Calcium Carbonate Shells Research Articles

Calcification in sea urchin larvae is associated with low metabolic costs.

The energetic costs to generate calcium carbonate skeletons and shells in marine organisms remain largely speculative due to the scarcity of empirical data. However, this information is critical to estimate energetic limitations of marine calcifiers that can explain their sensitivities to changes in sea water carbonate chemistry in past, present and future marine systems. The cost of calcification was evaluated using larval stages of the purple sea urchin, Strongylocentrotus purpuratus. We developed a skeleton re-mineralization assay, in which the skeleton was dissolved in live larvae followed by a re-mineralization over a few days. During skeleton re-mineralization, energetic costs were estimated through the measurement of key metabolic parameters including whole animal metabolic rates, citrate synthase (CS) enzyme activities and mRNA expression as well as mitochondrial densities in the calcifying primary mesenchyme cells (PMCs). Minor increases in a CS activity and a 10-15% increase in mitochondrial densities in PMCs were observed in re-mineralizing larvae as compared to control larvae. Re-mineralization under three different pH conditions (pH 8.1, pH 7.6 and pH 7.1) decreased with decreasing pH accompanied by pronounced increases in CS expression levels and increased mitochondrial densities in PMCs at pH 7.6. Despite a prominent increase in mitochondrial density of primary mesenchyme cells, particularly in the calcifying cohort of this cell type, this work demonstrated a low overall metabolic response to increased mineralization rates on the whole animal level under both, high and low pH conditions. We conclude that calcification in sea urchin larvae is compromised under low pH conditions, associated with low energetic efforts to fuel compensatory processes.

Effect of emulsification step on calcium carbonate encapsulated eicosane and incorporation into geopolymer

AbstractThe effect of the emulsification process of the organic n‐eicosane as a phase change material (PCM) in an aqueous solution of sodium dodecyl sulfate (SDBS) as a surfactant has been studied regarding the properties of the CaCO3 microcapsules. Such microcapsules aim to limit interactions between the PCM and the matrix (i.e., leakage and unwanted reactions). Optical and scanning electron microscopy (SEM) shows that the mean size of the n‐eicosane capsule is of the order of 5 μm. However, large non‐spherical objects which could be clusters of flocculated capsules or the results of encapsulation of coalescing n‐eicosane droplets, are observed, particularly when mechanical stirring (MS) is used rather than when an ultra‐turrax (UT) or sonotrode (S) is used in the initial emulsification step. These large, partially encapsulated objects could be the cause of the poor results in leakage tests. It is possible to encapsulate n‐eicosane inside a calcium carbonate shell, with a greater than 50% encapsulation ratio. The yield of encapsulated n‐eicosane measured by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) is similar and shows that 55% n‐eicosane core in CaCO3 shell can be produced. Up to 33 wt.% CaCO3 microcapsules (with 55% n‐eicosane content) have been successfully incorporated into fresh geopolymer paste. This incorporation of 18% (55% × 33%) of PCM does not modify the hardening conditions of the geopolymer since demolding was possible after 2 days at room temperature. DSC curves confirm that the melting reaction with n‐eicosane is conserved inside the hardened geopolymer.

Encapsulation of alkali metal catalysts through in-situ formation of calcium carbonate shells for transportation by water

Alkali metal catalysts show great application potential in the gasification process of coal attributed to their characteristics of high activity and reusability. However, this type of catalysts has strong water absorption, which causes the agglomerating during storage and limits pipeline transportation by water. In order to solve the hydration of alkali metal catalysts and to release them at the target temperatures, they were encapsulated by cost effective and environment friend inorganic materials. The capsules were fabricated through in situ formation of calcium carbonate as shell. The water resistance, water erosion resistance and shell rupture temperature of the capsules were tested. And the effect of temperature on the properties of capsules was studied. The microstructure and composition were characterized by SEM and XRD. The results showed that the best performance of the capsules was obtained after heat treatment at 600 °C, with the pH of catalyst solution was reduced from 13.65 to 10.89 before and after encapsulation. The percentage of capsule breakage after 2 h of water scouring was 8.46 %. And the catalysts were fully released between 700–750 °C due to the crack of shell. The shell was composed mainly of CaCO3-AlPO4-Al4(P2O7)3. The shell was porous in the middle, gradually denser outwards, and eventually formed a dense layer in the outer layer. This was attributed to the volume expansion caused by the reaction of calcium oxide and calcium hydroxide to form calcium carbonate. This study provides a novel approach for the transportation of alkali metal catalyst and expands its application in coal gasification.

