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- Sörenson, Eva, 1979-
(author)
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Functional and structural characterizations of phytoplankton-bacteria interactions in response to environmental challenges
- 2020
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Doctoral thesis (other academic/artistic)abstract
- Microorganisms, such as phytoplankton and bacteria, make up ≈70% of aquatic biomass and contribute 50-85% of the oxygen in Earth’s atmosphere. The microbial loop concept and the discovery of the large diversity in microbial communities acknowledge that biotic interactions between microorganisms in addition to resource competition enable the recycling of energy and nutrients in aquatic food webs. In this thesis, I have studied interactions between phytoplankton and bacteria in three brackish systems of increasing complexity. Interactions were characterized in terms of structure and function, species-specificity aspects, influence on community resilience, and the link between interactions and cycling of energy and nutrients, using a combined approach of molecular techniques, morphology and biochemical analyses, and network analysis. Species-specific core microbiomes were identified in cultures of dinoflagellate isolates with varying genotypes or phenotypes, or from locations with varying levels of anthropogenic impact. We argue that the structure of phytoplankton-bacterial communities is influenced by predictable species-specific interactions, in addition to local abiotic conditions (such as salinity). When microalgal productivity exposed to seasonal variations in light and temperature was examined in photobioreactor polycultures, the stability of microalgal biomass linked to a high bacterial response diversity, primarily seen as shifts in taxonomy. When the structural and functional response of microalgae and bacteria to temperature shifts was coupled to resilience theories (adaptive cycles, panarchy and cross-scale resilience), results suggest that resilience was enabled through internal shifts in function and diversity within and across microalgal and bacterial levels, leading to maintenance of overall community function and diversity. Further, the results suggest that phytoplankton and bacteria in a coastal eutrophied location avoid competition for both energy and nutrients by resource partitioning, indicating that phytoplankton and bacteria might coexist more frequently in dynamic shallow coastal ecosystems than previously thought.The results from this thesis emphasize the importance of considering community interactions between phytoplankton and bacteria when studying aquatic microbial communities, both in cultures and in complex field environments.
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| 2. |
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Mikroalger : – vår tids miljöhjältar
- 2020
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Artistic workabstract
- Utställningen Mikroalger - vår tids miljöhjältar visade forskningen inom projektet ALGOLAND ett projekt inom Linnéuniversitetets spetsforskning inom ekologi och evolutionsforskning. Inom Algoland undersöker forskare mikroalgers potential att rena luft och vatten som kommer från industrier. I projektet kombineras marinekologisk forskning med kompetens från industrin för att nå innovativa, hållbara lösningar som minskar utsläpp av koldioxid och närsalter. Samtidigt produceras viktiga produkter som djurfoder och biobränslen. Metoden har potential att bidra till sänkta växthusgasutsläpp i framtiden. Syftet med utställningen var att sprida kunskap om mikroalgers förmåga att rena luft och vatten samt bidra till en större medvetenhet kring vatten generellt. Målgrupper var befintliga och presumtiva studenter, anställda på Linnéuniversitetet, allmänhet samt skolbarn.
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| 3. |
- Sörenson, Eva, 1979-, et al.
(author)
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Resource Partitioning Between Phytoplankton and Bacteria in the Coastal Baltic Sea
- 2020
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In: Frontiers in Marine Science. - : Frontiers Media S.A.. - 2296-7745. ; 7, s. 1-19
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Journal article (peer-reviewed)abstract
- Eutrophication coupled to climate change disturbs the balance between competition and coexistence in microbial communities including the partitioning of organic and inorganic nutrients between phytoplankton and bacteria. Competition for inorganic nutrients has been regarded as one of the drivers affecting the productivity of the eutrophied coastal Baltic Sea. Yet, it is unknown at the molecular expression level how resources are competed for, by phytoplankton and bacteria, and what impact this competition has on the community composition. Here we use metatranscriptomics and amplicon sequencing and compare known metabolic pathways of both phytoplankton and bacteria co-occurring during a summer bloom in the archipelago of Åland in the Baltic Sea to examine phytoplankton bacteria resource partitioning. The expression of selected pathways of carbon (C), nitrogen (N), and phosphorus (P) metabolism varied over time, independently, for both phytoplankton and bacteria, indicating partitioning of the available organic and inorganic resources. This occurs regardless of eukaryotic plankton growth phase (exponential or stationary), based on expression data, and microbial community composition. Further, the availability of different nutrient resources affected the functional response by the bacteria, observed as minor compositional changes, at class level, in an otherwise taxonomically stable bacterial community. Resource partitioning and functional flexibility seem necessary in order to maintain phytoplankton-bacteria interactions at stable environmental conditions. More detailed knowledge of which organisms utilize certain nutrient species are important for more accurate projections of the fate of coastal waters.
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