Littérature scientifique sur le sujet « Biogenic calcium carbonate »

AbstractThe ability to discriminate biogenic from abiogenic calcium carbonate (CaCO3) would be useful in the search for extant or extinct life, since CaCO3can be produced by both biotic and abiotic processes on Earth. Bioprecipitated CaCO3material was produced during the growth of heterotrophic microbial isolates on medium enriched with calcium acetate or calcium citrate. These biologically produced CaCO3, along with natural and synthetic non-biologically produced CaCO3samples, were analysed by reflectance spectroscopy (0.35–2.5 μm), Raman spectroscopy (532 and 785 nm), and laser-induced fluorescence spectroscopy (365 and 405 nm excitation). Optimal instruments for the discrimination of biogenic from abiogenic CaCO3were determined to be reflectance spectroscopy, and laser-induced fluorescence spectroscopy. Multiple absorption features in the visible light region occurred in reflectance spectra for most biogenic CaCO3samples, which are likely due to organic pigments. Multiple fluorescence peaks occurred in emission spectra (405 nm excitation) of biogenic CaCO3samples, which also are best attributed to the presence of organic compounds; however, further analyses must be performed in order to better determine the cause of these features to establish criteria for confirming the origin of a given CaCO3sample. Raman spectroscopy was not useful for discrimination since any potential Raman peaks in spectra of biogenic carbonates collected by both the 532 and 785 nm lasers were overwhelmed by fluorescence. However, this also suggests that biogenic carbonates may be identified by the presence of this organic-associated fluorescence. No reliable spectroscopic differences in terms of parameters such as positions or widths of carbonate-associated absorption bands were found between the biogenic and abiogenic carbonate samples. These results indicate that the presence or absence of organic matter intimately associated with carbonate minerals is the only potentially useful spectral discriminator for the techniques that were examined, and that multiple spectroscopic techniques are capable of detecting the presence of associated organic materials. However, the presence or absence of intimately associated organic matter is not, in itself, an indicator of biogenicity.

ABSTRACTBiogenic minerals are widely studied materials for their particular properties derived from their hierarchical structure, using building blocks with sizes spanning several orders of magnitude. These special features can be assessed with different analytical tools, and it is important to know their capabilities and limitations. In order to determine the hierarchical structure of the shells, the nacre and prismatic layers of two marine animals were characterized by infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. Based on these assessments, we found that the combination of these three techniques is useful to describe each structure level, and to explain some of the unique properties observed in these natural materials.

Calcium carbonate is one of the most widespread natural material. Biogenic calcium carbonate nanoparticles are biocompatible. Currently, they are of great interest for their possible applications, especially in medicine. The aim of this introductory experimental study is to present a simple preparation of biogenic nanoparticles of calcium carbonate from natural resources with a subsequent specific behaviour of nanoparticles in aquatic environment. Different type of shells were used for the preparation of nanoparticles. All structures were burned at 850°C and then grounded to powder. The obtained powders were left in normal laboratory environment for 2 weeks and then placed in beakers with distilled water. Subsequently, two homogenization routes were used - stirring at 1000 rpm for 5 minutes and ultrasonic stirring for 5 minutes. One part of the particles was separated at the bottom of the beaker, but small formations started to create a fractal structure on the surface of water. These formations gradually increased. Crystalline interconnected structures built up with nanoparticles were confirmed by a subsequent analysis by a scanning electron microscope. EDX analysis confirmed the presence of calcium carbonate.

Due to the remarkable properties achieved under ambient conditions and with quite limited components, mollusk shells are very appealing natural bio-composites used as inspiration for new advanced materials. Calcium carbonate which is among the most widespread biominerals is used by mollusks as a building material that constitutes 95-99% of their shells. Within the investigation of calcium carbonate polymorphs present in the shells, diverse theoretical and experimental studies were performed, however, further research of these crystalline forms is required. There are very little researches on the energy landscapes of biogenic calcium carbonate which can provide us information about the free energies of already known as well as newly discovered plausible structures. To investigate the structural, mechanical, elastic, or vibrational properties and to predict new possible structures of biogenic calcium carbonate, different calculation methods could be employed. Some of these studies are presented and discussed in this paper.

