Carbon Production Rates Research Articles

Fabrication and evaluation of the Mn-promoted Ni/FeAl2O4 catalysts in the thermocatalytic decomposition of methane: Impact of various promoters

This research is focused on the designing and developing catalytic systems over various metal oxides (CuO, Cr2O3, Co3O4, ZnO, and MnO2) promoted NiO/FeAl2O4 catalysts in the thermocatalytic decomposition of CH4. The catalysts were synthesized based on the wet impregnation method, and the nominal NiO content was fixed at 50 wt% along with each transition metal at 10 wt%. The controlled preparation method caused the sample doped with MnO2 to show the highest specific surface area (46.8 m2/g) and the lowest particle size (10.6 nm) among the promoted samples. The activity test revealed that the MnO2(10)-NiO(50)/FeAl2O4 catalyst was the most active and stable catalyst in the CH4 decomposition reaction. At 700 °C, the CH4 conversion and H2 yield were 62.3 and 66 % over this catalyst. Also, the decline in its initial activity was only 3 % during the 300 min reaction time at 575 °C. Also, the results indicated that the catalytic efficiency and rate of carbon production increased by raising the MnO2 content from 5 to 10 wt%. However, the high amount of the deposited carbon and decline in metal dispersion led to the catalytic activity being reduced when the MnO2 loading was increased from 10 to 15 wt%. The impact of calcination temperature (600, 700, and 800 °C) was also investigated on the characterization features and conversion rate of the selected catalyst, and the results revealed that the catalyst calcined at 600 °C displayed the highest efficiency under studied conditions. Furthermore, the results indicated that the catalytic activity and stability decreased by increasing the GHSV value from 40000 to 60000 ml.h−1.g-1cat and CH4:N2 molar ratio from 10:90 to 30:70. Also, the CH4 conversion decreased from 47 to 28 % when the reduction temperature increased from 700 to 800 °C, respectively.

Upwelling, climate change, and the shifting geography of coral reef development

The eastern tropical Pacific is oceanographically unfavorable for coral-reef development. Nevertheless, reefs have persisted there for the last 7000 years. Rates of vertical accretion during the Holocene have been similar in the strong-upwelling Gulf of Panamá (GoP) and the adjacent, weak-upwelling Gulf of Chiriquí (GoC); however, seasonal upwelling in the GoP exacerbated a climate-driven hiatus in reef development in the late Holocene. The situation is now reversed and seasonal upwelling in the GoP currently buffers thermal stress, creating a refuge for coral growth. We developed carbonate budget models to project the capacity of reefs in both gulfs to keep up with future sea-level rise. On average, the GoP had significantly higher net carbonate production rates than the GoC. With an estimated contemporary reef-accretion potential (RAP) of 5.5 mm year−1, reefs in the GoP are projected to be able to keep up with sea-level rise if CO2 emissions are reduced, but not under current emissions trajectories. With an estimated RAP of just 0.3 mm year−1, reefs in the GoC are likely already unable to keep up with contemporary sea-level rise in Panamá (1.4 mm year−1). Whereas the GoP has the potential to support functional reefs in the near-term, our study indicates that their long-term persistence will depend on reduction of greenhouse gases.

Nitrogen-doped graphene prepared by high-temperature carbonization of polydopamine film

Inspired by the mussel sticky protein, polydopamine (PDA) has attracted wide attention due to its extremely strong adhesion ability, unique biocompatibility and hydrophilicity, which can be conformally coated on almost all materials. In addition, due to its excellent carbon production rate and excellent structural control capabilities under inert gas, PDA is also used as the source of carbon nanomaterials, its derived carbon materials are used in front-edge fields such as flexible electronics, energy storage. In this paper, polydopamine was carbonized at 800℃ and explores the structure of PDA after carbonized. It is found it forms a structure of nitrogen doped graphene.

