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Thermogenic travertine deposits in Thermopylae hot springs (Greece) in association with cyanobacterial microflora.
... The volcanic, magmatic and active tectonic processes in Greece result in the presence of a wide variety of terrestrial hot springs. While over 450 hot springs with temperatures up to ca 90 o C have been documented (Orfanos & Sfetsos, 1975;Gkioni-Stavropoulo u, 1983;Orfanos, 1985;Sfetsos, 1988), research on their Cyanobacteria microbial inhabit a nts has been limited (Anagnostidis, 1959(Anagnostidis, , 1961(Anagnostidis, , 1964(Anagnostidis, , 1967a(Anagnostidis, , 1967b(Anagnostidis, , 1968(Anagnostidis, , 1977Economou-Amilli, 1976;Anagnostidis & Economou-Amilli, 1978;Anagnostidis & Pantazidou, 1988; Anagnostidis Radea et al., 2010;Kanellopoulos et al., 2016a;Bravakos et al., 2016;Panou & Gkelis, 2022). Additionally, in some hot springs, thermogenic travertine deposition occurs, and there are cases where the role of Cyanobacteria along with inorganic processes has only been suggested (Kanellopoulos, 2011;Kanellopoulos et al., 2016a). ...
... While over 450 hot springs with temperatures up to ca 90 o C have been documented (Orfanos & Sfetsos, 1975;Gkioni-Stavropoulo u, 1983;Orfanos, 1985;Sfetsos, 1988), research on their Cyanobacteria microbial inhabit a nts has been limited (Anagnostidis, 1959(Anagnostidis, , 1961(Anagnostidis, , 1964(Anagnostidis, , 1967a(Anagnostidis, , 1967b(Anagnostidis, , 1968(Anagnostidis, , 1977Economou-Amilli, 1976;Anagnostidis & Economou-Amilli, 1978;Anagnostidis & Pantazidou, 1988; Anagnostidis Radea et al., 2010;Kanellopoulos et al., 2016a;Bravakos et al., 2016;Panou & Gkelis, 2022). Additionally, in some hot springs, thermogenic travertine deposition occurs, and there are cases where the role of Cyanobacteria along with inorganic processes has only been suggested (Kanellopoulos, 2011;Kanellopoulos et al., 2016a). ...
... The species Leptolyngbya ercegovicii was found to occupy an endolithic zone at a depth of about 3-5 mm, while in the upper layers, colonies of chroococcalean species were observed. A similar situation has been described at the thermal springs of Thermopylae associated with a thermoge nic travertine field (Kanellopoulos et al., 2016a). ...
The aim of this study is to identify the biomineralisation processes in hot springs of North‐West Euboea Island by assessing the physico‐chemical parameters of the hot water, the travertine mineralogical composition and facies, and the cyanobacterial microflora. In the studied area, the main mineral phases are calcite and aragonite, creating laminated and shrub facies of travertine deposits in close association with the cyanobacterial microflora. Microscopic analysis of fresh and cultured field samples shows the presence of 81 taxa of Cyanobacteria belonging to six orders, i.e. Oscillatoriales, Synechococcales, Spirulinales, Chroococcales, Nostocales and Chroococcidiopsidales with the main factors controlling biodiversity being temperature, salinity and access to sunlight. No Cyanobacteria species were identified in areas with temperatures over 65oC. In areas with high salinity (27‐37‰), the order Oscillatoriales predominates. On the other hand, in areas with high temperatures (63oC), fewer orders were observed, usually only Synechococcales and Spirulinales. In areas with lower temperatures (37oC), larger numbers of Cyanobacteria orders were identified. Additionally, salinity seems to regulate the presence of the Nostocales order. The combined geobiological study revealed the presence of four biomineralisation processes involving calcium carbonate minerals, i.e. (i) filamentous Cyanobacteria and extracellular polymeric substances trapping calcium carbonate crystals, (ii) extracellular polymeric substances acting as a template favouring mineral precipitation for crystal nucleation, (iii) formation of calcified Cyanobacteria sheaths and (iv) alteration of calcium carbonate crystals by endolithic Cyanobacteria. The identified biomineralisation processes suggest that the formation of calcium carbonate crystals is due to the metabolic activity of Cyanobacteria, or that the Cyanobacteria favour the deposition or the alteration of already existing crystals. The combination of these processes and the non‐biotic (abiotic) mineralisation result in the formation of hybrid carbonates in the study area.
... Based on morphology, the distribution of 31 cyanobacteria taxa (3038.2°C) from Thermopylae thermal spring in Greece were identified by Kanellopoulos et al. (2016). Singh et al. (2018b) reported 22 taxa under 11 genera based on the morphology at nine thermal springs in the northwestern Himalayas. ...
... It has been reported that there are different species compositions in different thermal springs depending on the substratum and the physicochemical parameters of springs (Ward and Castenholz, 2000;Papke et al., 2003). In the literature, there are many studies of the cyanobacterial flora in thermal springs (Sompong et al., 2005;Debnath et al., 2009;Heidari et al., 2013;Roy et al., 2015;Kanellopoulos et al., 2016;Singh et al., 2018a, Singh et al., 2018b. When compared with the literature, it may be seen that more cyanobacteria taxa were determined in this study. ...
... Phormidium incrustatum is known as the common taxa of the limestone/travertine/calcareous substrata (Pentecost, 2005;Couradeau et al., 2013;Kanellopoulos et al., 2016). P. incrustatum was sampled from T8, one of the stations with high carbonate and bicarbonate values in this study. ...
Thermal springs are very difficult environments for organisms due to the high temperature, and physicochemical parameters. Cyanobacteria, which are photosynthetic prokaryotes, are best adapted to these environments. Kütahya is an important thermal area in Turkey. The aim of the study was to determine the cyanobacterial flora with a morphologic and ecologic approach in the 11 thermal. The physicochemical properties of the thermal springs in Kütahya province were measured. The thermal springs are alkaline (pH6) with an average temperature of 52°C. As a result, 54 cyanobacteria taxa were identified. Oscillatoriales were the predominant order in terms of taxa diversity (24 taxa) and biomass size. Statistical analyses were conducted to reveal the physicochemical properties of the thermal springs and the distribution of cyanobacteria in detail. According to these analyses, the thermal springs were classified into two main groups with a Piper. As a result of the RDA analysis under CANOCO 5.0, the total variation was 55.45455, and the first two axes explained a total of 57.43% of the variance. There was a significant difference (P0.001) in the comparison of the physicochemical parameters including pH, EC, TDS, and temperature values of the thermal springs in the Kruskal Wallis tests. Bangladesh J. Plant Taxon. 28(2): 413-428, 2021 (December)
... However, Roy et al. (2015) reported that the combined effect of pH, K + , and HCO3was effective in the distribution of S. subsalsa. As in the study of Kanellopoulos et al. (2016), S. subsalsa and Phormidium terebriforme (C.Agardh ex Gomont) Anagnostidis & Komárek were sampled together from the travertine substrates in this study (D1). The travertines are frequently colonized with Cyanobacteria mats, commonly composed of more than one taxon (Pentecost 2003, Kanellopoulos et al. 2016. ...
... As in the study of Kanellopoulos et al. (2016), S. subsalsa and Phormidium terebriforme (C.Agardh ex Gomont) Anagnostidis & Komárek were sampled together from the travertine substrates in this study (D1). The travertines are frequently colonized with Cyanobacteria mats, commonly composed of more than one taxon (Pentecost 2003, Kanellopoulos et al. 2016. Pentecost (2003) reported that travertines are often covered with a mixture of Oscillatoria, Spirulina, and Phormidium taxa. ...
The algal flora and physio-chemical parameters of seven thermal springs in Denizli were studied for the first time. Samples for algal analyses were taken monthly between May 2013 and June 2014, while the physio-chemical parameters were measured seasonally. The mean pH value of the thermal springs was 6.3, and temperatures varied between 34-60 °C. The significant differences (P < 0.001) among the thermal springs were in their temperature and pH, as well as concentration of Cl^- , Fe^2+ , K^+ , Mg^+ , Na^+ , Li^+ , Ca^+ , HCO3^ - , and SO4^2- ions. A total of 43 Cyanobacteria and three Bacillariophyta taxa were determined.The most common taxon was Spirulina subsalsa Oersted ex Gomont, sampled from five sampling sites. According to the principal component analysis (PCA), the most important determining factor for the algae was temperature, followed by concentration of K^+ and Cl^- ions.
... The existing knowledge of Cyanobacteria from the wealth of Greek hot springs is rather limited (Anagnostidis, 1959(Anagnostidis, , 1961(Anagnostidis, , 1964(Anagnostidis, , 1967a(Anagnostidis, , 1967b(Anagnostidis, , 1968(Anagnostidis, , 1977Anagnostidis & Economou-Amilli, 1978;Anagnostidis & Pantazidou, 1988;Bravakos et al., 2016;Economou-Amilli, 1976 Gkelis, 2022;Radea et al., 2010;. Additionally, several Greek hot springs currently deposit thermogenic travertine, and previous studies have shown the participation of Cyanobacteria in such biomineralisation processes (Kanellopoulos et al., 2015(Kanellopoulos et al., , 2022. However, further information is needed especially for the pioneer species. ...
