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Inorganic minerals that form via regulated biological processes exhibit remarkable properties. This is due to the involvement of macromolecules that control biomineralization. Even though the interactions of these biopolymers with solid mineral phases are intensely studied, not much is known about their involvement in the preceding steps of intracellular transport of the mineral building blocks. In this work, the model system of coccolith calcite crystallization is utilized to address the role of mineral‐associated polysaccharides in the transport of calcium ions. State‐of‐the‐art cryo‐electron tomography is used to image in situ ion‐rich dense phases in the wild‐type and in two mutant strains, defected in coccolith production. The results show that the abundance and solubility of the calcium‐rich condensates need to be finely tuned for proper crystallization. When the native macromolecular assemblage is compromised, calcium is still present in the calcifying fluid as a solute, but this is not sufficient for coccolith development. These results suggest that biomineralizing systems achieve superior regulation of crystallization due to the use of dense macromolecule‐rich phases. [ABSTRACT FROM AUTHOR]

In mid-May 2020, a coccolithophore bloom of Gephyrocapsa oceanica Kamptner, 1943 was observed in Sagami Bay, Japan, possibly for the first time in 25 years. This species is a common yet elusive taxon in the waters around Japan, but there has only been one report of a bloom observation in Sagami Bay in 1995. The G. oceanica bloom in 2020 was observed by the combined approach of the JAXA ocean color remote sensing satellite "Shikisai" and field surveys. The true-color RGB images from the satellite showed the initial bloom in Tokyo Bay appears to have advected into Sagami Bay on May 5. On May 15, ad hoc field sampling was conducted based on visual confirmation from the shore. Nitrate, nitrite and phosphate concentrations at the sea surface were 3.28 µM, 0.11 µM and 0.29 µM, respectively, and higher than the median of May from 1997 to 2019. Chlorophyll a concentration was 2.23 µg L-1 at the sea surface, and cell density was 5.3 × 10³ cells mL-¹. The large bloom appears to have reached the western shorelines of the bay, and dispersed counterclockwise within the bay. The bloom reached an estimated 1119.02 km² surface expression on May 17, and completely disappeared by May 24. Further, the median value of 19'-hexanoyloxyfucoxanthin (a signature pigment of haptophytes, including coccolithophores) concentration has been increasing from 2017 to 2020, and the coastal area of Sagami Bay may have changed to a region favorable for haptophytes. [ABSTRACT FROM AUTHOR]

Coccolithophores are well-known haptophytes that produce small calcium carbonate coccoliths, which in turn contribute to carbon sequestration in the marine environment. Despite their important ecological role, only two of eleven haptophyte plastid genomes are from coccolithophores, and those two belong to the order Isochrysidales. Here, we report the plastid genomes of two strains of Ochrosphaera neapolitana (Coccolithales) from Spain (CCAC 3688 B) and the USA (A15,280). The newly constructed plastid genomes are the largest in size (116,906 bp and 113,686 bp, respectively) among all the available haptophyte plastid genomes, primarily due to the increased intergenic regions. These two plastid genomes possess a conventional quadripartite structure with a long single copy and short single copy separated by two inverted ribosomal repeats. These two plastid genomes share 110 core genes, six rRNAs, and 29 tRNAs, but CCAC 3688 B has an additional CDS (ycf55) and one tRNA (trnL-UAG). Two large insertions at the intergenic regions (2 kb insertion between ycf35 and ycf45; 0.5 kb insertion in the middle of trnM and trnY) were detected in the strain CCAC 3688 B. We found the genes of light-independent protochlorophyllide oxidoreductase (chlB, chlN, and chlL), which convert protochlorophyllide to chlorophyllide during chlorophyll biosynthesis, in the plastid genomes of O. neapolitana as well as in other benthic Isochrysidales and Coccolithales species, putatively suggesting an evolutionary adaptation to benthic habitats. [ABSTRACT FROM AUTHOR]