Experimental study on the calcium carbonate production rates and crystal size of EICP under multi-factor coupling

The production and microstructure of calcium carbonate are the fundamental indicators to evaluate the effectiveness of Enzyme-induced Carbonate Precipitation (EICP). Soybean urease is extracted, and the urease activity is controlled by the soybean powder concentration in this study. The urease reacts with the cementation solution with different concentrations of urea and calcium ions at different temperatures to determine the calcium carbonate production rates (RCC). The crystal sizes of calcium carbonate (SCC) are investigated by scanning electron microscopy (SEM) and image processing method. The RCC increase and subsequently decrease with increasing calcium ion concentration and peak at 0.75 M. A lower urea concentration is more favourable to the formation of CaCO3. Increased urease activity and temperature will lead to an increased RCC and SCC. Some crystals appear as capsules when the temperature goes up. The SCC decreases slightly with increasing calcium ion concentration under low urease activity and increases under high urease activity. The SCC increases first and subsequently decreases with increasing urea concentration under high urease activity, while the effect of urea concentration under low urease activity is not significant. XRD test results show that the calcium carbonate produced in this study is dominated by calcite crystals. The study provides additional data, a useful base to move forward toward a better understanding of the method of stabilization and its applications, for example, the treatment of different soils.

An equation for deriving spatial variations in carbonate production rates from sediment deposition rates and dilution: Application to Santa Maria Island, Azores

ABSTRACT Knowledge of how carbonates are produced on shelves is needed for working out how these “carbonate factories” generate stratigraphy by providing particles for potential export or local deposition. Production rates can be derived straightforwardly in low-energy environments from one-dimensional analysis (age–depth variations) but rates are less easily derived for high-energy hydrodynamical environments where particles are transported away from their sites of production. This particularly affects knowledge of spatial variations in production rates, needed for working out controlling influences of light, hydrodynamics, and nutrient availability. We show here that, if a non-carbonate component of the sediment, such as terrigenous particles arising from coastal and subaerial erosion, is conserved and thus acts as a tracer, rates of carbonate production can in principle be derived from carbonate content data, if sediment transport fluxes can also be constrained. In the equation developed here, the spatial rate of change of carbonate content is caused by dilution of the terrigenous component by the newly produced carbonate and depends on the sediment transport flux. We investigate this idea using data from Santa Maria Island, Azores, an inactive volcanic island in a temperate environment. Geochemical, X-ray diffraction (XRD), and X-ray fluorescence (XRF) data of surface–sediment grab samples indicate nearly simple mixing trends between two components (volcanic rock and marine carbonate), as needed for our simple dilution-based equation to apply. High-resolution boomer seismic data reveal thicker (> 1 m) deposits in the mid- to outer shelf of the island, which we interpret as having been emplaced during the Holocene. These effectively provide time-averaged depositional fluxes and, assuming conservation of mass, can be used to constrain transport fluxes. The derived equation is used to predict the observed deposit thicknesses into the mid-shelf alongside coincident increasing carbonate percentages. The thicknesses are replicated only if carbonate production rates increase with depth and distance away from the coastline into the mid-shelf, quantifying the variation of production of such a nearshore environment for the first time. We speculate that mollusks dominating the production have a preference for sand that is less frequently or strongly agitated by waves, although nutrient availability from occasional upwelling may also regulate growth to create this trend.

Specific PhytOC fractions in rice straw and consequent implications for potential of phytolith carbon sequestration in global paddy fields

