Calcite Production Research Articles

Growth and mortality of coccolithophores during spring in a temperate Shelf Sea (Celtic Sea, April 2015)

Coccolithophores are key components of phytoplankton communities, exerting a critical impact on the global carbon cycle and the Earth’s climate through the production of coccoliths made of calcium carbonate (calcite) and bioactive gases. Microzooplankton grazing is an important mortality factor in coccolithophore blooms, however little is currently known regarding the mortality (or growth) rates within non-bloom populations. Measurements of coccolithophore calcite production (CP) and dilution experiments to determine microzooplankton (≤63 µm) grazing rates were made during a spring cruise (April 2015) at the Central Celtic Sea (CCS), shelf edge (CS2), and within an adjacent April bloom of the coccolithophore Emiliania huxleyi at station J2.CP at CCS ranged from 10.4 to 40.4 µmol C m−3 d−1 and peaked at the height of the spring phytoplankton bloom (peak chlorophyll-a concentrations ∼6 mg m−3). Cell normalised calcification rates declined from ∼1.7 to ∼0.2 pmol C cell−1 d−1, accompanied by a shift from a mixed coccolithophore species community to one dominated by the more lightly calcified species E. huxleyi and Calciopappus caudatus. At the CCS, coccolithophore abundance increased from 6 to 94 cells mL−1, with net growth rates ranging from 0.06 to 0.21 d−1 from the 4th to the 28th April. Estimates of intrinsic growth and grazing rates from dilution experiments, at the CCS ranged from 0.01 to 0.86 d−1 and from 0.01 to 1.32 d−1, respectively, which resulted in variable net growth rates during April. Microzooplankton grazers consumed 59 to >100% of daily calcite production at the CCS. Within the E. huxleyi bloom a maximum density of 1986 cells mL−1 was recorded, along with CP rates of 6000 µmol C m−3 d−1 and an intrinsic growth rate of 0.29 d−1, with ∼80% of daily calcite production being consumed.Our results show that microzooplankton can exert strong top-down control on both bloom and non-bloom coccolithophore populations, grazing over 60% of daily growth (and calcite production). The fate of consumed calcite is unclear, but may be lost either through dissolution in acidic food vacuoles, and subsequent release as CO2, or export to the seabed after incorporation into small faecal pellets. With such high microzooplankton-mediated mortality losses, the fate of grazed calcite is clearly a high priority research direction.

Global perturbation of the marine calcium cycle during the Permian-Triassic transition

A negative shift in the calcium isotopic composition of marine carbonate rocks spanning the end-Permian extinction horizon in South China has been used to argue for an ocean acidification event coincident with mass extinction. This interpretation has proven controversial, both because the excursion has not been demonstrated across multiple, widely separated localities, and because modeling results of coupled carbon and calcium isotope records illustrate that calcium cycle imbalances alone cannot account for the full magnitude of the isotope excursion. Here, we further test potential controls on the Permian-Triassic calcium isotope record by measuring calcium isotope ratios from shallow-marine carbonate successions spanning the Permian-Triassic boundary in Turkey, Italy, and Oman. All measured sections display negative shifts in δ44/40Ca of up to 0.6‰. Consistency in the direction, magnitude, and timing of the calcium isotope excursion across these widely separated localities implies a primary and global δ44/40Ca signature. Based on the results of a coupled box model of the geological carbon and calcium cycles, we interpret the excursion to reflect a series of consequences arising from volcanic CO2 release, including a temporary decrease in seawater δ44/40Ca due to short-lived ocean acidification and a more protracted increase in calcium isotope fractionation associated with a shift toward more primary aragonite in the sediment and, potentially, subsequently elevated carbonate saturation states caused by the persistence of elevated CO2 delivery from volcanism. Locally, changing balances between aragonite and calcite production are sufficient to account for the calcium isotope excursions, but this effect alone does not explain the globally observed negative excursion in the δ13C values of carbonate sediments and organic matter as well. Only a carbon release event and related geochemical consequences are consistent both with calcium and carbon isotope data. The carbon release scenario can also account for oxygen isotope evidence for dramatic and protracted global warming as well as paleontological evidence for the preferential extinction of marine animals most susceptible to acidification, warming, and anoxia.