The marine biological calcification and photosynthesis, which can produce particulate inorganic and organic carbon (PIC and POC), have the opposite effects on seawater pCO2. Coccolithophores are a kind of marine unicellular algae with both of the two biological processes, and PIC and POC productions of them can shape the water column rain ratio as a dominant driver for Earth's carbon cycle. Thus, the changes in ancient coccolithophore PIC:POC can be important for the paleoceanographic and paleoclimatic studies of carbon cycle modeling. However, ancient coccolithophore PIC:POC is poorly constrained because of the occasional occurrences of intact coccospheres in deep ocean sediments, as detached coccoliths are commonly the remnants of fossilized coccolithophores. Here, we carry out the biometric analysis of coccosphere and coccolith from the living cells of Emiliania huxleyi and Gephyrocapsa oceanica in the South China Sea, and confirm a significant correlationship between their PIC:POC and lateral coccolith aspect ratio (ARL). ARL here is defined by the ratio of mean coccolith thickness with respect to coccolith length. A linear regression is given, PIC:POC=15.023∗ARL−0.083 $\mathrm{P}\mathrm{I}\mathrm{C}:\mathrm{P}\mathrm{O}\mathrm{C}=15.023\ast A{R}_{L}-0.083$ (R2 = 0.59, n = 121), for the reconstruction of ancient Noelaerhabdaceae coccolithophore PIC:POC based on individual coccoliths in marine sediments. Based on this equation, we reconstruct ancient Noelaerhabdaceae coccolithophore PIC:POC since 14 million years ago (Ma) using published coccolith data, which reveal a long‐term decrease in PIC:POC from 7 to 4 Ma. We suggest that such a change in coccolithophore physiology may be induced by a simultaneous long‐term decline in seawater calcium concentration. Plain Language Summary: Coccolithophores are a kind of marine algae which produce calcium carbonate through calcification. Photosynthesis of coccolithophores uses seawater CO2, on the contrary, calcification releases CO2. Therefore, the relative strength of calcification and photosynthesis, that is termed PIC:POC, can determine whether coccolithophore growth is a net CO2 sink or source. The knowledge of ancient coccolithophore PIC:POC is important to understand the mechanisms of Earth carbon cycle and climate changes in the geological history, as coccolithophores are one of the major components of marine carbon cycle. However, it remains unclear the characters of ancient coccolithophore PIC:POC, because detached or loosened coccoliths, which are the exoskeleton of a coccolithophore cell, are more commonly found in marine sediments, rather than intact coccospheres. Here, based on the biometric analysis of coccosphere and coccolith morphology, we refine a method to estimate ancient coccolithophore PIC:POC based on detached coccolith geometry. Key Points: Coccosphere PIC content is estimated based on coccosphere geometryPIC:POC of Emiliania huxleyi and Gephyrocapsa oceanica is estimated in the modern South China SeaAncient coccolithophore PIC:POC can be estimated by coccolith geometry in sediments [ABSTRACT FROM AUTHOR]

The calcite platelets of coccolithophores (Haptophyta), the coccoliths, are among the most elaborate biomineral structures. How these unicellular algae accomplish the complex morphogenesis of coccoliths is still largely unknown. It has long been proposed that the cytoskeleton plays a central role in shaping the growing coccoliths. Previous studies have indicated that disruption of the microtubule network led to defects in coccolith morphogenesis in Emiliania huxleyi and Coccolithus braarudii. Disruption of the actin network also led to defects in coccolith morphology in E. huxleyi, but its impact on coccolith morphology in C. braarudii was unclear, as coccolith secretion was largely inhibited under the conditions used. A more detailed examination of the role of actin and microtubule networks is therefore required to address the wider role of the cytoskeleton in coccolith morphogenesis. In this study, we have examined coccolith morphology in C. braarudii and Scyphosphaera apsteinii following treatment with the microtubule inhibitors vinblastine and colchicine (S. apsteinii only) and the actin inhibitor cytochalasin B. We found that all cytoskeleton inhibitors induced coccolith malformations, strongly suggesting that both microtubules and actin filaments are instrumental in morphogenesis. By demonstrating the requirement for the microtubule and actin networks in coccolith morphogenesis in diverse species, our results suggest that both of these cytoskeletal elements are likely to play conserved roles in defining coccolith morphology. [ABSTRACT FROM AUTHOR]

We present a new high-resolution reconstruction of annual sea-surface temperatures (SSTa) and net primary productivity (NPP) using novel coccolithophore-based models developed for the Eastern Equatorial Pacific (EEP). We combined published coccolithophore census counts from core-tops in the Eastern Pacific with 32 new samples from the Equatorial region, to derive a new statistical model to reconstruct SSTa. Results show that the addition of the new EEP samples improves existing coccolithophore-based SST-calibrations, and allow reconstructing SSTa in the EEP with higher confidence. We also merged the relative abundance of deep-photic species Florisphaera profunda in the same surface sediment samples with existing calibration datasets for tropical regions, to reconstruct annual NPP. Both temperature and productivity calibrations were successfully applied to fossil coccolith data from Ocean Drilling Project Site 1240, in the EEP. The coccolith-based SSTa estimates show a cooling during the Last Glacial Maximum (LGM) and the Younger Dryas, and warming at the start of the Holocene. This pattern differs in the timing and magnitude of the temperature changes from other available SST-reconstructions based on biogeochemical and faunal proxies. We discuss these discrepancies to be the result of different proxy sensitivities to insolation forcing, seasonal bias, and/or preservation artifacts. Reconstructed annual NPP shows a general decreasing trend from the late last glacial period to recent times, which we relate to the weakening of wind-driven equatorial upwelling towards the Holocene. We also calculated carbon export using our SSTa and NPP reconstructions, and compared to other geochemical-based reconstructions for the same location. Our coupled SSTa-NPP reconstruction provides key data to more fully assess the evolution of primary and export productivity as well as organic carbon burial in the EEP, with implications for its role in global biogeochemical cycles across glacial terminations.