The boron isotope compositions (δ¹¹B) of biogenic carbonates have proven to be an invaluable tool for investigating changes in ocean carbonate chemistry, especially the impacts of declining seawater pH due to rising levels of atmospheric CO₂.

Abstract. The boron isotope composition (δ11B) of marine biogenic carbonates has been predominantly studied as a proxy for monitoring past changes in seawater pH and carbonate chemistry. However, a number of assumptions regarding chemical kinetics and thermodynamic isotope exchange reactions are required to derive seawater pH from δ11B biogenic carbonates. It is also probable that δ11B of biogenic carbonate reflects seawater pH at the organism's site of calcification, which may or may not reflect seawater pH. Here, we report the development of methodology for measuring the δ11B of biogenic carbonate samples at the multi-collector inductively coupled mass spectrometry facility at Ifremer (Plouzané, France) and the evaluation of δ11BCaCO3 in a diverse range of marine calcifying organisms reared for 60 days in isothermal seawater (25 °C) equilibrated with an atmospheric pCO2 of ca. 409 µatm. Average δ11BCaCO3 composition for all species evaluated in this study range from 16.27 to 35.09 ‰, including, in decreasing order, coralline red alga Neogoniolithion sp. (35.89 ± 3.71 ‰), temperate coral Oculina arbuscula (24.12 ± 0.19 ‰), serpulid worm Hydroides crucigera (19.26 ± 0.16 ‰), tropical urchin Eucidaris tribuloides (18.71 ± 0.26 ‰), temperate urchin Arbacia punctulata (16.28 ± 0.86 ‰), and temperate oyster Crassostrea virginica (16.03 ‰). These results are discussed in the context of each species' proposed mechanism of biocalcification and other factors that could influence skeletal and shell δ11B, including calcifying site pH, the proposed direct incorporation of isotopically enriched boric acid (instead of borate) into biogenic calcium carbonate, and differences in shell/skeleton polymorph mineralogy. We conclude that the large inter-species variability in δ11BCaCO3 (ca. 20 ‰) and significant discrepancies between measured δ11BCaCO3 and δ11BCaCO3 expected from established relationships between abiogenic δ11BCaCO3 and seawater pH arise primarily from fundamental differences in calcifying site pH amongst the different species. These results highlight the potential utility of δ11B as a proxy of calcifying site pH for a wide range of calcifying taxa and underscore the importance of using species-specific seawater-pH–δ11BCaCO3 calibrations when reconstructing seawater pH from δ11B of biogenic carbonates.

Abstract Calcium carbonate-based biominerals, also referred as biocalcifications, are the most abundant biogenic mineralized products at the surface of the Earth. In this paper, we summarize general concepts on biocalcifications and we sketch macro-evolutionary trends throughout the history of the Earth, from Archean to Phanerozoic times. Then, we expose five fundamental issues that represent key-challenges in biocalcification researches for the coming decade: the first one concerns the comprehension of the micro- and nano-structure of calcium carbonate biominerals from a mineral viewpoint, while the second one deals with the understanding of the dynamic process of their fabrication. The third one treats the subtle interplay between organics and the mineral phase. The fourth issue focuses on an environmental challenge related to ocean acidification (OA); at last, the diagenetic processes that affect biogenic calcium carbonate mineral constitute the fifth issue.

