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No evidence of increased growth or mortality in fish exposed to oxazepam in semi-natural ecosystems
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
Umeå University, Faculty of Science and Technology, Department of Chemistry.
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2018 (English)In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 615, p. 608-614Article in journal (Refereed) Published
Abstract [en]

An increasing number of short-term laboratory studies on fish reports behavioral effects from exposure to aquatic contaminants or raised carbon dioxide levels affecting the GABAAreceptor. However, how such GABAergic behavioral modifications (GBMs) impact populations in more complex natural systems is not known. In this study, we induced GBMs in European perch (Perca fluviatilis) via exposure to a GABA agonist (oxazepam) and followed the effects on growth and survival over one summer (70 days) in replicated pond ecosystems. We hypothesized that anticipated GBMs, expressed as anti-anxiety like behaviors (higher activity and boldness levels), that increase feeding rates in laboratory assays, would; i) increase growth and ii) increase mortality from predation. To test our hypotheses, 480 PIT tagged perch of known individual weights, and 12 predators (northern pike, Esox lucius) were evenly distributed in 12 ponds; six control (no oxazepam) and six spiked (15.5 ± 4 μg l− 1 oxazepam [mean ± 1 S.E.]) ponds. Contrary to our hypotheses, even though perch grew on average 16% more when exposed to oxazepam, we found no significant difference between exposed and control fish in growth (exposed: 3.9 ± 1.2 g, control: 2.9 ± 1 g [mean ± 1 S.E.], respectively) or mortality (exposed: 26.5 ± 1.8 individuals pond− 1, control: 24.5 ± 2.6 individuals pond− 1, respectively). In addition, we show that reduced prey capture efficiency in exposed pike may explain the lack of significant differences in predation. Hence, our results suggest that GBMs, which in laboratory studies impact fish behavior, and subsequently also feeding rates, do not seem to generate strong effects on growth and predation-risk in more complex and resource limited natural environments.

Place, publisher, year, edition, pages
Elsevier, 2018. Vol. 615, p. 608-614
Keywords [en]
GABA(A), Behavioral modifications, Ecological effects, Perca fluviatilis, Esox lucius
National Category
Environmental Sciences
Identifiers
URN: urn:nbn:se:umu:diva-142442DOI: 10.1016/j.scitotenv.2017.09.070ISI: 000414922600066PubMedID: 28988097OAI: oai:DiVA.org:umu-142442DiVA, id: diva2:1162884
Available from: 2017-12-05 Created: 2017-12-05 Last updated: 2018-08-28Bibliographically approved
In thesis
1. Fish on drugs: behaviour modifying contaminants in aquatic ecosystems
Open this publication in new window or tab >>Fish on drugs: behaviour modifying contaminants in aquatic ecosystems
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Contamination of surface waters is a worldwide problem. One group of emerging contaminants that reach aquatic ecosystems via sewage treatment plant effluents and agricultural run-offs is pharmaceuticals. Impacts of pharmaceuticals on the behaviour of aquatic organisms can have important ecological and evolutionary consequences because behaviour is directly linked to fitness. The aim of my doctoral thesis was to increase our understanding of the fate and effects of behaviour modifying drugs in aquatic ecosystems.

While studying an aquatic ecosystem spiked with pharmaceuticals, I found that the benthic species at the bottom of the food chain were the main receivers (highest bioaccumulation factor; BAF) while fish at the top of the food web had the lowest uptake of the studied drugs. Interestingly, the BAF of the anxiolytic pharmaceutical oxazepam, increased in fish (perch; Perca fluviatilis) over the study period, suggesting that this drug can be transferred between trophic levels in food webs. To assess whether oxazepam could affect growth and survival in perch, I exposed perch populations to oxazepam for 2-months in a replicated pond experiment. In this study, I tested the hypothesis that oxazepam exposed perch would grow faster but also suffer from increased predation. Oxazepam has been shown previously to induce ‘anti-anxiety’ behaviours that improve foraging but may also make individuals more exposed to predators. In contrast, I found no statistically significant increase in growth and mortality in the exposed perch. However, the study revealed that the natural predator of perch (pike; Esox lucius) became less effective at catching prey when exposed to oxazepam. This exposure effect on predation efficiency likely contributed to the absence of predation effects in the exposed ponds. In two following laboratory studies I investigated effects of behaviour modifying drugs (oxazepam and a growth hormone, 17β-trenbolone) in combination with additional stressors (temperature and predator cues). Drug and temperature interactions were found for 17β-trenbolone, where water temperature interacted with treatment to induce changes in predator escape behaviour, boldness, and exploration in mosquitofish (Gambusia holbrooki). However, in the other study, we found that oxazepam, temperature, and predator cue all affected perch ‘anti-anxiety’ behaviours, but independently.

I conclude that pharmaceuticals can alter ecologically important behaviours in fish, and that at least some, can accumulate in aquatic food webs. It seems that in situ effects of behaviour modifying drugs in aquatic ecosystems depend on both species-specific responses and abiotic interactions. As such, it is far from straightforward to predict net ecosystem effects based on experiments conducted using single species and static conditions. Future studies should assess the effects of pharmaceuticals in aquatic ecosystems under more complex conditions for us to gain a better understanding of what consequences behaviour modifying drugs have in the environment.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2018. p. 33
Keywords
Aquatic ecosystems, Behavioural effects, Ecotoxicology, Endocrine disruptors, Pharmaceuticals, Interaction effects
National Category
Environmental Sciences
Research subject
Ecotoxicology
Identifiers
urn:nbn:se:umu:diva-151138 (URN)978-91-7601-912-2 (ISBN)
Public defence
2018-09-21, Lilla Hörsalen, KB.E3.01, KBC-huset, Umeå, 12:00 (English)
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Available from: 2018-08-31 Created: 2018-08-28 Last updated: 2018-08-30Bibliographically approved

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Lagesson, AnnelieBrodin, TomasFahlman, JohanFick, JerkerJonsson, MicaelByström, PärKlaminder, Jonatan

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