Unicellular marine microalgae are responsible for one of the largest carbon sinks on Earth. This is in part due to intracellular formation of calcium carbonate scales termed coccoliths. Traditionally, the influence of changing environmental conditions on this process has been estimated using poorly constrained analogies to crystallization mechanisms in bulk solution, yielding ambiguous predictions. Here, we elucidated the intracellular nanoscale environment of coccolith formation in the model species Pleurochrysis carterae using cryoelectron tomography. By visualizing cells at various stages of the crystallization process, we reconstructed a timeline of coccolith development. The three-dimensional data portray the native-state structural details of coccolith formation, uncovering the crystallization mechanism, and how it is spatially and temporally controlled. Most strikingly, the developing crystals are only tens of nanometers away from delimiting membranes, resulting in a highly confined volume for crystal growth. We calculate that the number of soluble ions that can be found in such a minute volume at any given time point is less than the number needed to allow the growth of a single atomic layer of the crystal and that the uptake of single protons can markedly affect nominal pH values. In such extreme confinement, the crystallization process is expected to depend primarily on the regulation of ion fluxes by the living cell, and nominal ion concentrations, such as pH, become the result, rather than a driver, of the crystallization process. These findings call for a new perspective on coccolith formation that does not rely exclusively on solution chemistry. [ABSTRACT FROM AUTHOR]

Summary: The development of calcification by the coccolithophores had a profound impact on ocean carbon cycling, but the evolutionary steps leading to the formation of these complex biomineralized structures are not clear. Heterococcoliths consisting of intricately shaped calcite crystals are formed intracellularly by the diploid life cycle phase. Holococcoliths consisting of simple rhombic crystals can be produced by the haploid life cycle stage but are thought to be formed extracellularly, representing an independent evolutionary origin of calcification.We use advanced microscopy techniques to determine the nature of coccolith formation and complex crystal formation in coccolithophore life cycle stages.We find that holococcoliths are formed in intracellular compartments in a similar manner to heterococcoliths. However, we show that silicon is not required for holococcolith formation and that the requirement for silicon in certain coccolithophore species relates specifically to the process of crystal morphogenesis in heterococcoliths.We therefore propose an evolutionary scheme in which the lower complexity holococcoliths represent an ancestral form of calcification in coccolithophores. The subsequent recruitment of a silicon‐dependent mechanism for crystal morphogenesis in the diploid life cycle stage led to the emergence of the intricately shaped heterococcoliths, enabling the formation of the elaborate coccospheres that underpin the ecological success of coccolithophores. See also the Commentary on this article by Mock, 231: 1663–1666. [ABSTRACT FROM AUTHOR]

The crystallographic orientation and its relationship to the morphology of coccoliths were investigated for the Neogene-Quaternary calcareous nannoplankton Umbilicosphaera lineage using scanning electron microscopy (SEM) and electron back-scattered diffraction (EBSD). The c -axis of the calcite forming the distal shield elements was inclined upward at 66–68° (U. sibogae), 65–68° (U. foliosa), 57–58° (U. rotula), and 55–57° (U. patera) from the coccolith plane. Accordingly, the outward dip angle of one of the { 10 1 ¯ 4 } faces forming the surface of the distal shield of U. patera coccolith was shallower than those of U. sibogae and U. foliosa , explaining the nearly flat distal shield and the steep inner slope, formed by another equivalent { 10 1 ¯ 4 } face, around the central opening of U. patera. Our results showed that the evolution from U. rotula to U. patera during the Late Miocene was not accompanied by a change in crystallographic orientation. In contrast, the evolution from U. patera to U. sibogae and U. foliosa during the Pliocene was accompanied by a rotation of the orientation. The crystallographic orientation of calcite nuclei on the baseplate with a combination of other factors would have resulted in species-specific differences in shield shape and suture lines within the same phylogeny, consequently producing morphological diversity in the coccolith throughout geological time. • The crystallographic orientation and its relationship to the morphology of coccoliths were investigated for Umbilicosphaera lineage using SEM-EBSD. • The c-axis of the calcite forming the distal shield elements was inclined upward at 55°–68° from the coccolith plane. • The evolution from U. patera to U. sibogae and U. foliosa was accompanied by a rotation in the crystallographic orientation. • The orientation of the crystals that are first precipitated on the baseplate play an important role in species-specific differences of the coccoliths within the same phylogeny. [ABSTRACT FROM AUTHOR]

