Controls on the shuttling of manganese over the northwestern Black Sea shelf and its fate in the euxinic deep basin

Lenstra, Wytze K.; Séguret, Marie J.M.; Behrends, Thilo; Groeneveld, R.K.; Hermans, Martijn; Witbaard, Rob; Slomp, Caroline P.

doi:10.1016/j.gca.2020.01.031

Cited by 31 publications

(31 citation statements)

References 104 publications

(196 reference statements)

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“…Elemental maps of Fe, Mn, P and Ca (30 µm resolution) were retrieved using a desktop EDAX Orbis µXRF analyser (Rh tube set at 30 kV, 500 µA, 300 ms dwell time, equipped with a poly-capillary lens). Similar µXRF maps for Fe, Mn and P in epoxy-embedded surface sediment were obtained for two field sites, namely (1) the Gulf of Finland (GOF5) for sediments collected in June 2016, as described by Hermans et al (2020), and Lake Grevelingen (Den Osse basin, S1) for sediments collected in January and May 2012, as described in Sulu-Gambari et al (2016a, 2018.…”

Section: Elemental Mapping Of Fe Mn P and Camentioning

confidence: 53%

“…Such focusing of Fe, Mn, P and associated elements within a thin subsurface layer, as a consequence of cable bacteria activity, also occurs in the field. This was demonstrated by Hermans et al (2020) in a study of a coastal site in the Gulf of Finland where cable bacteria were recently active. Here, µXRF mapping of resin-embedded sediments revealed strong focusing of Fe oxides, Mn (II) phosphates and Fe-bound P within a 3 mm thick layer near the sediment-water interface (Fig.…”

Section: Sediment Marker For Cable Bacteria Activitymentioning

confidence: 84%

“…The tick marks represent 1 mm intervals. µXRF maps of the surface sediment (a) from the incubation experiment, (b) from the Gulf of Finland at site GOF5 in June (Hermans et al, 2020), (c) from Lake Grevelingen (Den Osse basin, S1) in January (when cable bacteria become active) and (d) from Lake Grevelingen (Den Osse basin, S1) in May (showing the effects of bioturbation as described in Seitaj et al (2015). zone), a linear relationship -with some scatter -emerges for days 12 to 621 (Fig.…”

Section: Organic Matter Degradationmentioning

confidence: 99%

“…higher availability of FeS and siderite compared to the availability of Mn carbonates in the sediment that was used for incubation (Lenstra et al, 2020). The peaks in dissolved Fe 2+ and Mn 2+ in the pore water broadened over time, spanning a depth of > 5 cm (Figs.…”

Section: Impact Of Cable Bacteria On Fe Mn and S Cyclingmentioning

confidence: 99%

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Biogeochemical impact of cable bacteria on coastal Black Sea sediment

et al. 2020

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Abstract. Cable bacteria can strongly alter sediment biogeochemistry. Here, we used laboratory incubations to determine the potential impact of their activity on the cycling of iron (Fe), phosphorus (P) and sulfur (S). Microsensor depth profiles of oxygen, sulfide and pH in combination with electric potential profiling and fluorescence in situ hybridisation (FISH) analyses showed a rapid development (<5 d) of cable bacteria, followed by a long period of activity (>200 d). During most of the experiment, the current density correlated linearly with the oxygen demand. Sediment oxygen uptake was attributed to the activity of cable bacteria and the oxidation of reduced products from the anaerobic degradation of organic matter, such as ammonium. Pore water sulfide was low (< 5 µM) throughout the experiment. Sulfate reduction acted as the main source of sulfide for cable bacteria. Pore water Fe2+ reached levels of up to 1.7 mM during the incubations, due to the dissolution of FeS (30 %) and siderite, an Fe carbonate mineral (70 %). Following the upward diffusion of Fe2+, a surface enrichment of Fe oxides formed. Hence, besides FeS, siderite may act as a major source of Fe for Fe oxides in coastal surface sediments where cable bacteria are active. Using µXRF, we show that the enrichments in Fe oxides induced by cable bacteria are located in a thin subsurface layer of 0.3 mm. We show that similar subsurface layers enriched in Fe and P are also observed at field sites where cable bacteria were recently active and little bioturbation occurs. This suggests that such subsurface Fe oxide layers, which are not always visible to the naked eye, could potentially be a marker for recent activity of cable bacteria.

