Organic micropollutants in freshwater ecosystems : pollution dynamic and adverse effects at population genetic level in a model freshwater population

The environment, and particularly freshwater ecosystems, is permanently under anthropogenic pressure, mainly due to the need of mankind to satisfy the ongoing demand of goods and services in order to support our society. However, continuous requests of ecosystem services undoubtedly evoke environmental consequences. Chemical contaminations are widely known for their harmful impacts on aquatic organisms and are today discussed as being responsible for increasing global impairments of ecological balance. In addition to direct effects, sublethal effects on the genetic level are increasingly suggested to provide versatile indicators for the assessment of hazardous chemicals. Such genetic effects of chemical stressors on aquatic organisms have so far been poorly addressed. The aim of this thesis is to contribute to our understanding how anthropogenic pressures, particularly chemical and non-chemical stressors, may impair aquatic ecosystem functioning. The novel approach presented here is based on the analytical and thematic combination of evolutionary ecotoxicology and body burden analysis of organic micropollutants. The CHAPTER 1 offers an overview of the state-of-the-art regarding the occurrence and potential ecological effects of organic micropollutants in aquatic environments. Furthermore, a concept regarding the likely value of including evolutionary ecotoxicology in future assessments is presented. In CHAPTER 2, a multi-target screening method based on pulverised liquid extraction and a modified QuEChERS approach with additional hexane phase was developed and optimised. This method allows the extraction and measurement of a wide range of organic micropollutants, acknowledging the emerging relevance of biological environmental tissues in environmental chemistry and ecotoxicology. The new method developed here was successfully applied in different freshwater ecosystems, including the River Danube along its watercourse and the River Holtemme in Central Germany. The method exhibited particularly robust performance compared to other published analytical methods. In essence, low quantification limits and high recovery rates make this method suitable to detect pesticides, such as insecticides, herbicides and fungicides and wastewater-derived pollutants such as industrial chemicals and pharmaceuticals, in tissues of biological samples. The results obtained with this method were combined with other environmental matrices in order to examine the environmental dynamics of emerging organic micropollutants in the River Holtemme. In CHAPTER 3, a multi-compartment approach based on chemical activity, equilibrium and predicted baseline toxicity was developed. A direct injection, pressurised liquid extraction methods, and the multi-target screening method developed in CHAPTER 2 were used in order to quantify emerging organic micropollutants in water, sediment and biota, respectively. Freely dissolved concentrations of compounds quantified in the River Holtemme and their corresponding chemical activities were calculated in the water, sediment and biota (Gammarus pulex tissues) compartments. The bioavailable fraction of pollutants and thus the fate and distribution of emerging compounds were assessed. According to equilibrium partitioning theory, the chemical activity of an organic compound is equal in sediment organic carbon, in exposed biota and in pore water, if equilibrium is reached between these phases. Sediments showed highest chemical activities and significant differences were quantified between water and biota compartments. The findings obtained suggest that the system studied here was in disequilibrium based on the equilibrium partitioning theory. Additionally, sediment samples exhibited the highest potential toxicity. Hazard assessment of the quantified contaminants showed a strong dependency on which compartment is analysed. CHAPTER 4 demonstrates the biological effects of long-term exposure to pollution on a model freshwater invertebrate population. Briefly, the adverse effects of global and emerging anthropogenic pressures were assessed using a novel approach based on evolutionary ecotoxicology and body burden analysis of organic micropollutants. This approach was then successfully applied to G. pulex populations occurring along the River Holtemme. The results provide empirical evidence of both direct and indirect effects due to chemical and non-chemical stressors. The analyses revealed pollutant-induced changes in the genetic structure as well as higher mutation rates downstream of a wastewater treatment plant. Furthermore, hindered gene flow due to physical barriers (i.e. weirs) separating upstream and downstream waters in the River Holtemme was detected. Although, these findings offer new insights into the field of ecotoxicology in general, and allows for new interpretation of the role of wastewater treatment plants as sources of chemical stress in the environment