Coccolithophores represent a major component of the marine phytoplankton and contribute to the bulk of biogenic calcite formation on Earth. These unicellular protists produce minute calcite scales (coccoliths) within the cell, which are secreted to the cell surface. Individual coccoliths and their arrangements on the cell surface display a wide range of morphological variations. This review explores some of the recent evidence that points to similarities and differences in the mechanisms of calcification, focussing on the transport mechanisms that bring substrates to, and remove products from the site of calcification, together with new findings on factors that regulate coccolith morphology. We argue that better knowledge of these mechanisms and their variations is needed to inform more generally how different species of coccolithophore are likely to respond to changes in ocean chemistry. Coccolithophores, minute single celled phytoplankton are the major producers of biogenic carbonate on Earth. They also represent an important component of the ocean's biota and contribute significantly to global carbon fluxes. Coccolithophores produce intricate calcite scales (coccoliths) internally that they secrete onto their external surface. This review presents some recent key findings on the mechanisms underlying the production of coccoliths. It also considers the factors that regulate the rate of production as well as the variety of shapes of individual coccoliths and their arrangements at the cell surface. Understanding these processes is needed to allow better predictions of how coccolithophores may respond to changing ocean chemistry associated with climate change. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Dimethylsulfoniopropionate (DMSP) is produced in surface seawater by phytoplankton. Phytoplankton culture experiments have shown that nanoeucaryotes (NANO) display much higher mean DMSP-to-Carbon or DMSP-to-Chlorophyll (Chl) ratios than Prochlorococcus (PRO), Synechococcus (SYN) or diatoms (DIAT). Moreover, the DMSP-lyase activity of algae which cleaves DMSP into dimethylsulfide (DMS) is even more group specific than DMSP itself. Ship-based observations have shown at limited spatial scales, that sea surface DMS-to-Chl ratios (DMS:Chl) are dependent on the composition of phytoplankton groups. Here we use satellite remote sensing of Chl (from SeaWiFS) and of Phytoplankton Group Dominance (PGD from PHYSAT) with ship-based sea surface DMS concentrations (8 cruises in total) to assess this dependence on an unprecedented spatial scale. PHYSAT provides PGD (either NANO, PRO, SYN, DIAT, Phaeocystis (PHAEO) or coccolithophores (COC)) in each satellite pixel (1/4° horizontal resolution). While there are identification errors in the PHYSAT method, it is important to note that these errors are lowest for NANO PGD which we typify by high DMSP:Chl. In summer, in the Indian sector of the Southern Ocean, we find that mean DMS:Chl associated with NANO + PHAEO and PRO + SYN + DIAT are 13.6±8.4 mmol g−1 (n=34) and 7.3±4.8 mmol g−1 (n=24), respectively. That is a statistically significant difference (P

Culture experiments with coccolithophore algae—the dominant group of marine calcifying phytoplankton—imply a strong sensitivity in growth rate, degree of cellular calcification, and cell size to changes in the carbon chemistry of their growth environment. These results underpin recent studies that have explored how these physiological parameters have varied on geological time scales, in response to changing surface ocean habitats and the concentrations of carbon in the ocean‐atmosphere system. Here, we add to this work with a study of reticulofenestrid coccolith size—the dominant coccolithophore family of the Cenozoic—over the Oligocene to Early Miocene time interval. We examine sediments from contrasting latitudes and regional environmental settings, comparing sites using coherent, updated age models to distinguish globally synchronous trends in cell size from regional trends. Our results confirm several changes in coccolith size—which is strongly correlated to cell size—that are globally reproducible within the ~1 Myr age uncertainty, including a reduction in mean size by >2 μm from 30.2 to 27 and 24.5 to 23 Ma, and then increase in mean size after 20 Ma. The main difference among regions is the presence/absence of coccoliths larger than 8 μm. We evaluate which scenarios of change in carbon dioxide, temperature, and nutrient availability could have exerted selective pressure on cell size for different size classes to produce the observed size trends at each studied site. These million‐year scale adaptations of ancient coccolithophores contribute to the understanding of phytoplankton physiology in the transition to the modern "icehouse" world. Key Points: Long‐term evolutionary coccolith size trends are found globally in low and middle latitudes with minima at 27 and 23 MaRegional differences in size exist when paleoproductivity drives the presence of large coccoliths [ABSTRACT FROM AUTHOR]

Coccolithophores are important contributors to global calcium carbonate through their species-specific production of calcite coccoliths. Nannofossil coccolith calcite remains an important tool for paleoreconstructions through geochemical analysis of isotopic and trace element incorporation including Sr, which is a potential indicator of past surface ocean temperature and productivity. Scyphosphaera apsteinii (Zygodiscales) exhibits an unusually high Sr/Ca ratio and correspondingly high partitioning coefficient (D Sr = 2.5) in their two morphologically distinct types of coccoliths: flat muroliths and barrel-like lopadoliths. Whether or not this reflects mechanistic differences in calcification compared to other coccolithophores is unknown. We therefore examined the possible role of Sr in S. apsteinii calcification by growing cells in deplete (0.33 mmol/mol Sr/Ca), ambient (9 mmol/mol Sr/Ca), and higher than ambient Sr conditions (36 and 72 mmol/mol Sr/Ca). The effects on growth, quantum efficiency of photosystem II (F v /F m), coccolith morphology, and calcite D Sr were evaluated. No effect on S. apsteinii growth rate or F v /F m was observed when cells were grown in Sr/Ca between 0.33–36 mmol/mol. However, at 72 mmol/mol Sr/Ca growth rate was significantly reduced, although F v /F m was unaffected. Reducing the Sr/Ca from ambient (9 mmol/mol) did not significantly alter the frequency of malformed and aberrant muroliths and lopadoliths, but at higher than ambient Sr/Ca conditions coccolith morphology was significantly disrupted. This implies that Sr is not a critical determining factor in normal coccolith calcite morphology in this dimorphic species. Using energy dispersive spectroscopy (EDS) we observed an increase in [Sr] and decrease in D Sr of coccoliths as the Sr/Ca of the growth medium increased. Interestingly, muroliths had significantly lower Sr/Ca than lopadoliths at ambient and elevated [Sr], and lopadolith tips had lower Sr than bases in ambient conditions. In summary, the Sr fractionation behavior of S. apsteinii is distinct from other coccolithophores because of an unusually high D Sr and inter- and intra-coccolith variability in Sr/Ca. These observations could be explained by mechanistic differences in the selectivity of the Ca2+ transport pathway or in the Sr-and Ca-binding capacity of organic components, such as polysaccharides associated with coccolithogenesis. [ABSTRACT FROM AUTHOR]

