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New sedimentological data of facies and diagenesis as well as chronological data including strontium (87Sr/86Sr)-isotope ratios and uranium (U)-series dating, radiocarbon (14C) accelerator mass spectrometry (AMS) dating and biostratigraphy from elevated reef terraces (makatea) in the southern Cook Islands of Mangaia, Rarotonga and Aitutaki contribute to controversial discussions regarding age and sea-level relationships of these occurrences during the Neogene and Quaternary. The oldest limestones of the uplifted makatea island of Mangaia include reef-related facies which are mid-Miocene in age, based on new Sr-isotope and biostratigraphical data. In between these older deposits and the lowest coastal reef terrace of marine isotope stage (MIS) 5e, various older Pleistocene reef-related facies were identified. Based on Sr-isotope ratios, these were deposited during earlier Pleistocene highstands (as old as 2.28 Ma). Rare reef terraces on Rarotonga belong to the Plio-Pleistocene and the late Miocene, according to 87Sr/86Sr ratios. The late Miocene age is enigmatic as it exceeds the age of subaerially exposed volcanic rocks of Rarotonga island. The fossil reef could have formed on an older submarine volcanic high that was later displaced by younger volcanism to its present position, or the Sr-age could be too old due to diagenetic resetting. The Plio-Pleistocene Rarotonga reef terraces are overlain irregularly by Holocene reef deposits that are interpreted as storm rubble. Reef terraces on Aitutaki represent evidence of a higher-than-present (up to 1 m) sea-level during the late Holocene, based on 14C AMS age data. They are very similar to elevated late Holocene reefs of adjacent French Polynesia with regard to composition, elevation and age.

Dysregulated calcium homeostasis is common in chronic kidney disease and causally associated with disorders of bone mineralization. However, radiological measures and biomarkers do not allow accurate evaluation of bone calcium balance. Non-radioactive calcium isotopes, 42Ca and 44Ca, are present in our diet and sequestered into body compartments following principles of kinetic isotope fractionation. Isotopically light 42Ca is preferentially incorporated into bone, while heavier 44Ca is excreted. The ratio (44/42Caserum) increases when bone formation exceeds resorption and vice versa, reflecting bone calcium balance. We measured these calcium isotopes by inductively coupled plasma mass-spectrometry in blood, urine and feces of 42 children with chronic kidney disease and 92 receiving dialysis therapy. We compared the isotope ratios with bone biomarkers and determined total bone mineral content by dual-energy x-ray absorptiometry and peripheral quantitative CT expressed as age-adjusted z-scores. The 44/42Caserum ratio positively correlated with serum calcium, 25-hydroxyvitamin D and alkaline phosphatases and inversely with serum parathyroid hormone and other bone resorption markers. The 44/42Caserum ratio positively correlated with age-adjusted z-scores of tibial trabecular bone mineral density and total bone mineral content measured by peripheral quantitative CT, and hip bone mineral density measured by dual-energy X-ray absorptiometry. Significant and independent predictors of total bone mineral content, measured by, were the 44/42Caserum ratio and parathyroid hormone. The 44/42Caserum ratio, repeated after four weeks, highly correlated with baseline values. When adjusted for calcium-containing medications and kidney impairment, the 44/42Caserum ratio in patients receiving dialysis was 157% lower than that of age-matched children and 29% lower than levels in elderly women with osteoporosis, implying significantly lower bone mineral content. Thus, calcium isotope ratios may provide a novel, sensitive and non-invasive method of assessing bone calcium balance in chronic kidney disease.

The detailed reconstruction of reef geometry, composition and evolution during the mid-late Holocene brings valuable information regarding coral reef dynamics and coastal processes during periods of higher sea level and wave energy regimes.This study provides a high-resolution reconstruction of the reef growth history in French Polynesia and their response to low-amplitude, high-frequency relative sea-level (RSL) changes and associated environmental changes over the past 6,000 years. After the stabilisation of sea level at its present position, the newdevelopment of reef systems was initiated by the creation of accommodation space due to a glacio-eustatic sea-level rise from 6.0 to 4.1 kyr BP, and controlled by the antecedent topography of the islands. A single,short-lived sea-level highstand of less than one metre between 4.1 and 3.4 kyr BP is documented preceding a fall in sea level between 3.6 and 1.2 kyr BP. The reported RSL changes are characterized by slow rates ranging from a few tens of millimetres per year up to 2.5 mm/yr and by significant sea-level stability (stillstands) lasting more than a century and up to 250 years, defining a step-like pattern.Regionally, the persistence of stable and optimal depositional environments over the last 6,000 years is demonstrated by the constant overall composition and diversity of reef communities and the almost continuouswidespread development of microatoll fields and reef flat units. The facies distribution as well as the lateral extension and shift of facies belts have been governed by variations in accommodation space, which are controlled by RSL changes and antecedent topography. The recurrent sea-level stillstands that punctuated the mid-late Holocene sea-level history have played a significant role in the development of dense reef frameworks.The widespread development of mid-late Holocene reef deposits in coastal areas, especially reef flat units and storm conglomerate deposits, suggests that they have played a prominent role in the formation and shaping of modern islands and islets, creating significant topographic features that formed the foundations of these islands.