Sandy beaches are critical resources for low-lying Pacific atoll communities, providing protection during storms, and land area for many coastal villages. Information on the nature of atoll beach sediment, its geochemistry and composition, can help to establish priorities to effectively protect the sources of Pacific island beach sediment. To understand sand sources, this study evaluated its physical characteristics including grain-size, geochemistry and composition, from windward and leeward beach profiles around Abaiang Atoll, Kiribati. Beach sand was >99% carbonate, averaging 37% coral fragments, 30% mollusc shells, 12% foraminifera, and 20% calcareous algae. Significant differences were found between reef and lagoonal sites in proportions of coral and mollusc fragments and foraminifera tests, with lagoon beaches having higher mollusc and coral proportions and lower foraminifera relative to reef beaches. This is attributed to high foraminiferal productivity offshore of reef beaches, and taphonomic durability of coral fragments in longshore drift into the lagoon. Mean sediment diameter increased from the upper to lower beaches at all sites, but fine sediment was lacking, attributed to its dissolution by rainfall and groundwater outflow. Geochemical analysis showed a mean of 84% Ca-Mg carbonates, of which 80% was calcium carbonate. There was no significant difference in the mean calcium percentage or calcium carbonate composition of the sediment between lagoon and reef beach sediment sources. Magnesium and magnesium carbonate content were significantly higher at reef sites relative to lagoon sites, attributed to higher proportions of foraminifera. Sediment-producing near shore habitats are critical to village protection through provision of beach sand, and this study shows the need to better conserve and manage coral reefs and habitats such as lagoon seagrass beds, to ensure continued atoll beach sand supply.