Precise Regulation of Reactive Oxygen Species in Tumor Microenvironment for Alleviating Inhibitory Immunogenic Cell Death.

High level of C (ROS) within the tumor microenvironment (TME) not only damage tumor cells but also diminish the efficacy of immunogenic cell death (ICD) and the activity of tumor-infiltrating T lymphocytes, thereby limiting the effectiveness of immunotherapy. Therefore, precise modulation of ROS level is crucial to effectively eliminate tumor cells and activate ICD-induced immunotherapy. Here, an intelligent yolk shell nanoplatform (SPCCM) that features calcium carbonate shells capable of decomposing under acidic TME conditions, thereby releasing the natural antioxidant proanthocyanidins (PAs) and the photosensitizer Ce6 is designed. PAs scavenge ROS within tumors, extending the survival time of T lymphocytes, while Ce6, as an ICD inducer, generates high ROS concentrations upon laser irradiation, thus reaching the toxic threshold within tumor cells and inducing apoptosis. The resulting apoptotic cells serve as tumor-associated antigens, promoting dendritic cells (DCs) maturation, and activating ICD. By effectively neutralizing ROS in the TME, PAs sustainably reduce ROS level, thereby enhancing DCs activation and restoring antitumor immune cell activity suppressed by ROS (resulting in an eightfold increase in DCs activation). This study demonstrates effective synergistic effects between photodynamic therapy and immunotherapy by precisely modulating ROS level.

Multiple carbonate system parameters independently govern shell formation in a marine mussel

Calcification is vital to marine organisms that produce calcium carbonate shells and skeletons. However, how calcification is impacted by ongoing environmental changes, including ocean acidification, remains incompletely understood due to complex relationships among the carbonate system variables hypothesized to drive calcification. Here, we experimentally decouple these drivers in an exploration of shell formation in adult marine mussels, Mytilus californianus. In contrast to models that focus on single parameters like calcium carbonate saturation state, our results implicate two independent factors, bicarbonate concentration and seawater pH, in governing calcification. While qualitatively similar to ideas embodied in the related substrate-inhibitor ratio (bicarbonate divided by hydrogen ion concentration), our data highlight that merging bicarbonate ion and hydrogen ion concentrations into a simple quotient obscures important features of calcification. Considering a dual-parameter framework improves mechanistic understanding of how calcifiers interact with complex and changing chemical conditions.

Photothermal superhydrophobic composite coatings based on n-tetradecane@CaCO3/TiN microcapsules for anti-/deicing

Ice accumulation on equipment and building surfaces is a scientific and modern engineering problem to be solved urgently. Compared to the energy-intensive and expensive active anti-/deicing approaches, passive energy-free technology based on advanced materials and surface engineering has received more attention. Herein, we successfully encapsulated n-tetradecane in calcium carbonate shell by in situ precipitation method, and the microcapsules reveal good energy-storage capability (99.9 %), latent heat (108.1 J g−1), and long-term durability. Combining the microcapsule with low-cost titanium nitride and low-surface-energy PDMS (polydimethylsiloxane) materials, the multifunctional superhydrophobic composite coating has been successfully prepared. The composite coating surface possesses strong absorption in UV–vis-NIR bands with high photothermal conversion and storage capability. The results indicate that the composite coating successfully prolongs the icing time compared to traditional photothermal superhydrophobic surfaces, and accelerates the melting of ice droplets under light illumination, which demonstrates great potential in both anti-icing and deicing applications.

