Major Carbonate Producers Research Articles

Crustose red algae in deep time environments: Palaeoecological insights from northeastern India and Türkiye (Turkey)

Crustose red calcareous algae are key organisms in benthic ecosystems worldwide with critical functions like reef-building and substrate stabilization. Coralline algae thrived as major carbonate producers, with corals and/or larger benthic foraminifera (LBF) in numerous shallow-marine Tethyan carbonate platforms from the early Palaeogene to the Neogene. The Palaeocene–Eocene limestone successions in the Jaintia and Khasi Hills, Meghalaya, northeastern India, encompass two principal community types — algal-foraminiferal and coralline algal, with no associated colonial corals, while the Oligocene–Miocene carbonates from the Sivas basin and Siirt province in Türkiye are characterized by an algal-foraminifera assemblage with bryozoans, corals, and molluscs as other noteworthy components pertinent to the carbonate platform environment. We found that the diversity and ecology of these algal communities were influenced by systematic structure of the algal assemblage, sediment input, substrate stability, water depth, and hydrodynamic energy. The algal assemblages from different epochs and varying localities diverge based on the sedimentary regime, environmental settings, and the predominant taxa. The climatic transition from the Palaeocene–Eocene greenhouse to the Oligocene–Miocene icehouse corresponded to a shift from crustose algal assemblages dominated by Sporolithales to assemblages dominated by Hapalidiales.

Quantifying the contribution of major carbon producers to increases in vapor pressure deficit and burned area in western US and southwestern Canadian forests

Increases in burned forest area across the western United States and southwestern Canada over the last several decades have been partially driven by a rise in vapor pressure deficit (VPD), a measure of the atmosphere’s drying power that is significantly influenced by human-caused climate change. Previous research has quantified the contribution of carbon emissions traced back to a set of 88 major fossil fuel producers and cement manufacturers to historical global mean temperature rise. In this study, we extend that research into the domain of forest fires. We use a global energy balance carbon-cycle model, a suite of climate models, and a burned area (BA) model to determine the contribution of emissions traced to the major carbon producers to the long-term increase in VPD during 1901–2021 and to cumulative forest fire area during 1986–2021 in the western US and southwestern Canada. Based on climate model data, we find that emissions traced to these carbon producers contributed 48% (interquartile range (IQR) 38%–63%) of the long-term rise in VPD between 1901 and 2021. BA modeling indicates that these emissions also contributed 37% (IQR 26%–47%) of the cumulative area burned by forest fires between 1986 and 2021 in the western US and southwestern Canada. The increase in VPD in this region is linked to both increased fire activity and the region’s current and prolonged megadrought. As loss and damage from these hazards mounts, this research can inform public and legal dialogues regarding the responsibility carbon producers bear for addressing past, present, and future climate risks associated with fires and drought in the western US and southwestern Canada.

Stratigraphy and facies of the Apennine Carbonate Platform (southern Italy): the record of Mesozoic OAEs and Miocene transgression

The Apennine Carbonate Platform of southern Italy witnesses nearly 150 Myr (Late Triassic to Late Cretaceous) of shallow-water carbonate sedimentation in the subtropical central Tethys. During this field trip, you will have a look at the stratigraphy and facies across some key intervals of global palaeoenvironmental perturbation and at some important stratigraphic discontinuities in the history of the platform.During the first day, you will visit three localities of the Matese Mts. At San Lorenzello you will look at Milankovitch cyclicity expressed in Lower Cretaceous (Valanginian-Hauterivian) peritidal carbonates. At Pietraroja you will have a look at the foramol facies of the Cusano formation, marking the Early Miocene transgression on top of the eroded Cretaceous substrate. Moving north, at the Regiapiana you will see the abandoned mines that exploited the mid-Cretaceous karst bauxites, which mark a prolonged subaerial exposure. Moreover, you will walk through the Middle Miocene synorogenic history of the platform, from its exposure and erosion in the forebulge to its incipient flexural subsidence, highlighted by the Lower Miocene carbonates of the Cusano formation, to its drowning below the photic zone, marked by a phosphatic hardground overlain by the Orbulina marls of the Longano formation.During the second day, you will head south toward Salerno. In a quarry at Mercato San Severino, you will look at the record of the early Toarcian oceanic anoxic event, marked by the abrupt demise of lithiotid bivalves and dasycladalean algae, the major carbonate producers of the Lower Jurassic carbonate platforms. At the base of Mt Tobenna, you will look at the Aptian Orbitolina level: a marker bed whose palaeoenvironmental meaning has been long debated. From Mt Tobenna you will move south toward Monteforte Cilento where you will look at the record of the Cenomanian-Turonian OAE2 in the Apennine Carbonate Platform.

