Pollution fingerprints in eels as models for the chemical status of rivers

The 2006 EU Water Framework Directive (WFD) proposed the monitoring of a selection of priority substances in the aquatic phase, including lipophilic substances. However, there are strong arguments for measuring lipophilic substances in biota. Yellow eel is a good candidate because it is widespread, sedentary, and accumulates many lipophilic substances in its muscle tissue. Several authors have described the indicative value of measured concentrations, yet few studies have investigated to what extent the spectrum of contaminants present characterizes the local environmental pollution pressure. To evaluate the value of the pollution profile of an eel as a fingerprint of the chemical status of the local environment, two datasets were selected from the Flemish Eel Pollutant Network database. The pollution profiles in individual eels along a river ( even at distances,5 km) proved to be significantly different. Analysis of pooled contaminant data from multiple sites and sampling years within rivers allows characterization of river-specific chemical pressures. These results highlight the usefulness of eels as bio-indicators for monitoring pollution with lipophilic chemicals, such as polychlorinated biphenyls and organochlorine pesticides, in rivers. As such, eels may be used effectively within the monitoring programme for a selection of priority substances referred to in the WFD.