Dimethylsulfide (DMS) atmospheric and oceanic concentrations and eddy covariance air/sea fluxes were measured over the N. Atlantic Ocean during July 2007 from Iceland to Woods Hole, MA, USA. Seawater DMS levels north of 55°N ranged from 3 to 17 nM, with variability related to the satellite-derived distributions of coccoliths and to a lesser extent, chlorophyll. For the most intense bloom region southwest of Iceland, DMS air/sea fluxes were as high as 300 μmol m−2 d−1, larger than current model estimates. The observations imply that gas exchange coefficients in this region are significantly greater than those estimated using most gas transfer parameterizations. South of 55°N, DMS levels were lower and the gas transfer coefficients were similar to those observed in other regions of the ocean. The data suggest that DMS emissions from the bloom region may be significantly larger than current estimates. The anomalous gas exchange coefficients likely reflect strong near-surface, water column DMS gradients influenced by physical and biological processes.

A high‐resolution study of coccolithophores in a sediment core from the East China Sea (ECS) region of the Northwest Pacific revealed that fluctuations in coccolithophore assemblages responded well to the Pacific Decadal Oscillation (PDO) during 1901–2013. Emiliania huxleyi and Gephyrocapsa oceanica were the most dominant species, accounting for more than 97% of all the ten detected species. The variation of the two dominant species showed a significant positive correlation, and they both increased during peak values of the PDO. Decreased stratification and increased nutrient supplementation from the bottom water induced by lower sea surface temperatures in the ECS, which were associated with high PDO values, were responsible for the dominant coccolithophore increase. Similarly, the increase of Calcidiscus leptoporus also corresponded to low‐temperature and high‐nutrient conditions associated with the cold phase in the ECS (positive phase of the PDO). The responses of decadal C. leptoporus variations to changes in cold and warm phases of the PDO in the Northwest and Northeast Pacific indicate that C. leptoporus preserved in sediment cores represents a potential indicator for reconstructing phase changes of the PDO during ancient times. [ABSTRACT FROM AUTHOR]

Abstract In this study, we report a cognate pair of the aptamer-based sandwich-type electrochemical biosensor for type 2 diabetes biomarker (Vaspin) using coccolith modified electrodeposited on the screen-printed gold electrode (CME-SPGE). The coccolith derived from E. huxleyi used in this study were known to be highly-structured microparticles with many nano-sized pores. The CME-SPGE was successfully fabricated by drop-casting coccoliths, followed by Au sputtering and electrodeposition of Au. On this CME-SPGE electrode, the sandwich-type electrochemical aptasensor was fabricated by using a cognate pair of aptamers. The morphological, electrochemical characteristics and the performances of both the CME-SPGE and the completely fabricated sandwich-type aptasensor were investigated by SEM, EDAX, cyclic voltammetry, and chronoamperometry. Due to the synergic effect of a cognate pair of aptamers on CME-SPGE, this newly developed sandwich-type electrochemical biosensor for Vaspin showed high specificity, and good sensitivity with a limit of detection (LOD) of 298 pM, along with more widen the linear range. To the best of our knowledge, this is the first report about the use of a coccolith modified electrode with a cognate pair aptamer resulting in sandwich-type binding in an electrochemical biosensor. With the advantages of using highly-structured biomineral microparticles and a cognate pair of aptamers, this new study may pave the innovative way to design a novel sandwich-type electrochemical aptasensor platform. Highlights • The original SPGE surface was successfully modified uniformly with the highly-structured coccolith microparticles. • A cognate pair of aptamers was applied to fabricate sandwich-type electrochemical aptasensor successfully. • This newly developed sandwich-type electrochemical biosensor was highly sensitive to type 2 diabetes biomarker, Vaspin. [ABSTRACT FROM AUTHOR]

Biomineralization by calcifying microalgae is a precisely controlled intracellular calcification process that produces delicate calcite scales (or coccoliths) in the coccolithophore Emiliania huxleyi (Haptophycea). Despite its importance in biogeochemical cycles and the marine environment globally, the underlying molecular mechanism of intracellular coccolith formation, which requires calcium, bicarbonate, and coccolith-polysaccharides, remains unclear. In E. huxleyi CCMP 371, we demonstrated that reducing the calcium concentration from 10 (ambient seawater) to 0.1 mM strongly restricted coccolith production, which was then recovered by adding 10 mM calcium, irrespective of inorganic phosphate conditions, indicating that coccolith production could be finely controlled by the calcium supply. Using this strain, we investigated the expression of differentially expressed genes (DEGs) to observe the cellular events induced by changes in calcium concentrations. Intriguingly, DEG analysis revealed that the phosphatidylinositol-specific phospholipase C (PI-PLC) gene was upregulated and coccolith production by cells was blocked by the PI-PLC inhibitor U73122 under conditions closely associated with calcium-induced calcification. These findings imply that PI-PLC plays an important role in the biomineralization process of the coccolithophore E. huxleyi.