Multiple phyla, one time resolution? Similar time averaging in benthic foraminifera, mollusk, echinoid, crustacean, and otolith fossil assemblages

Abstract Time averaging of fossil assemblages determines temporal precision of paleoecological and geochronological inferences. Taxonomic differences in intrinsic skeletal durability are expected to produce temporal mismatch between co-occurring species, but the importance of this effect is difficult to assess due to lack of direct estimates of time averaging for many higher taxa. Moreover, burial below the taphonomic active zone and early diagenetic processes may alleviate taxonomic differences in disintegration rates in subsurface sediments. We compared time averaging across five phyla of major carbonate producers co-occurring in a sediment core from the northern Adriatic Sea shelf. We dated individual bivalve shells, foraminiferal tests, tests and isolated plates of irregular and regular echinoids, crab claws, and fish otoliths. In spite of different skeletal architecture, mineralogy, and life habit, all taxa showed very similar time averaging varying from ~1800 to ~3600 yr (interquartile age ranges). Thus, remains of echinoids and crustaceans—two groups with multi-elemental skeletons assumed to have low preservation potential—can still undergo extensive age mixing comparable to that of the co-occurring mollusk shells. The median ages of taxa differed by as much as ~3700 yr, reflecting species-specific timing of seafloor colonization during the Holocene transgression. Our results are congruent with sequestration models invoking taphonomic processes that minimize durability differences among taxa. These processes together with temporal variability in skeletal production can overrule the effects of durability in determining temporal resolution of multi-taxic fossil assemblages.

Development and collapse of the early Cambrian shallow-water carbonate factories in the Hannan-Micangshan area, South China

The development of carbonate factories has potential importance in studies of paleoenvironment, sedimentology, and reservoir geology, but the mechanisms controlling the growth and demise of the large amount of carbonate sedimentation have not been broadly investigated, especially in terms of deep-time sedimentary records. Here, we provide a high-resolution study of the development and collapse of a series of tropical shallow-water carbonate factories distributed in the Hannan-Micangshan area of the South China Craton during the early Cambrian (Age 3). Unlike modern tropical shallow-water factories, the major carbonate producers in the early Cambrian factories contained ooids, benthic microbial communities (predominantly calcified microbes), and symbiotic microbial-skeletal organisms (i.e., calcimicrobial–archaeocyath bioherms). The ooid factories were mostly distributed in the tidal sand complexes around the Hannan-Micangshan massif; and some of the mixed quartz-ooid deposits may have been remodeled by terrigenous sands sourced from the adjacent fluviodeltaic delivery. The microbial carbonate factory was primarily characterized by thrombolites in terms of the lithological composition, with a small contribution of stromatolites and oncolites (grain sizes mostly of 2–4 cm). The thrombolites formed not only mound architectures individually (length of ~1–5 m, and height of ~0.5–2.5 m), but also small- to large-scale bioherms associated with reef-building skeletal organisms (i.e., archaeocyaths). Nutrient conditions may have played an essential role in regulating the distributions of the microbial and microbial-skeletal factories (mesotrophic conditions), but they did not have a significant effect on the ooid factories. These tropical shallow-water carbonate factories were located in oxygenated aqueous environments with some small transient low-oxygen intervals that corresponded to barrier microbial and microbial-skeletal factories in the study area. Hydrodynamic condition and other controls (e.g., wind) may have played roles in shaping the factory morphology and distribution features in the study area. The chemical index of alteration (CIA; values of 60–65) and petrological features (occurrence of large-scale ooid sand complexes) support a warm and dry climate during the development of these tropical shallow-water factories. Finally, the transition from carbonate-dominated to siliciclastic-dominated depositional systems driven by wetter climate conditions (CIA, close to 70) may have been responsible for the cessation of the shallow-water carbonate factories in the Hannan-Micangshan area, which resulted in a rapid drowning, and subsequently, continuous input of a high volume of siliciclastics in late Age 3 to early Age 4 (Yanwangbian Formation). This study provides clues to understanding the growth and demise of deep-time tropical carbonate factories and serves as a valuable reference for studies of other regions and time periods. • We present a high-resolution study of the tropical shallow-water carbonate factories. • These factories contained ooids, calcified microbes, and skeletal organisms. • Nutrient conditions may have played a key role in regulating factory distributions. • Hydrodynamic condition and wind shaped the factory morphology and distribution. • The shift of the depositional system was likely responsible for factory collapse.

