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RESEARCH PRODUCT
Biological and physical modification of carbonate system parameters along the salinity gradient in shallow hypersaline solar salterns in Trapani, Italy
Naohiko OhkouchiVinicio ManziTakazo ShibuyaMarco RoveriNanako O. OgawaAtsushi SuzukiToshihiro YoshimuraHodaka KawahataYuta IsajiFrancisco J. Jiménez-espejoStefano LugliAndrea SantulliJunichiro Kurodasubject
0301 basic medicine010504 meteorology & atmospheric sciencesEvaporiteMineralogyengineering.materialBiogeochemical cycle01 natural sciences03 medical and health scienceschemistry.chemical_compoundMicrobial matGeochemistry and PetrologyCompound-specific isotope analysishemic and lymphatic diseasesDissolved organic carbonPhotosynthetic pigmentSulfate0105 earth and related environmental sciencesHypersaline environmentSalinity030104 developmental biologyCalcium carbonatechemistryBiogeochemical cycle; Carbonate system; Compound-specific isotope analysis; Hypersaline environment; Microbial mat; Photosynthetic pigments;Photosynthetic pigmentsengineeringHaliteCarbonateSeawaterCarbonate systemCompound-specific isotope analysiGeologycirculatory and respiratory physiologydescription
Abstract We investigated changes in the chemical characteristics of evaporating seawater under the influence of microbial activity by conducting geochemical analyses of the brines and evaporite sediments collected from solar salterns in Trapani, Italy. The microbial activity had a substantial effect on the carbonate system parameters. Dissolved inorganic carbon (DIC) was substantially removed from the brine during the course of evaporation from the seawater to the point where calcium carbonate precipitates, with an accompanying decrease in its carbon isotopic composition (δ 13 C DIC ) to as low as −10.6‰. Although the removal of DIC was due to calcium carbonate precipitation, photosynthesis, and the degassing of CO 2 (aq) induced by evaporation, the presence of 13 C-depleted δ 13 C DIC in ponds where calcium carbonate precipitates can be attributed to the dissolution of atmospheric CO 2 because of intensive CO 2 (aq) uptake by photosynthesis, and/or mineralization of organic matter by sulfate reduction. In contrast, δ 13 C DIC increased up to 7.2‰ in the salinity range where halite precipitates, which can be ascribed to the domination of the effect of degassing of CO 2 (aq) under conditions with reduced microbial activity. A gradual decrease in microbial activity was also reflected in compound-specific δ 13 C of photosynthetic pigments; isotopic fractionation associated with DIC assimilation increased linearly as the evaporation proceeded, indicating DIC-limited conditions within the microbial mats and gypsum crusts because of restricted DIC diffusion from the overlying brine and/or suppression of primary production at higher salinity.
| year | journal | country | edition | language |
|---|---|---|---|---|
| 2017-07-01 |