Long-term warming modulates diversity, vertical structuring of microbial communities, and sulfate reduction in coastal Baltic Sea sediments

Laura Seidel; Varvara Sachpazidou; Marcelo Ketzer; Samuel Hylander; Anders Forsman; Mark Dopson

doi:10.3389/fmicb.2023.1099445

Long-term warming modulates diversity, vertical structuring of microbial communities, and sulfate reduction in coastal Baltic Sea sediments

Front Microbiol. 2023 Mar 29:14:1099445. doi: 10.3389/fmicb.2023.1099445. eCollection 2023.

Authors

Laura Seidel¹, Varvara Sachpazidou¹, Marcelo Ketzer¹, Samuel Hylander¹, Anders Forsman¹, Mark Dopson¹

Affiliation

¹ Centre for Ecology and Evolution in Microbial Model Systems (EEMiS), Linnaeus University, Kalmar, Sweden.

Abstract

Coastal waters such as those found in the Baltic Sea already suffer from anthropogenic related problems including increased algal blooming and hypoxia while ongoing and future climate change will likely worsen these effects. Microbial communities in sediments play a crucial role in the marine energy- and nutrient cycling, and how they are affected by climate change and shape the environment in the future is of great interest. The aims of this study were to investigate potential effects of prolonged warming on microbial community composition and nutrient cycling including sulfate reduction in surface (∼0.5 cm) to deeper sediments (∼ 24 cm). To investigate this, 16S rRNA gene amplicon sequencing was performed, and sulfate concentrations were measured and compared between sediments in a heated bay (which has been used as a cooling water outlet from a nearby nuclear power plant for approximately 50 years) and a nearby but unaffected control bay. The results showed variation in overall microbial diversity according to sediment depth and higher sulfate flux in the heated bay compared to the control bay. A difference in vertical community structure reflected increased relative abundances of sulfur oxidizing- and sulfate reducing bacteria along with a higher proportion of archaea, such as Bathyarchaeota, in the heated compared to the control bay. This was particularly evident closer to the sediment surface, indicating a compression of geochemical zones in the heated bay. These results corroborate findings in previous studies and additionally point to an amplified effect of prolonged warming deeper in the sediment, which could result in elevated concentrations of toxic compounds and greenhouse gases closer to the sediment surface.

Keywords: 16S rRNA gene amplicon; climate change; depth profile; microbial communities; sediments.

Grants and funding

MD thanks the Swedish Research Council for Sustainable Development, Formas (contract FR-2020/0008), AF thanks the Swedish Research Council, Vetenskaprådet (contract 2020-03519), SH acknowledges the Crafoord Foundation (grant number: 20170539), and AF acknowledges the Magnus Bergvalls Stiftelse (grant number: 2019-03116) for financial support. A portion of this research was performed under the Facilities Integrating Collaborations for User Science (FICUS) initiative and used resources at the DOE Joint Genome Institute and the Environmental Molecular Sciences Laboratory, which are DOE Office of Science User Facilities. Both facilities are sponsored by the Office of Biological and Environmental Research and operated under Contract Nos. DE-AC02-05CH11231 (JGI) and DE-AC05-76RL01830 (EMSL) via a CSP FY18 Q3 New Investigator Proposal (CSP 503869) to SH.