The Impact of Sea Ice Cover on Microbial Communities in Antarctic Shelf Sediments

Abstract

The area around the Antarctic Peninsula (AP) is facing rapid climatic and environmental changes, with so far unknown impacts on the benthic microbial communities of the continental shelves. In this study, we investigated the impact of contrasting sea ice cover on microbial community compositions in surface sediments from five stations along the eastern shelf of the AP using 16S ribosomal RNA (rRNA) gene sequencing. Redox conditions in sediments with long ice-free periods are characterized by a prevailing ferruginous zone, whereas a comparatively broad upper oxic zone is present at the heavily ice-covered station. Low ice cover stations were highly dominated by microbial communities of Desulfobacterota (mostly Sva1033, Desulfobacteria, and Desulfobulbia), Myxococcota, and Sva0485, whereas Gammaproteobacteria, Alphaproteobacteria, Bacteroidota, and NB1-j prevail at the heavy ice cover station. In the ferruginous zone, Sva1033 was the dominant member of Desulfuromonadales for all stations and, along with eleven other taxa, showed significant positive correlations with dissolved Fe concentrations, suggesting a significant role in iron reduction or an ecological relationship with iron reducers. Our results indicate that sea ice cover and its effect on organic carbon fluxes are the major drivers for changes in benthic microbial communities, favoring potential iron reducers at stations with increased organic matter fluxes.

Manganese reduction and associated microbial communities in Antarctic surface sediments

“…At the study site, this taxon likely plays an important role as indicated by its high relative abundance in the in situ sediments ( Supplementary Figure S8 ) and its high presence already at the start and throughout the experiment. This is in agreement with previous studies investigating Antarctic sediments ( Aromokeye et al, 2021 ; Baloza et al, 2023 ) and sub-Antarctic sediments around South Georgia ( Wunder et al, 2021 ). Sva1033 was shown before to oxidize acetate and reduce iron oxides in sediments of Potter Cove ( Aromokeye et al, 2021 ; Wunder et al, 2021 ), and also here it showed higher relative 16S rRNA abundance in acetate amended treatments.…”

“…It has been studied in different Arctic, manganese oxide rich sediments of the Barents Sea ( Vandieken et al, 2006c ), Beaufort Sea ( Magen et al, 2011 ) and Svalbard fjords ( Vandieken et al, 2006a ; Wehrmann et al, 2014 ). There are only few studies that investigated specific organic matter degradation processes, e.g., iron reduction, and the related microbial communities in Antarctic subsurface sediments ( Monien et al, 2014a ; Aromokeye et al, 2021 ; Wunder et al, 2021 ; Baloza et al, 2022 , 2023 ; Burdige and Christensen, 2022 ). The occurrence of manganese reduction and the respective microbial players have not been studied in any Antarctic sediments yet.…”