... The contribution of Cyanobacteria to biomineralisation processes in hot spring environments is known (Fouke, 2011;Fouke et al., 2003;Kanellopoulos et al., 2015Kanellopoulos et al., , 2022Pentecost, 2005). However, it is still unclear whether the biomineralisation processes start from the early stages (i.e. in few hours) or in mature stages. ...
Cyanobacteria are considered to be among the first microorganisms to settle in hot springs where they form a favourable environment for further biological establishment. Nevertheless, the exact pioneer species and how early they start participating in the biomineralisation processes remain unknown. The aim of the present study was twofold, i.e. to identify the pioneer Cyanobacteria in hot springs (i.e. Aedipsos area, Greece) and to record their early biomineralisation processes. The in situ experimental approach included the setup of sterile glass and/or plexiglass slides in several locations to facilitate colonisation by Cyanobacteria, and removal of slides for study after 48 to 202 hours. Synechococcales (37%) and Oscillatoriales (33%) were the dominant orders, followed by Chroococcales (15%) and Spirulinales (11%); whereas Chroococcidiopsidales (4%) was found only in a few sites. The order Nostocales was not observed at the early stages of colonisation although it was present in mature stages. Forty‐three species of Cyanobacteria were identified as pioneer microorganisms, with Spirulina subtilissima being the most frequently found. The most common pioneers were multicellular filamentous Cyanobacteria, i.e. organisms with a large surface area able to form significant amounts of extracellular polymeric substances. Among the pioneers, thermophilic species of Cyanobacteria were typical such as Chroococcidiopsis thermalis, Chroococcus thermalis, Leptolyngbya thermalis, Spirulina subtilissima and Symploca thermalis, as well as typical limestone substrate species such as Chroococcus lithophilus and Leptolyngbya laminosa. Temperature seems to affect biodiversity. Also, pioneers were found to contribute to the biomineralisation processes from their first appearance. In the studied samples, three biomineralisation processes were identified, i.e. i) calcification of cyanobacterial sheaths, ii) trapping of carbonate crystals on a crystal retention lattice formed by extracellular polymeric substances and filaments, and iii) trapping and confinement of carbonate crystals around filamentous Cyanobacteria.
... However, four species dominated in biofilms grown under high LI: Rubrivivax gelatinosus 47 and Rhodoferax saidenbachensis 48 in early development stages and Neosynechococcus sphagnicola 49 and Leptolyngbya spp. 50 in matured biofilms. In comparison to this, different levels of SS displayed no significant influence upon bacterial community composition, with Pseudomonas taiwanensis constituting the only exception, with a stronger appearance in biofilms cultivated under high flow velocity. ...
... Considering these structural aspects, the two detected dominant cyanobacteria might also be of high relevance, as they form long filaments up to 5 mm in length. 50 On one hand, these extended chains of single cells constitute an option to increase micro turbulence and availability of nutrients. On the other hand, these fibers can act as anchor points for settling cells and can be linked and tangled up, which can increase the stability of the biofilm network. ...
Holger Schmidt,1 Moritz Thom,2 Silke Wieprecht,3 Werner Manz,1 Sabine Ulrike Gerbersdorf3 1Institute for Integrated Natural Sciences, University of Koblenz-Landau, Koblenz, 2Forschungszentrum Küste, Leibniz Universität Hannover, Hannover, 3Institute for Modelling Hydraulic and Environmental Systems, University of Stuttgart, Stuttgart, Germany Abstract: Biofilms constitute an important issue in microbial ecology, due to their high ecological and economic relevance, but the impact of abiotic conditions and microbial key players on the development and functionality of a natural biofilm is still little understood. This study investigated the effects of light intensity (LI) and bed shear stress (BSS) and the role of dominant microbes during the formation of natural biofilms and particularly the process microbial biostabilization. A comprehensive analysis of microbial biomass, extracellular polymeric substances produced, and the identification of dominant bacterial and algal species was correlated with assessment of biofilm adhesiveness/stability. LI and BSS impacted the biofilms in very different ways: biofilm adhesiveness significantly increased with LI and decreased with BSS. Moreover, microbial biomass and the functional organization of the bacterial community increased with LI, while the dynamics in the bacterial community increased with BSS. Most stable biofilms were dominated by sessile diatoms like Achnanthidium minutissimum or Fragilaria pararumpens and bacteria with either filamentous morphology, such as Pseudanabaena biceps, or a potential high capacity for extracellular polymeric-substance production, such as Rubrivivax gelatinosus. In contrast, microbes with high motility, such as Nitzschia fonticola, Pseudomonas fluorescens, and Caulobacter vibrioides, dominated the least adhesive biofilms. Their movement and potential antibiotic production could have had a disruptive impact on the biofilm matrix, which decreased its stability. This is the first study to unveil the link between abiotic conditions and resulting shifts in key microbial players to impact the ecosystem-service microbial biostabilization. Keywords: microbial biostabilization, natural biofilms, abiotic factors, microbial community, mesocosm
... Based on whole rock geochemical analysis, the Thermopylae's travertines are presenting lower concentrations of almost all trace elements, compared to Euboea's travertines (Kanellopoulos et al., 2017a). Kanellopoulos et al. (2016a) identified biotic processes contributing to the deposition of the Thermopylae's travertines, alongside with the abiotic processes. As concerns Kamena Vourla, until now, no significant travertine deposition has been identified. ...
... Kanellopoulos et al. (2016b;unpublished data) presented the controlling faults in the case of Euboea's hot springs and demonstrated that they are located in junctions of fault systems. Recent interdisciplinary geological and biological studies (Kanellopoulos et al., 2016a;Kanellopoulos et al., 2017b) at the hot springs and at the thermogenic deposition of Euboea and Sperchios revealed a great variety of bacteria species, adding valuable information to the limited existing knowledge concerning the Greek hot-springs extreme environments biodiversity (Anagnostidis, 1961;Anagnostidis, 1967;Anagnostidis and Pantazidou, 1988;Kilias et al., 2013;Bravakos, 2016;Mizerakis et al., 2017). Additionally, new information about the contribution of these bacteria species to the deposition processes of simple and iron-rich thermogenic travertines were presented. ...
In Greece, several areas are presenting geothermal anomaly, which is controlled by the tectonic setting of each area, such as active graben and continental rift systems and in many cases these anomalies are related also to the recent volcanism. Two of these areas are the northwestern Euboea Island and the neighboring part of the mainland, i.e. eastern Sperchios area, Greece. These areas include several hot springs and active thermogenic travertine deposits, which are the surface manifestations of a geothermal system, recognized as having one of the highest geothermal gradient in Greece, just after the south Aegean active volcanic arc areas. Field surveys verified the presence of hot springs with fluid temperature over 82 oC. Geological, geochemical and isotopic data, alongside with drilling data suggest the presence of several medium and low enthalpy geothermal resources in these areas. Until now, the only use of these renewable energy resources is limited to thermal bath / spa therapies. Taking under consideration the geological, geomorphological, climate characteristics, the economic activities of the local societies, and the existing infrastructure, we suggest a series of targeted geothermal direct use applications that could be easily applied in these areas. Their application will have multiple positive socio-economic effects to national and regional level, resulting to the sustainable development of the areas, through the exploitation of a renewable energy resource i.e. the geothermal energy.
... A salient feature of the geothermal activity in northern Euboea and neighboring part of the mainland in eastern Central Greece (Sperchios area), is the dominance of thermogenic travertine deposition from the hot springs (Kanellopoulos, 2011(Kanellopoulos, , 2012(Kanellopoulos, , 2013Kanellopoulos et al. 2016a). Kanellopoulos (2011Kanellopoulos ( , 2012 reported Fe-rich varieties among the studied travertines. ...
... Although the formation of these thermogenic travertines is dominantly controlled by abiotic factors, also biotic factors are proposed to be contributing (Kanellopoulos, 2014b;Kanellopoulos et al., 2016a). ...