A synergetic biomineralization strategy for immobilizing strontium during calcification of the coccolithophore Emiliania huxleyi.

The coccolithophore species Emiliania huxleyi has one of the most global distributions in the modern oceans. They are characteristically covered with calcite scales called coccoliths. In this study, stable strontium immobilization during the calcification process was investigated to indirectly assess a proposed bioremediation approach for removing Sr2+ contamination from marine environments. Results indicate that E. huxleyi has high Sr2+ tolerance and removal efficiency in response to Sr2+ stress ranging from 5.6 to 105.6ppm. Sr2+ immobilization during E. huxleyi calcification indicates a concentration-dependent synergistic mechanism. At lower concentrations of Sr2+ (25.6ppm), Sr2+ is incorporated into coccoliths through competitive supply between Sr2+ and Ca2+. In addition, calcite productivity decreases with increased Sr2+ removal efficiency due to crystallographic transformation of coccoliths from hydrated calcite into aragonite at 55.6ppm Sr2+. Further formation of strontianite at 105.6ppm Sr2+ is due to precipitation of Sr2+ on the edge of the rims and radial arrays of the coccoliths. Our study implies that coccolithophores are capable of significant removal of Sr2+ from the marine environment.

Induction of calcite precipitation through heightened production of extracellular carbonic anhydrase by CO2 sequestering bacteria

The thermo-alkalotolerant bacterium exhibiting heightened extracellular carbonic anhydrase (CA) activity, survived at 100 mM sodium bicarbonateand 5% gaseous CO2 was identified as Bacillus sp. by 16S rRNA sequencing. Extracellular carbonic anhydrase was purified by ammonium sulfate precipitation, gel filtration chromatography and affinity chromatography with a yield of 46.61% and specific activity of 481.66 U/mg. The size of purified carbonic anhydrase was approximately 28 kDa in SDS-PAGE gel filtration and further their role in calcium carbonate production was correlated. The purified enzyme was stable with half-life of 25.36 min at 90 °C and pH 8. KM and Vmax values of the enzyme were 1.77 mg/mL and 385.69 U/mg respectively. The production of calcite was confirmed by Scanning Electron Microscopy (SEM) analysis, FTIR, and Energy-Dispersive X-ray (EDX) analysis. Carbonic anhydrase and calcite deposition coupled with CO2 fixingbacteria is a significant approach for CO2 sequestration.

In-situ capture and conversion of atmospheric CO2 into nano-CaCO3 using a novel pathway based on deep eutectic choline chloride-calcium chloride

This study presents a newfangled method and provides a new approach toward capturing-entrapping the toxic and harmful greenhouse gas CO2 and subsequently employing it as a useful precursor for the production of value-added calcite (CaCO3) nanoparticles. All the processes are done in a single system (one-pot and in-situ processing) based on deep eutectic choline chloride-calcium chloride (Calcoline) at mild temperature of 50 °C in direct contact with air. The Calcoline eutectic mixture shows the calcite production yield of 6.2 mg/ml that is reduced up to 22.6% upon recycling. The eutectic mixture provides an interesting all-in-one system acting as carbon dioxide trapper/adsorbent, solvent to solubilize CO2, and reagent to convert solubilized CO2 into pure calcite nanoparticles with average particle size of 30 nm. The featured properties of the developed method including simplicity, recyclability, mobility, affordability, and sustainability make it feasible for large scale applications by which the simultaneous elimination of CO2 from the environment and conversion of it into value added nano-products will be practicable.

탄산칼슘 생성 균주의 분리 및 다양한 칼슘원에 따른 토양 고결화

The physical method used to prevent a landslide has the risk of environmental pollution. Calcite forming bacteria (CFB) have been received increasing attention as a novel and environmental friendly strategy for the soil improvement. In this study, we selected 11 CFB strains with high calcite production. We also examined survivability and calcite productivity of the strains under various stress conditions to select strains with high resistance to various stresses. Two strains was selected by environment stress. Sphingobacterium sp. KJ-32 and Viridibacillus arenosi B-25 precipitate calcite more than other strains at pH 5 and 15oC respectively. Bio-consolidated soil cakes were made using various calcium salts (calcium chloride, calcium acetate, calcium lactate, calcium gluconate) with mixed culture of 2 strains. Among them, the calcite made using calcium chloride was the largest. These observations demonstrate that this bio-consolidation technology has the potential for eco-friendly prevention of landslide and soil improvement.