Phytoliths are silica biomineralization products within plants and have been considered as a promising material to sequester carbon (C). However, there is considerable uncertainty and controversy regarding the C content in phytoliths due to the lack of detailed information on variation of C under different extraction procedures. Herein, we established a series of batch digestion experimental procedures coupled with analyses of phytoliths using Scanning Electron Microscopy and Energy-Dispersive X-ray Spectroscopy to divide phytoliths into three fractions. We then reported an approach for standardizing across hundreds of values found in the literature. Combining this standardized approach with C contents in phytoliths extracted from different digestion degrees, we revaluated the potential production rates of phytolith-occluded carbon (PhytOC) input globally in rice paddy fields. The results showed that the C content in recovered phytoliths exhibited a significantly fitting exponential relationship (p < 0.01) with digestion degrees and decreased from 30 to 75 g kg−1 under moderate digestion to <5 g kg−1 under over digestion. On a global scale, the production of total PhytOC in the world paddy fields reached up to (2.71 ± 0.85) × 106 t year−1. Therein, the contribution of sub-stable PhytOC fraction, stable PhytOC fraction, and recalcitrant PhytOC fraction was 63 %, 28 %, and 9 %, respectively. Our results imply that the estimation of phytolith C sequestration potential across the global paddy fields is associated with specific PhytOC fractions. Therefore, further determining the storage time limits of these specific PhytOC fractions after returning to soil will be vital for predicting terrestrial biogeochemical C sequestration potentials of phytoliths.

Climate-driven paleoceanography change controls on petrology and organic matter accumulation in the upper Permian Dalong Formation, western Hubei Province, southern China

The influence of paleoclimate on shale sedimentary processes and organic matter accumulation is of great significance for reconstructing the “deep time” paleoclimate as well as for oil and gas exploration. Here, a detailed study on the Lopingian Dalong Formation organic-rich shales in the western Hubei area of the Middle Yangtze region is performed to understand how paleoclimate affects the depositional process and organic matter accumulation of shales. By combining a detailed core description and microscopic observations, along with mineralogical and geochemical analysis, two major lithological facies were identified from the H1 drilling core, including siliceous shale and clay/carbonate bearing mixed shale. The changes in depositional observations and geochemical indicators (including detritus index, Ln (Al2O3/Na2O), CuEF, ZnEF, UEF, MoEF, Cd/Mo and Co × Mn) indicate that the siliceous shale was deposited in an anoxic basin with well-developed upwelling under warm and semihumid conditions. However, the clay/carbonate bearing mixed shale was deposited in a hypoxic basin with weakly developed upwelling, and the climate was arid and hot. These deposits suggest that paleoclimates developed into hot and arid climates over time and that such climate change trends may be a response to global warming at the end of the late Permian. High temperatures inhibit the development of upwelling but increase the input of terrigenous clastic materials by enhancing weathering, and controlling the shale deposition. The average total organic carbon (TOC) content of the basin varies significantly in different lithological facies. We infer that the organic matter accumulation of clay/carbonate bearing mixed shale is comprehensively controlled by the carbonate production rate and primary productivity, while the organic matter accumulation of siliceous shale is primarily controlled by the authigenic quartz production rate. When the detrital index in the study area reaches 80 %, TOC does not increase or even decrease. Therefore, in the presence of authigenic quartz silicon, the increased silicate content is not always conducive to the accumulation of organic matter.

A biotic perspective on the Oligo-Miocene evolution of the Maldives carbonate platform from forward stratigraphic modelling (Indian Ocean)

Forward stratigraphic modelling is a fast-developing modelling approach, used to test conceptual models, and predict stratigraphic architecture and depositional facies from basin to reservoir scales. Published subsurface applications demonstrate its added value by integrating multidisciplinary data as well as geological concepts into its constraints. When applied to carbonate depositional systems, composed of multiple sediment factories, the co-operating and interdependent production mechanisms remain poorly studied. By applying the technique to a well-studied section of the Maldives carbonate platform, a specific model design—adapted to the geological age and setting, and constrained by available data—sheds light on the interaction of its carbonate producers. The results yield a naturalistic depositional facies distribution and offer insight in the changing relationship between biotic communities during the platform evolution. After calibration, the reference model unequivocally links the formerly proposed genetic model to the seismostratigraphic architecture. Furthermore, the results show how environmental changes (seemingly of secondary impact compared to changes in physical accommodation in the stratigraphic record) can induce substantial fluctuations in carbonate production rates of biotic communities, affect the ecological accommodation, and thus impact the platform architecture. Therefore, it is crucial to treat carbonate production rates during periods of environmental change as variables with associated uncertainties in a forward stratigraphic model setup.

