Sedimentary facies analyses from nano- to millimetre scale exploring past microbial activity in a high-altitude lake (Lake Son Kul, Central Asia)

Pacton, Muriel; Sorrel, Philippe; Bevillard, Benoit; Zacaï, Axelle; Vinçon‐Laugier, Arnauld; Oberhänsli, Hedi

doi:10.1017/s0016756814000831

Cited by 17 publications

(9 citation statements)

References 121 publications

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“…The potential role of viruses in near-surface geological processes has not been explored in any detail; indeed, the very presence of viruses in geological materials has only recently been appreciated. The association of likely viral particles with mineral precipitation is clearly shown in the examples presented here and has also been documented by Pacton et al (2014) from microbial mats in a hypersaline lagoon in Brazil; in lacustrine carbonates from Central Asia (Pacton et al, 2015); and by De Wit et al (2015) from a salt lake in north-west Spain where viruses are closely associated with Ca-Mg-carbonates. The ability of viruses and EPS to attract cations through their negative charge is a key feature in the precipitation of crystallites containing alkalimetal (Ca, Mg, Ba and Sr) and other elements.…”

Section: Nanospheressupporting

confidence: 80%

“…The association of likely viral particles with mineral precipitation is clearly shown in the examples presented here and has also been documented by Pacton et al . () from microbial mats in a hypersaline lagoon in Brazil; in lacustrine carbonates from Central Asia (Pacton et al ., ); and by De Wit et al . () from a salt lake in north‐west Spain where viruses are closely associated with Ca–Mg‐carbonates.…”

Section: Discussionmentioning

confidence: 99%

“…a spheroid with flat sides, as is seen in the nanospheres of the Qatar mat. The nanospheres are also in the correct size range (30 to 300 nm) for viruses; their close association with bacterial, especially coccoid (prokaryotic), cells is also characteristic (Pacton et al ., ). The SEM observation of nanospheres upon the external wall of bacterial cells (Fig.…”

Section: Discussionmentioning

confidence: 99%

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Carbonate and silicate biomineralization in a hypersaline microbial mat (Mesaieed sabkha, Qatar): Roles of bacteria, extracellular polymeric substances and viruses

Tucker²,

et al. 2017

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In a modern peritidal microbial mat from Qatar, both biomediated carbonates and Mg‐rich clay minerals (palygorskite) were identified. The mat, ca 5 cm thick, shows a clear lamination reflecting different microbial communities. The initial precipitates within the top millimetres of the mat are composed of Ca–Mg–Si–Al–S amorphous nanoparticles (few tens of nanometres) that replace the ultrastructure of extracellular polymeric substances. The extracellular polymeric substances are enriched in the same cations and act as a substrate for mineral nucleation. Successively, crystallites of palygorskite fibres associated with carbonate nanocrystals develop, commonly surrounding bacterial bodies. Micron‐sized crystals of low‐Mg calcite are the most common precipitates, together with subordinate aragonite, very high‐Mg calcite/dolomite and ankerite. Pyrite nanocrystals and framboids are present in the deeper layers of the mat. Calcite crystallites form conical structures, circular to triangular/hexagonal in cross‐section, evolving to crystals with rhombohedral terminations; some crystallite bundles develop into dumb‐bell and stellate forms. Spheroidal organo‐mineral structures are also common within the mat. Nanospheres, a few tens of nanometres in diameter, occur attached to coccoid bacteria and within their cells; these are interpreted as permineralized viruses and could be significant as nuclei for crystallite‐crystal precipitation. Microspheres, 1 to 10 μm in diameter, result from intracellular permineralization within bacteria or the mineralization of the bacteria themselves. Carbonates and clay minerals are commonly aggregated to form peloids, tens of microns in size, surrounded by residual organic matter. Magnesium silicate and carbonate precipitation are likely to have been driven by pH – saturation index – redox changes within the mat, related to microenvironmental chemical changes induced by the microbes – extracellular polymeric substances – viruses and their degradation.