Serum calcium isotopes (δ44/42Ca) have been suggested as a non-invasive and sensitive Ca balance marker. Quantitative δ44/42Ca changes associated with Ca flux across body compartment barriers relative to the dietary Ca and the correlation of δ44/42CaSerum with bone histology are unknown. We analyzed Ca and δ44/42Ca by mass-spectrometry in rats after two weeks of standard-Ca-diet (0.5%) and after four subsequent weeks of standard- and of low-Ca-diet (0.25%). In animals on a low-Ca-diet net Ca gain was 61 ± 3% and femur Ca content 68 ± 41% of standard-Ca-diet, bone mineralized area per section area was 68 ± 15% compared to standard-Ca-diet. δ44/42Ca was similar in the diets, and decreased in feces and urine and increased in serum in animals on low-Ca-diet. δ44/42CaBone was higher in animals on low-Ca-diet, lower in the diaphysis than the metaphysis and epiphysis, and unaffected by gender. Independent of diet, δ44/42CaBone was similar in the femora and ribs. At the time of sacrifice, δ44/42CaSerum inversely correlated with intestinal Ca uptake and histological bone mineralization markers, but not with Ca content and bone mineral density by µCT. In conclusion, δ44/42CaBone was bone site specific, but mechanical stress and gender independent. Low-Ca-diet induced marked changes in feces, serum and urine δ44/42Ca in growing rats. δ44/42CaSerum inversely correlated with markers of bone mineralization.

Carbon cycle history Marine carbon includes organic and inorganic components, both of which must be accounted for to understand the global carbon cycle. Paytan et al. assembled a record of stable strontium isotopes ( 88 Sr and 86 Sr) derived from pelagic marine barite and used it to reconstruct changes in the deposition and burial of biogenic calcium carbonate in marine sediments. These data, when combined with measurements of 87 Sr/ 86 Sr, can help to reveal past changes in the sources and sinks of strontium, as well as variations in carbonate deposition that affect the carbon cycle. Science , this issue p. 1346

Ocean environmental conditions can be inferred from the chemical composition of bamboo coral skeletons. The high magnesium calcite internodes of these long-living octocorals may therefore represent a potential archive for seawater properties such as salinity or temperature where instrumental time series are absent. To extend these time series into the past using a natural archive the principles of temperature and salinity signal incorporation into cold-water coral skeletal material need to be investigated. Since skeletal Na and S concentrations have been proposed as environmental proxies, we mapped the spatial distribution and concentration of these elements in two Atlantic specimens of Keratoisis grayi (family Isididae). These measurements were conducted with an electron microprobe applying a spatial resolution of 4 μm. The mean apparent distribution coefficient of Na/Ca for the two samples was within 2.5 and 2.8*10−4, while that of S shows a similar depletion relative to seawater with 3.8 and 3.6*10−3. The two elements show an inverse correlation in bamboo coral skeletons. The mean apparent distribution coefficient of Na is similar to that of abiotic calcites. This similarity can be interpreted as the absence of significant vital effects for skeletal Na/Ca. Hence it corroborates the idea that the average skeletal composition of bamboo corals holds the potential to record past seawater conditions. In contrast, it appears unlikely that the spatial variations of the element distribution of seemingly simultaneously precipitated material along growth rings are exclusively controlled by environmental factors. We further exclude Rayleigh fractionation, ion-specific pumping, and Ca/proton exchange as the driver of Na and S distribution in bamboo corals. Instead, we adapt a calcification model originally proposed for scleractinians to bamboo corals. This model can explain the observed distribution of Na and S in the skeleton by a combination of Ca/proton pumping, bicarbonate active transport, and the formation of an organic skeletal matrix. The adapted model can further be used to predict the theoretical behaviour of other elements and disentangle vital effects from external factors influencing compositional features. It is therefore a useful tool for future studies on the potential of bamboo corals as environmental archives.

