-
Proceedings of the National Academy of... Oct 2022Carbonate mud represents one of the most important geochemical archives for reconstructing ancient climatic, environmental, and evolutionary change from the rock record....
Carbonate mud represents one of the most important geochemical archives for reconstructing ancient climatic, environmental, and evolutionary change from the rock record. Mud also represents a major sink in the global carbon cycle. Yet, there remains no consensus about how and where carbonate mud is formed. Here, we present stable isotope and trace-element data from carbonate constituents in the Bahamas, including ooids, corals, foraminifera, and algae. We use geochemical fingerprinting to demonstrate that carbonate mud cannot be sourced from the abrasion and mixture of any combination of these macroscopic grains. Instead, an inverse Bayesian mixing model requires the presence of an additional aragonite source. We posit that this source represents a direct seawater precipitate. We use geological and geochemical data to show that "whitings" are unlikely to be the dominant source of this precipitate and, instead, present a model for mud precipitation on the bank margins that can explain the geographical distribution, clumped-isotope thermometry, and stable isotope signature of carbonate mud. Next, we address the enigma of why mud and ooids are so abundant in the Bahamas, yet so rare in the rest of the world: Mediterranean outflow feeds the Bahamas with the most alkaline waters in the modern ocean (>99.7th-percentile). Such high alkalinity appears to be a prerequisite for the nonskeletal carbonate factory because, when Mediterranean outflow was reduced in the Miocene, Bahamian carbonate export ceased for 3-million-years. Finally, we show how shutting off and turning on the shallow carbonate factory can send ripples through the global climate system.
Topics: Bayes Theorem; Calcium Carbonate; Carbonates; Geologic Sediments; Seawater
PubMed: 36252022
DOI: 10.1073/pnas.2210617119 -
Annual Review of Marine Science Jan 2023Constraining rates of marine carbonate burial through geologic time is critical for interpreting reconstructed changes in ocean chemistry and understanding feedbacks and... (Review)
Review
Constraining rates of marine carbonate burial through geologic time is critical for interpreting reconstructed changes in ocean chemistry and understanding feedbacks and interactions between Earth's carbon cycle and climate. The Quaternary Period (the past 2.6 million years) is of particular interest due to dramatic variations in sea level that periodically exposed and flooded areas of carbonate accumulation on the continental shelf, likely impacting the global carbonate budget and atmospheric carbon dioxide. These important effects remain poorly quantified. Here, we summarize the importance of carbonate burial in the ocean-climate system, review methods for quantifying carbonate burial across depositional environments, discuss advances in reconstructing Quaternary carbonate burial over the past three decades, and identify gaps and challenges in reconciling the existing records. Emerging paleoceanographic proxies such as the stable strontium and calcium isotope systems, as well as innovative modeling approaches, are highlighted as new opportunities to produce continuous records of global carbonate burial.
Topics: Carbonates; Climate; Geologic Sediments
PubMed: 35773213
DOI: 10.1146/annurev-marine-031122-031137 -
Scientific Reports May 2022The oxygen isotope compositions of carbonate and phosphatic fossils hold the key to understanding Earth-system evolution during the last 500 million years....
The oxygen isotope compositions of carbonate and phosphatic fossils hold the key to understanding Earth-system evolution during the last 500 million years. Unfortunately, the validity and interpretation of this record remain unsettled. Our comprehensive compilation of Phanerozoic δO data for carbonate and phosphate fossils and microfossils (totaling 22,332 and 4615 analyses, respectively) shows rapid shifts best explained by temperature change. In calculating paleotemperatures, we apply a constant hydrosphere δO, correct seawater δO for ice volume and paleolatitude, and correct belemnite δO values for O enrichment. Similar paleotemperature trends for carbonates and phosphates confirm retention of original isotopic signatures. Average low-latitude (30° S-30° N) paleotemperatures for shallow environments decline from 42.0 ± 3.1 °C in the Early-to-Middle Ordovician to 35.6 ± 2.4 °C for the Late Ordovician through the Devonian, then fluctuate around 25.1 ± 3.5 °C from the Mississippian to today. The Early Triassic and Middle Cretaceous stand out as hothouse intervals. Correlations between atmospheric CO forcing and paleotemperature support CO's role as a climate driver in the Paleozoic.