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Section: Nanospheressupporting

confidence: 80%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Carbonate and silicate biomineralization in a hypersaline microbial mat (Mesaieed sabkha, Qatar): Roles of bacteria, extracellular polymeric substances and viruses

Tucker²,

et al. 2017

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“…Our results demonstrate that interactions among Mg 2+ , EPS, and silica are instrumental in the biologically mediated silicification of modern marine cyanobacteria. Indeed, magnesium‐rich silica phases that nucleate around cyanobacterial cells and organic particles have been reported in modern microbial mats from various localities (Kremer et al., 2008; Pacton et al., 2015; Perri et al., 2018; Zeyen et al., 2015). Already abundant in seawater, Mg 2+ would have been even more concentrated in supratidal hypersaline environments such as those that preserved many silicified Proterozoic fossils and similar interactions between Mg 2+ and organic surfaces may have played a role in the preservation of fossils and organic matter during the Proterozoic.…”

Section: Discussionmentioning

confidence: 99%

A new model for silicification of cyanobacteria in Proterozoic tidal flats

et al. 2021

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Microbial fossils preserved by early diagenetic chert provide a window into the Proterozoic biosphere, but seawater chemistry, microbial processes, and the interactions between microbes and the environment that contributed to this preservation are not well constrained. Here, we use fossilization experiments to explore the processes that preserve marine cyanobacterial biofilms by the precipitation of amorphous silica in a seawater medium that is analogous to Proterozoic seawater. These experiments demonstrate that the exceptional silicification of benthic marine cyanobacteria analogous to the oldest diagnostic cyanobacterial fossils requires interactions among extracellular polymeric substances (EPS), photosynthetically induced pH changes, magnesium cations (Mg2+), and >70 ppm silica.

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“…5000-4500 cal. yr BP (Huang et al, 2014; Lauterbach et al, 2014; Mathis et al, 2014; Pacton et al, 2015; Schwarz et al, 2017). The sediment core examined in this study was first investigated by Lauterbach et al (2014) using sedimentological, (bio)geochemical, isotopic, and palynological evidence to reconstruct phases of enhanced allochthonous sediment input through snowmelt, reflecting increased winter snowfall brought by episodically intensified Westerlies in Central Kyrgyzstan during the last 6000 years.…”

Section: Introductionmentioning

confidence: 99%

Ecosystem shifts at two mid-Holocene tipping points in the alpine Lake Son Kol (Kyrgyzstan, Central Asia)

et al. 2020

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Tipping points can be defined as critical ecosystem thresholds that start self-enforced dynamics pushing systems into new stable states. Many lake ecosystems of arid Central Asia are sensitive to hydrological changes as they are located at the intersection of the influence of the dry Siberian Anticyclone and the relatively humid mid-latitude Westerlies, and their sediment records can be used to study past tipping points. We studied subfossil chironomid remains preserved in a ca. 6000-year-long sediment record from the Central Asian lake Son Kol (Central Kyrgyzstan) to reconstruct past ecosystem dynamics. Our results show abrupt transitions from a chironomid fauna dominated by macrophyte-associated, salinity-indicating taxa, to a vegetation-independent fauna, and subsequently to a macrophyte-associated, freshwater-indicating fauna. A comparison of the chironomid-based environmental reconstruction to other proxy indicators from the same record suggests a phase of increased Westerly strength starting about 4900 cal. yr BP. This increase led to enhanced precipitation and sediment fluxes into the lake, which in turn led to high turbidity levels and consequently to a macrophyte collapse causing abrupt changes in the chironomid fauna. At 4300 cal. yr BP, a weakening of the Westerlies in combination with higher lake levels led to lower turbidity and ultimately to the recovery of the macrophyte population and associated changes in the chironomid assemblage. These two sequences of events show how the occurrence of a gradual change in an external trigger (Westerlies) can trigger a cascade of within-lake processes (turbidity, macrophyte density) and may ultimately lead to an abrupt reorganization of the ecosystem (chironomid fauna), providing models for tipping points.

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Sedimentary facies analyses from nano- to millimetre scale exploring past microbial activity in a high-altitude lake (Lake Son Kul, Central Asia)

Abstract: International audienc

Cited by 17 publications

References 121 publications

Carbonate and silicate biomineralization in a hypersaline microbial mat (Mesaieed sabkha, Qatar): Roles of bacteria, extracellular polymeric substances and viruses

Carbonate and silicate biomineralization in a hypersaline microbial mat (Mesaieed sabkha, Qatar): Roles of bacteria, extracellular polymeric substances and viruses

A new model for silicification of cyanobacteria in Proterozoic tidal flats

Ecosystem shifts at two mid-Holocene tipping points in the alpine Lake Son Kol (Kyrgyzstan, Central Asia)

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