The relevance of environmental quality standards for biota in the evaluation of the ecological quality of aquatic ecosystems

Aquatic chemical pollution, mainly of anthropogenic origin, is a global issue. A specific group of persistent pollutants with distinct hydrophobic/lipophilic characteristics tend to biomagnify (i.e. reaching high concentrations in higher trophic levels) and exhibit low detection rates in water samples. Therefore, within the Water Framework Directive, Environmental Quality Standards were derived for 11 priority compounds and their derivatives. These are to be measured in biota specifically (EQSbiota), in order to assess the risk of secondary poisoning of top predators (including humans) and include hexachlorobenzene (HCB), hexachlorobutadiene (HCBD), mercury (Hg), brominated diphenyl ethers (PBDE), perfluorooctane sulfonate (PFOS), hexabromocyclododecane (HBCD), dicofol, dioxins and dioxin-like compounds, heptachlor and heptachlor epoxide, fluoranthene and benzo(a)pyrene. In this PhD, the relevance of the current EQSbiota with regards to ecological quality of aquatic freshwater and brackish ecosystems was evaluated. The study was built around the EQSbiota monitoring in Flanders on 44 sampling locations. The abovementioned compounds and PCBs were analysed in indigenous European perch (Perca fluviatilis) and eel (Anguilla anguilla) in its juvenile ‘yellow eel’ stage. However, benzo(a)pyrene and fluoranthene were analysed in transplanted caged bivalves because of their fast metabolization in fish. Accumulated concentrations were checked for compliance against the current standards and compared to passive sampler data. The main motivation for this PhD was that, despite frequent exceedances of the some EQSbiota (often with a large factor), no apparent effects on the aquatic ecosystem (including secondary poisoning) are reported in literature. Next, two case studies were included on accumulation patterns of Hg and PFAS. In contrast to the other lipophilic compounds, they show a high affinity for proteins. For Hg, accumulation in muscle and liver tissue was compared between the two fish species and linked to size (i.e. proxy for age). PFAS profiles were compared between mussels and fish, allowing for the interpretation of trophic magnification. Furthermore, the effects of environmental (water and sediment) concentrations and abiotic characteristics on bioaccumulated concentrations were investigated. Eventually, the ecological relevance of the EQSbiota for the ecological quality, based on the macro-invertebrate community was studied. The human health risk was assessed for all compounds as well. Finally, results for exceedances of the standards, human health risk and ecological relevance were combined to interpret the overall relevance and protection level of the current EQSbiota. These results might serve as an important first indication for the need to revise or fine-tune the standards for specific compounds.

Publication year:2022

Keywords:Doctoral thesis

Accessibility:Open