Ocean chemistry has oscillated throughout Earth history to favour the dominant non-biogenic polymorph of calcium carbonate (CaCO3) to be either calcite or aragonite (Sandberg, 1983). Throughout the Phanerozoic these oscillations have occurred to facilitate aragonite-dominant conditions three times and calcite-dominant conditions twice. These aragonite-calcite seas conditions have previously been viewed as a global phenomenon where conditions fluctuate over time, but not in space, and represent the main environmental context in which the evolution of CaCO3 biomineralisation has occurred (Stanley and Hardie, 1998). CaCO3 is one of the most widely distributed minerals in the marine environment, occurring throughout geological history, both biogenically and non-biogenically (Lowenstam and Weiner, 1989). Marine non-biogenic precipitates are commonly found as carbonate ooids, sedimentary cements and muds (Nichols, 2009). Biogenic CaCO3 is formed via biomineralisation in calcifying organisms (Lowenstam and Weiner, 1989; Allemand et al., 2004), and is much more abundant than the non-biogenic forms. Although CaCO3 is abundant, it only accounts for a small proportion of the global carbon budget. Biogenic CaCO3 is representative of a larger proportion of the global carbon budget than non-biogenically formed CaCO3 (Berelson et al., 2007). The main driving force controlling the precipitation of CaCO3 polymorphs is the Mg:Ca molar ratio of seawater (Morse et al., 2007). However, other parameters such as temperature (Burton and Walter, 1984; Morse et al, 1997; Balthasar and Cusack, 2015), pCO2 (Lee and Morse, 2010), and SO4 (Morse et al., 2007) are also known to influence CaCO3 polymorph formation but are often overlooked in the context of aragonite-calcite seas. Fluctuations in these parameters of Mg:Ca ratio, SO42+ and pCO2 of seawater have been suggested to cause shifts in original composition of non-biogenic marine carbonates, and in turn viewed as the main driving mechanisms facilitating the switch between aragonite and calcite dominance (Morse et al., 1997; Lee and Morse, 2010; Bots et al., 2011). Specifically the influence of temperature is important because it is likely to result in aragonite-calcite sea conditions to vary spatially (Balthasar and Cusack, 2015). Today marine temperatures are changing across the latitudes due to environmental factors. Global CO2 levels have increased significantly since industrialisation (Doney et al., 2009), with 33% entering the oceans and reducing pH (Raven et al., 2005) accelerating climate change (IPCC, 2013) and influencing marine calcification (Fitzer et al., 2014a; 2015b; Bach, 2015; Zhao et al., 2017). Strong links between the carbon cycle and climate change observed in the rock record give evidence that environmental changes such as pCO2 and global warming have impacts on calcification and marine biota (Hönish et al., 2012). The first objective was to determine the influence of Mg:Ca ratio, temperature and water movement on the first-formed precipitates of non-biogenic CaCO3 precipitation yielded via a continuous addition technique experiments (Chapter 3). CaCO3 precipitation was induced by continuously adding bicarbonate to a bulk solution of known Mg:Ca ratio (1,2 or 3), and fixed salinity of 35 (practical salinity scale), at 20°C and 30ºC in still conditions, and then repeated with the solution being shaken at 80rpm mimicking more natural marine conditions. The mineralogy and crystal morphology of precipitates was determined using Raman Spectroscopy and Scanning Electron Microscopy. Results in Chapter 3 indicated that polymorphs co-precipitate, with the ratio of aragonite to calcite increasing with increased Mg:Ca ratio and elevated temperature. The main difference between still and shaken conditions was that overall, more crystals of aragonite compared to calcite precipitate in shaking conditions. The crystal size is less influenced in aragonite, but calcite crystals were smaller. These results contradict current views on aragonite-calcite seas as spatially homogenous ocean states need to be re-examined to include the effect of temperature on the spatial distribution of CaCO3 polymorphs. Examining polymorph growth under these experimental constraints allows us to gain a better understanding of how temperature and Mg:Ca together control non-biogenic aragonite and calcite precipitation providing a more realistic environmental framework in which to evaluate the evolution of biomineralisation. To further this work, the same continuous addition technique was used with the presence of sulphate in the mother solution (Chapter 4). Sulphate being the 4th most common marine ion (Halvey et al., 2012) and known to have an influence on mineralogy (Kontrec et al., 2004). The presence of sulphate increase the aragonite to calcite proportion formed compared to sulphate-free conditions (Chapter 4). Elevated temperature with sulphate further increased the proportion of aragonite to calcite facilitated (Chapter 4). In the presence of sulphate the main difference between sulphate-free environments and those with sulphate environments was: in still conditions the presence of sulphate increased the crystal number more than the crystal size at 20°C; at 30°C or in shaken conditions the presence of sulphate increased the crystal size of aragonite to calcite much more than it had influence on the crystal number. Non-biogenically the influence of sulphate lowered the threshold of Mg:Ca ratio that the switch between calcite and aragonite would be facilitated at (Bots et al., 2011). This would have implications for marine calcification as pure calcite seas would become very rare and imply that organisms would be forming calcified hard parts out with the supported mineralogies. Biogenic application of these results is complex however as organisms often have the ability to select aragonite as their main polymorph for their own functional requirements (Weiner and Dove, 2003). The growth parameters of non-biogenic polymorph formations grown from artificial seawater can be used to understand how organism control can influence the polymorph formation under similar conditions (Kawano et al., 2009). Assessing the elemental composition of mussel shells grown under know conditions of temperature and pCO2 allowed the environmental influences on mineralogy be assessed under possible the projected changes in climate forecast to occur by 2100 by IPCC (2013). Prior to this research, no study had used Mytilus edulis shell elemental composition to test the influence of aragonite-calcite sea conditions on mineralogy. This research compiles a detailed source of information on the constraints from environmental sources such as temperature and pCO2, on the elemental concentrations within shell formation and what potential changes could occur in response to a changing marine environment (Chapter 5). Here elevated temperature significantly increased the concentration of magnesium in calcite, but did not influence the magnesium concentration of aragonite unless combined with elevated pCO2. The concentrations of sulphur in calcite were significantly decreased at elevated pCO2 or combined increased temperature and pCO2 as concentrations of sodium were found to be increased under these conditions. In aragonite the concentrations of both sulphur and sodium were significantly different under all scenarios. Strontium did not yield any significant results in this research in either calcite or aragonite. Results observed indicate that the shell elemental concentrations are influenced differently in aragonite or calcite, and further influenced by environmental conditions based on the original mineralogy. This suggests that physiological mechanisms under the constraints of increased temperature and pCO2 can override the seawater chemistry influences of aragonite-calcite seas impacting on mineralogy.
This research allows comparison of how non-biogenic and biogenic CaCO3 formation is influenced by seawater chemistry and environmental parameters to determine the dominant mineralogy. Increased temperature in both formations has shown to increase the impact of magnesium on calcite enabling the facilitation of aragonite. However, magnesium has influence on biogenic aragonite in extreme combined conditions of elevated temperature and pCO2. This work indicates that CaCO3 formation is complex and requires a multi-variable approach to understanding the mechanisms that facilitate the dominant mineralogy. By including variables such as temperature, this research suggests that aragonite-calcite seas conditions do not facilitate globally homogeneous switches in mineralogy, but the mineralogy is indeed influenced on latitudinal scales by other factors that influence the mechanisms involved.

