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Role of ecological processes in determining effects of contaminants in aquatic ecosystems
Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Aquatic ecosystems cover approximately 70% of the Earth’s surface and support a wide range of ecosystem services. Despite their importance, aquatic ecosystems are increasingly exposed to anthropogenic stressors, such as contaminants and climate change impacts. Ecosystems comprise a complex web of interactions both between organisms and between organisms and the abiotic environment. While there is extensive evidence for the importance of ecological processes in determining net ecosystem effects of contaminants, most often their effects are studied in isolation and in a single species setting.

The aim of this thesis is to investigate the ecological effects of contaminants in aquatic ecosystems, ranging from cellular to ecosystem endpoints, by using model ecosystems of increasing complexity. This thesis studies the effects of ionising radiation on the biochemical composition of microalgae and how these may affect consumers (Paper I), as well its effects on an artificial freshwater ecosystem (microcosms) in terms of ecological processes (Paper II) and carbon flows (Paper III). Finally, the thesis investigates the combined effects of a flame retardant and increased temperature on a model ecosystem comprised of a semi-natural Baltic Sea community (Paper IV).

Ionising radiation caused biochemical changes in primary producers that affected the next trophic level, where the consumer responded with an increased feeding rate, suggesting a change in the food quality of the primary producer (Paper I). The microcosms exposed to ionising radiation showed significant dose related effects on photosynthetic parameters for all macrophyte species. Dose dependent trends were seen in snail grazing rates and reproduction indicating a potential for long-term effects (Paper II). Similarly, the carbon flow networks (Paper III) also indicated that the main effect of radiation was a decline in primary production of the macrophytes, while pelagic bacterial production increased. However, the relative distribution of flows from dissolved carbon changed only slightly with increasing dose rates, which mainly triggered an increase in the amount of carbon dissipated through respiration. Finally, in Paper IV, higher temperatures induced the release of PO4 from the sediment, which stimulated the growth of the cyanobacteria, in turn leading to an increase in copepod abundance.

These results demonstrate that the effects of contaminants on ecosystems depend on ecological processes, which may influence species-specific responses and lead to indirect effects. This thesis builds on a body of literature calling for a more holistic approach of ecotoxicology and radioecology, where ecosystem level responses to contaminants are taken into consideration.

Place, publisher, year, edition, pages
Stockholm: Department of Ecology, Environment and Plant Sciences, Stockholm University , 2019. , p. 33
Keywords [en]
ecosystem approach, ionizing radiation, HBCDD, microcosm, species interactions, indirect effects
National Category
Ecology
Research subject
Marine Ecotoxicology
Identifiers
URN: urn:nbn:se:su:diva-166096ISBN: 978-91-7797-618-9 (print)ISBN: 978-91-7797-619-6 (electronic)OAI: oai:DiVA.org:su-166096DiVA, id: diva2:1288561
Public defence
2019-04-05, Vivi Täckholmssalen (Q-salen), NPQ-huset, Svante Arrhenius väg 20, Stockholm, 09:30 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Manuscript. Paper 2: Manuscript. Paper 3: Manuscript.

Available from: 2019-03-13 Created: 2019-02-13 Last updated: 2019-03-07Bibliographically approved
List of papers
1. Gamma radiation induced changes in the biochemical composition of aquatic primary producers and their effect on grazers
Open this publication in new window or tab >>Gamma radiation induced changes in the biochemical composition of aquatic primary producers and their effect on grazers
(English)Manuscript (preprint) (Other academic)
Keywords
untargeted metabolite profiling, phytoplankton, food quality, biochemical changes, ionizing radiation
National Category
Ecology
Research subject
Marine Ecotoxicology
Identifiers
urn:nbn:se:su:diva-166077 (URN)
Available from: 2019-02-13 Created: 2019-02-13 Last updated: 2019-12-12Bibliographically approved
2. Radiation effects and ecological processes in a freshwater microcosm
Open this publication in new window or tab >>Radiation effects and ecological processes in a freshwater microcosm
Show others...
2019 (English)In: Journal of Environmental Radioactivity, ISSN 0265-931X, E-ISSN 1879-1700, Vol. 203, p. 71-83Article in journal (Refereed) Published
Abstract [en]