Similar to their tropical counterparts, cold-water corals (CWCs) are able to build large three-dimensional reef structures. These unique ecosystems are at risk due to ongoing climate change. In particular, ocean warming, ocean acidification and changes in the hydrological cycle may jeopardize the existence of CWCs. In order to predict how CWCs and their reefs or mounds will develop in the near future one important strategy is to study past fossil CWC mounds and especially shallow CWC ecosystems as they experience a greater environmental variability compared to other deep-water CWC ecosystems. We present results from a CWC mound off southern Norway. A sediment core drilled from this relatively shallow (~ 100 m) CWC mound exposes in full detail hydrographical changes during the late Holocene, which were crucial for mound build-up. We applied computed tomography, 230Th/U dating, and foraminiferal geochemical proxy reconstructions of bottom-water-temperature (Mg/Ca-based BWT), δ18O for seawater density, and the combination of both to infer salinity changes. Our results demonstrate that the CWC mound formed in the late Holocene between 4 kiloannum (ka) and 1.5 ka with an average aggradation rate of 104 cm/kiloyears (kyr), which is significantly lower than other Holocene Norwegian mounds. The reconstructed BWTMg/Ca and seawater density exhibit large variations throughout the entire period of mound formation, but are strikingly similar to modern in situ observations in the nearby Tisler Reef. We argue that BWT does not exert a primary control on CWC mound formation. Instead, strong salinity and seawater density variation throughout the entire mound sequence appears to be controlled by the interplay between the Atlantic Water (AW) inflow and the overlying, outflowing Baltic-Sea water. CWC growth and mound formation in the NE Skagerrak was supported by strong current flow, oxygen replenishment, the presence of a strong boundary layer and larval dispersal through the AW, but possibly inhibited by the influence of fresh Baltic Water during the late Holocene. Our study therefore highlights that modern shallow Norwegian CWC reefs may be particularly endangered due to changes in water-column stratification associated with increasing net precipitation caused by climate change.

Highlights • Sr isotope composition in different minerals is an excellent proxy, that can be used to reconstruct the environmental conditions of their precipitation. In order to study Strontium (Sr) isotope fractionation during the precipitation of strontianite (SrCO3) as a function of the specific precipitation rate (R*) and temperature (T), strontianite was precipitated at 12.5, 25.0 and 37.5 °C by diffusing NH3 and CO2 gases into aqueous solutions. The specific precipitation rate R* (mol/cm2.h) for every sample was determined by applying the initial rate method. The mean isotope difference between bulk solution and precipitate (∆88/86Srstrontianite-solution) was found to be −0.279 ± 0.005‰ (2σmean) independent of both rate and temperature. Hence, Sr isotope fractionation in strontianite is completely different from that in calcite and aragonite, where a strong dependency from both rate and temperature can be observed. The latter is interpreted to reflect the competition between Sr2+ and Ca2+ ions for incorporation into the calcium carbonate crystal lattice, which is absent during the precipitation of pure strontianite. The isotope difference between strontianite and bulk solution then simply reflects the intermolecular forces in the aqueous solutions as well as the kinetic effect. The difference in the (∆88/86Srstrontianite-solution between experiments then reflects the dehydration energy of Sr ions in the adsorption layer of SrCO3.