Most biominerals in nature are formed from both organic and inorganic (mineral) compounds, and are thus by definition a composite material. They are hierarchically ordered from the nanoscale and often have superior mechanical properties compared to synthetic ceramics [1]. This study focusses on the structural characterisation of aragonite and calcite biominerals, combined with the investigation of formation mechanisms through the synthesis of bio-inspired or biomimetic crystals. To this end a multi-length scale study of aragonite and calcite based minerals is presented, based primarily on electron microscopy techniques and supported by Raman spectroscopy and chemical analysis of the organic compounds. Aragonite skeletal material from corals is studied in detail from the nano-to microscale. This is compared to calcium carbonate crystals precipitated in the presence of organic molecules with hydroxyl-groups, namely ethanol. Secondly, we look at the calcite based system of coccolithophores (marine algae) which precipitate their exoskeleton intracellulary. Such crystals formed in confinement are compared to the structure of synthetically produced calcite nanowires, grown in track-etch membranes. The coral’s spherulites (roughly 10-20 µm in size) were found to consist of three distinct crystalline phases. This microstructural sequence could for the first time be directly correlated to diurnal growth bands observed in optical transmission images and are linked to a light enhanced calcification process. The synthetic CaCO3 precipitation experiments showed that increasing ratios of ethanol resulted in a shift of crystal phase and morphology from single crystal rhombohedral calcite to branched polycrystalline aragonite, the latter being similar to the coral. The calcite coccoliths of Rhabdosphaera clavigera exhibit centrally positioned, several micrometre long five-fold symmetric spines. The spines are made up of spiral staircase arrangements of {104} single crystal calcite rhombohedra. However the rim of the coccolith has complex shaped, kinked, crystal elements. It was found that such unconventional crystal shapes can be promoted by external anisotropic surface stresses as was seen for the calcite nanowires investigated in this study.