Ecosystem response to gamma radiation exposure depends on the different species sensitivities and the multitude of direct and indirect pathways by which individual organisms can be affected, including the potential for complex interactions across multiple trophic levels. In this study, multi-species microcosms were used to in- vestigate effects of ionizing radiation in a model freshwater ecosystem, including endpoints at both structural and functional levels and ecological interactions. Microcosms were exposed for 22 days to a gradient of gamma radiation with four dose rates from 0.72 to 19mGyh−1, which are within the range of those seen at con- taminated sites. Results showed significant dose related effects on photosynthetic parameters for all macrophyte species. No significant effects of radiation were observed for the consumers in the microcosms, however trends indicate the potential for longer-term effects. We also witnessed a different response of Daphnia magna andLemna minor compared to previous single-species studies, illustrating the importance of multispecies studies, which aim to encompass systems more realistic to natural ecosystems. Microcosms allowed us to isolate specific relationships between interacting species in an ecosystem and test the effects, both direct and indirect, of ra- diation on them. In addition, the ecological pathways and processes, and the experimental design itself, was central to understanding the results we witnessed. This type of study is important for radioecology research that has been very much limited to high dose rates and single species studies. This approach to radioecology has been strongly promoted in recent decades and, to our knowledge, this is the first microcosm study performed at dose rates similar to those at contaminated field sites.

Keywords
microcosm, gamma radiation, ecosystem approach, species interactions, indirect effects
National Category
Ecology
Research subject
Marine Ecotoxicology
Identifiers
urn:nbn:se:su:diva-166079 (URN)10.1016/j.jenvrad.2019.03.002 (DOI)000465051100009 ()
Available from: 2019-02-13 Created: 2019-02-13 Last updated: 2019-12-12Bibliographically approved
3. Carbon flow in a model ecosystem exposed to ionising radiation
Open this publication in new window or tab >>Carbon flow in a model ecosystem exposed to ionising radiation
(English)Manuscript (preprint) (Other academic)
National Category
Ecology
Research subject
Marine Ecotoxicology
Identifiers
urn:nbn:se:su:diva-166080 (URN)
Available from: 2019-02-13 Created: 2019-02-13 Last updated: 2019-12-12Bibliographically approved
4. Coastal Ecosystem Effects of Increased Summer Temperature and Contamination by the Flame Retardant HBCDD
Open this publication in new window or tab >>Coastal Ecosystem Effects of Increased Summer Temperature and Contamination by the Flame Retardant HBCDD
2017 (English)In: Journal of Marine Science and Engineering, E-ISSN 2077-1312, Vol. 5, no 2, article id 18Article in journal (Refereed) Published
Abstract [en]

The combined effects of ocean warming and contaminants on marine ecosystems are poorly understood. In this study, we exposed model ecosystems comprising typical shallow coastal Baltic Sea communities to elevated temperature (+5 °C) and the flame retardant hexabromocyclododecane (HBCDD), both singly and in combination, for 13 days. Higher temperatures caused the release of PO4 from the sediment, which in turn stimulated the growth of the cyanobacteria Dolichospermum sp. This in turn led to an increase in the copepod Acartia bifilosa and other indirect effects in the plankton, interpreted as being caused by changes in predation, grazing, and competition. Elevated temperatures also stimulated benthic primary production and increased production of benthic mollusk larvae. Although increased temperature was the dominant driver of effects in these systems, HBCDD also appeared to have some effects, mainly in the zooplankton (both direct and indirect effects) and benthic meiofauna (an interactive effect with temperature). Although the study used model ecosystems, which are an approximation of field conditions, it highlights that interactive ecosystem effects between two stressors are possible and demonstrates the ecological and temporal complexity of such responses. Such unpredictable responses to warming and contaminants are a major challenge for ecosystem management to deal with multistressor situations in the Baltic Sea.

Keywords
global warming, flame retardant, Baltic Sea, brackish, multiple stressors, benthic-pelagic coupling, community ecology, indirect effects, Macoma balthica, cosm
National Category
Ecology
Research subject
Marine Ecotoxicology
Identifiers
urn:nbn:se:su:diva-150749 (URN)10.3390/jmse5020018 (DOI)000423689700004 ()
Available from: 2018-01-04 Created: 2018-01-04 Last updated: 2019-02-13Bibliographically approved

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