Department Surface Waters - Research and Management

Biogeochemical cycling at oxic-anoxic boundaries

Blick über das anoxische Südbecken des Zugersees und ein Highlight der chemischen Struktur des Übergangs vom Oxischen zum Anoxischen.


In the absence of oxygen, other elements such as iron and manganese are used in microbial respiration. This fundamentally ties the cycling of these metals to Earth’s major elements (carbon, oxygen, sulfur, nitrogen). This project will investigate the biogeochemical cycling of iron, manganese, and other trace elements, across the oxic-anoxic interface of Lake Zug using chemical, physical, and microbial techniques. Compared to other anoxic lakes, Lake Zug is unique based on its high manganese but low iron and sulfur concentrations, making it a particularly interesting study site.

Anoxic settings are found throughout the modern Earth, and were the major state of Earth’s waters through most of its history. Therefore, these anoxic settings not only allow unique environments for studying modern processes, but also act as analogs to study biogeochemical cycling through Earth’s history.
Another goal of this project is assessing how the chemical tracers we use to reconstruct major states of the Earth (metal abundance, stable isotopes, and speciation) are affected by anoxic conditions in Lake Zug and other anoxic lakes.

Publications

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      authors => protected'Janssen, D. J.; Bauer, K. W.; Bruggmann, S.; Crowe,
          S. A.' (92 chars)
      title => protected'The global biogeochemical cycle of chromium at the Earth's surface' (66 chars)
      journal => protected'Global Biogeochemical Cycles' (28 chars)
      year => protected2025 (integer)
      volume => protected39 (integer)
      issue => protected'6' (1 chars)
      startpage => protected'e2025GB008525 (43 pp.)' (22 chars)
      otherpage => protected'' (0 chars)
      categories => protected'' (0 chars)
      description => protected'The biogeochemistry of Cr and its cycling in Earth's surface environments is
          reviewed. A synthesis and critical evaluation of the major processes contro
         lling Cr mobility and isotope composition (δ<sup>53</sup>Cr) is presented, 
         taking a source to sink view beginning with Cr mobilization from Earth's cru
         st. Transport and cycling in inland waters and input to the oceans are discu
         ssed. Anthropogenic mobilization of Cr results in contributions to the atmos
         phere and inland waters that are of similar orders of magnitude as natural p
         rocesses. The principal sources of Cr to the oceans are rivers and diffusive
          fluxes from marine sediments. Internal cycling of Cr in the ocean is largel
         y controlled by reductive removal onto particles, particularly in O<sub>2</s
         ub>-depleted waters, and redistribution through ocean circulation. Chromium 
         removal from the oceans occurs primarily in organic carbon-rich, O<sub>2</su
         b>-poor shelf sediments. Despite theoretically poor mobility of Cr(III), red
         uctive removal in anoxic waters is non-quantitative. As a result, isotope fr
         actionation drives δ<sup>53</sup>Cr offsets in removed Cr as well as residu
         al dissolved Cr(III), which accumulates in anoxic water, compared to the cor
         responding source. The implications for δ<sup>53</sup>Cr-based reconstructi
         ons are discussed, along with an outlook for future proxy applications based
          on the processes controlling Cr incorporation into sediments. The roles of 
         different source and sink processes are quantified in an updated mass balanc
         e for the global ocean. Finally, priority topics for future research are sug
         gested, which at present are the primary uncertainties of the modern Cr biog
         eochemical cycle and aspects of the Cr isotope mass balance.' (1732 chars)
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      doi => protected'10.1029/2025GB008525' (20 chars)
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      authors => protected'Janssen,&nbsp;D.&nbsp;J.; Damanik,&nbsp;A.; Tournier,&nbsp;N.; Tolu,&nbsp;J.
         ; Winkel,&nbsp;L.; Cahyarini,&nbsp;S.&nbsp;Y.; Vogel,&nbsp;H.' (137 chars)
      title => protected'Biogeochemical cycling of trace elements and nutrients in ferruginous waters
         : constraints from a deep oligotrophic ancient lake' (127 chars)
      journal => protected'Limnology and Oceanography' (26 chars)
      year => protected2024 (integer)
      volume => protected69 (integer)
      issue => protected'11' (2 chars)
      startpage => protected'2775' (4 chars)
      otherpage => protected'2790' (4 chars)
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      description => protected'Iron-rich, ferruginous waters were the dominant geochemical regime for most 
         of Earth's history. Modern ferruginous waters are found in stratified, sulfu
         r-poor lakes, and serve as crucial analogs for biogeochemical cycling throug
         hout Earth's past. Here we present the first depth-resolved data of physical
          structure, nutrients and trace elements from Lake Poso (Indonesia), a deep 
         oligotrophic ancient lake. Lake Poso is ferruginous, with anoxia below ~ 9
         0 m depth, placing it among the world's largest ferruginous lakes. Physica
         l stratification is weaker than other tropical anoxic lakes, indicating sens
         itivity for paleoclimate reconstructions. Trace elements and nutrients are p
         redominantly shaped by the oxic–anoxic transition. Manganese– and Fe oxy
         hydroxide–driven biogeochemical cycling occurs at distinct depth horizons,
          with Co and Ni controlled by Mn and showing shallow release in anoxic water
         s, while V, Cr, P, and As are controlled by Fe, with release in surface sedi
         ments and diffusive transport. Chromium is nonquantitatively removed in anox
         ic waters, in contrast to widespread assumptions in Cr-based paleoreconstruc
         tions. Oxycline U and Se removal corresponds to a local N minimum, suggestin
         g biological reduction and/or uptake. These first ferruginous water Se data 
         also show removal in sediments, indicating sediment signals reflect multiple
          removal processes and informing Se-based paleoreconstructions, while the ab
         sence of sediment U removal contrasts other anoxic basins. A comparison with
          other ferruginous lakes demonstrates how local influences drive deviations 
         from expectations in other systems, and highlight common, generalizable ferr
         uginous basin features. Therefore, these data will guide research in ferrugi
         nous settings across space and time, and improve paleoreconstructions from f
         erruginous sediment records.' (1852 chars)
      serialnumber => protected'0024-3590' (9 chars)
      doi => protected'10.1002/lno.12687' (17 chars)
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The global biogeochemical cycle of chromium at the Earth's surface

