Carbonate Precipitation in Mixed Cyanobacterial Biofilms Forming Freshwater Microbial Tufa

Abstract

: Mixed cyanobacteria-dominated biofilms, enriched from a tributary of the Mérantaise (France) were used to conduct laboratory experiments in order to understand the relationship between the morphology of carbonate precipitates and the biological activity (e.g., cyanobacterial exopolymeric substances (EPS) production, photosynthetic pH increases). DNA sequencing data showed that the enriched biofilm was composed predominantly of two types of filamentous cyanobacteria that belonged to the Oscillatoriaceae and Phormidiaceae families, respectively. Microscopic analysis also indicated the presence of some coccoid cyanobacteria resembling Gloeocapsa. Analysis of carbonate precipitates in experimental biofilms showed three main morphologies: micro-peloids with different shapes of mesocrystals associated with Oscillatoriaceae filaments and theirs EPS, lamellae of carbonate formed directly on Phormidiaceae filaments, and rhombic sparite crystals wrapped in EPS. All crystals were identified by FT-IR spectroscopy as calcite. Similar structures as those that formed in laboratory conditions were observed in the microbial-tufa deposits collected in the stream. Microscopic and spectroscopic analysis of laboratory and natural samples indicated a close proximity of the cyanobacterial EPS and precipitated carbonates in both. Based on the laboratory experiments, we conclude that the microbial tufa in the stream is in an early stage of formation.

The Role of the Substrate on the Mineralization Potential of Microbial Mats in A Modern Freshwater River (Paris Basin, France)

“…The laboratory experiments, in which part of the natural community of microorganisms was present, indicated that the lamellas presented the first stage of calcium carbonate precipitation by Phormidium sp. The micro-peloids found in tufa microbialites of our investigation were also observed by Payandi-Rolland et al [89], who contributed their formation to the activity of the filamentous cyanobacteria Oscillatoriales sp. and EPS.…”

“…Our SEM investigations on microbial mats and biofilms of the Mérantaise tributary stream have highlighted the role of biotic components, especially microorganisms and EPS, in the mineralization processes and the formation of tufa (Figure 5a-f). Calcite lamellas encrusting the filaments, similar to those obtained in laboratory studies [89] were observed in the tufa microbialites. The laboratory experiments, in which part of the natural community of microorganisms was present, indicated that the lamellas presented the first stage of calcium carbonate precipitation by Phormidium sp.…”

“…and Pseudanabaenales (Leptolyngbya sp. ), as revealed by morphological (this study) and phylogenetic analyzes [89]. Two main size classes were present in the dense filamentous laminae in which the cyanobacteria are positioned vertically.…”

Mg-Rich Authigenic Carbonates in Coastal Facies of the Vtoroe Zasechnoe Lake (Southwest Siberia): First Assessment and Possible Mechanisms of Formation

“…The associations of hydromagnesite microcrystals likely inherit the characteristic cellular alveolar structure of degrading EPS films [73], as is known for calcite-forming cyanobacteria [25,74]. It is possible that diatoms can play an important role in the precipitation of carbonates due to their potentially significant contribution to the formation of EPS [61,75,76]. Further, the specific features of the initial geometry of diatom frustules, having a high surface area and cation-binding sites [77], can contribute to the formation of nucleation zones via their service as templates for authigenic mineral nucleation.…”

“…Confocal laser-scanning microscopy (CLSM) is often used to identify signs related to the activity of living organisms within stromatolites and microbialites [25,60,61]. Selected thin sections of algae mats and microbialites were examined using a Zeiss LSM 780 NLO confocal laser-scanning microscope (Carl Zeiss, Oberkochen, Germany).…”