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
This thesis aimed to investigate the impact of exposure dynamics, relative contributions of ENPs(particle) and ENPs(ion), and dosing regimens on the toxicity of ENPs varying in different physico... Show moreThis thesis aimed to investigate the impact of exposure dynamics, relative contributions of ENPs(particle) and ENPs(ion), and dosing regimens on the toxicity of ENPs varying in different physico-chemical properties, on the composition and functioning of soil microbial communities. The physico-chemical properties of ENPs could change their fate, and the exposure dynamics thus need to be taken into consideration for realistically characterizing the time-variable exposure in assessing toxicity. The metabolic profile of microbial community could change according to ENPs shapes, with nanoplates being more toxic than nanospheres and polygons. Regarding the microbial community composition, the effect of ENPs depended on exposure time and concentration. However, the alterations in community composition were not expressed in terms of community functioning, which indicates that genus specific changes occurred but not yet necessarily reflected biological significance with regard to community functioning. Functional redundancy might contribute to community tolerance to ENPs exposure. When exposed to more realistic ENPs exposure scenarios with multiple dosing frequencies instead of one-time injection, the repetitive exposure with low-dosing could induce a tendency towards larger alteration of both community composition and functioning. Our study thus provided further insights in understanding the impact of NPs on soil microbial communities towards environmentally relevant assessment. Show less