The northwestern Euboea Island and the neighboring part of the mainland in eastern Central Greece, i.e. Sperchios area, contain several hot springs and active thermogenic travertine deposits, which are the surface manifestations of an active hydrothermal system, controlled by active tectonics, and supplied with heat by a 7–8 km deep magma chamber, with surface manifestation, the Plio-Pleistocene trachyandesitic volcanic center of Lichades. This hydrothermal system is fueled by a mixture of seawater and deep magmatic fluid with only limited meteoric water contribution. Thermal water samples show extreme pH, temperature and Electrical Conductivity values, with maximum values always recorded in two locations (Aedipsos and Ilia). The observed similarities in fluid compositions for most of the analyzed anions, major and trace elements, suggesting a stronger hydrothermal signature for the Northern Euboea area, perhaps reflecting greater proximity to the heat source of the hydrothermal system. The hydrothermal fluids collected and analysed were found to be highly enriched in a number of metallic and non-metallic elements e.g. up to 100 μg/L As, up to 1.1 wt.% Fe, up to 340 μg/L Ba, up to 65 μg/L Cu, up to 2.1 wt.% Cl, up to 3700 mg/L SO42−, up to 390 μg/L Se. Some of the enrichments are reflected directly in the travertines lithogeochemistry and the metallic mineral phases found inside the travertines. A number of mineral phases including sulfides (such as pyrite, arsenopyrite, galena, chalcopyrite, sphalerite and stibnite), native elements (such as Pb and Ni), alloys (such as Au ± Cu-Ag) fluorite and REE-bearing phases (such as Ce-, Nd- and La-bearing members of hydroxylbastnäsite, cackinsite, lanthanite and sahamalite) were identified syngenetically enclosed as clastic grains within the pores of all studied travertines; the ore grade concentrations of some iron-rich travertines (up to 28.9 wt.% Fe and up to 1.83 wt.% As), as well as the high concentration of precious and base metals at the hydrothermal fluid, strongly suggest active mineralizing processes throughout the studied system. Travertines containing elevated Fe ± As and consisting of ferrihydrite in addition to aragonite/calcite, were deposited on the surface, most likely after mixing of ascending reducing hydrothermal fluids with cool seawater. The high REE content in the Fe ± As-rich travertines (up to ~465 mg/kg ΣREE) is caused by adsorption of REE-bearing phases by iron oxyhydroxides. Mineralogical and geochemical evidence (such as the presence of elements in their native form, of alloys such as Au ± Cu-Ag, the enrichment of metalloids and the abundance of REE) may indicate magmatic contribution to the hydrothermal system and accordingly to the studied travertines. We support the hypothesis that metals and metalloids were mainly derived from magmatic fluids, which successively mixed with heated-, and with oxygenated, cool seawaters at depth and on the surface respectively, resulting in the deposition of carbonate hosted sulfide mineralization at depth, and of Fe ± As-rich travertines at the surface. The northwestern Euboea Island and Sperchios area hydrothermal system represents the first documented active terrestrial mineralizing hydrothermal system associated with ore-bearing travertines in Greece.
... transformation of bright spars to micrite) in the studied travertine is informative to understand abiotic and biotic micritization. Microorganisms, especially fungal and algal endoliths, which have been frequently reported in travertines (Pentecost et al., 1997;Norris and Castenholz, 2006;Kanellopoulos et al., 2016), might bore biochemically into carbonate grains (Bathurst, 1966) and crystals (i.e. sparmicritization, Kahle, 1977) and subsequent infilling of these boreholes with micrite would cause micritization. ...
Travertines are generally considered as carbonate deposits related to Ca-rich hot springs. Ca-deficiency hot springs, however, can also produce travertines under suitable conditions and little is known about the travertine deposition and diagenesis in these systems. Therefore, we studied a fossil perched Ca-deficiency spring system at Shihuadong, China to discuss its genesis and diagenesis. This system is a platform-like build-up with travertines developing mainly in the steep frontal area. The travertines were deposited from high-temperature fluids (dom-inantly 45°C to 55°C) with strong interaction mostly with underground Gaoligong Group metamorphic rocks. Their parent CO 2 was originated from magmatic CO 2 and a little soil CO 2. The travertine-depositing paleofluid was predominantly Ca-deficiency hot spring water, but stream water possibly from cold springs on surrounding hills might make a small contribution. The low calcium levels and flat substrate on the top area of the studied system handicapped the travertine deposition, only developing a small perched travertine channel entirely composed of crystalline crust. On the contrary, progressive CO 2 degassing in the top area and increasing CO 2 degassing and water flow rates in the frontal area induced the formation of abundant travertines. However, water scattering/dispersion in the frontal area might not heavily increase the water flow rate and only induced boundstone deposition. After the travertine deposition, underground thermal water, meteoric water, and microbial activity progressively altered the primary fabrics, forming mosaic and need fiber calcite cements, dissolution pores, microborings, and dissolution-induced and microbe-induced micritization. The studied perched spring system shows limited scales, notable progradation but slight aggradation, and the dearth of distal autochthonous travertines, unlike those formed by Ca-rich hot springs, which might extend widely and produce striking distal travertine deposits away from the frontal slope/waterfall. These findings suggest the significant roles of water chemistry and local topography in travertine deposition and the influence of slowly underground thermal water seeping on the diagenesis of travertines in hilly areas and might be used to recognize fossil Ca-deficiency and Ca-rich hot spring systems.
... Very few studies have been conducted in the Thermopyles and these were focused on geochemical features and measurements of physicochemical properties (Lambrakis and Kallergis, 2005;Verros et al., 2007;Duriez et al., 2008;Lambrakis et al., 2014;Zarikas et al., 2014) or the investigation of travertine deposits in association with Cyanobacteria (Kanellopoulos et al., 2016). Investigation of geochemical features has shown the increased concentration of hydrogen sulfide mainly produced by pyrite oxidation and reduced species of sulfates (Lambrakis and Kallergis, 2005;Duriez et al., 2008). ...
The recovery of metagenome-assembled genomes (MAGs) from metagenomic data has recently become a common task for microbial studies. The strengths and limitations of the underlying bioinformatics algorithms are well appreciated by now based on performance tests with mock data sets of known composition. However, these mock data sets do not capture the complexity and diversity often observed within natural populations, since their construction typically relies on only a single genome of a given organism. Further, it remains unclear if MAGs can recover population-variable genes (those shared by >10% but <90% of the members of the population) as efficiently as core genes (those shared by >90% of the members). To address these issues, we compared the gene variabilities of pathogenic Escherichia coli isolates from eight diarrheal samples, for which the isolate was the causative agent, against their corresponding MAGs recovered from the companion metagenomic data set. Our analysis revealed that MAGs with completeness estimates near 95% captured only 77% of the population core genes and 50% of the variable genes, on average. Further, about 5% of the genes of these MAGs were conservatively identified as missing in the isolate and were of different (non-Enterobacteriaceae) taxonomic origin, suggesting errors at the genome- binning step, even though contamination estimates based on commonly used pipelines were only 1.5%. Therefore, the quality of MAGs may often be worse than estimated, and we offer examples of how to recognize and improve such MAGs to sufficient quality by (for instance) employing only contigs longer than 1,000 bp for binning.
... Very few studies have been conducted in the Thermopyles and these were focused on geochemical features and measurements of physicochemical properties (Lambrakis and Kallergis, 2005;Verros et al., 2007;Duriez et al., 2008;Lambrakis et al., 2014;Zarikas et al., 2014) or the investigation of travertine deposits in association with Cyanobacteria (Kanellopoulos et al., 2016). Investigation of geochemical features has shown the increased concentration of hydrogen sulfide mainly produced by pyrite oxidation and reduced species of sulfates (Lambrakis and Kallergis, 2005;Duriez et al., 2008). ...
Geothermal springs are essentially un‐affected by environmental conditions aboveground as they are continuously supplied with subsurface water with little variability in chemistry. Therefore, changes in their microbial community composition and function, especially over a long period, are expected to be limited but this assumption has not yet been rigorously tested. Toward closing this knowledge gap, we applied whole metagenome sequencing to 17 water samples collected between 2010 and 2016 from the Thermopyles sulfur‐rich geothermal springs in central Greece. As revealed by 16S rRNA gene fragments recovered in the metagenomes, Epsilonproteobacteria‐related operational taxonomic units (OTUs) dominated most samples and grouping of samples based on OTU abundances exhibited no apparent seasonal pattern. Similarities between samples regarding functional gene content were high, with all samples sharing >70% similarity in functional pathways. These community‐wide patterns were further confirmed by analysis of metagenome‐assembled genomes (MAGs), which showed that novel species and genera of the chemoautotrophic Campylobacterales order dominated the springs. These MAGs carried different pathways for thiosulfate or sulfide oxidation coupled to carbon fixation pathways. Overall, our study showed that even in the long term, functions of microbial communities in a moderately hot terrestrial spring remain stable, presumably driving the corresponding stability in community structure. This article is protected by copyright. All rights reserved.
... Their deposits are one of the best evidence to interpret the paleoenvironment conditions (Kele et al., 2011;Osácar et al., 2013;Wang et al., 2014). Some factors include organic (such as photosynthesis) and inorganic (such as ion exchange, solution and weathering) as well as evaporation processes lead to CO2 outgassing, fluid saturation and rapid deposition of these types of carbonates (Kanellopoulos, 2012;Ascione et al., 2014;Kanellopoulos et al., 2016). The travertine morphology can be affect by spring situation, form of initial cone and their substrate, chemical composition of springs and surface waters (Ozkul et al., 2002). ...
Travertine deposits are a kind of continental carbonates that form in specific chemical, physical and biological conditions. Garab travertines in southeast of Mashhad are studied based on field, geochemistry (elemental and stable isotope analysis) and hydrogeochemistry analysis. Field and petrographic characterization led to recognize of crystalline crust, raft, foam, shrub, laminated, black mud and tufa lithofacies. These lithofacies are composed of calcite and aragonite mineralogy. They have high concentrations of Ca, Mg, S, Fe, Na and Sr and low concentration of Mn, P and Si. These lithofacies are enriched with respect to δ¹³C and depleted with respect to δ¹⁸O that can be related to algal origin and meteoric water, respectively. The type of Garab springs water is Ca- HCO3⁻ - SO4²- and Na- Cl. This water is saturated with respect to bicarbonate and sulfate. The water composition and dissolved ions have a close relation to geological units (carbonate and evaporite) in Garab area.