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Section: Elemental Mapping Of Fe Mn P and Camentioning

confidence: 53%

Section: Sediment Marker For Cable Bacteria Activitymentioning

confidence: 84%

Section: Organic Matter Degradationmentioning

confidence: 99%

Section: Impact Of Cable Bacteria On Fe Mn and S Cyclingmentioning

confidence: 99%

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Biogeochemical impact of cable bacteria on coastal Black Sea sediment

et al. 2020

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“…5). The twenty-fold higher dissolved Fe 2+ concentrations with respect to pore water Mn 2+ can be attributed to the relatively higher availability of FeS and siderite compared to the availability of Mn carbonates in the sediment that was used for incubation (Lenstra et al 2020). The peaks in dissolved Fe 2+ and Mn 2+ in the pore water broadened over time spanning a depth of >5cm ( Fig.…”

Section: Impact Of Cable Bacteria On Fe Mn and S Cyclingmentioning

confidence: 97%

Biogeochemical Impact of Cable Bacteria on Coastal Black Sea Sediment

Hermans¹,

Risgaard-Petersen²,

Meysman³

et al. 2020

Preprint

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Abstract. Cable bacteria can strongly alter sediment biogeochemistry. Here, we used laboratory incubations to assess whether cable bacteria can establish in iron (Fe) monosulphide-poor coastal Black Sea sediment and to determine the impact of their activity on the cycling of Fe, phosphorus (P) and sulphur (S). Microsensor depth profiles of oxygen, sulphide and pH in combination with electric potential profiling and FISH analyses showed a rapid development ( 200 days). During most of the experiment, the current density correlated linearly with the oxygen demand. Sediment oxygen uptake was attributed to activity of cable bacteria and the oxidation of reduced products from anaerobic degradation of organic matter, such as ammonium. Pore water sulphide was low (

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Coastal hypoxia and eutrophication as key controls on benthic release and water column dynamics of iron and manganese

Lenstra

Hermans

Séguret

et al. 2020

Limnology & Oceanography

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Continental shelves are a major source of iron (Fe) and manganese (Mn) to marine waters. Here, we investigate controls on benthic release of Fe and Mn and the impact on the water column in the Baltic Sea. We find high in situ benthic release rates of dissolved Fe and Mn at seasonally hypoxic sites (bottom water oxygen between 0-63 μmol L −1) receiving high inputs of organic matter. We find that benthic Fe and Mn release is sensitive to bottom water oxygen concentrations. Benthic Fe release is likely additionally controlled by Fe-sulfur redox chemistry in the surface sediment. For Mn, benthic release correlates positively with Mn oxide availability in the surface sediment. Benthic release contributes to high dissolved Fe and Mn concentrations in the water column and is amplified by repeated cycling of Fe and Mn between the sediment and overlying water through benthic release, oxidation in the water column, deposition as metal oxides, followed by reductive dissolution. Most water column Fe ($ 80%) is present in particulate form near the seafloor. In contrast to Fe, a large percentage of the Mn remains dissolved ($ 50%). We show that easily reducible Fe and Mn oxides are key forms of particulate Fe and Mn in suspended matter. The Baltic Sea represents a highly eutrophic, low oxygen end-member when compared to other modern coastal systems. Our results imply that, upon continued eutrophication and deoxygenation of the coastal ocean, benthic release of dissolved Fe and Mn from continental shelves could become greater than previously thought.

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Controls on the shuttling of manganese over the northwestern Black Sea shelf and its fate in the euxinic deep basin

Cited by 31 publications

References 104 publications

Biogeochemical impact of cable bacteria on coastal Black Sea sediment

Biogeochemical impact of cable bacteria on coastal Black Sea sediment

Biogeochemical Impact of Cable Bacteria on Coastal Black Sea Sediment

Coastal hypoxia and eutrophication as key controls on benthic release and water column dynamics of iron and manganese

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