Biocementation of Concrete Pavements Using Microbially Induced Calcite Precipitation.

In this study, the feasibility of introducing calcite-forming bacteria into concrete pavements to improve their mechanical performance was investigated. Lysinibacillus sphaericus WJ-8, which was isolated in a previous study and is capable of exhibiting high urease activity and calcite production, was used. When analyzed via scanning electron microscopy (SEM) and X-ray diffraction, WJ-8 showed a significant amount of calcite precipitation. The compressive strength of cement mortar mixed with WJ-8 cells and nutrient medium (urea with calcium lactate) increased by 10% compared with that of the controls. Energy dispersive x-ray spectroscopy analyses confirmed that the increase in strength was due to the calcite formed by the WJ-8 cells.

Trends in catchment processes and lake evolution during the late-glacial and early- to mid-Holocene inferred from high-resolution XRF data in the Yellowstone region

High-resolution records of geochemical data from four lakes in the Greater Yellowstone region were used to investigate watershed and lake history during the late-glacial and early-Holocene periods. Clastic input to regional lakes was high and variable during the early stages of lake development, when the surrounding landscape was geomorphically unstable and sparsely vegetated, and it decreased as vegetation gradually developed in each catchment. The decrease of clastic input was not regionally synchronous but occurred in a time-transgressive pattern from south to north. Long-term organic matter concentration and diatom production were inversely related to catchment erosion during the early stages of lake development and increased as temperatures warmed and in-lake nutrient concentrations increased. Similarly, calcite production usually was low following lake formation and increased over time, driven by climate change and its associated influences on lake-level, algal production, and lake thermal structure. Overall differences in the timing and pattern of geochemical change indicate that once the landscape had stabilized following deglaciation, changes in the geochemical character of the sediments were strongly influenced by local factors.

Green technological approach to synthesis hydrophobic stable crystalline calcite particles with one-pot synthesis for oil–water separation during oil spill cleanup

The process of separating oil and water from oil/water mixtures is an attractive strategy to answer the menace caused by industrial oil spills and oily wastewater. In addition, water coproduced during hydrocarbon exploitation, which can be an economic burden and risk for freshwater resources, can become an important freshwater source after suitable water-oil separation. For oil-water separation purposes, considerable attention has been paid to the preparation of hydrophobic-oleophilic materials with modified surface roughness. However, due to issues of thermodynamic instability, costly and complex methods as well as lack of ecofriendly compounds, most of hydrophobic surface modified particles are of limited practical application. The study presents a facile procedure, to synthesize crystalline particles of calcite, which is the most stable polymorph of CaCO3 from industrial CaCO3 using oleic acid as an additive in a one-pot synthesis method. The XRD results show that the synthesized particles were a well-crystallized form of calcite. The FTIR results reflect the appearance of the alkyl groups from the oleic acid in synthesized particles which promotes the production of calcite with ‘rice shape’ (1.64 μm) (aggregated by spherical nanoparticle of 19.56 nm) morphology with concomitant changes in its surface wettability from hydrophilic to hydrophobic. The synthesized particles exhibited near to super hydrophobicity with ∼99% active ratio and a contact angle of 143.8°. The synthesized hydrophobic calcite particles had an oleophilic nature where waste diesel oil adsorption capacity of synthesized calcium carbonate (HCF) showed a very high (>99%) and fast (7 s) oil removal from oil-water mixture. The functional group of long alkyl chain including of CO bounds may play critical roles for adsorption of diesel oils. Moreover, the thermodynamically stable crystalline polymorph calcite (compared to vaterite) exhibited excellent recyclability. The isothermal study reflects the comparatively high value of correlation coefficient (R2 = 0.94) for the Langmuir isotherm compared to those of the Freundlich isotherm (R2 = 0.82) showed that the adsorption of diesel oil onto the hydrophobic CaCO3 adsorbent was much better described by the Langmuir isotherm. The kinetics study of second-order rate expression (R2 = 0.99) more fitted with the experimental data compare to first-order model (R2 = 0.92). The synthesized calcite exhibited a significant dual oleophilic and hydrophobic nature that can be applicable for oil adsorption/or removal purpose in oil contaminated areas in environment and/or industrial oily wastewater for green, simple, and inexpensive environmental cleanup.