Despite the oceanographic and geological significance of coccolithophores, the cellular mechanisms that underlie the intracellular production and subsequent secretion of their CaCO3 coccoliths remain poorly understood. Tools for labeling coccoliths and coccospheres in order to track their production would be of great value. We therefore evaluated the use of calcein, a derivative of fluorescein, as a method to fluorescently label coccoliths. The calcein method readily labeled pre-existing coccospheres in a range of coccolithophore species, including diploid and haploid life history phases, without compromising the coccolith structure. Calcite staining was verified though epifluorescence and confocal microscopy, and both stained and unstained cells and coccoliths were readily distinguished using flow cytometry. The fluorescence of stained coccoliths was retained for >3 days allowing us to confirm their polar secretion by distinguishing pre-existing coccoliths from the accumulation and distribution of non-fluorescent coccoliths produced after calcein exposure. The calcein treatment had no significant effect on photosynthetic physiology, external calcite morphology, or growth rates of the cells over an 8-day period. The calcein staining method therefore represents a simple non-invasive, non-toxic optical technique to ‘tag’ calcium carbonate coccoliths and track their production in response to environmental manipulations or pharmacological treatments. Moreover, calcein staining of the coccosphere allowed for heterogenous patterns of calcification, growth, and cell division to be detected in a population of cells. This is the first description of the use of calcein to stain the biomineral structures of calcifying phytoplankton and this approach has the potential to be applied to detailed cytological investigations as well as high-throughput analysis of cultured cells or field populations.

This article reflects on the authors' work in investigating how audiovisual practices might represent the experience of disused or ruined structures. With backgrounds in visual and sound practice respectively, the authors have, in their most recent experimental film project Coccolith [UK: Coccolith Productions], conceived the Ramsgate wartime tunnels in Kent as a point of collision for divergent artistic approaches to the representation of space. Challenging the site's association with wartime mythology, the project sought to reconfigure the relationship between film and sound practice in order to articulate an alternative representation of the tunnels' history, heritage and temporality. The article reflects on the role of the sound designer in developing soundscapes that embodied the ruined space, and on the role of the director in visually conceiving a spatial experience of the tunnels characterized by the absence of sound - silence. We argue that in conceiving an audiovisual project in terms of texture and gesture, it is possible to reconceptualize both the role of the soundtrack in relation to a film's diegesis, and the role of the director in relation to sound design. [ABSTRACT FROM AUTHOR]

The potential use of two raw clays (Clay A: kaolin; Clay B: calcareous montmorillonite) as supplementary cementitious material (SCM) in blended cements was investigated. Cement replacement in mortars by 20% calcined Clay A and Clay B resulted in a considerable 28 day compressive strength improvement. The pozzolanic reactivity of Clay A and B is explained by characterisation of the structural changes upon calcination with XRD, ICP-MS, FT-IR, 27 Al NMR, Mössbauer spectroscopy and SEM. At the temperature giving highest pozzolanic reactivity, kaolinite and montmorillonite were completely dehydroxylated, while calcite from Clay B was not completely decomposed. FT-IR, 27 Al NMR and Mössbauer spectroscopy revealed considerable structural deformations of kaolinite in Clay A and montmorillonite in Clay B resulting in an amorphous, reactive state. Oxidation of iron in Clay B during calcination contributed to strong distortions of the octahedral sheet in the montmorillonite structure. Additionally, the formation of a glass phase due to reaction of coccoliths (CaCO 3 ) and montmorillonite was observed. [ABSTRACT FROM AUTHOR]

The calcite plates, or coccoliths, of haptophyte algae including Emiliania huxleyi are formed in intracellular vesicles in association with water–soluble acidic polysaccharides. These coccolith–associated polysaccharides (CAPs) are involved in regulating coccolith formation and have been recovered from sediment samples dating back to ∼180 Ma. Paired measurements of the carbon isotopic compositions of CAPs and coccolith calcite have been proposed as a novel paleo– p CO 2 barometer, but additional proxy validation and development are still required. Here we present culture results quantifying carbon isotopic offsets between CAPs and other cellular components: bulk organic biomass, alkenones, and calcite. E. huxleyi was grown in nitrate–limited chemostat experiments at growth rates (µ) of 0.20–0.62/d and carbon dioxide concentrations of 10.7–17.6 µmol/kg. We find that CAPs are isotopically enriched by 4.5–10.1‰ relative to bulk organic carbon, exhibiting smaller isotopic offsets at faster growth rates and lower CO 2 concentrations. This variability suggests that CAPs record a complementary signature of past growth conditions with different sensitivity than alkenones or coccolith calcite. By measuring the isotopic compositions of all three molecules and minerals of self-consistent origin, the ratio µ/[CO 2(aq) ] may be reconstructed with fewer assumptions than current approaches. [ABSTRACT FROM AUTHOR]

Abstract Many organisms form minerals from precursor phases that crystallize under strict biological control. The dynamic intracellular processes of formation, transport, and deposition of these precursor phases are challenging to identify. An unusual situation is recently revealed for the calcifying alga Emiliania huxleyi, as the cells contain a compartment filled with a concentrated Ca and P phase but the final calcite crystals, which are nucleated in a different compartment, are P‐free. Thus, the connection of the Ca–P‐rich pool to the mineralization process remains unclear. Here, pulse‐chase experiments are used with Sr to label the Ca–P‐rich phase in E. huxleyi cells, and cryo X‐ray absorption spectroscopy and analytical transmission electron microscopy to follow the Sr within cells. It is found that Sr is first found in the Ca–P‐rich phase and then becomes incorporated into the calcite. This demonstrates that the calcium used by the cells to build calcite originates from the Ca–P‐rich pool.

