Bruder, Andreas and Salis, Romana K. and Jones, Peter E. and Matthaei, Christoph D. (2017) Biotic interactions modify multiple-stressor effects on juvenile brown trout in an experimental stream food web. Global Change Biology, 23 (9). pp. 3882-3894. ISSN 13541013
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Agricultural land use results in multiple stressors affecting stream ecosystems. Flow reduction due to water abstraction, elevated levels of nutrients and chemical contaminants are common agricultural stressors worldwide. Concurrently, stream ecosystems are also increasingly affected by climate change. Interactions among multiple co-occurring stressors result in biological responses that cannot be predicted from single-stressor effects (i.e. synergisms and antagonisms). At the ecosystem level, multiple-stressor effects can be further modified by biotic interactions (e.g. trophic interactions). We conducted a field experiment using 128 flow-through stream mesocosms to examine the individual and combined effects of water abstraction, nutrient enrichment and elevated levels of the nitrification inhibitor dicyandiamide (DCD) on survival, condition and gut content of juvenile brown trout and on benthic abundance of their invertebrate prey. Flow velocity reduction decreased fish survival (−12% compared to controls) and condition (−8% compared to initial condition), whereas effects of nutrient and DCD additions and interactions among these stressors were not significant. Negative effects of flow velocity reduction on fish survival and condition were consistent with effects on fish gut content (−25% compared to controls) and abundance of dominant invertebrate prey (−30% compared to controls), suggesting a negative metabolic balance driving fish mortality and condition decline, which was confirmed by structural equation modelling. Fish mortality under reduced flow velocity increased as maximal daily water temperatures approached the upper limit of their tolerance range, reflecting synergistic interactions between these stressors. Our study highlights the importance of indirect stressor effects such as those transferred through trophic interactions, which need to be considered when assessing and managing fish populations and stream food webs in multiple-stressor situations. However, in real streams, compensatory mechanisms and behavioural responses, as well as seasonal and spatial variation, may alter the intensity of stressor effects and the sensitivity of trout populations.
| Item Type: | Scientific journal article, Newspaper article or Magazine article |
|---|---|
| Subjects: | Biological Sciences > Biology > Ecology Biological Sciences > Biology > Ecology > Ecosystem ecology & land use |
| Department/unit: | Dipartimento ambiente costruzioni e design > Istituto scienze della Terra |
| Depositing User: | Andreas Bruder |
| Date Deposited: | 23 May 2018 12:23 |
| Last Modified: | 23 May 2018 12:23 |
| URI: | http://repository.supsi.ch/id/eprint/9527 |
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