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Complex Microbial Communities Drive Iron and Sulfur Cycling in Arctic Fjord Sediments
J Buongiorno1, L C Herbert2, L M Wehrmann2
1Department of Microbiology, University of Tennessee, Knoxville, Knoxville, Tennessee, USA.
Applied and Environmental Microbiology
|May 12, 2019
Summary
Arctic glacial retreat alters iron and sulfur cycling in Svalbard fjords. Microbial communities in low-organic sediments near glaciers limit sulfate reduction, allowing iron to reach the ocean, fueling primary production.
Area of Science:
- * Arctic marine biogeochemistry
- * Microbial ecology
- * Geochemical cycling
Background:
- * Glacial retreat in the Arctic is altering ocean biogeochemical cycling.
- * Glacial runoff is a significant source of iron for oceanic shelf primary production.
- * Svalbard fjords are experiencing changes due to glacial retreat, impacting sediment biogeochemistry.
Purpose of the Study:
- * To investigate the role of microbial communities in iron and sulfur cycling in Svalbard fjord sediments.
- * To test the hypothesis that low organic matter limits sulfide generation, promoting iron mobility.
- * To understand how microbial community structure and function are influenced by organic matter availability and proximity to glaciers.
Main Methods:
- * High-depth-resolution 16S rRNA gene sequencing was performed on sediment samples from two sites in Van Keulenfjorden, Svalbard.
- * Sediment organic matter content was analyzed using delta C-13 and C/N ratios.
- * Network analysis was used to explore correlations between microbial taxa and geochemical parameters.
Main Results:
- * Microbial communities near glaciers showed abundant iron- and sulfur-cycling bacteria in upper sediments, with sulfate reducers dominating deeper layers.
- * Outer fjord sites exhibited a shallower transition to sulfate-reducing bacteria and higher sulfate reduction rates, correlated with increased labile organic matter.
- * Network analysis revealed distinct microbial community structures and increased correlations between iron- and sulfur-cycling taxa closer to glaciers.
Conclusions:
- * Microbial communities in Svalbard fjords catalyze complex redox cycling of iron and sulfur, influenced by organic matter availability.
- * Limited sulfate reduction in sediments near glaciers allows iron to flux into the water column, potentially supporting shelf primary production.
- * As glaciers recede and organic matter input increases, enhanced sulfate reduction in fjord sediments may reduce iron availability for oceanic primary production.
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