L’objectif principal de cette thèse est de mieux comprendre les différents facteurs contrôlant la pompe biologique de carbone en Atlantique Nord et dans l’Océan Austral, à proximité des îles Kerguelen, en utilisant notamment deux approches: le Thorium-234 (234Th) et le baryum biogénique (Baxs).En Atlantique Nord, les flux d’export de carbone organique particulaire (POC) augmentent lorsqu’ils sont associés à des minéraux biogéniques (silice biogénique et carbonate de calcium) et lithogènes, capable de lester les particules. L’efficacité d’export, généralement plus faible que précédemment supposé (< 10%), est inversement corrélée à la production, soulignant un décalage temporel entre production et export. La plus forte efficacité de transfert, i.e. la fraction de POC atteignant 400m, est reliée à des particules lestées par du carbonate de calcium ou des minéraux lithogènes.Les flux de reminéralisation mésopélagique sont similaires ou parfois supérieurs aux flux d’exports et dépendent de l’intensité du développement phytoplanctonique, de la structure en taille, des communautés phytoplanctoniques et des processus physiques (advection verticale).Comme observé pour le POC, l’export des éléments traces est influencé par les particules lithogènes provenant des marges océaniques, mais aussi des différentes espèces phytoplanctoniques.Dans l’Océan Austral, la zone à proximité de l’île de Kerguelen est naturellement fertilisée en fer, augmentant les flux d’export de fer, d’azote et de silice biogénique. Il a été démontré que la variabilité des flux dépendait des communautés phytoplanctoniques dans la zone fertilisée
The main objective of this thesis is to improve our understanding of the different controls that affect the oceanic biological carbon pump. Particulate export and remineralization fluxes were investigated using the thorium-234 (234Th) and biogenic barium (Baxs) proxies.In the North Atlantic, the highest particulate organic carbon (POC) export fluxes were associated to biogenic (biogenic silica or calcium carbonate) and lithogenic minerals, ballasting the particles.Export efficiency was generally low (< 10%) and inversely related to primary production, highlighting a phase lag between production and export. The highest transfer efficiencies, i.e. the fraction of POC that reached 400m, were driven by sinking particles ballasted by calcite or lithogenic minerals.The regional variation of mesopelagic remineralization was attributed to changes in bloom intensity, phytoplankton cell size, community structure and physical forcing (downwelling). Carbon remineralization balanced, or even exceeded, POC export, highlighting the impact of mesopelagic remineralization on the biological pump with a near-zero, deep carbon sequestration for spring 2014.Export of trace metals appeared strongly influenced by lithogenic material advected from the margins. However, at open ocean stations not influenced by lithogenic matter, trace metal export rather depended on phytoplankton activity and biomass.A last part of this work focused on export of biogenic silica, particulate nitrogen and iron near the Kerguelen Island. This area is characterized by a natural iron-fertilization that increases export fluxes. Inside the fertilized area, flux variability is related to phytoplankton community composition

碩士
崑山科技大學
機械工程研究所
96
Shellfish do not need to moult their shell as they grow. The color of shell at the aperture is an indicator of the fitness of clams. These two facts about shellfish may sound commonplace, but the calcifying mechanism behind them is rather interesting. Calcification is widespread among marine organisms, including corals, mollusks, plankton and algae. In present time, these organisms are threatened by increasing ocean acidification due to fossil fuel burning. According to fossil record, the earth has experienced a number of mass extinction events. At least three of the events mark severe loss of calcifying organisms due to ocean acidification. Calcium carbonate mostly occurs in two forms: metastable aragonite and stable calcite. Clams as well as many other species of mollusk produce aragonite first and then transform the crystal to calcite. The aragonite-calcite transformation is critical to physiology of clams. Besides chemical factors, mechanical effect also plays a certain role in controlling calcification since the stability of calcium carbonate crystal is dependent on pressure. Studying the details about calcification is an important and meaningful task.

There are several sources from which hydroxyapatite (HAp) can be obtained and may be broadly categorized as synthetic or biogenic. Elevated interest in recent times has pushed for the development of several procedures for extracting HAp from biogenic wastes due to their excellent composition and morphology resemblance to the human calcified tissue (B-type carbonated HAp). Notable biogenic sources reported for HAp extraction span bovine bones, fish scales, corals, eggshells, and snails among other calcium-rich sources. However, most of the synthetic methods are laborious and therefore result in high production costs. In this chapter, we discuss the synthesis of B-type carbonate substituted HAp from an untapped biogenic source, Achatina achatina shells, using a simple precipitation method and a controlled heat-treatment method. This unique treatment method affected the substitution resulting in different crystallographic parameters and revealed a novel material for bone implants and enamel applications.