Decrease in volume and density of foraminiferal shells with progressing ocean acidification

Rapid increases in anthropogenic atmospheric CO2 partial pressure have led to a decrease in the pH of seawater. Calcifying organisms generally respond negatively to ocean acidification. Foraminifera are one of the major carbonate producers in the ocean; however, whether calcification reduction by ocean acidification affects either foraminiferal shell volume or density, or both, has yet to be investigated. In this study, we cultured asexually reproducing specimens of Amphisorus kudakajimensis, a dinoflagellate endosymbiont-bearing large benthic foraminifera (LBF), under different pH conditions (pH 7.7–8.3, NBS scale). The results suggest that changes in seawater pH would affect not only the quantity (i.e., shell volume) but also the quality (i.e., shell density) of foraminiferal calcification. We proposed that pH and temperature affect these growth parameters differently because (1) they have differences in the contribution to the calcification process (e.g., Ca2+-ATPase and Ω) and (2) pH mainly affects calcification and temperature mainly affects photosynthesis. Our findings also suggest that, under the IPCC RCP8.5 scenario, both ocean acidification and warming will have a significant impact on reef foraminiferal carbonate production by the end of this century, even in the tropics.

Origin of a global carbonate layer deposited in the aftermath of the Cretaceous-Paleogene boundary impact

Microcrystalline calcite (micrite) dominates the sedimentary record of the aftermath of the Cretaceous–Paleogene (K–Pg) impact at 31 sites globally, with records ranging from the deep ocean to the Chicxulub impact crater, over intervals ranging from a few centimeters to more than seventeen meters. This micrite-rich layer provides important information about the chemistry and biology of the oceans after the impact. Detailed high-resolution scanning electron microscopy demonstrates that the layer contains abundant calcite crystals in the micron size range with a variety of forms. Crystals are often constructed of delicate, oriented agglomerates of sub-micrometer mesocrystals indicative of rapid precipitation. We compare the form of crystals with natural and experimental calcite to shed light on their origin. Close to the crater, a significant part of the micrite may derive from the initial backreaction of CaO vaporized during impact. In more distal sites, simple interlocking rhombohedral crystals resemble calcite precipitated from solution. Globally, we found unique calcite crystals associated with fossilized extracellular materials that strikingly resemble calcite precipitated by various types of bacteria in natural and laboratory settings. The micrite-rich layer contains abundant bacterial and eukaryotic algal biomarkers and most likely represents global microbial blooms initiated within millennia of the K–Pg mass extinction. Cyanobacteria and non-haptophyte microalgae likely proliferated as dominant primary producers in cold immediate post-impact environments. As surface-water saturation state rose over the following millennia due to the loss of eukaryotic carbonate producers and continuing river input of alkalinity, “whitings” induced by cyanobacteria replaced calcareous nannoplankton as major carbonate producers. We postulate that the blooms grew in supersaturated surface waters as evidenced by crystals that resemble calcite precipitates from solution. The microbial biomass may have served as a food source enabling survival of a portion of the marine biota, ultimately including life on the deep seafloor. Although the dominance of cyanobacterial and algal photosynthesis would have weakened the biological pump, it still would have removed sufficient nutrients from surface waters thus conditioning the ocean for the recovery of biota at higher trophic levels.

Foraminiferal holobiont thermal tolerance under future warming – roommate problems or successful collaboration?

Abstract. Understanding the response of marine organisms to expected future warming is essential. Large benthic foraminifera (LBF) are symbiont-bearing protists considered to be major carbonate producers and ecosystem engineers. We examined the thermal tolerance of two main types of LBF holobionts characterized by different algal symbionts and shell types (resulting from alternative biomineralization mechanisms): the hyaline diatom-bearing Amphistegina lobifera and the porcellaneous-dinoflagellate-bearing Sorites orbiculus. In order to assess the holobiont thermal tolerance we separately evaluated foraminiferal calcification rates and symbionts' net photosynthesis under present-day and future warming scenarios. Our results show that both holobionts exhibit progressive loss-of-life functions between 32 and 35 ∘C. This sensitivity differs in the magnitude of their response: calcification of A. lobifera was drastically reduced compared with S. orbiculus. Thus, future warming may significantly shift the relative contribution of the two species as carbonate producers. Moreover, A. lobifera exhibited a synchronous response of calcification and net photosynthesis. In contrast, in S. orbiculus the symbionts decreased net photosynthesis prior to calcification. This implies that algal symbionts limit the resilience of the halobiont.