Carbonate biomineralization and heavy metal remediation by calcifying fungi isolated from karstic caves

Microbially induced calcium carbonate precipitation (MICP) is a potential technology for creation of durable calcitic minerals. In the current study, we for the first time explored the potential of calcifying ureolytic fungi isolated from Moondyne cave of Western Australia for their biomineralization, metal and radionuclide remediation potential. Two ureolytic isolates Aspergillus sp. UF3 and Fusarium oxysporum UF8 showed significant production of calcite along with co-precipitation of heavy metal Lead and radionuclide Strontium as carbonates. Carbonic anhydrase production in synergism with urease is also reported. Micrographic results demonstrated association of fungal mycelium with biominerals. The biominerals precipitated by calcifying fungi were found to be calcite, vaterite, aragonite along with carbonates and hydroxides of Lead and Strontium. Effective biomineralization with calcium oxalate, a cheap calcium source is also reported. The results of current study suggest that ureolytic fungi from karstic environments bear immense potential for biomineralization, bioremediation and biorecovery of important metals.

Physiology regulates the relationship between coccosphere geometry and growth phase in coccolithophores

Abstract. Coccolithophores are an abundant phytoplankton group that exhibit remarkable diversity in their biology, ecology and calcitic exoskeletons (coccospheres). Their extensive fossil record is a testament to their important biogeochemical role and is a valuable archive of biotic responses to environmental change stretching back over 200 million years. However, to realise the full potential of this archive for (palaeo-)biology and biogeochemistry requires an understanding of the physiological processes that underpin coccosphere architecture. Using culturing experiments on four modern coccolithophore species (Calcidiscus leptoporus, Calcidiscus quadriperforatus, Helicosphaera carteri and Coccolithus braarudii) from three long-lived families, we investigate how coccosphere architecture responds to shifts from exponential (rapid cell division) to stationary (slowed cell division) growth phases as cell physiology reacts to nutrient depletion. These experiments reveal statistical differences in coccosphere size and the number of coccoliths per cell between these two growth phases, specifically that cells in exponential-phase growth are typically smaller with fewer coccoliths, whereas cells experiencing growth-limiting nutrient depletion have larger coccosphere sizes and greater numbers of coccoliths per cell. Although the exact numbers are species-specific, these growth-phase shifts in coccosphere geometry demonstrate that the core physiological responses of cells to nutrient depletion result in increased coccosphere sizes and coccoliths per cell across four different coccolithophore families (Calcidiscaceae, Coccolithaceae, Isochrysidaceae and Helicosphaeraceae), a representative diversity of this phytoplankton group. Building on this, the direct comparison of coccosphere geometries in modern and fossil coccolithophores enables a proxy for growth phase to be developed that can be used to investigate growth responses to environmental change throughout their long evolutionary history. Our data also show that changes in growth rate and coccoliths per cell associated with growth-phase shifts can substantially alter cellular calcite production. Coccosphere geometry is therefore a valuable tool for accessing growth information in the fossil record, providing unprecedented insights into the response of species to environmental change and the potential biogeochemical consequences.

