perch (Perca fluviatilis). The aim has been to obtain a general picture of the impact area of local deposits of cellulose fiber-rich sediments containing elevated levels of trace metals, e.g., Hg, and organochlorines, e.g., dioxins. In addition to analyzing contaminant levels in muscle and liver tissue, morphological measures in the fish that constitute biomarkers for health and reproductivity were measured. Another aim was to augment existing historical data sets to observe possible signs of environmental recovery. Overall, the results indicate only a minor elevation in contaminant levels and a minor impact on the fish health status in the polluted areas, which in several cases is an improvement from historical conditions. However, exceptions exist. Differences in the ecosystems' responses to pollution loads are primarily explained by abiotic factors such as water turnover rate, bottom dynamic conditions, and water chemistry. Weaknesses in the sampling methodology and processing of data were identified. After minor modifications, the applied survey strategy has the potential to be a management tool for decision-makers working on the remediation of contaminated areas.