Coccolithophores Biomineralization And Its Environmental Implications

Coccolithophore is unicellular ultrafine plankton widely distributed in marine,and is one of the most important primary producers in modern ocean.Therefore,it has an important influence on marine ecosystem.Coccolithophore can secret biogenic calcium carbonate in the process of its life.Coccoliths contain abundant geological information and have an very important significance in paleo-ocean.In this paper,we obtained the process of coccolithophore biomineralization and its environmental implications by taking coccolith as mineral typomorphism environmental typomorphism under the condition of varied environmental in the future.In this paper,the widely distribution of coccolithophore in the marine was studied.Coccolithophore biomineralization was studied under the coupling condotions that the change of carbon dioxide concentration and temperature adjusted by plant growth chamber and the change of major and trace elements such as Calcium,magnesium,iron in culturing medium.The growth curves,the ratios of particulate inorganic carbon to particulate organic carbon,reactive oxygen species(ROS),and Sr /Ca,Mg/Ca in coccolithophore were studied.In addition,ultraviolet-visible spectrum(UV-Vis)and infrared spectrum(FTIR)of coccolith(the mineral structure of the coccolith)was analyzed.moreover,the interaction of coccolithophore and marine clay minerals was studied by adding the usual marine clay minerals such as montmorillonite and illite to culturing medium.The growth curves,Sr / Ca,Mg / Ca and UV-Vis,FTIR of coccolith was studied under the influence of clay minerals.Then,the FTIR,XRD of clay minerals was analyzed under the action of the coccolithophore.Finally,the mineral typomorphism and environmental typomorphism of samples collected from the Holocene boreholes in seabed and the laboratory respectively were comparative studied to extract the related environmental information.The following conclusions can be drawn.(1)Under the coupling effect of temperature,carbon dioxide concentration,magnesium and calcium,the results showed that the coupling conditions had little effect on coccolithophore.To some extent,coccolithophore can adapt to the environmental changes.The addition of Ca had a direct effect on the calcium carbonate formed during the biomineralization process,which in turn affect ed the reflectance of the UV-vis.coccolithophore also was sensitive to the temperature.Too high or too low temperature was bad for growth of coccolithophore.The addition of excess Mg affected the structure of Ca CO3 in the culture medium,which would possibly form Mg CO3 and affect the ratio of Sr/Ca and Mg/Ca.(2)Under the effect of varied iron concentration to coccolithophore,the results showed that a certain amount of iron could promote the growth of coccolithophore,which was in accordance with the previous hypothesis of ‘iron fertilization'.However the excessive iron concentration could promote the production of reactive oxygen species(ROS)and damage the cell structure,ultimately inhibit the growth of coccolithophore,while the iron element had less effect on Sr/Ca and Mg/Ca in the cell.The UV-Vis of coccolith showed that moderate iron concentration would aggregate around the cell and impact the absorption of UV-Vis of coccolithophore,while it would promote the absorption of UV-Vis and further enhance photosynthesis.The ATR-FTIR of coccoliths showed that there is a tendency to change the direction of aragonite and amorphous calcium carbonate.(3)Under the interaction of coccolithophore and clay minerals,r esults showed that illite had ignore effect for coccolithophore.montmorillonite had significant influence on coccolithophore in growth curves,element ratios of Mg/Ca and Sr/Ca due to its adsorption and flocculation effect on nutrients.Metabolic Biomolecules failed to intercalate into the interlayer of illite.However,biomolecules secreted by the coccolithophore intercalated and stored in the interlayers of montmorillonite.The presented study indicated that the interaction between marine clay mineral of montmorillonite and marine microorganisms ha d important geological significance,which may need attracting attentions from geo-biologist for understanding of ancient marine environment.(4)By ocean drilling project(MD05-2901),we obtained the sediment coccoliths samples from different depths in the west of South China Sea.By mineralogical characterization of the samples,the results showed that the sediments in the west of the South China Sea are mainly influenced by terrestrial matters.The organic matter contained in sedimentary samples decreases with depth.Wild coccoliths samples mainly include silicate minerals,and the content of silicon in mineral increases with depth.