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Feeding Activity and Xenobiotics Modulate Oxidative Status in Daphnia magna: Implications for Ecotoxicological Testing
Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
2014 (English)In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 48, no 21, 12886-12892 p.Article in journal (Refereed) Published
Abstract [en]

To apply biomarkers of oxidative stress in laboratory and field settings, an understanding of their responses to changes in physiological rates is important. The evidence is accumulating that caloric intake can increase production of reactive oxygen species and thus affect background variability of oxidative stress biomarkers in ecotoxicological testing. This study aimed to delineate effects of food intake and xenobiotics on oxidative biomarkes in Daphnia magna. Antioxidant capacity measured as oxygen radical absorbance capacity (ORAC) and lipid peroxidation assayed as thiobarbituric acid reactive substances (TBARS) were measured. Food intake was manipulated by varying food densities or by exposing the animals to chemicals inhibiting feeding rate (pharmaceutical haloperidol and pesticide lindane). Feeding rate proved to affect both protein, ORAC, and TBARS in unexposed daphnids. However, there was no significant effect of feeding rate on the protein-specific ORAC values. Both substances affected individual protein and ORAC levels and changed their relationship to feeding rate. Our results show that inhibition of feeding rate influenced the interpretation of biomarker response and further emphasize the importance of understanding (1) baseline variability in potential biomarkers due to variations in metabolic state and (2) the contribution of feeding rate on toxic response of biomarkers.

Place, publisher, year, edition, pages
2014. Vol. 48, no 21, 12886-12892 p.
National Category
Earth and Related Environmental Sciences
Research subject
Applied Environmental Science
Identifiers
URN: urn:nbn:se:su:diva-110751DOI: 10.1021/es5044722ISI: 000344449100049OAI: oai:DiVA.org:su-110751DiVA: diva2:773216
Note

AuthorCount:4;

Available from: 2014-12-18 Created: 2014-12-17 Last updated: 2017-12-05Bibliographically approved
In thesis
1. Application and interpretation of biomarkers in ecotoxicology - from molecular to individual level responses
Open this publication in new window or tab >>Application and interpretation of biomarkers in ecotoxicology - from molecular to individual level responses
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The use of biomarkers is considered a promising alternative, or complement, to traditional ecotoxicological assays. Toxic effects are often initially manifested at the molecular or biochemical level, biomarkers are therefore used as sensitive indicators of toxic exposure. Ideally, biomarkers would also indicate reduced fitness and possible later effects at the individual or population levels. However, implementing biomarkers in ecotoxicology is challenging and few biomarkers have an established connection to reduced individual fitness. The aim of this thesis was to increase the value and improve the interpretation of biomarker responses in ecotoxicological studies by examining the impact of confounding factors and the relationship between oxidative biomarkers and reproductive effects in crustaceans.

The sensitivity of biomarkers was confirmed in paper I as toxic effects of pharmaceuticals with conserved drug target orthologs were observed at the molecular and biochemical levels both earlier and at lower concentrations than effects on mortality and reproduction. No toxic effects were observed for the pharmaceutical without identified drug target orthologs, thus stressing the importance of considering toxic mechanisms and being aware of the most likely target when evaluating toxic effects also in non-target species. Many xenobiotics and environmental stressors interfere with oxidative processes, making oxidative biomarkers interesting to study in ecotoxicology and stress ecology. Still, feeding rate was identified as a confounding factor for antioxidant capacity (assayed as oxygen radical absorbance capacity, ORAC) and lipid peroxidation in ecotoxicological studies (paper II). However, ORAC normalized to protein was independent of altered feeding rates, hence it can be applied as a suitable exposure biomarker without considering alterations and effects of feeding rate. The connection between reproduction and oxidative stress is dual, as reproduction both can be inhibited by oxidative stress and induce pro-oxidative processes. Further, a positive association was found between ORAC and the occurrence of embryo aberrations in the benthic amphipod Monoporeia affinis (paper III). An association between antioxidant defense and reproduction was also observed for Daphnia magna (paper IV). Threshold values for identification of exposed individuals and prediction of possible later reproductive effects were established for ORAC.

This thesis has contributed to diminishing some of the knowledge gaps limiting the use of oxidative biomarkers in ecotoxicology, by contributing to increased understanding of how oxidative biomarkers relate to important life-traits. Moreover, ORAC has been identified as a suitable biomarker of not only exposure, but also reproductive effects. Future research should continue to establish connections between biomarker responses and effects at higher levels, and focus on providing defined threshold values to enable predictions about later effects.   

Place, publisher, year, edition, pages
Stockholm: Department of Environmental Science and Analytical Chemistry, Stockholm University, 2015. 29 p.
Keyword
biomarkers, oxidative stress, ORAC, reproduction, Daphnia magna, toxicity, environmental stress
National Category
Environmental Sciences
Research subject
Applied Environmental Science
Identifiers
urn:nbn:se:su:diva-120161 (URN)978-91-7649-252-9 (ISBN)
Public defence
2015-10-16, De Geer-salen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.

Available from: 2015-09-24 Created: 2015-09-02 Last updated: 2015-09-16Bibliographically approved

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