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CaCO3 precipitation in multilayered cyanobacterial mats: clues to explain the alternation of micrite and sparite layers in calcareous stromatolites.

Kaźmierczak J, Fenchel T, Kühl M, Kempe S, Kremer B, Łącka B, Małkowski K - Life (Basel) (2015)

Bottom Line: The d13C values were about 2‰ heavier in carbonates from the living cyanobacterial zones as compared to those generated in the purple bacterial zones.The generated CaCO3 morphs were highly similar to morphs reported from heterotrophic bacterial cultures, and from bacterially decomposed cyanobacterial biomass emplaced in Ca-rich media.They are also similar to CaCO3 morphs precipitated from purely inorganic solutions.

View Article: PubMed Central - PubMed

Affiliation: Institute of Paleobiology, Polish Academy of Sciences, Twarda 51/55, 00-818 Warsaw, Poland. jkaz@twarda.pan.pl.

ABSTRACT
Marine cyanobacterial mats were cultured on coastal sediments (Nivå Bay, Øresund, Denmark) for over three years in a closed system. Carbonate particles formed in two different modes in the mat: (i) through precipitation of submicrometer-sized grains of Mg calcite within the mucilage near the base of living cyanobacterial layers, and (ii) through precipitation of a variety of mixed Mg calcite/aragonite morphs in layers of degraded cyanobacteria dominated by purple sulfur bacteria. The d13C values were about 2‰ heavier in carbonates from the living cyanobacterial zones as compared to those generated in the purple bacterial zones. Saturation indices calculated with respect to calcite, aragonite, and dolomite inside the mats showed extremely high values across the mat profile. Such high values were caused by high pH and high carbonate alkalinity generated within the mats in conjunction with increased concentrations of calcium and magnesium that were presumably stored in sheaths and extracellular polymer substances (EPS) of the living cyanobacteria and liberated during their post-mortem degradation. The generated CaCO3 morphs were highly similar to morphs reported from heterotrophic bacterial cultures, and from bacterially decomposed cyanobacterial biomass emplaced in Ca-rich media. They are also similar to CaCO3 morphs precipitated from purely inorganic solutions. No metabolically (enzymatically) controlled formation of particular CaCO3 morphs by heterotrophic bacteria was observed in the studied mats. The apparent alternation of in vivo and post-mortem generated calcareous layers in the studied cyanobacterial mats may explain the alternation of fine-grained (micritic) and coarse-grained (sparitic) laminae observed in modern and fossil calcareous cyanobacterial microbialites as the result of a probably similar multilayered mat organization.

No MeSH data available.


Related in: MedlinePlus

Microbiota associated with calcium carbonate layers in microstromatolites from the quasi-marine Satonda Crater Lake (Central Indonesia). (a) SEM image (top view) of a coccoid pleurocapsalean cyanobacterial mat growing today in the lake. (b) SEM image of vertical mat section showing mucilage sheaths (glycocalyx) of coccoid pseudocapsalean cyanobacteria permineralized in vivo with aragonite nanograins (micrite). (c–e) Micrographs of thin sections showing examples of remains of microbiota associated with aragonite layers (sparite) precipitated in decomposing biomass of coccoid cyanobacteria: diatoms (c), Chloroflexus-like bacteria (d) and aquatic fungi. Scale bars: (a) 20 μm, (b) 20 μm, (c) 10 μm, (d) 10 μm, (e) 20 μm.
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life-05-00744-f006: Microbiota associated with calcium carbonate layers in microstromatolites from the quasi-marine Satonda Crater Lake (Central Indonesia). (a) SEM image (top view) of a coccoid pleurocapsalean cyanobacterial mat growing today in the lake. (b) SEM image of vertical mat section showing mucilage sheaths (glycocalyx) of coccoid pseudocapsalean cyanobacteria permineralized in vivo with aragonite nanograins (micrite). (c–e) Micrographs of thin sections showing examples of remains of microbiota associated with aragonite layers (sparite) precipitated in decomposing biomass of coccoid cyanobacteria: diatoms (c), Chloroflexus-like bacteria (d) and aquatic fungi. Scale bars: (a) 20 μm, (b) 20 μm, (c) 10 μm, (d) 10 μm, (e) 20 μm.