... Kutzing ex Gomont 1892 (Oscillatoriales, Cyanobacteria), which participates in Polichnitos hot springs with six strains, is a polyphyletic genus, members of which have been isolated from freshwater, marine and terrestrial habitats. Several species of the genus have been also isolated from outflows of hot springs in various parts of the world, such as Greece (Anagnostidis and Pantazidou 1988;Kanellopoulos et al. 2016), the United States (Walter 1976), Thailand (Sompong et al. 2008), New Zealand (Jones et al. 2005), etc. Stromatolites formed in the shallow waters of hot springs are often composed of Phormidium sp. with the participation of other cyanobacteria as well (Jones et al. 2005). Some species (e.g., Ph. bijugatum, Ph. molle, Ph. papyraceum, Ph. uncinatum, Ph. autumnale) are considered to be producers of bioactive compounds having toxic effects on animals, but also on human cancer cell lines, presenting therefore a potential as sources of therapeutic agents (Teneva et al. 2005). ...
The bacterial diversity of the outflows of Polichnitos (Lesvos, Greece) hot spring has been investigated. Cyanobacteria showing high sequence homologies with Phormidium sp. and Cyanobacterium aponinum were found. Members of the Alphaproteobacteria closely related to Rhodobium sp. Albidovulum sp., Rhodobacter sp., Microvigra sp., Nitratireductor sp. and Phaeobacter sp. Gammaproteobacteria, Betaproteobacteria and Firmicutes were represented by members of Idiomarina sp., Marinobacter sp., Shinella sp., Bacillus sp. and Clostridium sp. with sequence homologies ranging from 92% to 100%. Members of the Bacteroidetes and Planctomycetes were represented by sequences of novel phylogenetic linkages exhibiting 87–90% sequence homology with type strains. When the hot spring consortium was cultivated in bioreactor repeated batch culture under photo-autotrophic growth conditions at temperature < 30 °C, Cyanobacterium sp. dominated over Phormidium sp. Cyanobacterium sp. seems to have biotechnological potential since its extracellular broth exhibited a strong insecticidal activity against larvae of Aedes aegypti (a vector of important human diseases) and significant anti-cancer activity against the PC3 human prostate cancer cell line, while its toxicity against human endothelial cells was relatively low.
... Biogenic (especially cyanobacteria) influence on CaCO 3 deposition causes no doubt (Pentecost, 1995;Chafetz and Folk, 1984;Visscher et al., 1998;Fouke et al., 2000;Pedley and Rogerson, 2010;Dupraz et al., 2004Dupraz et al., , 2009Pentecost, 2005;Rainey and Jones, 2009;Jones and Renaut, 2010;Okumura et al., 2012;Cantonati et al., 2016;Kanellopoulos et al., 2016). Extracellular polymeric substances (EPS) from microbial films are considered as one of the main source of cations (Ca +2 , Mg +2 ). ...
Calcareous tufa deposits have been discovered in the Chibitka River valley near Lake Cheybek-Kohl, at the junction of the Kurai and Teletsk-Kurai large active faults in the southeastern Gorny Altai, Russia, at an altitude of 1800–2000 m. Fossil tufa is composed of calcite and cements Holocene grey colluvium and glacial till deposited by the Late Glacial Chibitka Glacier. Current tufa precipitation has been observed from a low-flow spring with cold (10 °C) HCO3-SO4–Ca-Mg water, рН = 6.86. The stable isotope composition of spring water is − 5.8‰ VPDB δ¹³C of dissolved inorganic carbon and − 14.5‰ VSMOW δ¹⁸O. Modern tufa consists of thin laminated Mg-calcite and Sr-aragonite crusts, with abundant algae and biofilms on their surfaces. Both modern and fossil tufas are depleted in REE (a total of 0.40–16.4 ppm and 0.40–3.80 ppm, respectively) and share similar PAAS-normalised REE + Y spectra with HREE enrichment and slight progressive LREE depletion. The modern tufas show positive δ¹³C values of 0.1‰ to 0.9‰ VPDB while the fossil ones have an isotopically lighter composition of δ¹³C = − 4.1‰ to − 1.9‰ VPDB; the δ¹⁸O range is very narrow (− 13.0 to − 13.8‰ VPDB). Both stable isotope and trace-element signatures (including REE patterns) of the tufas indicate precipitation from cold groundwaters subjected to prolonged interaction with a carbonate aquifer (the Baratal Group of limestone and dolostone) in a cold continental climate similar to the present conditions. Tufa deposition in the Lake Cheybek-Kohl area began with the onset of post-Late Glacial global warming and permafrost degradation. Unlike the fossil tufa formation, current precipitation of freshwater carbonates has been microbially mediated. The discovered tufa deposits provide new palaeoclimatic and active tectonic proxies in the southeastern Gorny Altai.
In the aquifers of hard rock, spring water is a good indicator for evaluating the interaction of rock water and water level changes. Maku area is located in West Azarbaijan province in northwestern Iran. Supplying part of the water needed for agriculture in the region through travertine-maker springs, the role of these springs in the travertine deposition process and the effect of the chemical composition of the waters on the travertine discoloration has made the study of hydrogeochemical properties of springs in the study area important. Thus, in this research, the assessment of hydrogeochemical characteristics, chemical composition and the water origin of springs were evaluated by water sampling, sediment deposits and rock units around the springs. The results of hydrogeochemical diagrams, ionic ratios and saturation index showed that the reservoir of the aquifer is impure limestone and the water of springs is saturated to supersaturated with respect to carbonate minerals and undersaturated for sulfate minerals and chemical type mainly is Ca- HCO3. The high pressure of carbon dioxide and its removal from the water composition of the springs has caused the limestone springs of the region to have a high deposition ability and formation of Fissure-ridge and vein-type travertine with relatively high height and expansion. The results of geochemical analysis of the elements in the composition of sediments around the springs show that the correlation between CaO and Al2O3, SiO2, TiO2, Fe2O3 is negative, also the correlation between CaO and Ba and Sr is positive and also the correlation between SiO2 and Fe2O3 and Al2O3, is positive, therefore, the water source of the spring can be considered mostly thermogenic.
These fresh-water springs are very rich in H2S. Probably as a result of this, the carbonate sediments are largely constructed by bacteria instead of algae. Even the chemically-precipitated forms of calcite show a variety of bizarre characteristics, some of them probably due to the interaction of S with the calcite crystal lattice. Among these are thick crusts of radial fibrous calcite crystals up to a meter long, that show probable daily lamination due to the diurnal activity of photosynthetic bacteria and have depositional rates of as much as one meter per year.-from Authors
from highly irregular forms (bacterial shrubs) to features that display regular geometric patterns (crystal shrubs and ray-crystal crusts). The bacterial shrubs have been previously recognized as the product of bacterially induced precipitation whereas the ray-crystal crusts have been described as due to dominantly abiotic precipitation. The bacterial shrubs have a highly irregular morphology, similar to woody plants, in contrast, end member crystal shrubs display distinct crystal habits and regular repeating morphologies, i.e., they commonly have attributes of noncrystallographic as well as crystallographic dendrites. There is a complete gradational relationship between the bacterial shrubs and crystal shrubs. Ray-crystal crusts are large fan-shaped features composed of subparallel, extremely coarse bladed crystals of calcite. All three types (bacterial shrubs, crystal shrubs, and ray-crystal crusts) contain either a dense tangle of bacterial body fossils and=or micron-sized pores. The micropores are bacterial molds. The immediately enveloping spar crystals around all three morphologic types are devoid of bacterial body fossils and micropores. The bacterial shrubs, crystal shrubs, and ray-crystal crusts are, to differing degrees, the product of bacterially induced precipitation as well as abiotic mineral precipitation. The differences in morphology are due to the relative contribution of bacterially induced precipitation as compared with that of abiotic mineral precipitation. Bacterially induced precipitates can form in environments too chemically harsh or otherwise inhospitable for other taxa to thrive. Epiphyton and Renalcis commonly formed in occult environments under conditions inhospitable to other taxa. Consideration of the published descriptions and interpretations concerning Epiphyton and Renalcis, and by analogy the origin of bacterial shrubs, have led to the conclusion that Epiphyton and Renalcis also are bacterially induced precipitates.
Microbial carbonate mineralization is widespread in nature and among microorganisms, and of vast ecological and geological importance. However, our understanding of the mechanisms that trigger and control processes such as calcification, i.e., mineralization of CO2 to calcium carbonate (CaCO3), is limited and literature on cyanobacterial calcification is oftentimes bewildering and occasionally controversial. In cyanobacteria, calcification may be intimately associated with the carbon dioxide-(CO2) concentrating mechanism (CCM), a biochemical system that allows the cells to raise the concentration of CO2 at the site of the carboxylating enzyme ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) up to 1000-fold over that in the surrounding medium. A comprehensive understanding of biologically induced carbonate mineralization is important for our ability to assess its role in past, present, and future carbon cycling, interpret paleontological data, and for evaluating the process as a means for biological carbon capture and storage (CCS). In this review we summarize and discuss the metabolic, physiological and structural features of cyanobacteria that may be involved in the reactions leading to mineral formation and precipitation, present a conceptual model of cyanobacterial calcification, and, finally, suggest practical applications for cyanobacterial carbonate mineralization.