This study was funded by the European Union's Horizon 2020 research and innovation programme under the grant agreement No. 643084 - Marie Sklodowska-Curie Innovative Training Network (ITN) ‘BASE-LiNE Earth’. Lithium has proven a powerful tracer of weathering processes and chemical seawater evolution. Skeletal components of marine calcifying organisms, and in particular brachiopods, present promising archives of Li signatures. However, Li incorporation mechanisms and potential influence from biological processes or environmental conditions require a careful assessment. In order to constrain Li systematics in brachiopod shells, we present Li concentrations and isotope compositions for 11 calcitic brachiopod species collected from six different geographic regions, paralleled with data from culturing experiments where brachiopods were grown under varying environmental conditions and seawater chemistry (pH–pCO2, temperature, Mg/Ca ratio). The recent brachiopod specimens collected across different temperate and polar environments showed broadly consistent δ7Li values ranging from 25.2 to 28.1‰ (with mean δ7Li of 26.9 ± 1.5‰), irrespective of taxonomic rank, indicating that incorporation of Li isotopes into brachiopod shells is not strongly affected by vital effects related to differences among species. This results in Δ7Licalcite–seawater values (per mil difference in 7Li/6Li between brachiopod calcite shell and seawater) from −2.9‰ to −5.8‰ (with mean Δ7Licalcite–seawater value of −3.6‰), which is larger than the Δ7Licalcite–seawater values calculated based on data from planktonic foraminifera (~0‰ to ~−4‰). This range of values is further supported by results from brachiopods cultured experimentally. Under controlled culturing conditions simulating the natural marine environment, the Δ7Licalcite–seawater for Magellania venosa was −2.5‰ and not affected by an increase in temperature from 10 to 16 °C. In contrast, a decrease in Mg/Ca (or Li/Ca) ratio of seawater by addition of CaCl2 as well as elevated pCO2, and hence low-pH conditions, resulted in an increased Δ7Licalcite-seawater up to −4.6‰. Collectively, our results indicate that brachiopods represent valuable archives and provide an envelope for robust Li-based reconstruction of seawater evolution over the Phanerozoic. Publisher PDF

Nutrient depletion in the ecosystem mainly occurred via the base cations leach from the ecosystems. Isotope technology can provide new information on the nutrients’ behavior (cycle) in ecosystems. To better understand the strontium (Sr) biogeochemical cycle in the forest, radiogenic and stable Sr isotopes were determined in various environmental samples (rainwater, groundwater, calcareous soil, vegetation, and bedrocks) collected from a karst forest ecosystem, Southwest China. The Sr supplies are supported via the deposition of atmospheric materials and the weathering of carbonate rock in this area. These supplied sources observably influence the Sr isotope compositions (both stable and radiogenic isotope). Across the ecosystem, the varied ranges of 87Sr/86Sr ratios increased in the order: bedrock (0.708) ~ groundwater (0.708–0.709) ~ rainwater (0.709–0.711) ~ vegetation (0.709–0.710)

The Taputapuatea marae of Ra’iatea is an emblematic landmark known throughout the world and sacred place for the Ma’ohi of Eastern Polynesia and the centre of a vast political-religious-cultural network in the Polynesian triangle. The erected stones constituting the ahu have been described as “limestone slabs” without precision by previous authors. These are in fact microatolls: corals (Porites) living in very shallow water and developing laterally, with a growth in height being limited by the lowest tide at the time of growth. A total of 38 samples were U/Th dated, of which 19 microatolls result in ages between 3 and 5 millennia. These are fossil microatolls that existed at a Holocene sea level of 0.80 m higher than today, when the Polynesians had not yet arrived. Other samples (molluscs, coral filling blocks) date back to the construction of the marae during the 17th-18th centuries. We hypothesize that the erected microatolls of the ahu were collected by Polynesians at the site and that others are still underground.

Assessing the physicochemical variability of the deeper ocean is currently hampered by limited instrumental time series and proxy records. Bamboo corals (Isididae) form a cosmopolitan family of calcitic deep sea corals that could fill this information gap via geochemical information recorded in their skeletons. Here we evaluate the suitability of high-resolution chemical imaging of bamboo coral skeletons for temperature and nutrient reconstruction. The applied elemental mapping techniques allow to verify the suitability of the chosen transect on the sample section for paleo-reconstructions and enhance the statistical precision of the reconstruction. We measured Mg/Ca via electron microprobe at 1 µm resolution and Ba/Ca via laser ablation ICP-MS at 35 µm resolution in a historic specimen of Keratoisis grayi from the Blake Plateau off Eastern Florida. Long-term growth temperatures of 7.1 ± 3.4 °C (± 2 SD) that are in agreement with recent ambient temperature range can be reconstructed from Mg/Ca ratios provided that anomalously Mg-enriched structural features around the central axis and isolated features related to tissue attachment are avoided for reconstruction. Skeletal Ba/Ca measurements reflect mean seawater barium [Ba]SW concentrations ([Ba]SW = 51 ± 24 nmol kg-1 (± 2 SD)), in agreement with instrumental data (47 nmol kg-1). We show for the first time that Ba/Ca forms concentric structures in a bamboo coral skeleton section. Our investigations suggest that, while bamboo coral skeletons do record environmental parameters in their mean chemical composition, the magnitude of environmental variability reconstructed from high-resolution chemical maps exceeds that expected from instrumental time series. This necessitates additional investigation of the factors driving bamboo coral skeletal composition.