Anatomy of a platform margin during a carbonate factory collapse: implications for the sedimentary record and sequence stratigraphic interpretation of poisoning events

Sequence stratigraphic interpretations are limited in their prediction of sedimentary architecture and changes in sea-level when used in systems characterized by marked fluctuations in sediment supply, particularly in carbonate-dominated environments. Pronounced variations in sediment supply occurred during the Pliensbachian–Toarcian transition, when significant perturbations of the carbon cycle and intense environmental disturbances led to a global shutdown of carbonate production. We studied the impact of this event on sedimentation and stratal stacking patterns in the Moroccan central High Atlas. We reconstructed the lateral variations in facies and sedimentary geometries along a carbonate platform margin and slope in the field by tracking six key discontinuity surfaces covering the Pliensbachian–Toarcian transition from the platform margin to the toe-of-slope. This work highlights the difficulties in sequence stratigraphic interpretations in cases of neritic carbonate factory collapse without assessments of shoreline movement because the stacking patterns in open marine environments do not necessary reflect the regional variation in base level in disturbed carbonate systems. This study also emphasizes the uncertainties associated with focusing solely on lower offshore strata to assess the history and causes of palaeoenvironmental perturbations because decreases in the rate of carbonate production dampen neritic carbonate shedding and therefore favour the creation of a hiatus in deep water settings.

Effects of Catalytic Promoter Mn on Ni/ZSM-5 Catalyst to Catalyst Waste Plastic Syngas to Prepare Carbon Nanotubes for Co-Production of Hydrogen

Carbon nanotubes (CNTs) produced by catalytic reforming of the waste plastic syngas is a high value-added by-product of hydrogen production. Catalysts play an important role in the growth of carbon nanotubes. The influences of Ni/ZSM-5 catalyst, Ni–Mn/ZSM-5 catalyst and temperature were performed in a lab-scale tubular reactor. The catalysts and product carbon were analyzed by different characterization methods, including temperature-programed reduction/oxidation, X-ray diffractometer, scanning electron microscope, transmission electron microscope, X-ray energy spectrometer. The results showed that in the presence of Ni–Mn/ZSM-5 catalyst with the addition of catalytic promoter Mn, 650 °C was the optimum temperature during the operating temperature range of 600 °C~800 °C for the rate of carbon production and hydrogen production, and the carbon production was the highest, which was 2.95gCNTs/gCatalyst (wherein the Multi-walled carbon nanotubes (MWCNTs) were main product), and compared with the monometallic Ni/ZSM-5 catalyst, the Ni–Mn/ZSM-5 catalyst with Mn addition increased the H2 content in the syngas from 14 Vol.% to 39 Vol.%. The highest carbon nanotubes proportion of 95.81% to total carbon deposition was obtained under the conditions of 750 °C. The introduction of catalytic promoter Mn transforms the growth mode of carbon nanotubes from top growth mode to bottom growth mode, and obtains carbon nanotubes with more regular structure. It suggested that Ni–Mn/ZSM-5 catalyst had the potential for high quality carbon nanotubes and H2-riched gas production from waste plastic syngas.