Mollusks have a well-deserved reputation for being expert mineralizers based only on their much-admired shell-making abilities. Table 6.1 shows that the reputation is deserved 10-fold as shell formation is just one of many different processes that these animals perform in which biogenic minerals are utilized. The table lists no less than 21 different minerals and about 17 different functions! The list contains both amorphous minerals (amorphous fluorite, calcium carbonate, calcium phosphate, calcium pyrophosphate, and silica) and many crystalline ones, including rather uncommon ones such as weddelite, calcium fluorite, barite, magnetite, lepidocrocite, and goethite. Weddelite, for example, is a calcium oxalate mineral frequently formed pathologically in vertebrates. Certain gastropods use the rather soft weddelite nonpathologically to cap pestlelike objects (gizzard plates) in their stomachs (Lowenstam 1968), which they use for crushing shelled prey. One mollusk, the chambered Nautilus, forms no less than five different minerals. An individual tooth of a chiton contains three different mature minerals that are products of two other transient minerals. In addition to the more familiar functions of mineralized tissues, mollusks use biogenic minerals as buoyancy devices, trap doors, egg shells, and love darts. The varieties of crystal shapes, sizes, organizational arrays, and tissue sites present a picture of overwhelming diversity all within one phylum. It is illustrative to compare the mollusks with the echinoderms. The echinoderms also use minerals for a wide variety of functions, but in contrast to the mollusks they use essentially the same “building material” for many different purposes. Thus, understanding how one echinoderm mineralized tissue forms provides insight into how most of the others form. This is not so with mollusks. It seems futile to expect that they too have adapted one basic process to form all their mineralized tissues. It seems just as futile to look for a different explanation for each type of mineralized product. The mollusks force us to seek a level of understanding of mineralization that identifies common approaches, strategies, and principles and, at the same time, appears to dispel any “dreams” about discovering the mechanism of mineralization. The mollusk phylum contains seven different taxonomic classes.

In the field of biomineralization the phylum Chordata is the most intensively studied, as one of its subphyla, the Craniata, includes our own species. The Craniata are often referred to as the vertebrates, a term that alludes to the importance of the endoskeleton in denning the essential character of these animals. The phylum Chordata also contains three other subphyla, only one of which has members that form mineralized hard parts. They belong to the Urochordata or tunicates. In fact, mineralization is confined to several families of a single class of urochordates, the Ascidiacea. Table 9.1 is a compilation of the known biogenic minerals formed by members of the Chordata, together with the sites at which they form and their presumed functions. The table includes no less than 17 different minerals, which should dispel any notion that mineralization in the chordates is synonymous with "calcium phosphate" deposition. It is, of course, true that the mineralized skeletal hard parts of most of the Craniata or vertebrates contain a calcium phosphate mineral, usually in the carbonated form called dahllite. However, the vertebrates also form four different carbonate minerals that are most commonly found in the vestibulary apparatus (see Chapter 10). They form three different iron minerals, which includes magnetite found in the navigation system of various vertebrate genera. The Ascidiacea also form a diverse array of minerals. Interestingly, however, their diversity is essentially confined to one class, the Pyuridae, which form no less than six different minerals, including two phosphate minerals. In this chapter we first describe biomineralization processes in the Ascidiacea followed by detailed discussions of mineralization processes in the Chordata or vertebrates. For convenience, the section on vertebrate mineralization is divided according to the major mineralized tissues: bone (dentin), cartilage, and tooth enamel. Mineralization in the vestibulary apparatus is discussed in Chapter 10.

For the most part, the minerals that organisms form do not form abiologically in the environment in which the organism lives. In fact, some of them do not form abiologically anywhere in the biosphere. A striking example is the crystalline strontium sulfate test of the Acantharia, a group of planktonic proctoctists that is found in most of the world’s oceans. Seawater is undersaturated with respect to strontium sulfate. Thus, the biological environment of mineral formation is isolated from the surroundings. This is, in fact, a generally observed phenomenon (Chapter 3) and it is, therefore, surprising to find that in a wide variety of organisms, the environment does still in some ways influence these biogenic minerals. This can manifest itself in the particular mineral deposited (for example, the deposition of the calcium carbonate polymorph calcite as opposed to aragonite or vice versa), the concentration of minor and trace elements, the stable isotopic composition of the mineral, and, at the ultrastructural level of the tissue, the distribution of growth lines. The degree to which the environment can affect biomineralization is a function of how isolated the process is from the outside world. Poorly controlled mineralization processes are expected to be affected more than well-controlled processes, although as we show in this chapter each case must be examined individually. There are examples of a clear environmental effect occurring in one species of a particular genus, whereas another species or even subspecies of the same genus appears to be unaffected (Lowenstam 1954c). The environmental effect can and very often is filtered out by the physiological processes of the organism, which either completely or partially determine the solution characteristics of the microenvironment in which the crystals grow. A lack of appreciation of this fact has caused considerable confusion in the literature, with some investigators concluding that an environmental influence on biogenic minerals does not exist in a whole taxonomic group, because they found that it was absent in one or a number of species (Bornhold and Milliman 1973; Taylor et al. 1969). The first published documentation of this phenomenon (Lowenstam 1954a) clearly showed that closely related organisms can differ in this respect and that extrapolations and sweeping conclusions are not justified.