Mentions: An instructive example of such diagenetic transformation of the primary calcium carbonate morphs in micrite and sparite layers are subfossil (micro) stromatolites from the quasi-marine Satonda Crater Lake (Central Indonesia) formed by colonial coccoid (pleurocapsalean) cyanobacteria [5,11,78,79]. The lamination in these stromatolites is extremely well-expressed, whereby the micritic laminae are as a rule thinner than the sparitic ones (Figure 5a,b). The micritic laminae are composed of aragonite nanograins, with some admixture of Mg silicate nanograins, both apparently precipitated in the common mucilage sheaths (glycocalyx). A few diatoms were found in these laminae between colonies of coccoid cyanobacteria. Similarly as in the case of the studied artificial mats, the microbiota from the micritic laminae (Figure 5c) indicate an aerobic character of the microenvironment sustaining the origin of the aragonite nanograins. The sparitic laminae in turn consisted of vertically well-ordered aragonite fibres which, as indicated by the presence of highly degraded remains of sheaths of coccoid cyanobacteria (Figure 5d), precipitated in a decaying cyanobacterial necromass. The remains of filaments of Chloroflexi-like phototrophic bacteria, partially desilicified diatom frustules and saprophytic fungi abundant in the sparitic laminae suggest, similarly as in the artificial mats, a dysoxic or anoxic microenvironment conditions for these laminae (Figure 6). It is known that the well-laminated Satonda Crater Lake stromatolites developed in a quasi-marine environment (Table 2) with increased alkalinity that is characterized by alternating dry and wet seasons [5,11,78] controlling not only mat growth but possibly also enforcing two basically different calcifications processes observed in the mats: (i) the in vivo precipitation of micritic aragonite in the living cyanobacterial layer due to high CaCO3 saturation in the mat ambience during dry season, and (ii) the post-mortem precipitation of sparitic aragonite in the decaying layers of coccoid cyanobacteria growing uncalcified or weakly calcified during the wet season when CaCO3 saturation in the mat ambience was lower. Stable carbon isotope (δ13C) signatures from neighboring individual laminae of the Satonda stromatolites, obtained with laser ablation sampler for stable isotope extraction (LASSIE) (Figure 5b), show values consistent with those obtained from the studied cultured mats (Figure 2). In both cases the values from the micritic laminae were almost always 0.5‰ to almost 2‰ heavier than those from the underlying sparitic laminae. This suggests that the results of δ13C measurements made on bulk samples of fossil stromatolites may not exactly reflect the stable carbon isotopic signals in the water of the mats ambience (for discussion see e.g., [63,64,80,81,82]).


CaCO3 precipitation in multilayered cyanobacterial mats: clues to explain the alternation of micrite and sparite layers in calcareous stromatolites.

Kaźmierczak J, Fenchel T, Kühl M, Kempe S, Kremer B, Łącka B, Małkowski K - Life (Basel) (2015)

Microbiota associated with calcium carbonate layers in microstromatolites from the quasi-marine Satonda Crater Lake (Central Indonesia). (a) SEM image (top view) of a coccoid pleurocapsalean cyanobacterial mat growing today in the lake. (b) SEM image of vertical mat section showing mucilage sheaths (glycocalyx) of coccoid pseudocapsalean cyanobacteria permineralized in vivo with aragonite nanograins (micrite). (c–e) Micrographs of thin sections showing examples of remains of microbiota associated with aragonite layers (sparite) precipitated in decomposing biomass of coccoid cyanobacteria: diatoms (c), Chloroflexus-like bacteria (d) and aquatic fungi. Scale bars: (a) 20 μm, (b) 20 μm, (c) 10 μm, (d) 10 μm, (e) 20 μm.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4390877&req=5