An analysis of seashell calcium carbonate dissolution caused by ocean acidification based on chemistry equilibrium

Ocean acidification is a serious marine ecosystem problem caused by the abundant human emission of CO2. It is now a prevalent cognition that the dissolution of CO2 tends to raise the concentration of H+ in the ocean and therefore make it more acidic. Anthropogenic CO2 emission exacerbates the situation. This will then lead to another obvious problem---the dissolution of calcium carbonate shells of certain ocean organisms. This article will present a brief dissolution model, which can provide an analysis of the acidification effects from two perspectives---both the forming and the dissolution of seashells. The model shows an exponential relationship between the dissolved Ca2+ concentration and the pH of seawater. It also presents the anticipation regarding a dissolution turning point in (approximately) 2090 under the RCP8.5 scenario. This turning point indicates an abrupt acceleration of calcium carbonate shells dissolution. The result depicts the drastic but possible change in the seawater solution system and gives a warning signal of a probable deadline for us to control the CO2 emission. Hopefully, it will attract more scholars to pay attention to this topic and figure out methodologies to avoid the possible tragedy.

Advancing responsible genomic analyses of ancient mollusc shells.

The analysis of the DNA entrapped in ancient shells of molluscs has the potential to shed light on the evolution and ecology of this very diverse phylum. Ancient genomics could help reconstruct the responses of molluscs to past climate change, pollution, and human subsistence practices at unprecedented temporal resolutions. Applications are however still in their infancy, partly due to our limited knowledge of DNA preservation in calcium carbonate shells and the need for optimized methods for responsible genomic data generation. To improve ancient shell genomic analyses, we applied high-throughput DNA sequencing to 27 Mytilus mussel shells dated to ~111-6500 years Before Present, and investigated the impact, on DNA recovery, of shell imaging, DNA extraction protocols and shell sub-sampling strategies. First, we detected no quantitative or qualitative deleterious effect of micro-computed tomography for recording shell 3D morphological information prior to sub-sampling. Then, we showed that double-digestion and bleach treatment of shell powder prior to silica-based DNA extraction improves shell DNA recovery, also suggesting that DNA is protected in preservation niches within ancient shells. Finally, all layers that compose Mytilus shells, i.e., the nacreous (aragonite) and prismatic (calcite) carbonate layers, with or without the outer organic layer (periostracum) proved to be valuable DNA reservoirs, with aragonite appearing as the best substrate for genomic analyses. Our work contributes to the understanding of long-term molecular preservation in biominerals and we anticipate that resulting recommendations will be helpful for future efficient and responsible genomic analyses of ancient mollusc shells.

Acidic Apple Snails: Effects of Climate Change on the Mechanical Properties of an Invasive Gastropod.

Climate change can directly and indirectly affect species distribution. Warming may allow for invasive species, such as apple snails, to migrate to higher latitudes where temperatures are more conducive to their survival and invasion success. Higher temperatures and lower pH ranges have been previously documented to affect the form and function of calcium carbonate shells, which serve many functions, including protection from predators and thermoregulation. This study aimed to quantify differences in the morphology and mechanical properties of invasive apple snail, Pomacea maculata, shells after altering temperature and pH. We mechanically tested shells among three five-week treatments: control, higher temperature, and lower pH. Ultimate Strength increased in shells that were exposed to higher temperatures, but Young's Modulus and Peak Load did not differ among control, temperature, and pH treatments. Apple snails in higher temperature tanks increased their shell length over the five-week trials. Although snail morphometrics did not differ between sexes, male shells exhibited a higher Peak Load, Young's Modulus, and Ultimate Strength compared to female shells. Our findings are consistent with previous gastropod studies, in that a lower pH is associated with a decrease in shell size, and higher temperatures yield larger snail shells with a higher ultimate strength. Peak Load did not significantly differ among treatments, which suggests that the cross-sectional area is relatively important when considering this species mechanical performance today and in future climates. Due to the intense nutritional and calcium demands of egg production, female snails may be more susceptible to weakened shells due to low pH environments caused by climate change.

Nano‐Calcium Carbonate with Core–Shell Structure was Prepared by Dopamine Chelation Using Pluronic F‐127 as Template

AbstractHerein, a new template carbonization method is used to prepare calcite‐type nano‐calcium carbonate (CaCO3) with a core–shell structure using calcium hydroxide as a solute and Pluronic F‐127 as a templating and pore‐forming agent. Dopamine hydrochloride is added to control the size of calcium hydroxide particles. The morphology, particle size, and crystal type of CaCO3 are characterized via transmission electron microscopy, X‐ray diffraction, nanoparticle size, and zeta potentiometer. The creation of core–shell calcium carbonate nanoparticles is examined in relation to reaction circumstances (i.e., additive sequence, additive amount, and additive mixing time), carbonization temperature, liquid flow rate, and templates with varying chain lengths. Furthermore, a discussion is held regarding the formation mechanism of spherical core–shell calcium carbonate that is created using the innovative template carbonization method. The results show that the order, amount, liquid flow rate, and template type of additives have a significant effect on the crystal shape of calcium carbonate nanoparticles. The mixing time of additives has a significant effect on the particle size of calcium carbonate nanoparticles. Interestingly, the thickness of the shell depends on the carbonization temperature, and too slow or too fast flow rate will lead to the formation of cyclic calcium carbonate nanoparticles.