Abstract Seawater injection is an EOR success in the North Sea carbonate reservoirs due to wettability alteration toward a more water-wet state, this process is triggered by the difference in composition between injection and formation water. "Smart Water" with optimized ionic composition can be easily made under laboratory conditions to improve oil recovery beyond that of seawater, however, in the field, its preparation may require specific water treatment processes, e.g., desalination, nano-filtration or addition of specific salts. In this work, a naturally occurring salt called polysulphate (PS) is investigated as an additive to produce Smart Water. Outcrop chalk from Stevns Klint, consisting of 98% biogenic CaCO3, was used to investigate the potential and efficiency of the polysulphate brines to alter wettability in chalk. Solubility of polysulphate in seawater and de-ionized water and brine stability at high temperatures were measured. Energy Dispersive X-Ray and ion chromatography were used to determine the composition of the polysulphate salt and EOR-solutions, and to evaluate the sulphate adsorption on the chalk surface, a catalyst for the wettability alteration process. Spontaneous imbibition, for evaluating wettability alteration, of polysulphate brines into mixed-wet chalk was performed at 90 and 110°C and compared against the recovery performance of formation water and seawater. The solubility tests showed that the salt was easily soluble in both de-ionized water and seawater with less than 5% solid residue. The de-ionized polysulphate brine contained sulphate and calcium ion concentration of 31.5 millimolar (mM) and 15.2 mM, respectively, and total salinity was 4.9 g/L. This brine composition is very promising for triggering wettability alteration in chalk. The seawater polysulphate brine contained 29.6 mM calcium ions and 55.9 mM sulphate ions, and a total salinity of 38.1 g/L. Compared to ordinary seawater this brine has the potential for improved wettability alteration in chalk due to increased sulphate content. Ion chromatography revealed that the sulphate adsorbed when polysulphate brines were flooded through the core, which is an indication that wettability alteration can take place during brine injection, the reactivity was also enhanced by increasing the temperature from 25 to 90 °C. Finally, the oil recovery tests by spontaneous imbibition showed that polysulphate brines were capable of inducing wettability alteration, improving oil recovery beyond that obtained by formation water injection. The difference in oil recovery between ordinary seawater and seawater polysulphate injection was smaller due to the already favorable composition of seawater. Polysulphate brines showed a significant potential for wettability alteration in carbonates and are validated as a potential EOR additives for easy and on-site preparation of Smart Water brines for carbonate oil reservoirs. Polysulphate salt, added to the EOR-solution, provides the essential ions for the wettability alteration process, but further optimization is needed to characterize the optimal mixing ratios, ion compositions, and temperature ranges at which EOR effects can be achieved.

A complex of modern physical investigations of carbonate crusts covering Lower Miocene bryozoan limestone from the Kazantip Cape showed that bryozoans built a biohermal skeleton due to the synsedimentation of bioinduced cement. The mineral association (Mg-calcite + aragonite) indicates the existence of near-bottom environment typical for gas-hydrate biogenic mineral formation as a result of bacterial methane oxidation during the formation of bioherms. The presence of bitumen, pyrite, strontianite, barite, kutnohorite and traces of vital activity of carbonate-depositing methanotrophic bacteria in the composition of carbonate crusts is concerned with a significant influence of near-bottom local gas-fluid seeps.