Potentially Active Iron, Sulfur, and Sulfate Reducing Bacteria in Skagerrak and Bothnian Bay Sediments

Abstract

In many marine surface sediments, the reduction of manganese (Mn) and iron (Fe) oxides is obscured by sulfate reduction, which is regarded as the predominant anaerobic microbial respiration process. However, many dissimilatory sulfate and sulfur reducing microorganisms are known to utilize alternative electron acceptors such as metal oxides. In this study, we tested whether sulfate and sulfur reducing bacteria are linked to metal oxide reduction based on biogeochemical modeling of porewater concentration profiles of Mn 2C and Fe 2C in Bothnian Bay (BB) and Skagerrak (SK) sediments. Steady-state modeling of Fe 2C and Mn 2C porewater profiles revealed zones of net Fe (0-9 cm BB; »10 and 20 cm SK) and Mn (0-5 cm BB; 2-8 cm SK) species transformations. 16S rRNA pyrosequencing analysis of the in-situ community showed that Desulfobacteraceae, Desulfuromonadaceae and Desulfobulbaceae were present in the zone of Fereduction of both sediments. Rhodobacteraceae were also detected at high relative abundance in both sediments. BB sediments appeared to harbor a greater diversity of potential Fe-reducers compared to SK. Additionally, when the upper 10 cm of sediment from the SK was incubated with lepidocrocite and acetate, Desulfuromonas was the dominant bacteria. Real-time quantitative polymerase chain reaction (qPCR) results showed decreasing dsrA gene copy numbers with depth coincided with decreased Fe-reduction activity. Our results support the idea that sulfur and sulfate reducing bacteria contribute to Fe-reduction in the upper centimeters of both sediments.

Rates and Microbial Players of Iron-Driven Anaerobic Oxidation of Methane in Methanic Marine Sediments

“…In order to estimate increase in biomass of ANME phylotypes in the incubations experiments over 250 days, abundances from their respective depths were considered as baseline proxy. qPCR assay was done following reference (Reyes et al, 2017) with few modifications. Standard templates were prepared by amplifying ANME clones using plasmid specific M13 primer pairs and the AmpliTaq DNA polymerase kit.…”

Sensitivity of Bacterioplankton to Environmental Disturbance: A Review of Baltic Sea Field Studies and Experiments

“…Recent work on bacterial populations and their activity at the seafloor of the Baltic Sea has shown a plethora of interesting dynamics and lifestyles including, an active community that was previously deemed unlikely (Glaubitz et al, 2009(Glaubitz et al, , 2014Berg et al, 2013Berg et al, , 2015Broman et al, 2017a,b;Reyes et al, 2017;Zinke et al, 2017). Detailed studies with concomitant measurements of bacterioplankton community composition and function are required in deep-waters and sediments of the Baltic Sea to determine the role of bacteria in key biogeochemical cycles (e.g., of C, N, P, and S) in general, and in relation to hypoxia in particular.…”

Solute Reservoirs Reflect Variability of Early Diagenetic Processes in Temperate Brackish Surface Sediments

“…The Fe * profiles often showed a characteristic shape with a maximum close to the sediment water interface, a minimum at~5-10 cm depth and a second, often broader peak below. Decreasing contents of reactive Fe and Mn with depth (Figure 2) indicate active reduction of the oxidized phases, either sulfide-mediated or via microbial dissimilatory metal reduction (Lovley, 1991;Reyes et al, 2017). Released Fe 2+ and Mn 2+ migrate up and down along pore water concentration gradients ( Figure 6) and precipitate as oxides or (oxyhydr)oxides on contact with oxygen near the sediment surface.…”