Freshwater is an important resource, but at a great risk of species decline due to habitat loss, pollution and over-exploitation, and invasive alien species. European and national regulation... Show moreFreshwater is an important resource, but at a great risk of species decline due to habitat loss, pollution and over-exploitation, and invasive alien species. European and national regulation dictate the monitoring of freshwater quality in the Water Framework Directive. The biological elements of these assessments focus on the organisms living in freshwater systems, such as fish, macroinvertebrates, and plants. Traditional monitoring of quality relies on labor-intensive and expensive collection and morphological identification of specimens. Recent developments in molecular techniques allow for easier identification through (meta)barcoding and species detection using environmental DNA (eDNA). This thesis explores the possibilities to integrate genetic tools into freshwater quality monitoring and impact assessments, by investigating the ability of DNA-based methods to approximate morphologically determined species occurrences and the influence of their abundance on quality ratios. Additionally, it examines the effects of replication strategies in eDNA sampling, and studies the implications of using eDNA monitoring across several trophic levels of the ecosystem in impact assessments. Combined with a growing body of literature, the findings in this thesis illustrate that molecular techniques will contribute to a better ecosystem understanding and allow for more effective monitoring and management of freshwater systems, safeguarding the ecosystem services provided to humankind. Show less