In order to better constrain calcium cycling in natural soil and in soil used for agriculture, we present the δ44/40Ca values measured in rainwater, groundwater, plants, soil, and bedrock samples from a representative karst forest in SW China. The δ44/40Ca values are found to differ by ≈3.0‰ in the karst forest ecosystem. The Ca isotope compositions and Ca contents of groundwater, rainwater, and bedrock suggest that the Ca of groundwater primarily originates from rainwater and bedrock. The δ44/40Ca values of plants are lower than that of soils, indicating the preferential uptake of light Ca isotopes by plants. The distribution of δ44/40Ca values in the soil profiles (increasing with soil depth) suggests that the recycling of crop-litter abundant with lighter Ca isotope has potential effects on soil Ca isotope composition. The soil Mg/Ca content ratio probably reflects the preferential plant uptake of Ca over Mg and the difference in soil maturity. Light Ca isotopes are more abundant in mature soils than nutrient-depleted soils. The relative abundance in the light Ca isotope (40Ca) is in the following order: farmland &gt, burnt grassland &gt, forests &gt, grassland &gt, shrubland. Our results further indicate that biological fractionation in a soil–plant system is a vital factor for Ca–geochemical transformations in soil surface systems.

Thecideide brachiopods are an anomalous group of invertebrates. In this study, we discuss the evolution of thecideide brachiopods from the Triassic to the Holocene and base our results and conclusions on microstructure and texture measurements gained from electron backscatter diffraction (EBSD). In fossil and Recent thecideide shells, we observe the following mineral units: (1) nanometric to small granules; (2) acicles; (3) fibres; (4) polygonal crystals; and (5) large roundish crystals. We trace for thecideide shells the change of mineral unit characteristics such as morphology, size, orientation, arrangement and distribution pattern. Triassic thecideide shells contain extensive sections formed of fibres interspersed with large, roundish crystals. Upper Cretaceous to Pleistocene thecideide hard tissues consist of a matrix of minute to small grains reinforced by acicles and small polygonal crystals. Recent thecideide species form their shell of mineral units that show a wide range of shapes, sizes and arrangements. We find from Late Triassic to Recent a gradual decrease in mineral unit size, regularity of mineral unit morphology and orientation and the degree of calcite co‐orientation. While crystallite co‐orientation is the highest for fibrous microstructures, it is strikingly low for taxa that form their shell out of nanogranular to acicular mineral units. Our results indicate that Upper Jurassic species represent transitional forms between ancient taxa with fibrous shells and Recent forms that construct their shells of acicles and granules. We attribute the observed changes in microstructure and texture to be an adaptation to a different habitat and lifestyle associated with cementation to hard substrates., H2020 Marie Skłodowska‐Curie Actions http://dx.doi.org/10.13039/100010665, WOA Institution: LUDWIG‐MAXIMILIANS‐UNIVERSITAET MUNCHEN

The Eocene-Oligocene Transition (~34.4–33.7 Ma) marks a major step in the long-term evolution from the greenhouse climate of the Early Palaeogene to the icehouse regime of the Late Neogene and Quaternary. However, it remains uncertain which landmasses were covered by ice sheets during the Early Oligocene Glacial Maximum (~33.7–33.2 Ma), an interval of peak glaciation inferred from deep-sea benthic foraminifera oxygen isotope records that immediately follows the Eocene-Oligocene Transition. The scarcity of Late Eocene and Early Oligocene continental and shallow-marine records in both Arctic and Antarctic regions has prevented the reconstruction of environmental conditions and ice-sheet extent during the Early Oligocene, which is critical for assessing ice–ocean–atmosphere interactions during early stages of the Cenozoic icehouse. Here, we present the first Early Oligocene shallow-marine record from the Pacific margin of West Antarctica, recovered from the central Amundsen Sea Embayment shelf on RV Polarstern expedition PS104 at Site 21. Marine mudstones recovered at this site document the presence of a vegetated archipelago at a palaeo-latitude of 73.5°S. Pollen assemblages and organic biomarker proxies indicate a cool-temperate Nothofagus-dominated forest situated within a productive marine archipelago. No evidence for marine terminating ice was detected in the cores from Site 21, thus indicating that the West Antarctic Ice Sheet was small or entirely absent during the Early Oligocene.