In the northern part of Euboea Island and the neighbouring part of the mainland in eastern central Greece, many hot springs exist and some of them create travertine deposits. The objectives of the study were to identify and describe the various morphological types of the thermogenic travertine deposits. The samples were studied at the lab with optical microscopy, X-Ray Diffraction, Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS), in order to verify their main mineralogical composition and their mineral chemistry. The studied travertine deposits consist mainly of aragonite and calcite, but in some cases, as main mineral phase, an amorphous hydrous ferric oxyhydroxide (ferrihydrite), was also identified. The morphological types that were identified were of great variety (mounds, travertine caves etc) and some of them were quite rare (cascades, remora etc). Morphological data and field observations suggest possible inorganic and organic controls on carbonate precipitation. Similar morphological types have been recorded at large travertine systems like Mammoth hot springs, Yellowstone National Park in USA and at Rapolano Terme, Italy.
Geochemical, mineralogical and microbiological data from four freshwater streams in central region of Mexico indicate the importance of Blennothrix ganeshii mats (Cyanobacteria, Oscillatoriales) in promoting the formation of calcium carbonate crystals. The streams were characterized by alkaline waters and relative physicochemical stability during three seasons (cold dry, warm dry and warm rainy). Calcification took the form of a thick, dense layer of calcium carbonate crystals surrounding the extracellular polymeric substances produced by B. ganeshii filaments, giving an appearance of micritic tubes (structures formed by crystallization in the spaces between filaments) along the sheath surfaces. The precipitate was analyzed using X-ray diffraction and energy dispersal X-ray spectrometry, and the calcite crystal habit was determined. The photosynthetic activity of cyanobacterial growth and the presence of abundant extracellular polymeric substances and epiphytic species promote the absorption of ions and mineral nucleation on the surface of the sediment and contribute to the formation of travertine in tropical regions.
Microorganisms have long been thought to impact CaCO3 precipitation, but determining the extent of their influence on sediment formation has been hampered by our inability to obtain direct experimental evidence about mineral formation processes in natural environments. We address this problem by conducting kinetic experiments within a modern terrestrial carbonate spring to determine aragonite precipitation rates and to quantify the relative influences of aragonite saturation state (Ωa), microbial biomass concentration and microbial viability on CaCO3 mineralization in advection-dominated transport regimes. At an Ωa value consistent with modern seawater (3.63 ± 0.09), our controlled in situ kinetic experiments show that: (1) the natural steady-state aragonite precipitation rate is more than twice that determined when microbial biomass on the aragonite mineral surface is depleted by 0.2 µm filtration; and (2) inhibiting microbial viability with ultraviolet (UV) irradiation has no significant effect on the mean precipitation rate. Furthermore, our modeling of the CaCO3 precipitation process, which uses the empirical crystal growth rate expression and additional in situ kinetic measurements, reveals that reducing biomass concentrations by 45% can decrease the empirical rate constant by more than an order of magnitude. These findings strongly suggest that microorganisms catalyze CaCO3 precipitation in advection-dominated systems and imply that changes in carbonate mineralization rates may have resulted from changes in local microbial biomass concentration throughout geologic history.
The cyanophyte vegetation and flora of various thermal springs of Hellas have been
intensively studied (Anagnostidis1961,1966,1968,1977, Anagnostidis & Golubic 1966, Anagnostidis & Schwabe 1966, Anagnostid is & Rathsack-
Konzenbach 1967). However, little information is available about the endolithic
blue-green algae occurring in the carbonate deposits o f the hellenic hot springs
(Anagnostidis 1968). Generally, the euendolithic cyanophytes of thermal spings
have not been yet investigated; the presence o f a “cyanophyte” found in hot springs
of Western India and identified as Tryponema indicum Thomas et Gonzalves (1965)
is considered as debatable. Genus Tryponema Ercegovic (1929) does not represent
a cyanophyte according to Geitler (1942).
In the framework of our project concerning the study o f endolithic
microorganisms of various habitats o f Hellas, a survey on endolithic cyanophytes was
included from the saline thermal springs o f Aedipsos, NW Euboea Island, Greece
(T = 32—82 °C, pH = 6.6—7.2, Cl“ = 18.649 gr/1). During this investigation some
cryptoendolithic and euendolithic cyanophytes were observed.
From the various outflows of the hot springs, two distinct biotopes have been
selected for investigation. The first (Fig. 1) is a typical semi-cave with stalagmites
formed at the calcareous substrate (water temperature 34—37 °C). The second
biotope includes collecting sites at the outflow o f the warm water to the sea where
a high level o f CaC03 deposition is ascertained (Figs. 5—7). The latter habitat has
been selected to determine the impact of thermal spring to the littoral zone of euendoliths;
thus, some adjacent sites at the littoral zone were also investigated for comparison.
At the semi-cave, the dominant cyanophyte is Chroococcidiopsis thermalis
G e it l . (Geitler & Ruttner 1935/1936) reported for the first time from Greece
(Figs. 2-4), which was accompanied mainly by species of the genera Spirulina,
In the northwestern part of Euboea Island and the neighbouring part of the mainland in eastern central Greece, many hot springs exist. We collected and analysed the newly formed material around the hot springs. The samples were studied at the lab with X-Ray Diffraction, Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). In all cases the studied materials were thermogenic travertine presenting many different lithotypes. The studied travertine deposits consist mainly of aragonite and calcite, but in some cases, as the main mineral phase, an amorphous hydrous ferric oxyhydroxide, probably ferrihydrite (creating a laminated iron-rich travertine deposit), was identified. The lithotypes that were identified were of great variety (spicular, shrubs, etc). Some of them (pisoliths, rafts and foam rock types) are quite rare and one of them (framework type) is described for the first time. Morphological data and field observations suggest possible inorganic and organic controls on carbonate precipitation. Similar lithotypes have been recorded at Mammoth hot springs, Yellowstone National Park in USA and at Rapolano Terme, Italy.
Multiple abiotic and biotic factors combine in nature to influence the formation of calcium carbonate limestone deposits. Systems Geobiology studies of how micro-organisms respond to, or sometimes even control, the coupled effects of environmental change and mineralization will permit more accurate interpretation of the fossil record of ancient microbial life. Mammoth Hot Springs in Yellowstone National Park, USA, serves as a natural laboratory for tracking how the dynamic interplay of physical, chemical and biological factors come together to form hot-spring limestone (called ‘travertine’). Systematic downstream correlations occur at Mammoth Hot Springs between travertine deposition (geomorphology, crystalline structure and geochemistry), microbial communities (mat morphology, pigmentation, and phylogenetic and metabolic diversity) and spring-water conditions (temperature, pH, geochemistry and flow). Field-based microscale and mesoscale experimentation indicates that microbes directly influence travertine growth rate and crystalline structure. At the macroscale, time-lapse field photography and numerical modelling suggest that travertine terrace geomorphology is influenced strongly by hydrology, heat dispersion and geochemistry. These results from Mammoth Hot Springs allow establishment of a conceptual framework across broad spatial and temporal scales in which to track how multiple geological and biological factors combine to control CaCO3 crystal precipitation and the resulting formation of travertine deposits.
AB STRA CT Travertines and calcareous tufa are porous deposits formed by interactions between ambient precipitation of calcium carbonate and resident organisms under different temperature regimes. The distinctions between travertine as ther-mal spring deposits and calcareous tufa (Kalktuff) as deposits in the springs and rivers at ambient temperatures are fl uid. Both represent end points in bio-and physico-chemical calcifi cation processes across a broad gradient of tem-perature, mineral composition and ion saturation levels. Ecological preferences of micro-and macroorganisms in travertine depositional systems result in the re-distribution of water fl ow, modifi cation of the landscape and its ecol-ogy. The resulting sedimentary structures include new environmental settings with different and diversifi ed biota. They also include different microenvironments of diagenesis with different timings of the processes involved. Condi-tions in modern ambient temperature travertines of the Plitvice system of lakes and waterfalls are compared with the similar, ancient system of Rocchetta a Volturno, in the central Apennines. Diagenetic alterations are described and illustrated starting with biologically identifi ed primary deposits.
Microbial mats are ecosystems that arguably greatly affected the conditions of the biosphere on Earth through geological time. These laminated organosedimentary systems, which date back to > 3.4 Ga bp, are characterized by high metabolic rates, and coupled to this, rapid cycling of major elements on very small (mm-µm) scales. The activity of the mat communities has changed Earth's redox conditions (i.e. oxidation state) through oxygen and hydrogen production. Interpretation of fossil microbial mats and their potential role in alteration of the Earth's geochemical environment is challenging because these mats are generally not well preserved.Preservation of microbial mats in the fossil record can be enhanced through carbonate precipitation, resulting in the formation of lithified mats, or microbialites. Several types of microbially-mediated mineralization can be distinguished, including biologically-induced and biologically influenced mineralization. Biologically-induced mineralization results from the interaction between biological activity and the environment. Biologically-influenced mineralization is defined as passive mineralization of organic matter (biogenic or abiogenic in origin), whose properties influence crystal morphology and composition. We propose to use the term organomineralization sensu lato as an umbrella term encompassing biologically influenced and biologically induced mineralization. Key components of organomineralization sensu lato are the “alkalinity” engine (microbial metabolism and environmental conditions impacting the calcium carbonate saturation index) and an organic matrix comprised of extracellular polymeric substances (EPS), which may provide a template for carbonate nucleation. Here we review the specific role of microbes and the EPS matrix in various mineralization processes and discuss examples of modern aquatic (freshwater, marine and hypersaline) and terrestrial microbialites.