Topics: Carbon Dioxide; Carbonates; Oceans and Seas; Phosphates; Seawater; Temperature
PubMed: 35624298
DOI: 10.1038/s41598-022-11493-1 -
Environmental Science & Technology Jun 2022The spectrophotometric methodology for carbonate ion determination in seawater was first published in 2008 and has been continuously evolving in terms of reagents and... (Review)
Review
The spectrophotometric methodology for carbonate ion determination in seawater was first published in 2008 and has been continuously evolving in terms of reagents and formulations. Although being fast, relatively simple, affordable, and potentially easy to implement in different platforms and facilities for discrete and autonomous observations, its use is not widespread in the ocean acidification community. This study uses a merged overdetermined CO system data set (carbonate ion, pH, and alkalinity) obtained from 2009 to 2020 to assess the differences among the five current approaches of the methodology through an internal consistency analysis and discussing the sources of uncertainty. Overall, the results show that none of the approaches meet the climate goal (± 1 % standard uncertainty) for ocean acidification studies for the whole carbonate ion content range in this study but usually fulfill the weather goal (± 10 % standard uncertainty). The inconsistencies observed among approaches compromise the consistency of data sets among regions and through time, highlighting the need for a validated standard operating procedure for spectrophotometric carbonate ion measurements as already available for the other measurable CO variables.
Topics: Calcium Carbonate; Carbon Dioxide; Carbonates; Hydrogen-Ion Concentration; Oceans and Seas; Seawater; Spectrophotometry
PubMed: 35670676
DOI: 10.1021/acs.est.1c06083 -
Fungal Biology 2023Cerium is the most sought-after rare earth element (REE) for application in high-tech electronic devices and versatile nanomaterials. In this research, biomass-free...
Cerium is the most sought-after rare earth element (REE) for application in high-tech electronic devices and versatile nanomaterials. In this research, biomass-free spent culture media of Aspergillus niger and Neurospora crassa containing precipitant ligands (oxalate, carbonate) were investigated for their potential application in biorecovery of Ce from solution. Precipitation occurred after Ce was mixed with biomass-free spent culture media and >99% Ce was recovered from media of both organisms. SEM showed that biogenic crystals with distinctive morphologies were formed in the biomass-free spent medium of A. niger. Irregularly-shaped nanoparticles with varying sizes ranging from 0.5 to 2 μm and amorphous biominerals were formed after mixing the carbonate-laden N. crassa supernatant, resulting from ureolysis of supplied urea, with Ce. Both biominerals contained Ce as the sole metal, and X-ray diffraction (XRD) and thermogravimetric analyses identified the biominerals resulting from the biomass-free A. niger and N. crassa spent media as cerium oxalate decahydrate [Ce(CO)·10HO] and cerium carbonate [Ce(CO)·8HO], respectively. Thermal decomposition experiments showed that the biogenic Ce oxalates and carbonates could be subsequently transformed into ceria (CeO). FTIR confirmed that both amorphous and nanoscale Ce carbonates contained carbonate (CO) groups. FTIR-multivariate analysis could classify the biominerals into three groups according to different Ce concentrations and showed that Ce carbonate biominerals of higher purity were produced when precipitated at higher Ce concentrations. This work provides new understanding of fungal biotransformations of soluble REE species and their biorecovery using biomass-free fungal culture systems and indicates the potential of using recovered REE as precursors for the biosynthesis of novel nanomaterials.
