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Chemical exposure and stress responses in UK fish

Pottinger, Tom G.; Henrys, Peter A.; Williams, Richard J.; Matthiessen, Peter. 2012 Chemical exposure and stress responses in UK fish. Defra, 42pp. (CEH Project Number: C04329)

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Abstract/Summary

1. This scoping study was conducted to assess whether evidence exists for effects of wastewater treatment works (WWTW) effluent on the adaptive stress axis of fish. 2. A total of 427 three-spined sticklebacks were sampled during March and April 2011 from sites downstream of ten WWTWs serving rural and urban areas with population equivalents of between 1,000 and 120,000. Sticklebacks were also sampled from three sites with known heavy metal contamination and from a laboratory population maintained in uncontaminated water. 3. Somatic (mass, length, sex) data were collected from the sticklebacks to provide information on the relative growth and condition of the sampled populations. Indices of stress (whole-body cortisol and glucose) were measured both prior to and following a standardised stressor to establish both the baseline activity and stress-induced responsiveness of the stress axis in fish at each site. Biomarkers of chemical exposure (metallothionein, cytochrome P4501A, choriogenin gene expression) were measured to provide information on the relative exposure of fish at each site to polycyclic aromatic hydrocarbons, heavy metals and estrogenic compounds, all of which are known to modify the activity of the stress axis in fish. 4. The relative impact of the selected WWTWs on the receiving waters was characterised by three indirect measures: (i) population equivalents, (ii) dry weather flow and (iii) the percentage of effluent calculated to be present at each sampling site. 5. There was considerable between-site variation in all the parameters measured. For the fish sampled downstream of the WWTWs much of this was found to be related to the impact metrics of the upstream WWTWs, particularly the percent effluent present at the study site. 6. For the sticklebacks sampled downstream of WWTWs mass, length, and to a much lesser extent condition, were positively related to the concentration of effluent present at the sample site. This is consistent with previous findings that indicate the positive effects of effluent-derived enrichment and elevated temperature on fish growth. Somatic measurements for fish sampled from metal-contaminated sites were within the range of those for fish at WWTW sites. 7. Cortisol and glucose concentrations in unstressed sticklebacks downstream of WWTWs were positively related to the percent effluent concentration at each site. Variation in somatic data did not account for the variation in cortisol levels in unstressed fish. Cortisol and glucose concentrations in unstressed fish sampled from metal-contaminated sites were within the range of those of fish at WWTW sites. 8. After the exposure of sticklebacks to a standardised stressor (confinement) following capture, both cortisol and glucose concentrations in whole-body extracts of the stressed fish were elevated. In fish downstream of WWTWs the magnitude to which cortisol and glucose concentrations were elevated was reduced with increasing effluent concentration at each site. Cortisol and glucose concentrations in fish sampled from metal-contaminated sites and also subjected to a period of confinement were within the range of those for fish at WWTW sites 9. For sticklebacks downstream of the WWTWs little of the variation in biomarker gene expression between sites was explained by the variation in impact measures between the WWTWs. Overall there was a small but significant negative trend evident between percent effluent at each sample site and biomarker activity in the resident fish. The range in the magnitude of biomarker gene expression was similar among fish downstream of the WWTWs and fish sampled from metal-contaminated sites. 10. These data suggest that the function of the stress axis in sticklebacks downstream of these WWTWs was modified by exposure to the discharged effluent. In unstressed fish the stress axis was more active at sites receiving a higher proportion of effluent, which might be interpreted to indicate that exposure to the effluent constitutes a mild chronic stressor. The stress axis became less responsive to a stressor in fish exposed to higher effluent loads, suggesting that elements within the effluent impeded the normal functioning of the stress axis. 11. A lack of pronounced variation in biomarker gene expression across the range of WWTWs suggests that these alterations in the function of the stress axis are not directly the result of exposure to high concentrations of polycyclic aromatic hydrocarbons, heavy metals or estrogenic compounds. The effects may instead be mediated by a combination of components within the complex WWTW effluents, including possibly pharmaceuticals and personal care products (PPCPs). 12. The results of this scoping study suggest that exposure to WWTW effluents can perturb the function of the stress axis in sticklebacks. Further work is needed to (i) demonstrate that the effect is consistent across a wider range of sites, (ii) investigate the causality of the effect, and (iii) investigate the implications for the fitness of fish populations downstream of WWTWs.

Item Type: Publication - Report (UNSPECIFIED)
Programmes: CEH Topics & Objectives 2009 onwards > Water > WA Topic 2 - Ecohydrological Processes > WA - 2.3 - Assess the responses of river, lake and wetland ecosystems to ecohydrological drivers
CEH Sections: Parr
CEH fellows
Boorman
Funders/Sponsors: Defra
Additional Keywords: sewage, wastewater, stickleback, stress, stressors, cortisol, glucose, biomarkers
NORA Subject Terms: Biology and Microbiology
Zoology
Ecology and Environment
Hydrology
Date made live: 24 Apr 2012 09:11
URI: http://nora.nerc.ac.uk/id/eprint/16646

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