Using the fault plane mechanisms of the shallow earthquakes occurring along the Hellenic arc and the extent of the intermediate seismic belt, we make a quantitative estimate of the relative motion occurring between the Hellenic arc and the adjacent sea floor. This estimate is then used to evaluate the deformation in the Aegean area and to reconstruct the pattern of motion over the Eastern Mediterranean region for the last 13 m.y. It is shown that this pattern is compatible with the neotectonic and seismicity studies in Aegea. We then discuss the dynamics of the area and propose that, since Serravallian-Tortonian time, Aegea has been spreading gravitationally in front of the southwestward advancing Turkey. The reasons for this gravitational spreading are discussed.
Cyanobacteria that grow above seawater salinity at temperatures above 45 degrees C have rarely been studied. Cyanobacteria of this type of thermo-halophilic extremophile were isolated from siliceous crusts at 40-45 degrees C in a geothermal seawater lagoon in southwest Iceland. Iceland Clone 2e, a Leptolyngbya morphotype, was selected for further study. This culture grew only at 45-50 degrees C, in medium ranging from 28 to 94 g L(-1) TDS, It showed 3 doublings 24 h(-1) under continuous illumination. This rate at 54 degrees C was somewhat reduced, and death occurred at 58 degrees C. A comparison of the 16S rDNA sequence with all others in the NCBI database revealed 2 related Leptolyngbya isolates from a Greenland hot spring (13-16 g L(-1) TDS). Three other similar sequences were from Leptolyngbya isolates from dry, endolithic habitats in Yellowstone National Park. All 6 formed a phylogenetic clade, suggesting common ancestry. These strains shared many similarities to Iceland Clone 2e with respect to temperature and salinity ranges and optima. Two endolithic Leptolyngbya isolates, grown previously at 23 degrees C in freshwater medium, grew well at 50 degrees C but only in saline medium. This study shows that limited genotypic similarity may reveal some salient phenotypic similarities, even when the related cyanobacteria are from vastly different and remote habitats.
The global carbonate cycle has been controlled and maintained by life processes for at least 3.5 billion years. Within the exogenic carbonate cycle and in very different environments cyanobacteria appear in ‘key positions’ in that they actively and passively influence carbonate cycling. In the carbonate cycle, cyanobacteria play an important and sometimes decisive role. Cycling of carbon and carbonate is linked to biological processes. Some build up specific carbonate structures, some destroy carbonate substrates and others do both simultaneously. All these processes take place from the high mountains down to the sea in various terrestrial and freshwater as well as marine environments. The photosynthetic activity of cyanobacteria, their extracellular polymeric substances and possibly also their adherent heterotrophic bacteria are responsible for the construction of various carbonate structures and the ability to penetrate carbonate material. Boring activity of euendoliths results in biological corrosion and disintegration of carbonate surfaces. Grazing organisms on carbonate surfaces colonized by epi- and endolithic cyanobacteria produce specific biokarst forms and specific grains which can contribute to nearshore sedimentation. Biological corrosion and abrasion together constitute bioerosion. The results of all these processes are calcareous crusts, typical traces and biokarst forms which in many cases have a high fossilization potential, and therefore can be powerful ecological, palaeoecological and facies indicators in recent as well as in fossil environments.
In the last decade advances in high-throughput DNA and RNA sequencing have driven more intensive surveys of cyanobacterial diversity in geothermal systems worldwide and the development of a deeper understanding of well-studied hot spring cyanobacterial communities. As a consequence, it is now possible to build, atop the long-term studies of these systems based on morphological, pure-culture and initial 16S rRNA observations, a more thorough understanding of the biogeographical and local distributions of cyanobacteria in these settings. Population genetics studies with increased molecular, spatial and temporal resolution have begun to define the ecological species populations of thermophilic cyanobacteria and to reveal the processes that drove their evolution and current ecology. Metagenomic studies have begun to reveal the functional gene repertoire of the predominant cyanobacteria and associated members of communities in which they reside and with whom they interact. Gene expression studies, including metatranscritomic studies, have begun to reveal patterns of in situ gene expression. © 2012 Springer Science+Business Media B.V. All rights reserved.
This paper provides a review of the classification of travertines with emphasis on their morphology. Three criteria are used to describe them: geochemistry, microfabric and morphology. Geochemically, travertines may be divided into two groups, the meteogene travertines, where the carrier carbon dioxide originates in the soil and epigean atmosphere, and the thermal (thermogene) travertines where the carbon dioxide comes from thermally generated sources. Many travertine fabrics are influenced by bacteria and plants. These include 'stromatolitic' forms, many oncoids, shrubs, tufts, mats and moss travertines. Morphologically, travertines are conveniently divided into autochthonous (spring mounds and ridges, cascades, barrages, fluvial and lacustrine crusts, paludal deposits and cemented rudites) and the allochthonous or clastic travertines (valley-fills, back-barrage deposits, alluvial cones). Travertine deposits often include a wide range of fabrics and morphologies in one system. They are influenced locally by discharge, slope, vegetation, climate and human activity. Intergradations occur, both within travertine types but also with other freshwater deposits, e.g. calcrete and lake chalk. The influence of travertine deposition on the local hydrology and geomorphology is also discussed. The review emphasises the significance of scale and hydrology and aims to provide a unified scheme of travertine classification.
A large travertine mound at Pancuran Pitu, Central Java, Indonesia, displays various types of lamination reflecting different hydrological conditions. To understand the geomicrobiological processes of the laminated travertines, we investigated the mound's hydrology, water chemistry, texture, microbial composition, and volume percentage of carbonate mineral (VPC). We identified four types of travertines: dense travertine (80% VPC, flow rate ~ 200 cm/s), lithified microbial travertine (60% VPC, flow rate ~ 70 cm/s), fragile microbial travertine (30% VPC, flow rate ~ 10 cm/s), and poorly lithified microbial mat (< 10% VPC, flow rate < 5 cm/s). The first two types exhibited regular lamination at sub-mm intervals that was associated with the distribution of cyanobacteria and organic substances. The dense travertine consisted of alternation of crystalline and banded layers at ~ 160-μm intervals, which resembles the daily lamination of an aragonite travertine from southwest Japan. The banded layer formed during the day, exhibited porosity, and contained organic substances. Lamination in the lithified microbial travertine was likely formed by the daily growth cycles of filamentous cyanobacteria. The daytime surface of this travertine appeared to be sub-mm-thick cyanobacterial biofilm with spheroidal aggregates of aragonite, which covered a crystalline layer consisting of radially expanded needle crystals. The crystalline layer was likely formed during the night when the cyanobacterial growth was interrupted. These regularly laminated travertines fabrics appeared to be similar to certain Precambrian stromatolites. Regularity of the lamination was less in the other two microbe-rich types at low-flow sites. The majority of the aragonite occurred as spherical aggregates within the microbial mat, although thin (10–50 μm) crystal layers in the fragile microbial travertine may indicate daily intervals. As represented in the relationship among the VPC, flow rate, and precipitation rate of aragonite, the travertines were more consolidated with increasing hydrodynamic energy because of the activation of carbonate precipitation and the inhibition of thick cyanobacterial biofilm development.
The western part of the Chalkidiki peninsula in Northern Greece is a geothermally active area that contains high levels of naturally derived arsenic in its alkaline groundwaters (up to 3760 μg/L). Near wells, equilibration of these groundwaters with atmospheric carbon dioxide leads to the precipitation of travertines that contain very high levels of arsenic (up to 913 mg/kg). To determine the mechanism of arsenic uptake in these travertines, we analyzed two different types of travertine from this region using both bulk and micro-focused X-ray absorption spectroscopy (XAS and μ-XAS) and micro-focused X-ray fluorescence spectroscopy (μ-XRF). Bulk XAS showed that in all of the studied samples arsenic is present in the pentavalent oxidation state (arsenate). μ-XRF analyses indicated that arsenic is closely associated with the calcite matrix and that it generally does not correlate well with iron. The arsenic K-edge XAS spectra of all samples closely matched each other and closely resembled a reference spectrum for arsenate coprecipitated with calcite (rather than adsorbed or pure calcium arsenate). Iron on the other hand was found to be mainly present as a constituent of clay minerals, of presumably detrital origin, suggesting that iron-(hydr)oxides were not sufficiently abundant to act as major scavengers for arsenic in the Chalkidiki travertines. We estimated that calcite in these travertines could sequester at least 25% of aqueous arsenic in the form of As(V) and thus immobilize a substantial part of arsenic present in the geothermal groundwaters. These results may also be relevant for other areas where geothermal groundwaters carry arsenic to the surface and possibly as well for arsenic geochemistry in other environments with CO2-enriched water.