Stratigraphic evolution and karstification of a Cretaceous Mid‐Pacific atoll (Resolution Guyot) resolved from core‐log‐seismic integration and comparison with modern and ancient analogues

AbstractAtolls are faithful recorders helping us understand eustatic variations, the evolution of carbonate production through time, and changes in magmatic hotspots activity. Several early Cretaceous Mid‐Pacific atolls were previously investigated through ocean drilling, but due to the low quality of vintage seismic data available, few spatial constraints exist on their stratigraphic evolution and large‐scale diagenesis. Here, we present results from an integrated core‐log‐seismic study at Resolution Guyot and comparison with modern and ancient analogues. We identify six seismic‐stratigraphic units: (1) platform initiation with aggradation and backstepping through the Hauterivian which ended by platform emersion; (2) reflooding of the platform with progradation and aggradation through the Barremian till the early‐Aptian when ocean anoxic event 1a resulted in incipient drowning; (3) platform backstepping till the mid‐Aptian when the platform shifted to progradation and aggradation till the mid‐Albian; (4) platform emersion; (5) reflooding with backstepping ending at the latest‐Albian by platform emersion; and (6) final drowning. The stratigraphic surfaces bounding these units are coeval with some of the Cretaceous eustatic events, which suggest an eustatic control on the evolution of this atoll and confirm that several previously reported sea‐level variations in the early Cretaceous are driven by eustasy. Changes in subsidence and carbonate production rates and suspected later magmatism have also impacted the stratigraphic evolution. The suspected later magmatism could lead to environmental perturbations and potentially platform demise. Contrary to previous studies, we identify two emersion events during the mid‐ and late‐Albian which resulted in intensive meteoric dissolution and karstification. The platform margin syndepositional fractures interacted with the subaerial exposure events by focusing the dissolution which formed vertically stacked flank‐margin fracture‐cave system. The study gives a unique insight into the interplay between eustasy, subsidence, and volcanic activity(ies) on long‐term evolution of early Cretaceous shallow‐marine carbonates. It also documents the impact and distribution of hypogenic and epigenic fluid‐flow in atolls serving as an analogue for isolated carbonate platforms.

Estimating rates of coral carbonate production from aerial and archive imagery by applying colony scale conversion metrics

Recent interest in assessing coral reef functions has raised questions about how carbonate production rates have altered over the past few decades of ecological change. At the same time, there is growing interest in quantifying carbonate production on larger reef-scales. Resolving these issues is challenging because carbonate production estimates require three-dimensional survey data, which are typically collected in-situ over small spatial scales. In contrast, data that can be extracted from archive photograph or video imagery and high-resolution aerial imagery are generally planar. To address this disconnect, we collected data on the relationship between linear planar and 3D contour lengths of 62 common Indo-Pacific hard coral genera-morphotypes to establish appropriate conversion metrics (i.e. coral class rugosity values, hereafter termed Rcoral). These conversion values allow planar colony dimensions to be converted to estimates of 3D colony contour length, which can be employed within existing census budget methodologies like ReefBudget to estimate coral carbonate production (G, in kg CaCO3 m−2 yr−1). We tested this approach by comparing in-situ carbonate production data collected using the ReefBudget methodology against estimates derived from converted colony length data from video imagery. The data show a high level of consistency with an error of ~ 10%. We then demonstrate potential applications of the conversion metrics in two examples, the first using time-series (2006 to 2018) photo-quadrat imagery from Moorea, and the second using high-resolution drone imagery across different reef flat habitats from the Maldives. Whilst some degree of error must necessarily be accepted with such conversion techniques, the approach presented here offers exciting potential to calculate coral carbonate production: (1) from historical imagery to constrain past coral carbonate production rates; (2) from high quality aerial imagery for spatial up-scaling exercises; and (3) for use in rapid photograph or video-based assessments along reef systems where detailed surveys are not possible.