Radiogenic lead (Pb) and neodymium (Nd) isotope compositions extracted from authigenic phases in marine sediments are sensitive tracers to reconstruct past ocean circulation and water mass mixing. Chemical reductive leaching of hydrogenetic ferromanganese oxyhydroxides from bulk sediments is the most practical way to recover past seawater Pb and Nd isotope signatures in the Southern Ocean, due to the scarcity of alternative archives. However, the leached signal could be compromised if substantial quantities of Pb and Nd were released from non‐hydrogenetic sediment fractions during chemical extraction. Here we developed a very short 10‐s leaching method to extract reliable seawater Pb and Nd isotope signals from sediments in the Atlantic sector of Southern Ocean. The effect of a previously recommended MgCl2 pre‐wash, the role of chelate ligands in the leaching solution and length of leaching time were investigated. The results show that 10‐s exposure time of sediments to reductive leaching extracted sufficient and more reliable hydrogenetic Pb and Nd compared with the commonly used 30‐min leaching approaches. The robustness of our improved leaching method was validated via direct comparison of Pb and Nd isotope signatures with actual seawater, porewater, and corresponding sediment leachates from three stations in front of the Antarctic Filchner‐Rønne Ice Shelf. Our findings also indicate that in contrast previously studied sites on the West Antarctic continental shelf, the bottom seawater Nd concentration is less elevated through benthic fluxes in the area of the southern Weddell Sea shelf., Plain Language Summary: Individual modern ocean water masses can often be identified by the isotopic signature of dissolved trace metals lead (Pb) and neodymium (Nd) supplied from surrounding continents. By analyzing past seawater Pb and Nd isotope ratios preserved in the sedimentary archives, we can understand how the ocean circulation changed. In the Southern Ocean, archives preserving past seawater Pb and Nd isotope compositions are very scarce. Thus, the chemical extraction of Pb and Nd from seawater‐derived ferromanganese oxyhydroxides within deep marine sediments becomes the most practical way to recover past seawater signal. However, Southern Ocean sediments commonly contain substantial quantities of Antarctic continental fine‐grained sediment, which easily partially dissolve during extraction, thereby releasing Pb and Nd, which did not originate from past ambient seawater. Here we established a gentle and efficient extraction method to obtain reliable past Southern Ocean seawater signatures. In addition, via analysis of regional seawater‐derived Pb and Nd signatures in the Atlantic sector of Southern Ocean, we found that the sediments further away from Antarctica and volcanically active regions are better suited to preserve unaltered seawater Pb and Nd isotope signals, which strongly supports the unique possibility of tracing past water mass sourcing in the Southern Ocean with our analytical approach., Key Points: 10‐s reductive leaching is capable of reliably extracting seawater Pb and Nd isotope signals from Southern Ocean sediments. Natural porewater Pb isotopic compositions are analyzed for the first time in front of the Antarctic Filchner‐Rønne Ice Shelf. Identify potential sites for extracting seawater Pb and Nd isotopic signatures from bulk sediments in the Atlantic sector of Southern Ocean., China Scholarship Council (CSC)

Background Edema is commonly seen after surgical fixation of ankle fractures. Rest, ice, compression, and elevation (RICE) is an established combination to prevent swelling but hardly able to stimulate lymphatic resorption. Recently, an epicutaneously applied negative pressure suction apparatus (LymphaTouch®) has been introduced to stimulate lymphatic flow. While postoperative recovery, soft tissue, and osseous healing as well as functional outcome are probably linked to the amount of postoperative swelling, estimates on this relative to prevention (RICE) or prevention + stimulated resorption (RICE+) of fluid are scarce. Methods and analysis This is a single-center, evaluator-blinded randomized pilot trial to investigate postoperative swelling in adults requiring surgical fixation of a closed unilateral ankle fracture. A total of 50 patients will be recruited and randomly assigned to RICE or RICE+ prior to surgery. All patients will undergo evaluator-blinded measurements of the ankle volume the day before surgery and subsequently from the evening of the 2nd postoperative day every 24 h until discharge. RICE will be initiated right after surgery and continued until discharge from the hospital in all patients. Additional application of negative pressure therapy (RICE+) will be initiated on the morning of the 2nd postoperative day and repeated every 24 h until the time of discharge from the hospital. Outcome measures are (i) the relative amount and the time course of the postoperative swelling, (ii) the demand for analgesic therapy (type and amount) together with the perception of pain, (iii) the rate of complications, and (iv) mobility of the ankle joint and the recovery of walking abilities during a 12-weeks follow-up period. Serum and urine samples taken prior to sugery and during postoperative recovery will allow to evaluate the ratio of naturally occurring stable calcium isotopes (δ44/42Ca) as a marker of skeletal calcium accrual. Ethics and dissemination The protocol was approved by the institutional Ethics Committee (Rostock University Medical Center, Rostock, Germany) in accordance with the Declaration of Helsinki (approval number: A 2020-0092). The results of this study will be actively disseminated through scientific publications and conference presentations. Trial registration DRKS, DRKS00023739. Registered on 14 December 2020