Data from Macedonia (Greece), correlated with those reported from the Pontides (Turkey), indicate that the Pelagonian zone of the Hellenides represents a fragment of the Cimmerian continent which separated the Paleo-Tethys and Neo-Tethys Oceans. A Permo-Triassic age is suggested for separation of the Paleozoic continent and initial rifting in the 2 oceanic basins. As the Pelagonian zone represented the NW (European) end of the Cimmerian continent, the Paleo-Tethys and the N branch of Neo-Tethys would have been very close to each other on either side of this zone. Thus, both oceans at their European end closed within a short time of each other in the Late Jurassic-Early Cretaceous. The sequential development of the 2 oceans outlines a model for the geotectonic evolution of the Internal Hellenides in which a correlation of thrusting and folding phases is also given.-Author
The global carbonate cycle has been controlled and maintained by life processes for at least 3.5 billion years. Within the exogenic carbonate cycle and in very different environments cyanobacteria appear in ‘key positions’ in that they actively and passively influence carbonate cycling. In the carbonate cycle, cyanobacteria play an important and sometimes decisive role. Cycling of carbon and carbonate is linked to biological processes. Some build up specific carbonate structures, some destroy carbonate substrates and others do both simultaneously. All these processes take place from the high mountains down to the sea in various terrestrial and freshwater as well as marine environments. The photosynthetic activity of cyanobacteria, their extracellular polymeric substances and possibly also their adherent heterotrophic bacteria are responsible for the construction of various carbonate structures and the ability to penetrate carbonate material. Boring activity of euendoliths results in biological corrosion and disintegration of carbonate surfaces. Grazing organisms on carbonate surfaces colonized by epi- and endolithic cyanobacteria produce specific biokarst forms and specific grains which can contribute to nearshore sedimentation. Biological corrosion and abrasion together constitute bioerosion. The results of all these processes are calcareous crusts, typical traces and biokarst forms which in many cases have a high fossilization potential, and therefore can be powerful ecological, palaeoecological and facies indicators in recent as well as in fossil environments.
Cyanobacteria are the major oxygenic photosynthetic microorganisms of hot spring travertines. This review describes the known cyanobacterium flora of travertine-depositing waters > 37 °C. The communities develop either upon (epilithon) or within (endolithon) the travertine surface, where they may influence the travertine fabric by providing nucleation sites for calcium carbonate. Mat photosynthesis locally increases the amount of travertine deposited, but the importance of photosynthesis in travertine deposition is rarely significant because the main loss of CO2 is by atmospheric evasion of the hot, CO2-rich waters. The Oscillatoriales are the most important group of cyanobacteria in terms of their biomass, but the taxonomy of the order is in a state of chaos. Molecular methods will ultimately disclose the true affinities of the organisms but, at present, the use of form-taxa based upon morphological characters provides a practical alternative. Identification of fossilized cyanobacteria is problematic since few of the key characters survive as fossils. The known cyanobacterium flora is tabulated and an analytical key provided to identify the form-taxa of hot spring travertines.
We review the geodynamic evolution of the Aegean–Anatolia region and discuss strain localisation there over
geological times. From Late Eocene to Present, crustal deformation in the Aegean backarc has localised progressively
during slab retreat. Extension started with the formation of the Rhodope Metamorphic Core Complex
(Eocene) and migrated to the Cyclades and the northern Menderes Massif (Oligocene and Miocene),
accommodated by crustal-scale detachments and a first series of core complexes (MCCs). Extension then
localised in Western Turkey, the Corinth Rift and the external Hellenic arc after Messinian times, while the
North Anatolian Fault penetrated the Aegean Sea. Through time the direction and style of extension have
not changed significantly except in terms of localisation. The contributions of progressive slab retreat and
tearing, basal drag, extrusion tectonics and tectonic inheritance are discussed and we favour a model
(1) where slab retreat is the main driving engine, (2) successive slab tearing episodes are the main causes
of this stepwise strain localisation and (3) the inherited heterogeneity of the crust is a major factor for
localising detachments. The continental crust has an inherited strong heterogeneity and crustal-scale contacts
such as major thrust planes act as weak zones or as zones of contrast of resistance and viscosity that
can localise later deformation. The dynamics of slabs at depth and the asthenospheric flow due to slab retreat
also have influence strain localisation in the upper plate. Successive slab ruptures from the Middle Miocene to
the Late Miocene have isolated a narrow strip of lithosphere, still attached to the African lithosphere below
Crete. The formation of the North Anatolian Fault is partly a consequence of this evolution. The extrusion
of Anatolia and the Aegean extension are partly driven from below (asthenospheric flow) and from above
(extrusion of a lid of rigid crust).
Stromatolites are laminated, lithified, sedimentary growth structures that accrete away from a point or limited surface of attachment. They are commonly, but not necessarily, of microbial origin and calcareous composition. Although familiar to geologists, they remain enigmatic as to origin and uncertain as to their full potential for historical geology. The authors summarize here the results of collective inquiry and discussion concerning central problems of stromatolite morphogenesis. Focus is on relations between microstructure, laminar details, and gross morphology of ancient, probably biogenic, stromatolites and on the microbial composition and laminar characteristics of analogous modern microbial mats and sedimentary structures produced by them.
An aragonite travertine at Nagano-yu hot spring, SW Japan, exhibits clear sub-millimeter-order lamination that resembles ancient ministromatolites. Thirty-three hours of continuous observation showed that the lamination is formed daily with no changes in physicochemical properties except light intensity. Phylotype analysis and fluorescence in situ hybridization indicate that Hydrogenophaga sp. is dominant and concentrated in diurnal layers containing abundant extracellular polymeric substances. Growth of Hydrogenophaga sp. is activated in the daytime, likely due to extracellular polymeric substance production by cyanobacterial photosynthesis. Daytime development of Hydrogenophaga-dominant biofilms, and the concurrent inhibiting effect on aragonite precipitation, explains the daily lamination observed.
The word ‘stromatolite’ should only be applied to organosedimentary structures predominantly accreted by sediment trapping, binding and/or in situ precipitation as a result of the growth and metabolic activities of benthic, principally prokaryotic, micro-organisms. Structures of uncertain origin that resemble stromatolites should be called ‘stromatoloids’. This cautious approach would eliminate the currently common assumption that structures with mesoscopic morphological similarities to microbially accreted sedimentary structures must be biogenic, a misconception that hampers investigations into the antiquity of life.A hierarchical series of meso- and microstructural attributes of stromatolites can be used to assign gradually increasing probabilities of biogenicity to stromatoloids. This method is particularly useful for interpreting ancient noncolumnar stromatoloids with poor microstructural preservation. In a range of Early Archaean pseudocolumnar, nodular and stratiform stromatoloids from North Pole studied using this method, none could be proved to be stromatolites and only a few are probable or possible stromatolites. As these stromatoloids closely resemble previously reported structures from North Pole interpreted as stromatolites, we consider that the evidence for the existence of life c. 3500 my ago at North Pole is less definitive than previously supposed.
The travertines at Pamukkale contain a diverse assemblage of phototrophs: 17 species of cyanobacteria, 16 diatoms, and 5 Chlorophyceae. Two communities were recognized on the active travertines: (1) surficial mats dominated by filamentous cyanobacteria, particularly Lyngbya (Phormidium) laminosum forming soft weakly mineralized layers to 10 mm thick, and (2) a predominantly endolithic assemblage, also dominated by cyanobacteria developing 2–5 mm below the travertine surface. The distribution of these communities is determined largely by water flow and the de‐greee of desiccation. Two further communities are briefly described from nondeposit‐ing areas. Most of the active travertine consists of alternating layers of micrite and sparite 0.25–0.75 mm in thickness, which probably result from short‐term fluctuations in water flow rather than diel events (photosynthesis, temperature). The presence of needle‐fiber calcite in surface samples suggests that evaporation of water may play some part in travertine formation. The phototrophs appear to influence the travertine fabric only locally, where the surficial growths contain strings of calcite crystals adhering to the filaments, forming irregularly laminated layers. The hot‐spring water is believed to be contaminated with sewage and agricultural effluent, but there was no evidence to suggest that this is currently affecting the travertine deposits. The water is supersaturated with respect to calcite when it contacts the travertine, and precipitation is primarily the result of carbon dioxide evasion. Water chemistry and discharge measurements indicate a total travertine deposition rate of 35 tonnes per day.
Calcite dendrite crystals are important but poorly understood components of calcite travertine that forms around many hot springs. The Lýsuhóll hot-spring deposits, located in western Iceland, are formed primarily of siliceous sinters that were precipitated around numerous springs that are now inactive. Calcite travertine formed around the vent and on the discharge apron of one of the springs at the northern edge of the area. The travertine is formed largely of two types (I and II) of complex calcite dendrite crystals, up to 1 cm high, that grew through the gradual addition of trilete sub-crystals. The morphology of the dendrite crystals was controlled by flow direction and the competition for growth space with neighbouring crystals. Densely crowded dendrites with limited branching characterize the rimstone dams whereas widely spaced dendrites with open branching are found in the pools. Many dendrite bushes in the pools nucleated around plant stems. Growth of the dendrite crystals was seasonal and incremental. Calcite precipitation was driven by rapid CO2 degassing of CO2-rich spring waters during the spring and summer. During winter, when snow covered the ground and temperatures were low, opal-A precipitated on the exposed surfaces of the dendrites. Segmentation of dendrite branches by discontinuities coated with opal-A and overgrowth development around sub-crystals resulted from this seasonal growth cycle. The calcite dendrite crystals in the Lýsuhóll travertine differ in morphology from those at other hot springs, such as those at Lake Bogoria, Kenya, and Waikite in New Zealand. Comparison with the calcite dendrite crystals found at those sites shows that dendrite morphology is site-specific and probably controlled by carbonate saturation levels that, in turn, are controlled by the rate of CO2 degassing and location in the spring outflow system.