Climate change and fossil fuel production cuts: assessing global supply-side constraints and policy implications

ABSTRACT This paper presents the first global database of supply-side climate initiatives seeking to constrain fossil fuel production. There is a clear imperative to keep a large proportion of fossil fuel reserves underground to keep global temperature rise under 2°C above pre-industrial levels. Yet, there is no global overview of supply-side initiatives taken to constrain fossil fuel production, making it difficult to track trends, compare efforts across countries, and assess the effectiveness of different supply-side approaches. The Fossil Fuel Cuts Database presented here identifies 1302 initiatives implemented between 1988 and 2017 in 106 countries across the seven major types of supply-side approaches. Documenting temporal and geographical patterns, we show a rapid growth in the number of supply-side initiatives taken during the past decade and their highly uneven adoption across the world. Most initiatives occurred in countries with low economic dependence on fossil fuel production and limited fossil fuel exports, with the partial exception of Canada and Norway at the national level, and the US at the sub-national level. We discuss policy implications and the need for further research to identify adoption factors, effectiveness, and policy implications. The documentation of a wide range of supply-side initiatives serves as a reminder that constraints on fossil fuel production need to be analysed and considered on a par with demand-side interventions, including in Assessment Reports of the Intergovernmental Panel on Climate Change (IPCC). Key policy insights Supply-side constraint initiatives have increased in the past decade, suggesting growing policy take-up and potential mitigation impacts. Supply-side initiatives clearly emphasize the key role and responsibility of major carbon producers, and help mobilize demand for greater accountability. Supply-side initiatives take many forms and can suit the capabilities of different actors, from civil society organizations to governments. Supply-side initiatives can usefully complement demand-side measures and help tackle free-rider problems. Larger coalitions of fossil fuel producers are required to address uneven adoption, prevent the relocation of production, and help producers transition away from fossil fuels.

Attributing ocean acidification to major carbon producers

Recent research has quantified the contributions of CO2 and CH4 emissions traced to the products of major fossil fuel companies and cement manufacturers to global atmospheric CO2, surface temperature, and sea level rise. This work has informed societal considerations of the climate responsibilities of these major industrial carbon producers. Here, we extend this work to historical (1880–2015) and recent (1965–2015) acidification of the world’s ocean. Using an energy balance carbon-cycle model, we find that emissions traced to the 88 largest industrial carbon producers from 1880–2015 and 1965–2015 have contributed ∼55% and ∼51%, respectively, of the historical 1880–2015 decline in surface ocean pH. As ocean acidification is not spatially uniform, we employ a three-dimensional ocean model and identify five marine regions with large declines in surface water pH and aragonite saturation state over similar historical (average 1850–1859 to average 2000–2009) and recent (average 1960–1969 to average of 2000–2009) time periods. We characterize the biological and socioeconomic systems in these regions facing loss and damage from ocean acidification in the context of climate change and other stressors. Such analysis can inform societal consideration of carbon producer responsibility for current and near-term risks of further loss and damage to human communities dependent on marine ecosystems and fisheries vulnerable to ocean acidification.

Evolutionary significance of the microbial assemblages of large benthic Foraminifera