Investigating the role of differential biotic production on carbonate geometries through stratigraphic forward modelling and sensitivity analysis: the Llucmajor example

The geometry of carbonate platforms reflects the interaction of several factors. However, the impact of carbonate-producing organisms has been poorly investigated so far. This study applies stratigraphic forward modelling (SFM) and sensitivity analysis to examine, referenced to the Miocene Llucmajor Platform, the effect of changes of dominant biotic production in the oligophotic and euphotic zones on platform geometry. Our results show that the complex interplay of carbonate production rates, bathymetry and variations in accommodation space control the platform geometry. The main driver of progradation is the oligophotic production of rhodalgal sediments during the lowstands. This study demonstrates that platform geometry and internal architecture varies significantly according to the interaction of the predominant carbonate-producing biotas. The input parameters for this study are based on well-understood Miocene carbonate biotas with characteristic euphotic, oligophotic and photo-independent carbonate production in which it is crucial that each carbonate-producing class is modelled explicitly within the simulation run and not averaged with a single carbonate production–depth profile. This is important in subsurface exploration studies based on stratigraphic forward models where the overall platform geometry may be approximated through calibration runs, and constrained by seismic surveys and wellbores. However, the internal architecture is likely to be oversimplified without an in-depth understanding of the target carbonate system and a transfer to forward modelling parameters.

Spatial Variation in Primary Production in the Eastern Indian Ocean

To examine the spatial pattern and controlling factors of the primary productivity (PP) of phytoplankton in the eastern Indian Ocean (EIO), deck-incubation carbon fixation (a 14C tracer technique) and the related hydrographic properties were measured at 15 locations during the pre-summer monsoon season (February–April 2017). There are knowledge gaps in the field observations of PP in the EIO. The estimated daily carbon production rates integrated over the photic zone ranged from 113 to 817 mgC m–2 d–1, with a mean of 522 mgC m–2 d–1. The mixed-layer integrated primary production (MLD-PP) ranged from 29.0 to 303.7 mgC m–2 d–1 (mean: 177.2 mgC m–2 d–1). The contribution of MLD-PP to the photic zone-integrated PP (PZI-PP) varied between 19 and 51% (mean: 36%). Strong spatial variability in the carbon fixation rates was found in the study region. Specifically, the surface primary production rates were relatively higher in the Bay of Bengal domain affected by riverine flux and lower in the equatorial domain owing to the presence of intermonsoonal Wyrtki jets, which were characterized by a depression of thermocline and nitracline. The PZI-PP exhibited a linear (positive) relationship with nutrient values, but with no significance, indicating a partial control of macronutrients and a light limitation of carbon fixation. As evident from the vertical profiles, the primary production process mainly occurred above the nitracline depth and at high photosynthetic efficiency. Phytoplankton (&amp;gt;5 μm), including dinoflagellates, Trichodesmium, coccolithophores, and dissolved nutrients, are thought to have been correlated with primary production during the study period. The measured on-deck biological data of our study allow for a general understanding of the trends in PP in the survey area of the EIO and can be incorporated into global primary production models.

Differences in organic carbon release between conchocelis and thalli of Pyropia haitanensis and responses to changes in light intensity and pH

The large-scale cultivation of macroalgae has the potential to act as a carbon sink because macroalgae can release a large amount of organic carbon into the surrounding seawater. However, this needs to be evaluated on the basis of the entire life cycle under a background of changes in pH and light intensity. The present study investigated the difference in organic carbon release between conchocelis and thallus stages of the economically important red alga Pyropia haitanensis in response to three light intensities (10, 50, and 500 μmol m−2 s−1) and two pH conditions (current pH: 8.1, projected future pH: 7.5). The study found that regardless of the light intensity and pH values, the growth rates, production rates of tissue carbon, and dissolved organic carbon (DOC) of thalli tended to be higher than those of conchocelis, by more than 170%, 85%, and 106%, respectively. The DOC production rate was higher than the production rate of particulate organic carbon (POC) by at least two orders of magnitude. Positive correlations were found between growth rate and production rates of tissue carbon and growth rate and DOC production rate, but no clear relationship was found between growth and POC production. The DOC production rate of thallus tended to increase with light intensity but was not significantly influenced by ocean acidification. However, decay of tissue caused by exposure of the conchocelis to high light intensity resulted in increased POC and DOC production rates, indicating the complexity of organic carbon release by P. haitanensis. This study provides insights into the release of organic carbon during the complete life cycle of P. haitanensis, and the results can further our understanding of the carbon metabolism of this cultivated macroalgal species.