life-05-00744-f006: Microbiota associated with calcium carbonate layers in microstromatolites from the quasi-marine Satonda Crater Lake (Central Indonesia). (a) SEM image (top view) of a coccoid pleurocapsalean cyanobacterial mat growing today in the lake. (b) SEM image of vertical mat section showing mucilage sheaths (glycocalyx) of coccoid pseudocapsalean cyanobacteria permineralized in vivo with aragonite nanograins (micrite). (c–e) Micrographs of thin sections showing examples of remains of microbiota associated with aragonite layers (sparite) precipitated in decomposing biomass of coccoid cyanobacteria: diatoms (c), Chloroflexus-like bacteria (d) and aquatic fungi. Scale bars: (a) 20 μm, (b) 20 μm, (c) 10 μm, (d) 10 μm, (e) 20 μm.
Mentions: An instructive example of such diagenetic transformation of the primary calcium carbonate morphs in micrite and sparite layers are subfossil (micro) stromatolites from the quasi-marine Satonda Crater Lake (Central Indonesia) formed by colonial coccoid (pleurocapsalean) cyanobacteria [5,11,78,79]. The lamination in these stromatolites is extremely well-expressed, whereby the micritic laminae are as a rule thinner than the sparitic ones (Figure 5a,b). The micritic laminae are composed of aragonite nanograins, with some admixture of Mg silicate nanograins, both apparently precipitated in the common mucilage sheaths (glycocalyx). A few diatoms were found in these laminae between colonies of coccoid cyanobacteria. Similarly as in the case of the studied artificial mats, the microbiota from the micritic laminae (Figure 5c) indicate an aerobic character of the microenvironment sustaining the origin of the aragonite nanograins. The sparitic laminae in turn consisted of vertically well-ordered aragonite fibres which, as indicated by the presence of highly degraded remains of sheaths of coccoid cyanobacteria (Figure 5d), precipitated in a decaying cyanobacterial necromass. The remains of filaments of Chloroflexi-like phototrophic bacteria, partially desilicified diatom frustules and saprophytic fungi abundant in the sparitic laminae suggest, similarly as in the artificial mats, a dysoxic or anoxic microenvironment conditions for these laminae (Figure 6). It is known that the well-laminated Satonda Crater Lake stromatolites developed in a quasi-marine environment (Table 2) with increased alkalinity that is characterized by alternating dry and wet seasons [5,11,78] controlling not only mat growth but possibly also enforcing two basically different calcifications processes observed in the mats: (i) the in vivo precipitation of micritic aragonite in the living cyanobacterial layer due to high CaCO3 saturation in the mat ambience during dry season, and (ii) the post-mortem precipitation of sparitic aragonite in the decaying layers of coccoid cyanobacteria growing uncalcified or weakly calcified during the wet season when CaCO3 saturation in the mat ambience was lower. Stable carbon isotope (δ13C) signatures from neighboring individual laminae of the Satonda stromatolites, obtained with laser ablation sampler for stable isotope extraction (LASSIE) (Figure 5b), show values consistent with those obtained from the studied cultured mats (Figure 2). In both cases the values from the micritic laminae were almost always 0.5‰ to almost 2‰ heavier than those from the underlying sparitic laminae. This suggests that the results of δ13C measurements made on bulk samples of fossil stromatolites may not exactly reflect the stable carbon isotopic signals in the water of the mats ambience (for discussion see e.g., [63,64,80,81,82]).

Bottom Line: The d13C values were about 2‰ heavier in carbonates from the living cyanobacterial zones as compared to those generated in the purple bacterial zones.The generated CaCO3 morphs were highly similar to morphs reported from heterotrophic bacterial cultures, and from bacterially decomposed cyanobacterial biomass emplaced in Ca-rich media.They are also similar to CaCO3 morphs precipitated from purely inorganic solutions.

View Article: PubMed Central - PubMed

Affiliation: Institute of Paleobiology, Polish Academy of Sciences, Twarda 51/55, 00-818 Warsaw, Poland. jkaz@twarda.pan.pl.

ABSTRACT
Marine cyanobacterial mats were cultured on coastal sediments (Nivå Bay, Øresund, Denmark) for over three years in a closed system. Carbonate particles formed in two different modes in the mat: (i) through precipitation of submicrometer-sized grains of Mg calcite within the mucilage near the base of living cyanobacterial layers, and (ii) through precipitation of a variety of mixed Mg calcite/aragonite morphs in layers of degraded cyanobacteria dominated by purple sulfur bacteria. The d13C values were about 2‰ heavier in carbonates from the living cyanobacterial zones as compared to those generated in the purple bacterial zones. Saturation indices calculated with respect to calcite, aragonite, and dolomite inside the mats showed extremely high values across the mat profile. Such high values were caused by high pH and high carbonate alkalinity generated within the mats in conjunction with increased concentrations of calcium and magnesium that were presumably stored in sheaths and extracellular polymer substances (EPS) of the living cyanobacteria and liberated during their post-mortem degradation. The generated CaCO3 morphs were highly similar to morphs reported from heterotrophic bacterial cultures, and from bacterially decomposed cyanobacterial biomass emplaced in Ca-rich media. They are also similar to CaCO3 morphs precipitated from purely inorganic solutions. No metabolically (enzymatically) controlled formation of particular CaCO3 morphs by heterotrophic bacteria was observed in the studied mats. The apparent alternation of in vivo and post-mortem generated calcareous layers in the studied cyanobacterial mats may explain the alternation of fine-grained (micritic) and coarse-grained (sparitic) laminae observed in modern and fossil calcareous cyanobacterial microbialites as the result of a probably similar multilayered mat organization.

No MeSH data available.


Related in: MedlinePlus