The biogeochemistry of Cr and its cycling in Earth's surface environments is reviewed. A synthesis and critical evaluation of the major processes controlling Cr mobility and isotope composition (δ53Cr) is presented, taking a source to sink view beginning with Cr mobilization from Earth's crust. Transport and cycling in inland waters and input to the oceans are discussed. Anthropogenic mobilization of Cr results in contributions to the atmosphere and inland waters that are of similar orders of magnitude as natural processes. The principal sources of Cr to the oceans are rivers and diffusive fluxes from marine sediments. Internal cycling of Cr in the ocean is largely controlled by reductive removal onto particles, particularly in O2-depleted waters, and redistribution through ocean circulation. Chromium removal from the oceans occurs primarily in organic carbon-rich, O2-poor shelf sediments. Despite theoretically poor mobility of Cr(III), reductive removal in anoxic waters is non-quantitative. As a result, isotope fractionation drives δ53Cr offsets in removed Cr as well as residual dissolved Cr(III), which accumulates in anoxic water, compared to the corresponding source. The implications for δ53Cr-based reconstructions are discussed, along with an outlook for future proxy applications based on the processes controlling Cr incorporation into sediments. The roles of different source and sink processes are quantified in an updated mass balance for the global ocean. Finally, priority topics for future research are suggested, which at present are the primary uncertainties of the modern Cr biogeochemical cycle and aspects of the Cr isotope mass balance.
Janssen, D. J.; Bauer, K. W.; Bruggmann, S.; Crowe, S. A. (2025) The global biogeochemical cycle of chromium at the Earth's surface, Global Biogeochemical Cycles, 39(6), e2025GB008525 (43 pp.), doi:10.1029/2025GB008525, Institutional Repository

Biogeochemical cycling of trace elements and nutrients in ferruginous waters: constraints from a deep oligotrophic ancient lake

Iron-rich, ferruginous waters were the dominant geochemical regime for most of Earth's history. Modern ferruginous waters are found in stratified, sulfur-poor lakes, and serve as crucial analogs for biogeochemical cycling throughout Earth's past. Here we present the first depth-resolved data of physical structure, nutrients and trace elements from Lake Poso (Indonesia), a deep oligotrophic ancient lake. Lake Poso is ferruginous, with anoxia below ~ 90 m depth, placing it among the world's largest ferruginous lakes. Physical stratification is weaker than other tropical anoxic lakes, indicating sensitivity for paleoclimate reconstructions. Trace elements and nutrients are predominantly shaped by the oxic–anoxic transition. Manganese– and Fe oxyhydroxide–driven biogeochemical cycling occurs at distinct depth horizons, with Co and Ni controlled by Mn and showing shallow release in anoxic waters, while V, Cr, P, and As are controlled by Fe, with release in surface sediments and diffusive transport. Chromium is nonquantitatively removed in anoxic waters, in contrast to widespread assumptions in Cr-based paleoreconstructions. Oxycline U and Se removal corresponds to a local N minimum, suggesting biological reduction and/or uptake. These first ferruginous water Se data also show removal in sediments, indicating sediment signals reflect multiple removal processes and informing Se-based paleoreconstructions, while the absence of sediment U removal contrasts other anoxic basins. A comparison with other ferruginous lakes demonstrates how local influences drive deviations from expectations in other systems, and highlight common, generalizable ferruginous basin features. Therefore, these data will guide research in ferruginous settings across space and time, and improve paleoreconstructions from ferruginous sediment records.
Janssen, D. J.; Damanik, A.; Tournier, N.; Tolu, J.; Winkel, L.; Cahyarini, S. Y.; Vogel, H. (2024) Biogeochemical cycling of trace elements and nutrients in ferruginous waters: constraints from a deep oligotrophic ancient lake, Limnology and Oceanography, 69(11), 2775-2790, doi:10.1002/lno.12687, Institutional Repository