Growth and carbonate production of crustose coralline algae on a degraded turbid reef system

Crustose coralline algae (CCA) and other encrusting calcifiers drive carbonate production on coral reefs. However, little is known about the rates of growth and calcification of these organisms within degraded turbid reef systems. Here we deployed settlement cards (N = 764) across seven reefs in Singapore for two years to examine spatio-temporal variation in encrusting community composition and CCA carbonate production. Our results showed that CCA was the dominant encrusting taxa (63.7% ± 18.3SD) across reefs. CCA carbonate production rates (0.009–0.052 g cm−2 yr−1) were less than half of those reported for most Indo-Pacific reefs, but similar to other turbid reef systems. Highest CCA carbonate production rates were observed furthest from Singapore's main shipping port, due to a relative increase in CCA cover on the offshore reefs. Our results suggest that proximity to areas of high industrialisation and ship traffic may reduce the cover of encrusting calcifying organisms and CCA production rates which may have negative, long-term implications for the stabilisation of nearshore reefs in urbanised settings.

Constraints on coccolithophores under ocean acidification obtained from boron and carbon geochemical approaches

Ocean acidification (OA) appears to have diverse impacts on calcareous coccolithophores, but the cellular processes underlying these responses are not well understood. Here we use stable boron and carbon isotopes, B/Ca ratios, as well as inorganic and organic carbon production rates to investigate the carbon utilization and the internal pH regulation at the site of calcification in Emiliania huxleyi, Calcidiscus leptoporus and Pleurochrysis carterae cultured over a wide pCO2 range (180–1000 μatm). Despite large variability, the geochemistry data indicate species-specific modes of pH control and differences in the utilization of inorganic carbon. Boron isotope data suggest that all three species generally upregulate the pH of the calcification fluid (pHCF) compared to surrounding seawater, which coincides with relatively constant growth rates and cellular ratios of inorganic to organic carbon. Furthermore, species exhibit different strategies in regulating their pHCF, i.e., two species maintain homeostasis (pHCF = ∼8.7), while one species shows a constant offset to the surrounding seawater (ΔpH = ∼0.6 units) over the entire tested pCO2 range. In addition to these different strategies, carbon isotope data suggests that high plasticity in the utilization of dissolved inorganic carbon might be an explanation for species-specific differences in coccolithophore responses to OA.

Calcification moderates the biochemical responses of Gephyrocapsa oceanica to ocean acidification

ABSTRACT We compared the physiological performance of two sub-strains of coccolithophore Gephyrocapsa oceanica NIES-1318, the originally well-calcified strain, and its low-calcified counterpart that significantly decreased the capacity to calcify under present (400 µatm, LC) and elevated pCO2 (1000 µatm, HC) conditions. There were no significant differences in the growth rates between the two sub-strains under LC condition. The growth rates of both sub-strains reduced under HC conditions and the decrease was significantly higher in the high-calcified cells than the low-calcified ones. The low-calcified cultures exhibited reduced production rates of particulate organic carbon (POC) and particulate organic nitrogen (PON), irrespective of CO2 conditions. The decrease in the PON production rates was considerably higher than that in the POC production rates. Compared with the high-calcified cells, a slight decrease was observed in cellular POC contents in the low-calcified cells, whereas cellular PON contents decreased more prominently. The POC/PON ratio showed no significant difference between the two pCO2 treatments in the high-calcified cultures, whereas elevated CO2 increased the rates in the low-calcified cells. We believe that the nitrogen acquisition by low-calcified cells was more susceptible to ocean acidification, probably due to a lack of stabilized microenvironment provided by coccoliths. Our results demonstrate that the calcification level can affect the biochemical responses of G. oceanica to ocean acidification, with likely consequences for marine biogeochemical cycling.

