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Bacterial community responses to planktonic and terrestrial substrates in coastal northern Baltic Sea
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF). (EcoChange; UMFpub)
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).ORCID iD: 0000-0002-1298-3839
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF). Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.ORCID iD: 0000-0001-7819-9038
2023 (English)In: Frontiers in Marine Science, E-ISSN 2296-7745, Vol. 10, article id 1130855Article in journal (Refereed) Published
Abstract [en]

Bacteria are major consumers of dissolved organic matter (DOM) in aquatic systems. In coastal zones, bacteria are exposed to a variety of DOM types originating from land and open sea. Climate change is expected to cause increased inflows of freshwater to the northern coastal zones, which may lead either to eutrophication or to increased inputs of refractory terrestrial compounds. The compositional and functional response of bacterial communities to such changes is not well understood. We performed a 2-day microcosm experiment in two bays in the coastal northern Baltic Sea, where we added plankton extract to simulate eutrophication and soil extract to simulate increased inputs of refractory terrestrial compounds. Our results showed that the bacterial communities responded differently to the two types of food substrates but responded in a similar compositional and functional way in both bays. Plankton extract addition induced a change of bacterial community composition, while no significant changes occurred in soil extract treatments. Gammaproteobacteria were promoted by plankton extract, while Alphaproteobacteria dominated in soil extract addition and in the non-amended controls. Carbohydrate metabolism genes, such as aminoglycan and chitin degradation, were enriched by plankton extract, but not soil extract. In conclusion, the coastal bacterial communities rapidly responded to highly bioavailable substrates, while terrestrial matter had minor influence and degraded slowly. Thus, in the northern Baltic Sea, if climate change leads to eutrophication, large changes of the bacterial community composition and function can be expected, while if climate change leads to increased inflow of refractory terrestrial organic matter the bacterial communities will not show fast compositional and functional changes. Degradation of terrestrial organic matter may instead occur over longer periods of time, e.g. years. These findings help to better understand the ability of bacterial communities to utilize different carbon sources and their role in the ecosystem.

Place, publisher, year, edition, pages
Frontiers Media S.A., 2023. Vol. 10, article id 1130855
National Category
Ecology Microbiology
Identifiers
URN: urn:nbn:se:umu:diva-206867DOI: 10.3389/fmars.2023.1130855ISI: 000979525200001Scopus ID: 2-s2.0-85159867504OAI: oai:DiVA.org:umu-206867DiVA, id: diva2:1751777
Funder
Swedish Research Council Formas, 2019/0007Ecosystem dynamics in the Baltic Sea in a changing climate perspective - ECOCHANGEAvailable from: 2023-04-19 Created: 2023-04-19 Last updated: 2023-06-07Bibliographically approved
In thesis
1. Microbial communities: descriptors of environmental change in marine ecosystems
Open this publication in new window or tab >>Microbial communities: descriptors of environmental change in marine ecosystems
2023 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Mikrobiella samhällen : indikatorer på miljöförändringar i marina ekosystem
Abstract [en]

In northern marginal seas, like the northern Baltic Sea, climate change will lead to many alterations, for example increased inflows of nutrients and dissolved organic matter (DOM). Nutrients and DOM are fundamental drivers shaping marine microbial communities, including both bacterial and phytoplankton populations. Potentially microbial communities and their functions can be used as descriptors of environmental change in marine systems. 

Changed nutrient availability will affect the phytoplankton communities, which is widely used as descriptor of environmental state in aquatic systems. Traditionally phytoplankton is analyzed using microscopy in monitoring, while molecular methods holds a great potential for future development. I performed a comparative study between metabarcoding and microscopy. Metabarcoding and microscopy displayed relatively similar distribution pattern at the group level. The results showed that the relative abundances of the 18S rRNA amplicon at the group level best fitted the microscopy carbon biomass metric. The results are promising for implementing DNA metabarcoding as a complement to microscopy in phytoplankton monitoring, especially if databases would be improved and group level indexes could be applied to classify environmental state of water bodies.

Bacterioplankton are the main DOM processors in the marine food web. A shift in the quality and quantity of the DOM pool could affect the microbial community structure and alter their functioning. Presently it is poorly known how coastal bacteria respond compositionally and functionally to quality and quantity changes in DOM supply. To comprehensively address this question, there is a critical need for microcosm experimental studies as well as field studies. Thus, I used approaches from single species laboratory experiment to community levels in situ incubation experiments and community levels spatiotemporal field surveys to evaluate the impacts of climate shifts on microbial community. Intricate relationships between environmental factors and microbial communities, for example, links between key microbial functional genes and DOM conditions were identified. Results showed that bacteria isolated from coastal area harbor genes for the sequestration of autochthonously produced carbon substrates, while bacteria isolated from a river contained genes for the degradation of relatively refractive terrestrial organic matter. A field experiment showed that Gammaproteobacteria was promoted by plankton extract addition and the genes for chitin and cellulose catabolism are enriched by addition of autochthonous carbon sources. The field survey with comprehensive metagenomic investigation of microbial community composition indicated that the temporal variation is larger compare to spatial changes. Bacteroidia, Actinomycetia, Gammaproteobacteria, Acidimicrobiia, and Alphaproteobacteria were the dominant bacterial classes, with Bacteroidia being more abundant in inshore stations compared to offshore locations. The seasonal shift in the relative abundance of these bacterial classes suggests that environmental factors and ecological processes drive changes in the abundance of different bacterial classes over time. Overall, these studies strengthen our understanding of the relationships between microbial composition and biogeochemical processes in coastal areas.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2023. p. 23
National Category
Oceanography, Hydrology and Water Resources
Identifiers
urn:nbn:se:umu:diva-207755 (URN)978-91-8070-087-0 (ISBN)978-91-8070-088-7 (ISBN)
Public defence
2023-05-26, KB.E3.01, KBC-huset, Umeå, 09:00 (English)
Opponent
Supervisors
Available from: 2023-05-05 Created: 2023-05-02 Last updated: 2023-08-14Bibliographically approved

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Zhao, LiBrugel, SoniaRamasamy, Kesava PriyanAndersson, Agneta

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