Population-level Consequences Of Exposure Of Fish To Oestrogenic Wastewater Treatment Works Effluents

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A very significant amount of the water flowing in many UK rivers originates from the effluent of wastewater treatment works (WWTW) and this can affect the native wildlife. We have shown that reproduction in fish living in many UK Rivers, most notably in the roach, a common member of the carp family of fish, has been damaged by exposure to chemicals contained in the WWTW effluents that disrupt the body's sex hormone systems. The chemicals identified responsible for these effects were oestrogens (female sex hormone) and included natural oestrogen hormones, pharmaceutical oestrogens taken by women as part of the contraceptive pill, and some industrial chemicals similar in their structure to natural oestrogens. The presence of feminised fish in the wild is of concern because we have shown that they have a reduced capacity to breed and this may potentially lead to adverse effects for the population and impact the ecosystem more widely. Disorders in human reproductive health occur that are very similar in nature to effects seen in wild fish and some of these effects have been associated with exposure to oestrogens. Adding further concern about WWTW effluents in UK Rivers, long term exposures of fish have found additional adverse health effects including disruption to the immune system and genetic damage. This project seeks to investigate the likely consequences of exposure to oestrogenic WWTW effluents for the sustainability of fish populations living in UK Rivers, using the roach as sentinel species. Although the roach is very common in many polluted water systems, this can sometimes give misleading impressions of the health of the population. Arguably, it is better to count the number of breeding individuals in a population rather than the total number of fish because fish populations with low numbers of breeding fish have low genetic variation and inbreeding and may even be at risk of extinction. Given the results of our experiments performed to date, we think that populations of roach from more polluted sites will have smaller numbers of breeding individuals and will be more inbred than those from clean sites, because a higher proportion of fish will be unable to breed. To investigate this we will first make assessments on the ability of roach to breed in in groups that include fish that have been exposed throughout their whole lives to an oestrogenic WWTW effluent and fish that have been maintained throughout their lives in clean water. We will use a genetic technique (DNA microsatellites) to identify the parents of the offspring produced and in turn determine the reproductive success of individual fish in the competing groups and try to relate this success to their sexual physiology. We will then conduct experiments to investigate how exposure to the oestrogenic WWTW effluent over one and two generations impacts the development of the testes and ovaries and consequent breeding success in the second generation. In the final part of this project we will investigate the underlying genetic health of wild roach populations in UK Rivers using DNA microsatellites for populations collected from rivers sites with different levels of pollution with oestrogenic WWTW effluent. Ultimately, our results will enable us to assess the implications of life long exposure to oestrogenic WWTW effluents on both individuals and populations, advancing significantly knowledge on how the sustainability of roach populations in UK Rivers may be impacted. This work is intended to greatly improve the assessment of the health impacts of exposure to complex mixtures of chemical discharges on fish populations in the natural environment for the better protection of our aquatic resources and biodiversity. The work will have importance in the regulation of discharges and thus is of very wide interest to the government regulatory bodies, environment protection groups, industry and the wider public.