ABSTRACTLarge benthic Foraminifera (LBF) are major carbonate producers on coral reefs, and are hosts to a diverse symbiotic microbial community. During warm episodes in the geological past, these reef‐building organisms expanded their geographical ranges as subtropical and tropical belts moved into higher latitudes. During these range‐expansion periods, LBF were the most prolific carbonate producers on reefs, dominating shallow carbonate platforms over reef‐building corals. Even though the fossil and modern distributions of groups of species that harbour different types of symbionts are known, the nature, mechanisms, and factors that influence their occurrence remain elusive. Furthermore, the presence of a diverse and persistent bacterial community has only recently gained attention. We examined recent advances in molecular identification of prokaryotic (i.e. bacteria) and eukaryotic (i.e. microalgae) associates, and palaeoecology, and place the partnership with bacteria and algae in the context of climate change. In critically reviewing the available fossil and modern data on symbiosis, we reveal a crucial role of microalgae in the response of LBF to ocean warming, and their capacity to colonise a variety of habitats, across both latitudes and broad depth ranges. Symbiont identity is a key factor enabling LBF to expand their geographic ranges when the sea‐surface temperature increases. Our analyses showed that over the past 66 million years (My), diatom‐bearing species were dominant in reef environments. The modern record shows that these species display a stable, persistent eukaryotic assemblage across their geographic distribution range, and are less dependent on symbiotic photosynthesis for survival. By contrast, dinoflagellate and chlorophytic species, which show a provincial distribution, tend to have a more flexible eukaryotic community throughout their range. This group is more dependent on their symbionts, and flexibility in their symbiosis is likely to be the driving force behind their evolutionary history, as they form a monophyletic group originating from a rhodophyte‐bearing ancestor. The study of bacterial assemblages, while still in its infancy, is a promising field of study. Bacterial communities are likely to be shaped by the local environment, although a core bacterial microbiome is found in species with global distributions. Cryptic speciation is also an important factor that must be taken into consideration. As global warming intensifies, genetic divergence in hosts in addition to the range of flexibility/specificity within host–symbiont associations will be important elements in the continued evolutionary success of LBF species in a wide range of environments. Based on fossil and modern data, we conclude that the microbiome, which includes both algal and bacterial partners, is a key factor influencing the evolution of LBF. As a result, the microbiome assists LBF in colonising a wide range of habitats, and allowed them to become the most important calcifiers on shallow platforms worldwide during periods of ocean warming in the geologic past. Since LBF are crucial ecosystem engineers and prolific carbonate producers, the microbiome is a critical component that will play a central role in the responses of LBF to a changing ocean, and ultimately in shaping the future of coral reefs.

Responsible for what? Carbon producer CO2 contributions and the energy transition

Judgments of moral responsibility should be informed by both scientific analysis and societal standards. Society distinguishes responsibilities into positive and negative, general and special, and backward-looking and forward-looking. Ekwurzel et al. in Clim Chang 2017 shows that 90 major carbon producers have contributed most of the atmospheric CO2 emissions. Once it became clear no later than the 1960s that continuing CO2 emissions would progressively undermine the climate, the major carbon producers could see that they were marketing harmful products. The simple and merely negative responsibility to “do no harm” required them to reduce that harm rapidly either by modifying the product in order to capture its dangerous emissions or by developing safe substitutes to perform the same function, that is, by developing non-carbon-based forms of energy. The seriousness of the harms brought by climate change made this responsibility especially compelling. Ceasing to contribute to harm includes ending exploration for additional fossil fuels. The half century of failure by corporate carbon producers to reduce the harms caused by their products now gives them additional responsibility to correct the damage done by their decades of neglect of the underlying negative responsibility. If major carbon producers also wish to fulfill the general responsibility to make more than a minimal positive social contribution, their distinctive capacities of political power, wealth, and expertise qualify them for leadership in the transition to an energy regime that would be safe for future generations to rely on.

The rise in global atmospheric CO2, surface temperature, and sea level from emissions traced to major carbon producers

Researchers have quantified the contributions of industrialized and developing nations’ historical emissions to global surface temperature rise. Recent findings that nearly two-thirds of total industrial CO2 and CH4 emissions can be traced to 90 major industrial carbon producers have drawn attention to their potential climate responsibilities. Here, we use a simple climate model to quantify the contribution of historical (1880–2010) and recent (1980–2010) emissions traced to these producers to the historical rise in global atmospheric CO2, surface temperature, and sea level. Emissions traced to these 90 carbon producers contributed ∼57% of the observed rise in atmospheric CO2, ∼42–50% of the rise in global mean surface temperature (GMST), and ∼26–32% of global sea level (GSL) rise over the historical period and ∼43% (atmospheric CO2), ∼29–35% (GMST), and ∼11–14% (GSL) since 1980 (based on best-estimate parameters and accounting for uncertainty arising from the lack of data on aerosol forcings traced to producers). Emissions traced to seven investor-owned and seven majority state-owned carbon producers were consistently among the top 20 largest individual company contributors to each global impact across both time periods. This study lays the groundwork for tracing emissions sourced from industrial carbon producers to specific climate impacts and furthers scientific and policy consideration of their historical responsibilities for climate change.