Topics: Cerium; Oxalates; Carbonates; Biotransformation; Culture Media
PubMed: 37495308
DOI: 10.1016/j.funbio.2022.07.006 -
Geobiology Jan 2023The record of life during the Proterozoic is preserved by several different lithologies, but two in particular are linked both spatially and temporally: chert and... (Review)
Review
The record of life during the Proterozoic is preserved by several different lithologies, but two in particular are linked both spatially and temporally: chert and carbonate. These lithologies capture a snapshot of dominantly peritidal environments during the Proterozoic. Early diagenetic chert preserves some of the most exceptional Proterozoic biosignatures in the form of microbial body fossils and mat textures. This fossiliferous and kerogenous chert formed in shallow marine environments, where chert nodules, layers, and lenses are often surrounded by and encased within carbonate deposits that themselves often contain kerogen and evidence of former microbial mats. Here, we review the record of biosignatures preserved in peritidal Proterozoic chert and chert-hosting carbonate and discuss this record in the context of experimental and environmental studies that have begun to shed light on the roles that microbes and organic compounds may have played in the formation of these deposits. Insights gained from these studies suggest temporal trends in microbial-environmental interactions and place new constraints on past environmental conditions, such as the concentration of silica in Proterozoic seawater, interactions among organic compounds and cations in seawater, and the influence of microbial physiology and biochemistry on selective preservation by silicification.
Topics: Geologic Sediments; Fossils; Carbonates; Seawater; Silicon Dioxide
PubMed: 36268586
DOI: 10.1111/gbi.12527 -
Molecules (Basel, Switzerland) Nov 2020Microbiologically induced carbonate precipitation (MICP) is a well-known biogeochemical process that allows the formation of calcium carbonate deposits in the... (Review)
Review
Microbiologically induced carbonate precipitation (MICP) is a well-known biogeochemical process that allows the formation of calcium carbonate deposits in the extracellular environment. The high concentration of carbonate and calcium ions on the bacterial surface, which serves as nucleation sites, promotes the calcium carbonate precipitation filling and binding deteriorated materials. Historic buildings and artwork, especially those present in open sites, are susceptible to enhanced weathering resulting from environmental agents, interaction with physical-chemical pollutants, and living organisms, among others. In this work, some published variations of a novel and ecological surface treatment of heritage structures based on MICP are presented and compared. This method has shown to be successful as a restoration, consolidation, and conservation tool for improvement of mechanical properties and prevention of unwanted gas and fluid migration from historical materials. The treatment has revealed best results on porous media matrixes; nevertheless, it can also be applied on soil, marble, concrete, clay, rocks, and limestone. MICP is proposed as a potentially safe and powerful procedure for efficient conservation of worldwide heritage structures.
Topics: Bacteria; Calcium Carbonate; Carbonates; Chemical Phenomena; Chemical Precipitation; Hydrolysis; Microbiological Phenomena; Models, Theoretical; Spectrum Analysis; Tomography, X-Ray Computed; Urea
PubMed: 33255349
DOI: 10.3390/molecules25235499 -
Geobiology Sep 2022Marine and lacustrine carbonate minerals preserve carbon cycle information, and their stable carbon isotope values (δ C) are frequently used to infer and reconstruct...
Marine and lacustrine carbonate minerals preserve carbon cycle information, and their stable carbon isotope values (δ C) are frequently used to infer and reconstruct paleoenvironmental changes. However, multiple processes can influence the δ C values of bulk carbonates, confounding the interpretation of these values in terms of conditions at the time of mineral precipitation. Co-existing carbonate forms may represent different environmental conditions, yet few studies have analyzed δ C values of syndepositional carbonate grains of varying morphologies to investigate their origins. Here, we combine stable isotope analyses, metagenomics, and geochemical modeling to interpret δ C values of syndepositional carbonate spherules (>500 μm) and fine-grained micrite (<63 μm) from a ~1600-year-long sediment record of a hypersaline lake located on the coral atoll of Kiritimati, Republic of Kiribati (1.9°N, 157.4°W). Petrographic, mineralogic, and stable isotope results suggest that both carbonate fractions precipitate in situ with minor diagenetic alterations. The δ C values of spherules are high compared to the syndepositional micrite and cannot be explained by mineral differences or external perturbations, suggesting a role for local biological processes. We use geochemical modeling to test the hypothesis that the spherules form in the surface microbial mat during peak diurnal photosynthesis when the δ C value of dissolved inorganic carbon is elevated. In contrast, we hypothesize that the micrite may precipitate more continuously in the water as well as in sub-surface, heterotrophic layers of the microbial mat. Both metagenome and geochemical model results support a critical role for photosynthesis in influencing carbonate δ C values. The down-core spherule-micrite offset in δ C values also aligns with total organic carbon values, suggesting that the difference in the δ C values of spherules and micrite may be a more robust, inorganic indicator of variability in productivity and local biological processes through time than the δ C values of individual carbonate forms.