MİKRONİZE ÖĞÜTME VE KAPLAMA İŞLEMLERİNİN KALSİTİN RENK PARAMETRELERİ ÜZERİNDEKİ ETKİLERİNİN İNCELENMESİ

Calcite (CaCO 3 ) is used as a mineral filler in many industries such as plastics, paper and coating because of its white colour, low iron, silica content and easy grindability after it is ground in the micron sizes. The most important property requested by users is whiteness degree of calcite products. Colour parameters (L*, a*, b*) of calcite ore may change naturally after milling and coating process. The changes and colour difference (∆E) must be calculated from raw material and product. In this study; colour measurements and colour difference (ΔE) calculations are given for calcite ore in Nigde region. Keywords: Calcite, whiteness, colour parameters

KALSİTİN KARIŞTIRMALI BİLYALI DEĞİRMENDE KURU MİKRONİZE ÖĞÜTÜLMESİNDE BAZI İŞLEM PARAMETRELERİNİN ETKİSİNİN ARAŞTIRILMASI

In this study, dry grindability of calcite to micronized sizes in a laboratory scale stirred ball mill was investigated. Within the context, the effects of parameters such as stirrer speed, powder filling ratio, ball filling ratio and grinding aid dosage on product quantity (-5 µm %) were studied. Experiments were carried out using 2 4 full factorial designs. The main and interaction effects were evaluated using Yates’ method. The stirrer speed, ball filling ratio and grinding aid dosage play distinct roles (positive) on product quantity (-5 µm %). Micronized calcite product with a product quantity (-5 µm) of 71.49%, a volumetric surface area of 3.63 m 2 /cm 3 and a mean particle size (d 50 ) of 2.15 µm were obtained in the optimum grinding conditions. Keywords: Calcite, micronized grinding, grinding aid, stirred ball mill

Determination of nutrient values in drying citrus pulp with alternative drying methods

The present study was conducted to develop a drying technology for citrus (orange, lemon and grapefruit) pulps by using scrubber heat source and determination of nutrient values in dried citrus pulps. Scrubber heat source of a calcite production plant was equipped for a drying system which by provided a dried pulp production. Firstly, water content of pulps was reduced to approximately 12% by mechanical press centrifugation. The pulps were then transferred to the vibrio-fluidizer fluid bed. After than pre-dried pulps transferred to rotary drum dryer for three hours and total water content of the pulps was reduced to approximately 8%. Chemical values of powder dried orange, lemon and grapefruit pulps such as DM in the air (926.70, 885.30 and 774.00 g/kg), CP (31.50, 65.70 and 77.00 g/kg), CF (28.50, 12.30 and 14.60 g/kg), EE (204.40, 60.40 and 65.90 g/kg), ME Mcal/kg DM (1.584, 2.492 and 2.356), pH (6.94, 6.96 and 6.93) and percentage of digestibility (61.32, 47.85 and 61.44%) were determined. In conclude, citrus pulps could be used as re-cycled industrial feed in animal nutrition by drying with scrubber heat source dryer.

Environmental drivers of coccolithophore abundance and calcification across Drake Passage (Southern Ocean)

Abstract. Although coccolithophores are not as numerically common or as diverse in the Southern Ocean as they are in subpolar waters of the North Atlantic, a few species, such as Emiliania huxleyi, are found during the summer months. Little is actually known about the calcite production (CP) of these communities or how their distribution and physiology relate to environmental variables in this region. In February 2009, we made observations across Drake Passage (between South America and the Antarctic Peninsula) of coccolithophore distribution, CP, primary production, chlorophyll a and macronutrient concentrations, irradiance and carbonate chemistry. Although CP represented less than 1 % of total carbon fixation, coccolithophores were widespread across Drake Passage. The B/C morphotype of E. huxleyi was the dominant coccolithophore, with low estimates of coccolith calcite (∼ 0.01 pmol C coccolith−1) from biometric measurements. Both cell-normalised calcification (0.01–0.16 pmol C cell−1 d−1) and total CP (< 20 µmol C m−3 d−1) were much lower than those observed in the subpolar North Atlantic where E. huxleyi morphotype A is dominant. However, estimates of coccolith production rates were similar (0.1–1.2 coccoliths cell−1 h−1) to previous measurements made in the subpolar North Atlantic. A multivariate statistical approach found that temperature and irradiance together were best able to explain the observed variation in species distribution and abundance (Spearman's rank correlation ρ = 0.4, p < 0.01). Rates of calcification per cell and coccolith production, as well as community CP and E. huxleyi abundance, were all positively correlated (p < 0.05) to the strong latitudinal gradient in temperature, irradiance and calcite saturation states across Drake Passage. Broadly, our results lend support to recent suggestions that coccolithophores, especially E. huxleyi, are advancing polewards. However, our in situ observations indicate that this may owe more to sea-surface warming and increasing irradiance rather than increasing CO2 concentrations.