High-precision proton angular distribution measurements of C12(p,p′) for the determination of the E0 decay branching ratio of the Hoyle state

Background: In stars, carbon is produced exclusively via the $3\alpha$ process, where three $\alpha$ particles fuse to form $^{12}$C in the excited Hoyle state, which can then decay to the ground state. The rate of carbon production in stars depends on the radiative width of the Hoyle state. The radiative width can be deduced by combining three separately measured quantities, one of which is the $E0$ decay branching ratio. The $E0$ branching ratio can be measured by exciting the Hoyle state in the $^{12}$C$(p,p')$ reaction and measuring the pair decay of its Hoyle state and first $2^+$ state. Purpose: To reduce the uncertainties in the carbon production rate in the universe by measuring a set of proton angular distributions for the population of the Hoyle state ($0^+_2$) and $2^+_1$ state in $^{12}$C in $^{12}$C$(p,p')$ reactions between 10.20 and 10.70 MeV, used in the determination of the $E0$ branching ratio of the Hoyle state. Method: Proton angular distributions populating the ground, first $2^+$, and the Hoyle states in $^{12}$C were measured in $^{12}$C(p,p') reactions with a silicon detector array covering $22^\circ<\theta<158^\circ$ in 14 energy steps between 10.20 and 10.70 MeV with a thin ($60\ \mu$g/cm$^2$) $^{nat}$C target. Results: Total cross-sections for each state were extracted and the population ratio between the $2^+_1$ and Hoyle state determined at each energy step. By appropriately averaging these cross-sections and taking their ratio, the equivalent population ratio can be extracted applicable for any thick $^{12}$C target used in pair-conversion measurements. Conclusions: We present a general data set of high-precision $^{12}$C$(p,p')$ cross-sections that make uncertainties resulting from the population of the $2^+_1$ and $0^+_2$ states by proton inelastic scattering negligible for any future measurements of the $E0$ branching ratio in $^{12}$C.

Variations in carbonate-evaporite shoreline and ramp facies trends: Middle Miocene Fatha Formation, Kurdistan Region, NE Iraq

A sedimentological investigation of Miocene deposits at the periphery of the Zagros foreland basin, Kurdistan Region, NE Iraq, reveals a cyclical arrangement of carbonate-evaporite ramp facies. The study aims to provide rare insight into the lateral variability of microfacies and environments of such systems' inner ramp and shoreline. Between 10 and 40 depositional cycles are preserved, separated by a flooding surface, and recording an overall basinward progradation. In each cycle, a shallowing-upward trend from a lower-energy calcareous mudstone and mudstone-wackestone carbonate microfacies at the base to a higher-energy packstone-grainstone-rudstone or low-energy algal mat/stromatolitic carbonate microfacies above is evident. Evaporite deposits of supratidal sabkha origin cap each carbonate deposit. Red clastic sediments that advanced south-westward into the basin from the adjacent Zagros hinterland overlie each evaporite deposit. A flooding surface and return to calcareous mudstones mark the start of the next cycle. Outcrop and thin-section analysis of the carbonate deposits of each cycle reveals a shoaling-up to inner-ramp facies with varied environmental settings that developed under a range of hydrodynamic conditions. Microfacies analysis indicates that these environments included normal marine salinity open lagoons, hypersaline lagoons, restricted and shallow lagoons, sand shoals, intertidal and supratidal flats, supratidal ponds, and a coastal alluvial plain that included channelised deposits and palaeosols. The cyclical facies trend changes toward the top of the succession in that the relative rate of siliciclastic supply markedly increased, whereas the rate of carbonate and evaporite production decreased. Progradation and shoreline migration through time caused lateral and vertical facies changes and thickness variations over the succession. Repeated relative sea-level changes, associated changes in climate, and variations in sediment supply from the hinterlands during the collision of the Arabian and Iranian plates, combined with a variable rate of accommodation generation, are inferred to have controlled the preserved cyclicity.