Synthesis of drug-loaded H-ZIF-8@CaCO3-PEG nanocarrier for synergistic therapy

In this study, we synthesized DOX-loaded H-ZIF-8@CaCO3-PEG nanocarrier, which combined with calcium overload and photothermal therapy (PTT) for synergistic therapy. The nanocarrier comprised a PEG modified calcium carbonate (CaCO3) shell and a hollow imidazolate zeolite skeleton (H-ZIF-8) core, in which the chemotherapy drug doxorubicin hydrochloride (DOX) and photosensitizer indocyanine green (ICG) were simultaneously co-loaded. In vitro cellular experiments revealed that the lethality of DOX&ICG@H-ZIF-8@CaCO3-PEG against tumor cells was significantly higher than that of the single chemotherapy owing to the combination with chemotherapy and photothermal therapy as well as calcium overloading. This drug-loaded nanocarrier exhibits notable characteristics such as exceptional stability, elevated drug loading capacity and efficient release of the loaded drug, which provides a promising perspective for efficient synergistic therapy.

Ocean acidification detrimentally affects mineralization and photosynthetic efficiency of the brown alga Padina pavonica at a CO2 vent

Increasing atmospheric CO2 concentrations are causing ocean acidification potentially leading to significant consequences for marine organisms, particularly those that build calcium carbonate skeletons, shells, and tests. In the present study, we examined the effects of decreasing pH on the photosynthetic efficiency and spectral reflectance of the calcifying alga Padina pavonica naturally occurring along a natural pH gradient generated by a CO2 vent near the Island of Panarea (Italy). Based on the photoacoustic determination of photosynthetic light energy utilization efficiency, we found that the photosynthetic efficiency of P. pavonica decreased with decreasing pH. In the most acidified sites, calcium carbonate across the algae decreased while the changes in absorption light at 483 nm (carotenoids) in relation to green light (562 nm) ratio indicate an increase in the contribution of carotenoids to algal pigments towards the more acidic sites. Here we show, for the first time, the effects of seawater acidification on the optical properties of a Mediterranean calcifying phototroph under low pH conditions at CO2 vents.

Sea butterflies in a pickle: reliable biomarkers and seasonal sensitivity of Limacina retroversa to ocean acidification in the Gulf of Maine.

The passive dissolution of anthropogenically produced CO2 into the ocean system is reducing ocean pH and changing a suite of chemical equilibria, with negative consequences for some marine organisms, in particular those that bear calcium carbonate shells. Although our monitoring of these chemical changes has improved, we have not developed effective tools to translate observations, which are typically of the pH and carbonate saturation state, into ecologically relevant predictions of biological risks. One potential solution is to develop bioindicators: biological variables with a clear relationship to environmental risk factors that can be used for assessment and management. Thecosomatous pteropods are a group of pelagic shelled marine gastropods, whose biological responses to CO2 have been suggested as potential bioindicators of ocean acidification owing to their sensitivity to acidification in both the laboratory and the natural environment. Using five CO2 exposure experiments, occurring across four seasons and running for up to 15days, we describe a consistent relationship between saturation state, shell transparency and duration of exposure, as well as identify a suite of genes that could be used for biological monitoring with further study. We clarify variations in thecosome responses due to seasonality, resolving prior uncertainties and demonstrating the range of their phenotypic plasticity. These biomarkers of acidification stress can be implemented into ecosystem models and monitoring programmes in regions where pteropods are found, whilst the approach will serve as an example for other regions on how to bridge the gap between point-based chemical monitoring and biologically relevant assessments of ecosystem health.

