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Effects of complex discharges on the genetic diversity of fish populations - CB0447

The proposal requires a number of steps and diverse skills and will link the expertise in fish reproductive physiology and molecular biology at the University of Exeter, with the modelling knowledge and chemical analyses capabilities at CEH. The partnership will also involve the fisheries teams of the Environment Agency and indirectly Brunel University.

Whilst wastewater treatment works (WwTW) are successful in lowering the overall organic load from humans from reaching rivers, they were not designed to remove all contaminants. It is increasingly accepted that fish in British rivers are exposed to a very diverse range of chemicals such as heavy metals to persistent organic pollutants PCBs, PBDE, HCB, and more polar drugs and hormones associated with past, or present human activity. It is possible that some of these chemicals singly, or in combination affect fish through influencing their reproductive success. For example, it has been shown that male fish living in proximity to wastewater treatment work effluents in UK rivers are suffering from endocrine disruption and this can compromise their sexual development, leading to conditions such as intersex. Indeed, through the recent DEFRA/Environment Agency funded EDCAT 1 project it has been shown that ‘male’ roach (Rutilus rutilus) with moderate to severe intersex condition have a reduced ability to breed under competitive breeding scenarios (Harris, Hamilton et al., 2010). It has been further shown that long term exposure of roach to a WwTW effluent at full strength can cause complete sex reversal, resulting in an all female population (Lange et al., submitted). If it is the case that only a proportion of the resident males are capable of breeding successfully in wild fish living in British Rivers, whilst reproduction still occurs, genetic diversity may be reduced. Maintenance of genetic variability is important to reduce the likely risks of inbreeding within populations and it also provides the evolutionary potential for sustaining health of populations in the face of environmental changes. Environmental change is happening in the UK, and nowhere more so than Southern England with its projected population growth (more sewage, and greater demand for water) and projected lower flows (less dilution), and warmer water (less oxygen). Thus, with these changes to the water environment, the problem of limited genetic diversity and hence fitness could lead to the failure of impacted fish populations to adapt to environmental change. This proposal is highly relevant to some of the key environmental questions for the UK freshwater environment and will provide proof of concept on whether exposure to effluents form WwTW impacts on genetic diversity in roach populations inhabiting the River Thames.
1. Identification of hot spots (and cold spots) for WwTW effluent discharges and content in the River Thames (analyses of existing data). CEH
2. Identification of suitable study sites for analyses on the genetics on wild roach populations in the River Thames catchment. CEH/Exeter
3. Collection of fish scales from 4 study sites (2 heavily polluted with effluent from WwTW effluent, 2 reference sites). Environment Agency/CEH/Exeter
4. Extraction of DNA from 200 roach scales. Exeter
5. Analysis of 3000 microsatellite loci on the 200 roach samples. Exeter
6. Analyses to determine the following in the roach populations sampled: (a) Effective population size (b) Measures of genetic diversity (c) Evidence of historical bottlenecks. Exeter
7. Chemical analyses on 40 roach samples for a range of organic pollutants and metals collected from the relevant study sites. CEH
8. Report synthesis for DEFRA. Exeter/CEH
Time-Scale and Cost
From: 2010

To: 2013

Cost: £63,441
Contractor / Funded Organisations
Centre for Ecology and Hydrology, University - Exeter
Fields of Study
Chemicals and Nanotechnology