The carbonate content of calcareous nannofossils is dependent on seawater composition. One of the factors that affect seawater chemistry and consequently the degree of calcification in coccolithophores is temperature, as seen in present day warming oceans. The depth at which carbonates are dissolved (Calcite Compensation depth, CCD) can rise due to an increase in HCO 3 – and decrease in pH, leading to a major dissolution on the seabed and burndown. Similar processes have also been deduced for Eocene hyperthermal events, such as the PETM and ETM2. This study reports changes in coccolith carbonate mass from a hemipelagic setting (Gorrondatxe, at 1500 m paleodepth) during the core of a minor Eocene hyperthermal event, namely the C21r-H6 event (47.44–47.32 Ma). Image analysis techniques were used to determine differences in the carbonate mass of selected calcareous nannofossil taxa, revealing species-specific patterns. The CaCO 3 mass of Chiasmolithus solitus decreased by 50% over the course of the C21r-H6 event, and many specimens also lost their crossed central bars, an additional indication of mass loss; Reticulofenestra sp. (3–5 μm) showed a similar trend, but the percentage of mass lost was lower; Toweius pertusus , interpreted as being reworked, mirrored the behaviour of Chiasmolithus solitus , suggesting that the CaCO 3 mass loss may have occurred on the seabed, rather than in the water column. In general, it can be concluded that the lysocline rose to 1500 m paleobathymetry in the Bay of Biscay during the C21r-H6 event. Formation of corrosive bottom water in the North Atlantic Ocean is regarded as being responsible for the rise in the lysocline. [ABSTRACT FROM AUTHOR]

Haptophytes are one of the photosynthetic microalgae with red-algal-derived chloroplasts, and thought to be among the most important primary producers in oceans. Calcifying haptophytes (coccolithophores) have a significant effect on the global carbon cycle, as they fix dissolved inorganic carbon through photosynthesis and calcification. Given that these two processes occur in a single cell, intracellular ion and metabolite traffic is expected to be more complex than in other algae. Haptophytes synthesise and accumulate various compounds during photosynthesis, such as long chain unsaturated ketones (alkenones), β-glucan, mannitol, acid polysaccharides (APs), and dimethylsulphoniopropionate. Some compounds are not equally produced in all haptophytes but are produced by specific species or groups. For example, APs are produced only in coccolithophores and suggested to support morphogenesis of calcite scales. The structure of APs is highly species-specific. Alkenones are produced in only five haptophyte species regardless of their calcification ability. The occurrence of such variations in carbon metabolism across species is also a marked characteristic of haptophytes. This chapter introduces basic cellular features of haptophytes and focuses on features of their carbon metabolism and calcification. [ABSTRACT FROM AUTHOR]

Coccoliths, combined with sediment grain size, carbonate calcium and organic matters content, were analyzed to assess the ecological and taphonomical influences on coccolith distribution patterns in surface sediments in the continental shelf of the Yellow and East China Seas. Coccolith abundances ranged from 0 to 2.08×10 9 coccoliths g −1 sediment. The increasing abundance from the coastal inner shelf to the seaward middle shelf generally reflects the ecological fact that living coccolithophores are more abundant in the mesotrophic shelf waters than in the eutrophic coastal waters, although their deposits are still controlled by taphonomical effects, such as bottom (tidal) currents and calcite preservation conditions. Most abundant coccoliths are found in the fine-grained sediments of southwestern Cheju Island, where both ecology and taphonomy favor coccolith preservation. Still, large densities of coccoliths (>10 8 coccoliths g −1 sediment) are also found in coarse-grained relict sediments in the middle shelf. Coccolith assemblages were predominated by Gephyrocapsa oceanica and Emiliania huxleyi . The relative abundance of E. huxleyi , in addition to ecological reasons, may relate to selective post-mortem dissolution, since small E. huxleyi coccoliths are more susceptible to dissolution. Coccolith calcite has minor contributions (<1% to 12%) to total sediment CaCO 3 , and the main parts are attributed to terrigenous CaCO 3 debris and relict shell fragments. [ABSTRACT FROM AUTHOR]