Preparation of PW@CaCO3 phase change microcapsules modified by ZnO nanoparticles with excellent photocatalytic and thermal properties

We utilized an in-situ polymerization method to dope zinc oxide (ZnO) nanoparticles onto the surface of the inorganic calcium carbonate (CaCO3) shell capable of encapsulating paraffin wax (PW) cores, and synthesized a novel bifunctional microcapsule, which can be applied to optical catalysis and thermal energy storage. The PW@CaCO3/ZnO microcapsules with the varying ZnO nanoparticles were successfully synthesized. The micromorphology, chemical components, thermal properties, and photocatalytic applications of microcapsules doped with various ZnO concentrations were investigated. The results indicated that the PW@CaCO3/0.03%ZnO (i.e., the mass ratio of ZnO to PW of 0.03 wt%) exhibited the greatest thermal storage effectiveness and capacity with regard to all the samples. Under exposure to a particular wavelength of ultraviolet light, the PW@CaCO3/ZnO microcapsules can degrade the methylene blue dye solution by photocatalysis. The photocatalytic effect of the dye solution with PW@CaCO3/1.50%ZnO was the best after 12 h of exposure to ultraviolet radiation, and the degradation rate reached 98.97 %. In the spheres of energy conservation and environmental preservation, the PW@CaCO3/ZnO microcapsules offer a wide range of potential applications.

Natural carbonation process in cement paste particles in different relative humidities

Finely ground hardened cement pastes (hcp) under 75 μm were carbonated at varying relative humidities (23–95 % RH) to determine the carbonation rate that minimized CO2 diffusion in the bulk paste. The amounts of portlandite (CH) and calcium carbonate (CC) polymorphs were quantified, and the decalcification and decomposition of C-A-S-H were analyzed using TGA, XRD, mass balance calculation, FTIR, and 29Si MAS NMR spectroscopy. A higher RH accelerated the reaction rate, and CH dissolution stopped midway at 58 % RH or below because of the loss of connectivity with the pore solution in the CC shell around CH. The precipitated CC phase included calcite at high RH, whereas all three polymorphs formed at 58 % or lower RH; amorphous CC were detected at low RH. The decalcification and decomposition of C-A-S-H were observed at 45 % or higher RH; it was rarely carbonated at 33 % or lower RH.

Foraminifera: A Proxy for Ecology, Climate Change and Its Associated Hydro−Environment

Paleocanography, the study of ancient oceans, relies heavily on a wide range of proxies and methodologies to reconstruct past oceanic conditions. Among these tools, foraminifera, microscopic marine organisms with calcium carbonate shells, have played a pivotal role. Over the years, researchers have harnessed the insights provided by foraminifera to unlock the secrets of Earth's oceans throughout geological history. This comprehensive review explores the various ways in which foraminifera have been employed in paleocanography, shedding light on past climate, ocean circulation, ecology, and more. The application of foraminifera represents a sustainable approach with far-reaching implications for environmental, ecological, and geological research. Foraminifera, microscopic marine protists characterized by calcium carbonate shells, serve as valuable indicators of past and present environmental conditions. They are instrumental in the fields of paleoecology, stratigraphy, environmental impact studies, and ocean acidification research. This abstract highlights the sustainable aspect of using foraminifera as bioindicators to assess the health of marine ecosystems, monitor climate change, and investigate the impact of human activities. By providing insights into the past and present, foraminifera contribute to informed decision-making in conservation, resource management, and addressing critical environmental challenges. Their application stands as a testament to the enduring value of these microorganisms in understanding and safeguarding our planet's natural resources and ecosystems, exemplifying the sustainability of scientific research driven by a profound respect for the Earth's history and future well-being.

Media Representations and Farmer Perceptions: A Case Study of Reporting on Ocean Acidification and the Shellfish Farming Sector in British Columbia, Canada

ABSTRACT Ocean Acidification (OA) creates corrosive conditions that impact organisms that produce calcium carbonate shells, such as clams and oysters. The Salish Sea, a body of water where much of British Columbia's shellfish farming sector operates, has been growing more corrosive. We present a case study of reporting on OA and the shellfish farming sector in British Columbia, Canada. We convey results from a survey with shellfish farmers and a thematic analysis that sought to understand how the science and local implications of OA were presented in a sample of media articles. All articles employed narratives of crisis, and slightly over 75% conveyed scientific uncertainty. Just over 55% incorporated interviews with one or more of scientists, shellfish sector representatives, and shellfish farmers. Survey findings reveal that respondents saw OA as a threat but often deprioritized it relative to a wider range of operational challenges. We introduce “situatedness” and draw in ideas from “solutions journalism” to expand. While telling stories about people and places is important, we conclude that new opportunities for locally salient climate change reporting stand to be unlocked by looking beyond boundaries typically drawn around “the local” and the sorts of credentials typically ascribed to “environmental experts”.

