Variations of sedimentary Fe and Mn fractions under changing lake mixing regimes, oxygenation and land surface processes during Late-glacial and Holocene times

Makri, Stamatina; Wienhues, Giulia; Bigalke, Moritz; Gilli, Adrian; Rey, Fabian; Tinner, Willy; Vogel, Hendrik; Grosjean, Martín

doi:10.1016/j.scitotenv.2020.143418

Cited by 34 publications

(21 citation statements)

References 56 publications

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“…We have shown that sedimentary Mn, Fe, and P contents can be laterally highly variable within a lake, and therefore the analysis of a depth transect of sediment cores allows much better‐informed insights into geochemical processes in the lakes sediments. Our results underline that the interpretation of paleo‐redox conditions using sedimentary Mn and Fe should consider geochemical focusing and potential depletion or enrichment of these elements as authigenic minerals in sediments, corroborating earlier work of Naeher et al (2013) and Makri et al (2020). We think that geochemical focusing of Mn and Fe is a common process that is characteristic of aquatic systems, where an oxic water column is underlain by sediments with a redox potential that allows for reduction and subsequent diffusion of dissolved Mn and Fe across the benthic interface.…”

Section: Discussionsupporting

confidence: 91%

Geochemical focusing and burial of sedimentary iron, manganese, and phosphorus during lake eutrophication

Scholtysik

Goldhammer

Arz

et al. 2022

Limnology & Oceanography

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The redistributive transport of sedimentary, redox-sensitive metals such as iron (Fe) and manganese (Mn) along depth gradients in lakes or marine basins, and in particular the concentration of these elements at local depressions, has been described as "geochemical focusing." However, the impact of variable redox conditions at the sediment-water interface on this process is not entirely understood. In this study, we report that the enrichment and burial of Fe, Mn, and associated phosphorus (P) in dimictic Lake Arendsee, Germany, has been affected by a transition from oligo-mesotrophic to eutrophic conditions in the first half of the 20th century. Eleven sediment cores (<50 cm long) were obtained from water depths ranging from 38.5 to 49.5 m, and analyzed for their elemental composition. The older, non-varved section, which was deposited prior ca. 1940 during oligo-mesotrophic conditions, contains up to 10 times higher Mn and 2.5 times higher Fe contents at the deep sites compared to corresponding intervals at shallower sites. Due to their high Fe content, sediments in this interval also contain up to eight times more P, at least partly owing to vivianite authigenesis. Burial of Mn occurred via Mn-carbonate authigenesis, possibly as rhodochrosite. Since ca. 1940, calcite and diatom varves have formed under eutrophic conditions, whereas Fe enrichment decreased and finally stopped due to fixation as pyrite in the shallow sites. Our results suggest that redox-controlled geochemical focusing determines the distribution of Mn and Fe, as well as the occurrence of authigenic minerals such as vivianite and Mn-carbonate.

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Section: Discussionsupporting

confidence: 91%

Geochemical focusing and burial of sedimentary iron, manganese, and phosphorus during lake eutrophication

Scholtysik

Goldhammer

Arz

et al. 2022

Limnology & Oceanography

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“…The Mn/Fe ratio, often used to track past O 2 content in bottom waters and changing redox conditions, was used as a proxy for water-column oxygen concentration 46 . The Mn/Fe ratios display highest values at depths of 200, 150 and 60 cm, suggesting periods of permanent anoxia during warmer conditions and excessive nutrient inputs 47 . The Fe/Ti ratio provides information about fluvial sediment sources.…”

Section: Resultsmentioning

confidence: 99%

Holocene life and microbiome profiling in ancient tropical Lake Chalco, Mexico

Moguel

Pérez

Alcaraz

et al. 2021

Sci Rep

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Metagenomic and traditional paleolimnological approaches are suitable to infer past biological and environmental changes, however, they are often applied independently, especially in tropical regions. We combined both approaches to investigate Holocene Prokaryote and Eukaryote diversity and microbial metabolic pathways in ancient Lake Chalco, Mexico. Here, we report on diversity among a large number of lineages (36,722 OTUs) and functional diversity (27,636,243 non-clustered predicted proteins, and 6,144 annotated protein-family genes). The most abundant domain is Bacteria (81%), followed by Archaea (15%) and Eukarya (3%). We also determined the diversity of protein families and their relationship to metabolic pathways. The early Holocene (> 11,000 cal years BP) lake was characterized by cool, freshwater conditions, which later became warmer and hyposaline (11,000–6,000 cal years BP). We found high abundances of cyanobacteria, and fungi groups associated with mature forests in these sediments. Bacteria and Archaea include mainly anaerobes and extremophiles that are involved in the sulfur, nitrogen, and carbon cycles. We found evidence for early human impacts, including landscape modifications and lake eutrophication, which began ~ 6,000 cal years BP. Subsaline, temperate conditions were inferred for the past 5,000 years. Finally, we found nitrogen-fixing bacteria and protein-family genes that are linked to contaminated environments, as well as several fungal pathogens of crops in near-surface sediments.

