Abstract
In this study, we provide a descriptive assessment of how chemical and hydro-morphological stressors have affected the fish community along one of the most impacted rivers in Central Europe. In addition to the toxicity of combined pollutants (expressed in toxic units), a range of hydro-morphological characteristics were measured to assess which stressors have had an impact. No longitudinal spatial trend was observed in fish assemblage characteristics as individual sites were affected by different stressors. Instead, five largely artificial assemblage “zones” were identified corresponding to different combinations of stressors. Water quality (principally dissolved O2) and hydromorphology were the main drivers affecting fish presence and density, with self-purification processes, restocking from tributaries and geomorphology promoting fish survival and/or recovery, despite increasing toxic pressure downstream. Our results suggest that a) toxic units alone are insufficient to establish causative factors in fish community loss as they do not take account of hydro-morphological stressors, many of which interact with and/or mask each other, and b) that a single WFD monitoring site in such heavily impacted rivers is insufficient to assess ecological status; rather, the ecological status of specific “zones” (identified based on fish assemblage structure, habitat and water quality) should be assessed, with the ultimate aim of merging the zones and returning the river to a single functioning longitudinal ecosystem, accepting that this is unlikely to resemble the natural pre-industrial status of the river.
Highlights
Water resources in Europe are subject to strong anthropogenic stressors resulting in poor ecological status and loss of biodiversity
We examine the effect of multiple stressors on the fish community along perhaps the most impacted river in Central Europe, the River Bílina (Czech Republic)
Statistical analysis We identified three groups of predictors a priori that could influence fish assemblages: 1) habitat modification type; 2) pollution; and 3) water quality (O2 and temperature only as a) no pH data were available for 2007, and b) conductivity showed a strong correlation with temperature (Pearson correlation moment, R = 0.79, df = 14, P < 0.001)
Summary
Water resources in Europe are subject to strong anthropogenic stressors (i.e. water pollution, habitat degradation, loss of connectivity and flow modification) resulting in poor ecological status and loss of biodiversity. Assessments of stressor impact, are hampered by severe gaps in our knowledge of cause-and-effect relationships between single or multiple stressors and biodiversity loss In assessing the ecological status of a water body, the impact of all stressors should be. Impact of multiple stressors on the fish community pattern integrated, whether present simultaneously or separated in space and time. Some toxic chemicals may modify exposure of aquatic species to other stressors by affecting distribution, behaviour or habitat use (Couillard et al 2008). The combined impact of multiple stressors is a function of magnitude, frequency or duration and of species character, i.e. the ability of an ecosystem or species community to resist the stressor(s) (Wenger et al 2010, Jacquin et al 2020)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