Yolk-Shell Encapsulation of Cells by Biomimetic Mineralization and Visible Light-Induced Surface Graft Polymerization.

The pursuit of low-cytotoxicity modification strategies represents a prominent avenue in cell coating research, holding immense significance for the advancement of practical living cell-related technologies. Here, we presented a novel method to fabricate encapsulated yeast cells with a yolk-shell structure by biomimetic mineralization and visible-light-induced surface graft polymerization. In this approach, an amorphous calcium carbonate (ACC) shell was first deposited on the surface of a yeast cell (cell@ACC) modified with 4 layers of self-assembled poly(diallyl dimethylammonium chloride) (PDADMAC)/poly(acrylic acid) (PAA) film using a biomimetic mineralization technique. Subsequently, polyethylenimine (PEI) was absorbed on the surface of cell@ACC by electrostatic interaction. Then, a cross-linked shell was introduced by surface-initiated graft polymerization of poly(ethylene glycol) diacrylate (PEGDA) on cell@ACC under irradiation of visible light using thioxanthone catechol-O,O'-diacetic acid as the photosensitizer. After the removal of the inner ACC shell, the yolk-shell-structured yeast cells (cell@PHS) were obtained. Due to the mild conditions of the strategy, the cell@PHS could retain 98.81% of its original viability. The introduction of the shell layer significantly prolonged the lag phase of yeast cells, which could be tuned between 5 and 25 h by regulating the thickness of the shell. Moreover, the cell@PHS showed improved resistance against lyticase due to the presence of a protective shell. After 30 days of storage, the viability of cell@PHS was 81.09%, which is significantly higher than the 19.89% viability of native yeast cells.

The first healed injury in a hyolith operculum.

The Palaeozoic sediments of the Barrandian area are globally well-known as a classic example of rocks characterised by an abundant skeletal marine fauna, including well-preserved remains of hyoliths. Several tens specimens of malformed invertebrates such as trilobites, cephalopods and gastropods have been collected and documented from Cambrian to Devonian clastic sediments and carbonates in this area. However, no malformed hyolith specimen has yet been recorded. Hyoliths are Palaeozoic animals with small calcium carbonate shells composed of the conch (= oblong, conical and bilaterally symmetrical shell of diverse cross section and aperture at its wide end) and the operculum (= cap closing the conch aperture). Here we describe an operculum showing regeneration after non-lethal predatory attack in the Ordovician hyolith Elegantilites custos. This is the first record of regeneration in a hyolith operculum that has been repaired after a failed durophagous attack. Epibenthic/infaunal predatory echinoderms, such as ophiuroids, are considered as potential culprits.

Investigation on mechanical behaviour of calcium carbonate and groundnut shell filler added cocos nucifera fiber reinforced polyester composites

Natural fiber-reinforced composites have become superior materials due to their potential to replace synthetic fibers, because of their low density, lightweight, low-cost biodegradability, and high specific strength. This study finds out the mechanical properties of coir fiber-reinforced polyester matrix composites with the addition of filler content. The composites were fabricated using a compression molding machine with a dimension of (300x300x3) mm. Totally 6 laminates were fabricated with variations in fiber and filler content. The fabricated composites were cut the different types of ASTM standards. The mechanical properties of the calcium carbonate and groundnut shell-filler added coconut fiber- reinforced polyester composites were studied. The maximum tensile, flexural, and impact strength was achieved by 29.6 MPa, 56.8 MPa, and 34.8 kJ/m2 respectively. The addition of fillers in composite increases the mechanical strength. Fractography studies were used to analyze the fracture behaviour in fiber-reinforced composites. Coir fiber-reinforced composite materials are applicable for low load-bearing applications