New fault plane solutions, Landsat photographs, and seismic refraction records show that rapid extension is now taking place in the northern and eastern parts of the Aegean sea region. The southern part of the Aegean has also been deformed by normal faulting but is now relatively inactive. In northwestern Greece and Albania there is a band of thrusting near the western coasts adjacent to a band of normal faulting further east. The pre-Miocene geology of the islands in the Aegean closely resembles that of Greece and Turkey, yet seismic refraction shows that the crust is now only about 30 km thick beneath the southern part of the sea, compared with nearly 50 km beneath Greece and western Turkey. These observations suggest that the Aegean has been stretched by a factor of two since the Miocene. This stretching can account for the high heat flow. The sinking slab produced by subduction along the Hellenic Arc may maintain the motions, though the geometry and widespread nature of the normal faulting is not easily explained. The motions in northwestern Greece and Albania cannot be driven in the same way because no slab exists in the area. They may be maintained by blobs of cold mantle detaching from the lower half of the lithosphere, produced by a thermal instability when the lithosphere is thickened by thrusting. Hence generation and destruction of the lower part of the lithosphere may occur beneath deforming continental crust without the production of any oceanic crust.
A large number of chemical analyses of Greek thermal waters were evaluated in order to investigate spring water origin, water–rock interaction mechanisms, and estimate the thermal potential of the geothermal areas. Four water types were distinguished from geochemical diagrams. The relatively fresher waters include samples of Ca–HCO3 and Mg–HCO3 type waters originating from the schistose Rhodope Massif and the Quaternary basin of Aridea, respectively. Samples of the Na–HCO3 water type are typical of springs located in the post-orogenic basins of northern Greece. These hot, deep-rising Na–HCO3
waters circulate in a CO2-rich environment that favours the solubility of alkaline ions such as Na from siliceous rocks. Most of the samples belong to the Na–Cl water type and originate from Greek islands and coastal springs. These are characterized by the mixing of deep thermal solutions with seawater and fresh water. The presence of CO2 in thermal and mineral springs is due to the metamorphism of buried marine carbonate horizons while H2S is due to both local pyrite oxidation and the reduction of sulphates. The use of geothermometers suggested that the investigated geothermal areas have low enthalpy fluids at depth, while higher temperatures are likely present in Milos, Lesvos, Nisyros islands and Xanthi Basin.
This study stresses the role of specific bacterial outer structures (such as glycocalix and parietal polymers) on calcium carbonate crystallization in terrestrial environments. The aim is to compare calcium carbonate crystals obtained in bacterial cultures with those obtained during abiotically mediated synthesis to show implications of exopolysaccharides and amino acids in the mineralogy and morphology of calcium carbonate crystals produced by living bacteria. This is done using various amounts of purified exopolysaccharide (xanthan EPS) and L-amino acids with a range of acidities. Amino acids and increasing xanthan content enhance sphere formation in calcite and vaterite. Regarding calcite, the morphology of crystals evolves from rhombohedral to needle shape. This evolution is characterized by stretching along the c axis as the amino acid changes from glutamine to aspartic acid and as the medium is progressively enriched in EPS. Regarding vaterite, the spherulitic habit is preserved throughout the morphological sequence and starts with spheres formed by the agglomeration of short needles, which are produced in a xanthan-free medium with glutamine. Monocrystals forming spheres increase in size as xanthan is added and the acidity of amino acids (glutamic and aspartic acids) is increased. At high xanthan concentrations, amino acids, and mainly aspartic and glutamic acids, induce vaterite precipitation. The role of the carboxyl group is also probably critical because bacterial outer structures associated with peptidoglycan commonly contain carboxyl groups. This role, combined with the results presented here, clearly demonstrate the influence of bacterial outer structure composition on the morphology and mineralogy of bacterially induced calcium carbonate. This point should not be neglected in the interpretation of calcite cements and carbonate accumulations in terrestrial environments.
The chemical compositions of six travertine-depositing hot spring waters in Italy are described with emphasis on the carbon dioxide system. All springs contained high concentrations of CO2 (>20 mM l−1) with equilibrium partial pressures well above those which could have been formed in contact with a soil atmosphere. After surfacing, the CO2 is rapidly lost to the atmosphere, with evasion rates close to the springs ranging from 0.45–4.41 mM m−2 s−1. Partial pressures of C02 showed an exponential decline with distance, which is consistent with the static film model where temperature and turbulence are constant. Downstream CO2 transfer coefficients, which ranged from 66 to 360 cm h−1 were consistent with moderately turbulent flow, however, there was no correlation between turbulence, measured as the mean shear stress, and CO2 evasion rate. The channels investigated had all been modified by man and most possessed even widths and gradients.All waters became increasingly supersaturated with aragonite and calcite downstream and both of these minerals were present in fresh travertine deposits. The supersaturation was driven almost exclusively by gas evasion. Comparison of daytime and nighttime evasion rates demonstrated that photosynthetic activity was an insignificant source of CO2 flux in the reaches investigated. Carbon dioxide evasion is therefore primarily responsible for the supersaturation and probably also the deposition of travertine at these sites.The CaCO3 content of the travertines ranged from 91.3 to 96.0 wt% with 1.7–4.1% CaSO4, traces of organic matter and acid-insoluble minerals.
STROMATOLITES are laminated, accretionary structures, which are commonly regarded to have formed by the sediment-binding or precipitating activities of ancient microbial mats or biofilms (composed mainly of cyanobacteria), possibly supplemented by abiotic surface precipitation1-4. Stromatolites are thus considered to be a proxy for early life on Earth, as the record of these structures extends back to 3.5 Gyr ago5. But as stromatolites only rarely contain fossil microbes, their biogenicity is tacitly assumed on the basis of morphological comparisons with modern, demonstrably biological, structures6. Little is known about the physical, chemical and biological processes that controlled the growth of ancient stromatolites4 and, with pioneering exceptions7-9, the analysis of the inherent geometric characteristics of the structures has not been pursued. Here we present a morphological characterization of ancient stromatolites that have growth surfaces with self-afime fractal geometry. We deduce, from both the microscopic textures and the fractal dimension, a purely abiotic dynamical model of stromatolite surface growth that combines chemical precipitation on the growing interface, fallout and diffusive rearrangement of suspended sediment, and uncorrelated random noise. This result calls into question the assumption that organisms-even if present-necessarily played an essential role in determining stromatolite morphology during times when precipitation at the sea floor was common, such as the earlier Precambrian.
The primary objective of this study was to determine whether the long-term exclusion of ultraviolet (UV) radiation (UVR) from hot-spring microbial mats resulted in an alteration of microbial composition, such as a shift to more UV-sensitive species. Over a 1-3-month period, microbial mats in two alkaline geothermal streams in Yellowstone National Park were covered with filters that excluded or transmitted UVR. Over some, 25% transmission neutral density screens were also used. In the 40-47 degrees C range, there were no apparent changes in community composition during the summer with or without high or low UVR, as assessed by denaturing gradient gel electrophoresis (DGGE) profiles after polymerase chain reaction amplification of 16S-rRNA genes with general Bacteria and Cyanobacteria primers. Major bands were purified from the DGGE gels and sequenced. Only one of the cyanobacterial sequences matched known strains in the database; the others appear to be unique. Although the bacterial composition of these communities was apparently stable, surface layers of cyanobacteria protected from UVR were not as competent photosynthetically as those that had been maintained under UVR. This decrease in competence was expressed as a loss of the ability to perform at a maximum rate under full UVR plus visible irradiance. However, even +UV-maintained cyanobacteria performed better when UVR was excluded during the photosynthesis tests. It is probable that the large differences in photosynthetic competence observed reflect changes at the level of gene expression in the dominant species rather than changes in species composition.
Calcite nucleation on the surface of cyanobacteria of the Synechococcus leopoliensis strain PCC 7942 was investigated to assess the influence of photosynthetic uptake of inorganic carbon and active ion exchange processes across the cell membrane on the nucleation and precipitation mechanisms. We performed long-term precipitation experiments at a constant CO(2) level in ambient air by adding suspensions of previously washed cyanobacteria to solutions of NaHCO(3)/CaCl(2) which were supersaturated with respect to calcite. Induction times between 4 and 110 h were measured over a range of saturation states, Omega, between 8 and 4. The kinetics of CaCO(3) nucleation was compared between experiments: (i) with ongoing photosynthesis, (ii) with cells metabolizing but not undergoing photosynthetic uptake of inorganic carbon and (iii) in darkness without photosynthesis. No significant differences were observed between the three treatments. The results reveal that under low nutrient concentrations and permanent CO(2) supply, photosynthetic uptake of inorganic carbon predominantly uses CO(2) and consequently does not directly influence the nucleation process of CaCO(3) at the surface of S. leopoliensis. Furthermore, ion exchange processes did not affect the kinetics, indicating a passive nucleation process wherein the cell surface or extracellular polymers provided preferential sites for mineral nucleation. The catalyzing effect of the cyanobacteria on calcite nucleation was equivalent to a approximately 18% reduction in the specific interfacial free energy of the calcite nuclei. This result and the ubiquitous abundance of cyanobacteria suggest that this process may have an impact on local and global carbon cycling.