This work aims to provide new insights into environmental conditions during late Pleistocene Marine Isotope Stage 11 (MIS 11) in the Southern Ocean. We generated a multi-proxy coccolithophore dataset based on sediment core PS75/059-2. This core was retrieved at the western flank of the southern East Pacific Rise crest at ∼3600 m water depth. Coccolithophore assemblage counts indicated that the coccolith fraction (CF; <20 μm) during MIS 11 was dominated by Gephyrocapsa caribbeanica and subsequently by small Gephyrocapsa . Coccolith accumulation rates, CF Sr/Ca data and temperature-corrected CF Sr/Ca records were consistent and showed a steep increase in coccolithophore productivity as well as apparent coccolith calcification during Termination V. Maximum values were reached during MIS 11. We explain this high coccolithophore production during MIS 11 by changes in sea surface temperature and nutrient regimes, due to a re-organisation of the surface circulation patterns and a southward migration of the frontal systems. Furthermore, the immense carbonate production of the coccolithophores may have contributed to increased atmospheric CO 2 contents, causing a drawdown of the carbonate saturation and an increase in dissolution at the seafloor. However the atmospheric CO 2 did not reach higher values probably due to the effective ballasting of organic matter by coccoliths. [ABSTRACT FROM AUTHOR]

Carbonate dissolution and deposition in the deep ocean is a critical component of carbon cycle, but detailed pictures of carbonate dynamics below the Carbonate Compensation Depth (CCD) remains poorly understood. In this study, we present a ∼ 420 thousand years record of carbonate content below CCD in IODP Site U1433 at 4.4 km water depth in the South China Sea (SCS). Instead of carbonate-free sediment, we observed that the carbonate content in this deep site could reach as high as 40%. The dissolution-resistant biogenic carbonate, coccoliths, and stable isotope ratio of bulk carbonate were analyzed to trace the carbonate sources. The coccolith assemblage in IODP Site U1433 shows an unrealistic feature of high productivity, which indicates a lateral transport of coccoliths from the northern SCS to the central basin. Coccoliths' contribution to total carbonate was on average 30% and could be as high as ∼80%. Their contribution to carbonate increased at the expense of the dissolution of other biogenic carbonate, such as foraminifera, and decreased with the dilution of other terrestrial carbonate particles. According to the thickness of coccoliths, significant dissolution of coccoliths only happened when the carbonate content dropped below 3%. Marbles from Taiwan, with negative oxygen isotope ratios, and early diagenetic carbonates from carbonate platform nearby, with both negative carbon and oxygen isotope ratios, could be the other important sources besides the marine biogenic carbonate. With help of numerical simulations, we estimated that the lateral transport by turbidity currents could contribute up to 70–90% of the deep-sea sediment in the central basin of SCS. These new findings enrich our knowledge of the carbon fluxes from continental margins to the deep ocean as a key part of the carbon cycle. • Coccoliths in the SCS central basin contribute ∼30% to total carbonates. • Stable isotope ratios of carbonates indicate two mixing lines clearly. • Lateral transport dominates in the SCS deep-sea sediment. [ABSTRACT FROM AUTHOR]

A study of coccolith assemblages from a box core from the central South Yellow Sea (SYS) was performed revealing fluctuations on their relative abundance (%) that can be related to climatic and hydrographic changes over the last 230 years (1780-2011). Total coccolith abundances ranged from 7.0 to 55.1×10 coccoliths·g sediment. Although the abundance of different species varied widely throughout the core, seven taxa dominated the assemblage. Among these species, Gephyrocapsa oceanica was the most dominant species, and it showed an average percentage of 50.1%. The pattern of G. oceanica (eutrophic species) was opposite to that of the combined percentage of Braarudosphaera bigelowii and Umbilicosphaera sibogae (both oligotrophic species), indicating that in the Yellow Sea (YS), the distribution pattern of G. oceanica might be characteristic of nutrient availability. Similar patterns between G. oceanica and the Siberian High were observed on an inter-decadal time scale, indicating that the East Asian Winter Monsoon (EAWM) may be an important driver of ecological changes in the YS. When the EAWM prevails, both the Yellow Sea Coastal Current (YSCC) and Yellow Sea Warm Current (YSWC) strengthen, and the increasing nutrient availability and warmer water brought by the strengthened YSWC favor eutrophic and warm-water coccolithophore species, such as G. oceanica. This likely mechanism demonstrates that coccolith assemblages can be used as benign and reliable proxy for climate change and surface oceanography. [ABSTRACT FROM AUTHOR]

Coccolithophorids are enigmatic plankton that produce calcium carbonate coccoliths, which over geological time have buried atmospheric CO2 into limestone, changing both the atmosphere and geology of the Earth. However, the role of coccoliths for the proliferation of these organisms remains unclear; suggestions include roles in anti-predation, enhanced photosynthesis and sun-screening. Here we test the hypothesis that calcification stabilizes the pH of the seawater proximate to the organisms, providing a level of acidification countering the detrimental basification that occurs during net photosynthesis. Such bioengineering provides a more stable pH environment for growth and fits the empirical evidence for changes in rates of calcification under different environmental conditions. Under this scenario, simulations suggest that the optimal production ratio of inorganic to organic particulate C (PIC : POCprod) will be lower (by approx. 20%) with ocean acidification and that overproduction of coccoliths in a future acidified ocean, where pH buffering is weaker, presents a risk to calcifying cells. [ABSTRACT FROM AUTHOR]