Microfacies analysis of larger benthic foraminifera-dominated Middle Eocene carbonates: a palaeoenvironmental case study from Meghalaya, N-E India (Eastern Tethys)

Larger benthic foraminifera (LBF) show significant abundance and diversity in the Palaeogene carbonate sediments of Meghalaya, N-E India, but have previously received less attention from the palaeoenvironmental perspective. LBF are important contributors to recent as well as fossil shallow marine, tropical carbonate settings. They find wide application in biostratigraphy and palaeoenvironmental reconstructions. The larger foraminiferal turnover (LFT) during the Palaeocene-Eocene transition is very important with respect to their evolution in several parts of the world including the Eastern Tethys. The present microfacies analysis documents the status of LBF in the Middle Eocene sediments from the Prang Formation of the Sylhet Limestone Group in Meghalaya, N-E India. Five major facies types (MFTs)—miliolid grainstone-packstones, alveolinid-rotaliid grainstone-packstones, nummulitid-alveolinid grainstone-packstones, coralline algal-nummulitid packstone-wackestones and coralline algal wackestones have been recorded in the current study. Evaluation of the palaeoenvironmental parameters aids in understanding the seascape of this Eastern Tethyan domain. It is suggested that an oligotrophic nutrient regime supported the rapid evolution and dominance of the LBF. Most notable is the prolific augmentation in Alveolina and Nummulites populations. High surface water temperatures during the Late Palaeocene-Early Eocene global warming episode possibly persisted to a certain level during the Middle Eocene and continued to favour the larger foraminifera as the major carbonate producers instead of the vulnerable corals.

Regional‐scale dominance of non‐framework building corals on Caribbean reefs affects carbonate production and future reef growth

Coral cover on Caribbean reefs has declined rapidly since the early 1980's. Diseases have been a major driver, decimating communities of framework building Acropora and Orbicella coral species, and reportedly leading to the emergence of novel coral assemblages often dominated by domed and plating species of the genera Agaricia, Porites and Siderastrea. These corals were not historically important Caribbean framework builders, and typically have much smaller stature and lower calcification rates, fuelling concerns over reef carbonate production and growth potential. Using data from 75 reefs from across the Caribbean we quantify: (i) the magnitude of non-framework building coral dominance throughout the region and (ii) the contribution of these corals to contemporary carbonate production. Our data show that live coral cover averages 18.2% across our sites and coral carbonate production 4.1kg CaCO3 m(-2) yr(-1) . However, non-framework building coral species dominate and are major carbonate producers at a high proportion of sites; they are more abundant than Acropora and Orbicella at 73% of sites; contribute an average 68% of the carbonate produced; and produce more than half the carbonate at 79% of sites. Coral cover and carbonate production rate are strongly correlated but, as relative abundance of non-framework building corals increases, average carbonate production rates decline. Consequently, the use of coral cover as a predictor of carbonate budget status, without species level production rate data, needs to be treated with caution. Our findings provide compelling evidence for the Caribbean-wide dominance of non-framework building coral taxa, and that these species are now major regional carbonate producers. However, because these species typically have lower calcification rates, continued transitions to states dominated by non-framework building coral species will further reduce carbonate production rates below 'predecline' levels, resulting in shifts towards negative carbonate budget states and reducing reef growth potential.

Biomineralization ofSchlumbergerella floresiana, a significant carbonate‐producing benthic foraminifer

Most foraminifera that produce a shell are efficient biomineralizers. We analyzed the calcitic shell of the large tropical benthic foraminifer Schlumbergerella floresiana. We found a suite of macromolecules containing many charged and polar amino acids and glycine that are also abundant in biomineralization proteins of other phyla. As neither genomic nor transcriptomic data are available for foraminiferal biomineralization yet, de novo-generated sequences, obtained from organic matrices submitted to ms blast database search, led to the characterization of 156 peptides. Very few homologous proteins were matched in the proteomic database, implying that the peptides are derived from unknown proteins present in the foraminiferal organic matrices. The amino acid distribution of these peptides was queried against the uniprot database and the mollusk uniprot database for comparison. The mollusks compose a well-studied phylum that yield a large variety of biomineralization proteins. These results showed that proteins extracted from S.floresiana shells contained sequences enriched with glycine, alanine, and proline, making a set of residues that provided a signature unique to foraminifera. Three of the de novo peptides exhibited sequence similarities to peptides found in proteins such as pre-collagen-P and a group of P-type ATPases including a calcium-transporting ATPase. Surprisingly, the peptide that was most similar to the collagen-like protein was a glycine-rich peptide reported from the test and spine proteome of sea urchin. The molecules, identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry analyses, included acid-soluble N-glycoproteins with its sugar moieties represented by high-mannose-type glycans and carbohydrates. Describing the nature of the proteins, and associated molecules in the skeletal structure of living foraminifera, can elucidate the biomineralization mechanisms of these major carbonate producers in marine ecosystems. As fossil foraminifera provide important paleoenvironmental and paleoclimatic information, a better understanding of biomineralization in these organisms will have far-reaching impacts.