Chemical and physical controls on the transformation of amorphous calcium carbonate into crystalline CaCO3 polymorphs

Calcite and other crystalline polymorphs of CaCO3 can form by pathways involving amorphous calcium carbonate (ACC). Apparent inconsistencies in the literature indicate the relationships between ACC composition, local conditions, and the subsequent crystalline polymorphs are not yet established. This experimental study quantifies the control of solution composition on the transformation of ACC into crystalline polymorphs in the presence of magnesium. Using a mixed flow reactor to control solution chemistry, ACC was synthesized with variable Mg contents by tuning input pH, Mg/Ca, and total carbonate concentration. ACC products were allowed to transform within the output suspension under stirred or quiescent conditions while characterizing the evolving solutions and solids. As the ACC transforms into a crystalline phase, the solutions record a polymorph-specific evolution of pH and Mg/Ca.The data provide a quantitative framework for predicting the initial polymorph that forms from ACC based upon the solution aMg2+/aCa2+ and aCO32−/aCa2+ and stirring versus quiescent conditions. This model reconciles discrepancies among previous studies that report on the nature of the polymorphs produced from ACC and supports the previous claim that monohydrocalcite may be an important, but overlooked, transient phase on the way to forming some aragonite and calcite deposits. By this construct, organic additives and extreme pH are not required to tune the composition and nature of the polymorph that forms.Our measurements show that the Mg content of ACC is recorded in the resulting calcite with a ≈1:1 dependence. By correlating composition of these calcite products with the Mgtot/Catot of the initial solutions, we find a ≈3:1 dependence that is approximately linear and general to whether calcite is formed via an ACC pathway or by the classical step-propagation process. Comparisons to calcite grown in synthetic seawater show a ≈1:1 dependence. The relationships suggest that the local Mg2+/Ca2+ at the time of precipitation determines the calcite composition, independent of whether growth occurs via an amorphous intermediate or classical pathway for a range of supersaturations and pH conditions.The findings reiterate the need to revisit the traditional picture of chemical and physical controls on CaCO3 polymorph selection. Mineralization by pathways involving ACC can lead to the formation of crystalline phases whose polymorphs and compositions are out of equilibrium with local growth media. As such, classical thermodynamic equilibria may not provide a reliable predictor of observed compositions.

Diversity and biodeteriorative potential of fungal dwellers on ancient stone stela

Biodeterioration caused by fungal colonizers on an ancient stone stela, excavated from the former Roman settlement (Eastern Serbia) was investigated. According to selected biodeterioration elements, average deterioration index was assessed (0.8), prompting the need for conservation. Fungal somatic and reproductive structures, along with lichen thalli and moss fragments, were detected on the surface using different microscopy and cultivation methods. In situ microscopy on the site was implemented, for the first time, in the study of stone monuments. Biodeteriorative potential of 5 selected isolates was tested using qualitative biochemical tests, SEM-EDS and XRPD analyses. Fusarium proliferatum and Penicillium crustosum altered the pH value in broth minimal medium. Pigment production was demonstrated for F. proliferatum, while P. crustosum showed potential for calcite dissolution. All isolates induced biomineralization on solid medium with calcium acetate, where weddellite, calcite and subordinate whewellite crystals were confirmed via SEM-EDS and XRPD. Weddellite and calcite production was documented for P. crustosum in solid medium with calcium carbonate. Conservation treatment was carried out with benzalkonium chloride-based biocide, in addition to mechanical treatment. After conservation, in situ microscopy showed deteriorated stone surface covered with residual lichen thalli fragments, while mycelium and reproductive structures of micromycetes were not detected.