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“…The decrease in the Fe/Mn ratio since ∼1990 (Figure 7) may be indicative of redox‐controlled Fe mobilization and more reducing conditions in the hydrologically connected soils around Lake Bolmen. Since Mn is more readily reduced than Fe, a selective transport of Mn in relation to Fe has been interpreted to reflect reducing conditions in catchment soils (Engstrom & Wright, 1984), although the sedimentary Fe/Mn ratio as a proxy for past redox conditions should be interpreted with care as Fe and Mn accumulation are not solely redox driven (Makri et al., 2021). Moreover, the baseline shifts of Fe and color around 1999 (Figure 2) were likely triggered by a very wet period, and were observed also in lakes in Norway (Haaland et al., 2010; Riise et al., 2018).…”

Section: Discussionmentioning

confidence: 99%

Sediment Records Shed Light on Drivers of Decadal Iron Concentration Increase in a Boreal Lake

et al. 2022

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Iron (Fe) concentrations are increasing in lakes and running waters over a broad geographical scale (Björnerås et al., 2017). Together with dissolved organic matter (DOM), Fe is contributing to an ongoing browning-that is, an increase in water color in freshwaters-with consequences for light penetration and thermal stratification, affecting ecosystem functions such as primary productivity, as well as for the ecosystem services that aquatic systems provide (Kritzberg et al., 2019). Fe originates primarily from sources in the catchment, and the association with DOM is a prerequisite for the transport of Fe from soils to waters, since DOM increases Fe solubility in oxic circum-neutral waters (Stumm & Morgan, 1996). However, lake-internal processes, such as aggregation and sedimentation, remove Fe from the water column (Neubauer et al., 2013;von Wachenfeldt et al., 2008) and are important in determining the distribution of Fe between the water column and the sediments (Björnerås Abstract Increasing iron (Fe) concentrations are found in lakes on a wide geographical scale but exact causes are still debated. The observed trends might result from increased Fe loading from the terrestrial catchment, but also from changes in how Fe distributes between the water column and the sediments. To get a better understanding of the causes we investigated whether there has been any change in the sediment formation of Fe sulfides (FeS) as an Fe sink in response to declining atmospheric sulfur (S) deposition during recent decades. For our study, we chose Lake Bolmen in southern Sweden, a lake for which we confirmed that Fe concentrations in the water column have strongly increased along with water color during 1966-2018. Our investigations showed that Fe accumulation and speciation varied independently of S accumulation patterns in the Lake Bolmen sediment record. Thus, we were not able to relate the positive trend in Fe concentrations to reduced FeS binding in the sediments. Furthermore, we found that Fe accumulation rates increased along with lake water Fe concentrations, indicating that increased catchment loading rather than a change in the distribution between the sediments and the water column has driven the increase in Fe concentrations. The increased loading may be due to land-use change in the form of an extensive expansion of coniferous forest during the past century. Altered forest management practices and increased precipitation may have led to enhanced weathering and erosion of organic soil layers under aging coniferous forest. Plain Language Summary Iron concentrations are increasing in freshwaters in the NorthernHemisphere. One possible explanation is a decline in sulfur deposition in recent decades, which may have led to lower iron sulfide formation in soils and sediments, and thus to increased lake water iron concentrations. We tested this hypothesis by exploring iron concentrations in water and sediments of Lake Bolmen in southern Sweden in relation to changes in sulfur deposition, climate and catchment land-use. We ...

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Variations of sedimentary Fe and Mn fractions under changing lake mixing regimes, oxygenation and land surface processes during Late-glacial and Holocene times

Cited by 34 publications

References 56 publications

Geochemical focusing and burial of sedimentary iron, manganese, and phosphorus during lake eutrophication

Geochemical focusing and burial of sedimentary iron, manganese, and phosphorus during lake eutrophication

Holocene life and microbiome profiling in ancient tropical Lake Chalco, Mexico

Sediment Records Shed Light on Drivers of Decadal Iron Concentration Increase in a Boreal Lake

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