Mineralogy of Arctic bryozoan skeletons in a global context

Bryozoans are major carbonate producers in some ancient and Recent benthic environments, including parts of the Arctic Ocean. Seventy-six species of bryozoans from within the Arctic Circle have been studied using XRD to determine their carbonate mineralogies and the Mg content of the calcite. The majority of species were found to be calcitic, only four having bimineralic skeletons that combined calcite and aragonite, and none being entirely aragonitic. In almost all species, the calcite was of the low- (<4 mol% MgCO3) or intermediate-Mg (4–11.99 mol% MgCO3) varieties. Previous regional studies of bryozoan biomineralogy have found higher proportions of bimineralic and/or aragonitic species in New Zealand and the Mediterranean, with a greater number of calcitic species employing intermediate- and high-Mg calcite. The Antarctic bryozoan fauna, however, has a similar mineralogical composition to the Arctic. The lesser solubility of low-Mg calcite compared to both Mg calcite and aragonite in cold polar waters is most likely responsible for this latitudinal pattern. However, it is unknown to what extent environmental factors drive the pattern directly through eliciting an ecophenotypic response from the bryozoans concerned or the pattern reflects genetic adaptations by particular bryozoan clades.

Carbonate deposits on submerged seamounts in the northwestern Pacific Ocean

Abstract The lithology of shallow‐water carbonates collected from 19 sites on 16 seamounts in six areas of the northwestern Pacific Ocean using the Deep‐sea Boring Machine System are described. The areas include the Amami Plateau, Daito Ridge, Oki‐Daito Ridge, Urdaneta Plateau, Kyushu‐Palau Ridge and Ogasawara Plateau. Chronological constraint is provided by calcareous nannofossil biostratigraphy, planktonic foraminiferal biostratigraphy, larger foraminiferal biostratigraphy and strontium (Sr) isotope stratigraphy. Large amounts of shallow‐water carbonates accumulated on the seamounts during the Oligocene, a relatively cool period, whereas limited carbonate deposits formed during the Early Miocene, a relatively warm period. This might indicate that deposition of shallow‐water carbonates on seamounts in the northwestern Pacific Ocean was not necessarily controlled by climatic conditions, but was related to volcanism and tectonics that served as foundations for reef/carbonate‐platform formation. Remarkable differences in biotic composition exist between Cretaceous and Cenozoic shallow‐water carbonates. Late Cretaceous shallow‐water carbonates are distinguished by the occurrence of rudists, solenoporacean algae and microencrusters. Middle Eocene to Early Oligocene shallow‐water carbonates are dominated byHalimedaor nummulitid and discocyclinid larger foraminifers. Scleractinian corals became common from the Oligocene onward. Nongeniculate coralline algae and larger foraminifers were common to abundant throughout the Eocene to the Pleistocene. The replacement of major carbonate producers in the shallow‐water carbonate factory during post‐Cretaceous time is in accordance with previous studies and is considered to reflect a shift in seawater chemistry.

