Ramage, Calum
(2024)
Assessing the impacts of organic and inorganic contaminants on British rivers: from sediments to fish.
PhD thesis, University of Nottingham.
Abstract
Human activity is responsible for the release of harmful levels of environmental contaminants into the environment, with pesticides and trace elements amongst the most prevalent. Rivers are particularly vulnerable to the accumulation of chemical pollutants, posing significant health risks to local aquatic wildlife. However, relatively little is known about their presence, distribution, and impacts on UK aquatic ecosystems. This study aimed to assess the environmental impacts of trace element and pesticide pollution in English rivers, focusing on their environmental distribution, bioaccumulation in aquatic wildlife, and associated risks, particularly to fish.
Two typical but contrasting river catchments of mixed land-use, the River Tone (Somerset) and River Wensum (Norfolk) were chosen as study areas for their documented concerns about chemical pollution and ecological integrity, and for their representativeness of similar rivers throughout the UK. Water, sediment, fish (roach - Rutlius rutilus) and invertebrate samples were collected from multiple sites within each catchment. Targeted pesticide and trace element analyses were conducted to assess pollution levels and trophic transfer within the rivers.
Pesticide pollution was ubiquitous in both rivers, with complex pesticide mixtures detected throughout. Modern neonicotinoid insecticides, as well as banned pesticides, frequently exceeded environmental quality standards. Significant chronic and acute risks to algae, invertebrates, and fish were detected in both catchments, with the highest risks driven by neonicotinoids. Trace element pollution was also detected in both rivers, but concentrations were generally within natural geological ranges for the surrounding regions. Concentrations of copper, lead, and zinc occasionally exceeded aquatic and sediment toxicity thresholds and indicated risks to aquatic wildlife, but exceedances were rare and localised.
Fish in both rivers were chronically exposed to many pesticides and trace elements. Pesticides were detected in every single fish, with some individual chemicals detected in 90- 100% of sampled individuals. The potential implications of pesticide bioaccumulation for fish health, however, remain poorly understood. Elevated mercury concentrations were detected in roach from the River Tone and pose a risk to piscivorous wildlife. Meanwhile in the upper- Wensum, elevated selenium in roach ovaries, suspected to arise from agricultural pollution, exceeded US EPA benchmarks for fish health and indicate teratogenic risks.
To assess the condition of fish living in these two chronically polluted rivers, an in- depth fish health assessment using a multibiomarker approach was conducted. The relationship between health markers and chemical concentrations was also explored using multivariate analyses. In both rivers, biochemical marker responses indicated exposure to neurotoxic chemicals and oxidative stress-causing chemicals or other stressors. In the River Wensum, histopathological marker responses and high parasitic loads were indicative of prolonged physiological stress due to environmental conditions. Whilst the observed
responses are unlikely to cause death, they may reduce overall fitness and make fish more susceptible to other stressors, such as heat waves and eutrophication, both of which are predicted to become more common under climate change. Establishing clear causal relationships between chemicals and fish health proved challenging, but multiple lines of evidence implicate chemical pollution, particularly from agriculture, as a contributing factor affecting fish health.
Overall, both trace metal and pesticide pollution can have significant consequences to freshwater ecosystems. The present study provides evidence of widespread pollution in two typical English river catchments bringing significant risks to ecosystem health. Given their widespread distribution, and considering their persistence, potential for trophic transfer, and high toxicity, effective management solutions must be in place to limit the risks they pose. At the forefront of effective management must lie a robust monitoring network that is capable identifying risks before they translate into population and ecosystem-level consequences. In addition, further research should aim to bridge the significant knowledge gaps in our understanding of chemical pollution and risk to rivers in England.
| Item Type: |
Thesis (University of Nottingham only)
(PhD)
|
| Supervisors: |
Yon, Lisa
Johnson, Matthew
Vane, Christopher
Bailey, Elizabeth
Gardner, David |
| Keywords: |
River Pollution, Water quality, pesticides, trace elements, trace metals, environmental contaminants, fish health effects, ecotoxicology, bioaccumulation, chemical exposure |
| Subjects: |
T Technology > TD Environmental technology. Sanitary engineering |
| Faculties/Schools: |
UK Campuses > Faculty of Medicine and Health Sciences > School of Veterinary Medicine and Science |
| Item ID: |
79900 |
| Depositing User: |
Ramage, Calum
|
| Date Deposited: |
11 Dec 2024 04:40 |
| Last Modified: |
11 Dec 2024 04:40 |
| URI: |
https://eprints.nottingham.ac.uk/id/eprint/79900 |
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