Topics: Carbon; Carbon Isotopes; Carbonates; Lakes; Photosynthesis
PubMed: 35851522
DOI: 10.1111/gbi.12509 -
PloS One 2022This manuscript presents an inventory of the carbonate system from the main water masses comprising the marine current system on Brazil's northeast coast (South Atlantic...
This manuscript presents an inventory of the carbonate system from the main water masses comprising the marine current system on Brazil's northeast coast (South Atlantic Ocean). For this purpose, four transects were conducted with an approximate length of 357 km (each one) through the platform and continental slope of the Sergipe-Alagoas sedimentary basin. Water samples were then collected in vertical profiles measuring from 5 to 1,799 meters depth, totaling 34 stations. Total alkalinity, calcium, and total boron were obtained analytically from these samples and by relationships with salinity. Speciation and concentration of the carbonate system were obtained by means of thermodynamic modeling. The results revealed that the empirical models used to calculate the concentrations of TA, calcium and total boron showed relevant variation when compared to the analytical values (TA: 5.0-6.5%; Ca: 0.4-4.8%; BT: 7.0-18.9%). However, the speciation and concentration of the carbonate system (CA, DIC, [Formula: see text], CO2(aq), ΩCalc, and ΩArag) obtained from the empirical values of TA, calcium and total boron did not differ significantly from those obtained analytically (0.0-6.1%). On the other hand, the parameters of pH, [Formula: see text], [Formula: see text], CO2(aq), ρCO2, ΩCalc, and ΩArag varied significantly within the different water masses (p < 0.05). This study supports and encourages acidification monitoring projects in the South Atlantic Ocean, based on modeling the carbonate system parameters generated in real-time.
Topics: Atlantic Ocean; Boron; Brazil; Calcium; Calcium Carbonate; Carbon Dioxide; Carbonates; Hydrogen-Ion Concentration; Seawater; Water
PubMed: 35881635
DOI: 10.1371/journal.pone.0271875 -
Nature Communications May 2022Carbonatites are rare but worldwide occurring igneous rocks and their genesis remains enigmatic. Field studies show a close spatial but controversially debated genetic...
Carbonatites are rare but worldwide occurring igneous rocks and their genesis remains enigmatic. Field studies show a close spatial but controversially debated genetic relationship with alkaline silicate rocks, and petrological and experimental studies indicate liquid immiscibility from mantle-derived magmas being one viable model for the generation of carbonatites. However, unaltered carbonatitic melts are rare and the composition of primary carbonate liquids and their silicate conjugates is poorly constrained. Here we show an example of primary Ca-carbonatitic melt formed by liquid immiscibility from a phonolitic magma of the Laacher See volcano (Eifel, Germany). The conjugate blebs of carbonate-silicate liquids are found in hauyne-hosted melt inclusions. The Ca-carbonatite melts are moderately alkali-rich and contain high F and Cl at elevated SiO and AlO concentrations. Such carbonatite liquids are viable parental magmas to the globally dominating intrusive Ca-carbonatite complexes and may provide the missing link to extrusive Na-carbonatitic magmas.
Topics: Carbonates; Germany; Silicates; Silicon Dioxide
PubMed: 35610205
DOI: 10.1038/s41467-022-30500-7