Ocean circulation and calcareous nannoplankton evolution during the jurassic and cretaceous

Spatial and temporal distribution of calcareous nannoplankton aid in the reconstruction of ocean circulation during the Cretaceous. Biogeographic patterns of calcareous nannoplankton during the late Cretaceous are mostly zonal, reflecting mostly latitudinal gradients of surface water temperature. During the middle Cretaceous calcareous nannofossil assemblages are more strongly affected by surface water fertility (concentration of limiting nutrients) especially in a wide tropical belt between 50° and 45°N latitudes. Major upwelling regions off northwest Africa, in the south Atlantic, and the equatorial Pacific divergence are apparent. Temporal changes in the composition of middle Cretaceous nannofloras are indicative of changes in surface water fertility and vertical mixing at frequencies of tens to hundreds of kiloyears (ka). Changes in the intensity of atmospheric circulation with frequencies close to the Milankovitch cycles appear to be the ultimate cause of these minor changes in the circulation of the upper ocean. Calcareous nannofossil preservation patterns show that during the Middle Cretaceous deep waters were quite homogeneous with respect to carbonate saturation in the Atlantic Ocean but not in the Indo-Pacific Ocean where a more distinctive calcite compensation depth (CCD) is apparent. Water-mass structure of the major oceans during the Mesozoic was thus quite different. Taxonomic evolution of calcareous nannofossils was also strongly affected by ocean circulation and fertility. Major peaks in the rates of diversification coincide with anoxic events, that is periods of increased preservation of organic carbon in the oceans which coincide with high sea level stands. During anoxic events ocean circulation was sluggish, vertical mixing was slow, deep ocean ventilation poor, and the concentration of limiting nutrients in surface waters was low. Increased competition for limiting nutrients and possibly preferential cropping of the dominant forms by zooplankton resulted in increased rates oof speciation during anoxic events. Periods of major production of nannofossil carbonate coincided with low sea-level stands when oceans were more vigorously stirred and surface waters were more fertile. The first such period was the latest Jurassic when calcareous nannoplankton invaded the open oceans and became the major carbonate producers in the pelagic realm during the Mesozoic. The frequency of peaks and troughs in evolutionary rates is on the order of 10–30 Ma and appears to be irregular. The coincidence of periods of anoxia with high sea-level stands, which in turn appear to be caused by more rapid sea-floor spreading indicates that the ultimate diving forces of nannoplankton evolution are processes in the earth's mantle. These major tectonically driven fluctuations in ocean-atmosphere circulation with frequencies of a few million to a few tens of millions of years are hereby named Fischer cycles. Superimposed astronomically driven Milankovitch cycles affected relative abundance patterns but not taxonomic evolution of calcareous nannoplankton. Rates of nannoplankton extinction are about five times higher than background rates at the end of the Jurassic and orders of magnitude higher in the latest Cretaceous possibly indicating a terrestrial or extraterrestrial catastrophe.

The role of nutrient availability in bioerosion: Consequences to carbonate buildups

Zooxanthellate organisms, which are among the major carbonate producers on coral reefs, are highly adapted to nutrient-deficient conditions and tend to be outcompeted by filamentous or fleshy algae if nutrients are abundant. Reef-dwelling bioeroding organisms, on the other hand, seem to increase in abundance with increasing availability of nutrient and food resources. Maximum rates of calcium carbonate production in a reef system are comparable in magnitude to maximum rates of bioerosion. The dynamic interplay between accretion destruction of coral reefs is therefore likely to be strongly influenced by nutrient availability. Nutrient availability may also influence development of carbonate facies. In reef systems that develop in oligotrophic waters, skeletal sands and framework should dominate carbonate buildups. In systems that develop in mesotrophic waters, enhanced bioerosion should reduce much of the skeletal material to carbonate muds, increasing the prevalence of mud-rich facies. Eutrophic conditions should result in bioeroded hardgrounds and carbonate depositional hiatuses. When carbonate accumulation rates fail to equal or exceed rates of local relative sea-level rise, reefs drown. Bored and lithified pavements with crusts of ferromanganese oxides, phosphates, or glauconite often separate shallow-reef from overlying deeper-water deposits. Nondeposition, bioerosion, and evidence for low redox potentials at the sediment-water interface all implicate excess nutrient availability as a factor in reef drowning. Some carbonate depositional hiatuses and bioerosional surfaces are local phenomena, evidence of responses to local increases in nutrient availability resulting from submergence of soils, runoff, or topographic upwelling. Others appear to reflect regional or worldwide events. Because many carbonate-producing organisms have life history strategies specialized to nutrient-deficient conditions, they are unable to compete when nutrients become plentiful. Events that triggered ocean turnover or sharp increases in the rate of deep ocean circulation would have increased sea-surface nutrient availability worldwide. Such eutrophication could have caused widespread extinctions in reef communities. Because eutrophication promotes bioerosion, details of the fossil records of those events are probably lost in bioerosional hiatuses.