Spatial Distribution, Diversity, and Activity of Microbial Phototrophs in the Baltic Sea

Peihang Xu*, Christian Furbo Reeder, Carolin Regina Löscher


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Microbial plankton is essential for ocean biogeochemistry. As part of the prokaryotic phototrophic microbial community, both oxygenic phototrophs (OP) and anoxygenic phototrophs (AP) are widely distributed in the ocean and may play a significant role in carbon flow and oxygen production. However, comparative studies of microbial OP and AP have received very little attention, even though their different roles might be important in various marine environments, especially in oxygen minimum zones (OMZ). We explored the spatial distribution of the microbial community in the Baltic Sea, including an OMZ region, with a particular focus on the distribution and activity of OP and AP. We used 16S rRNA amplicon sequencing in combination with a qPCR-based quantification of photosynthesis marker genes. We found that specific bacterial groups dominated surface and intermediate depths, the OMZ, and deep waters, respectively. Salinity, temperature, oxygen, and depth were significant factors explaining the microbial community composition and distribution. A high diversity of OP and AP was observed, including OP-Chlorophyta, Diatoms, Cyanobacteria and Cryptomonads, and AP-Proteobacteria and Chloroflexota. OP were more abundant at most stations compared to AP. OP showed high photosynthetic activity and more photosynthesis activity in higher temperature and upper waters, while AP photosynthesis cannot be detected in most stations. Both, cyanobacterial and eukaryotic OP preferred to live in higher temperature and upper waters, but Cyanobacteria also preferred to live in oxic water while the whole OP community showed preference to live in higher salinity area. However, AP did not show any significant hydrochemical preference but prefer to live with OP community. The Baltic Sea is exposed to multiple climate change related stressors, such as warming, decreasing salinity, and deoxygenation. This study contributes to understanding and interpretation of how microbial community, especially phototrophic groups, might shift in their distribution and activity in a changing ocean like the Baltic Sea.

TidsskriftFrontiers in Marine Science
Antal sider19
StatusUdgivet - jan. 2022

Bibliografisk note

Funding Information:
Financial support was provided by the Villum Foundation (grants no: #24911, to CL; grants no. #16518 to D. Canfield).

Funding Information:
We appreciate the support from the captain, crew and the chief scientist J. Süling for Alkor 528 during the Cruise. We are grateful for the financial support for the Cruise provided by the European Union’s Horizon 2020 Research and Innovation Program (Grant agreement no. 774499 to J. Javidpour, GoJelly project). We acknowledge E. Laursen and R. Orloff Holm for their technical assistance. We further acknowledge the Nordcee labs at SDU and the GEOMAR-Helmholtz Centre for Ocean Research Kiel for giving access to their research facilities. We are grateful to the China Scholarship Council, for granting a scholarship to PX (China Scholarship Council Studentship with the University of Southern Denmark (grant no. 201908440275) and to the Villum Foundation (grant no. 24911). We acknowledge D. Canfield for supporting experiment supplies [Villum Foundation (grants no. 16518)]. We thank the reviewers KP and EC, as well as the editor for their help with improving the manuscript.

Publisher Copyright:
Copyright © 2022 Xu, Reeder and Löscher.


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