Species-specific calcite production reveals Coccolithus pelagicus as the key calcifier in the Arctic Ocean

Through the production and export of their calcite coccoliths, coccolithophores form a key component of the global carbon cycle. Despite this key role, very little is known about the biogeochemical role of different coccolithophore species in terms of calcite production, and how these species will respond to future climate change and ocean acidification. Here we present the first study to estimate species-specific calcite production, from samples collected in the Arctic Ocean and subarctic Iceland Basin in June 2012. We show that although the coccolithophorid Coccolithus pelagicus comprised only a small fraction of the total community in terms of abundance (2%), our estimates indicate that it was the major calcite producer in the Arctic Ocean and Iceland Basin (57% of total calcite production). In contrast, Emiliania huxleyi formed 27% of the total abundance and was responsible for only 20% of the calcite production. That C. pelagicus was able to dominate calcite production was due to its relatively high cellular calcite content compared with the other species present. Our results demonstrate for the first time the importance of investigating the complete coccolithophore community when considering pelagic calcite production, as relatively rare but heavily calcified species such as C. pelagicus can be the key calcite producers in mixed communities. The response of C. pelagicus to ocean acidification and climate change has the potential therefore to have a major impact on carbon cycling within the North Atlantic and Arctic Ocean.

Compressive Strength and Water Penetration of Concrete with <i>Enterococcus faecalis</i> and Calcium Lactate

This paper presents the compressive strength and water penetration of Bioconcrete with calcium lactate. The bacteria used in this concrete is Enterococcus faecalis, which was isolated and enriched to suit the concrete environment. Bioconcrete is a sustainable and environmentally friendly method to improve concrete properties, but the natural production of calcite by the bacteria is limited. Therefore, the objective of this research is to add in calcium lactate as additional food source for the bacteria and determine the effect on the compressive strength and water penetration of concrete. The Bioconcrete is fabricated in the standard size of 150mm × 150mm × 150mm cubes. The calcium lactate added into the mix is in concentrations of 0.001 mol/l, 0.005mol/l and 0.01 mol/l measured according to the amount of water used in fabrication. Both compressive strength and water penetration is tested after the 28th day by using Universal Testing Machine (UTM) and Water Permeability testing machine respectively. It is found that by adding calcium lactate into Bioconcrete, the compressive strength improves by a maximum of 16.4% which is 41.9 Mpa using the concentrations of 0.005 mol/l of calcium lactate. Compared to control which was 36 Mpa and concrete with only Enterococcus faecalis of 38.2 Mpa. The water penetration has a similar trend of decreasing the water penetration of concrete with Enterococcus faecalis and calcium lactate. A maximum decrease of water penetration is from calcium lactate of concentration 0.01 mol/l of 26.2% which is 8.7 cm compared to control of 11.8 cm and concrete with only Enterococcus faecalis of 9.2 cm. Adding calcium lactate as an additional food source for bacteria in concrete has positive results and further study with the same concept is encouraging

The summer distribution of coccolithophores and its relationship to water masses in the East China Sea

Coccolithophores are calcifying phytoplankton belonging to the phylum Haptophyta, and are thought to play an important role in the marine carbon cycle through the production and export of organic carbon and calcite. A quantitative scanning electron microscope study of coccolithophores was conducted to survey the spatial distribution of coccolithophore communities in surface water covering the continental shelf of the East China Sea (ECS) during the summer of 2014. The abundance of haptophytes was also revealed by fluorescence in situ hybridization with an 18S rRNA-specific probe. The abundance of coccolithophores in the surface-water ranged from 3.7 to 82.8 cells mL−1, contributing a mean 7.0 % to haptophyte abundance. Four distinct coccolithophore groups (A, B, C, and D) were categorized based on similarities of the coccolithophore communities among the stations. Group A was located in the north of the ECS in the Yellow Sea Mixed Water area, where coccolithophore abundance was low. Group B was dominated by Gephyrocapsa oceanica and was located in the south of the ECS in the Taiwan Warm Current. Group C represented the inner shelf assemblages, with Emiliania huxleyi as the major dominant species, and was influenced by the Changjiang discharges. Group D represented the Kuroshio assemblages, with communities dominated by E. huxleyi and Umbellosphaera tenuis in the outer shelf region. These results suggest that coccolithophores tend to migrate with the water masses in the ECS during the summer.