Local carbonate cycling in lagoon-estuarine systems, involving processes such as inorganic and biogenic carbonate precipitation/dissolution, represents an important but poorly constrained component of the coastal carbon budget. This study investigates the sensitivity of stable Sr isotope tracer (δ88/86Sr) with respect to carbonate saturation and salinity of local waters in the Coorong, Lower Lakes and Murray Mouth (CLLMM) estuary in South Australia. The CLLMM has an extensive range of salinity from fresh to hypersaline (from ∼0 to over 100 PSU), with corresponding variations in water chemistry and major ion composition that in turn controls mineral saturation states, and thus CaCO3 precipitation/dissolution in local waters. Here we use the novel δ88/86Sr tracer in tandem with the more established radiogenic Sr isotope ratio (87Sr/86Sr), where the latter is a robust proxy for Sr sources and thus water provenance. We also produced a geochemical (PHREEQC) model of calcium carbonate (CaCO3) saturation changes across this unique lagoon-estuarine system. The results indicate a systematically increasing trend of δ88/86Sr (from ∼0.25‰ to ∼0.45‰) with increasing salinity and CaCO3 (aragonite, calcite) saturation indices of the coastal waters, which in turn suggest an overall control of carbonate dissolution/precipitation processes on the stable Sr isotope composition in the CLLMM system. This was further corroborated by Ca isotope data (δ44/40Ca) published previously on the same samples from the Coorong, as well as a quantitative simulation of local carbonate removal in the lagoon based on Rayleigh modelling and Sr isotope data. Overall, our results confirm that a coupled Sr isotope approach (combining 87Sr/86Sr and δ88/86Sr) can be used to constrain not only the main water sources (continental versus marine Sr) but also local CaCO3 dissolution/precipitation processes, and thus inorganic carbon and coastal carbonate cycling in the CLLMM system. Finally, this coupled δ88/86Sr and 87Sr/86Sr approach can be potentially applied to fossil carbonate archives to reconstruct paleo-hydrology and salinity changes in the CLLMM and/or other carbonate-producing coastal systems.

The modern history of North Atlantic sea surface temperature shows variability coinciding with changes in air temperature and rainfall over the Northern Hemisphere. There is a debate about this variability and, in particular, whether it is internal to the ocean‐atmosphere system or is forced by external factors (natural and anthropogenic). Here we present a temperature record, obtained using the Sr/Ca ratio measured in a skeleton of a sclerosponge, that shows agreement with the instrumental record over the past 150 years as well as multidecadal temperature variability over the last 600 years. Comparison with climate simulations of the last millennium shows that large cooling events recorded, in the sclerosponge, are consistent with natural (primarily volcanic activity) and anthropogenic forcings. There are, however, multidecadal periods not connected to current estimates of external forcing over the last millennium allowing for alternative explanations, such as internally driven changes in ocean and atmospheric circulation.

This project was funded by the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement and project BASE-LiNE Earth (643084) and by the Slovak Research and Development Agency (APVV17-0555) and the Slovak Scientific Grant Agency (VEGA 0169/19). The loss of carbonate production during the Toarcian Oceanic Anoxic Event (T-OAE, ca.183 Ma) is hypothesized to have been at least partly triggered by ocean acidification linkedto magmatism from the Karoo-Ferrar large igneous province (southern Africa and Antarctica).However, the dynamics of acidification have never been directly quantified across theT-OAE. Here, we present the first record of temporal evolution of seawater pH spanning thelate Pliensbachian and early Toarcian from the Lusitanian Basin (Portugal) reconstructedon the basis of boron isotopic composition (δ11B) of brachiopod shells. δ11B declines by ~1‰across the Pliensbachian-Toarcian boundary (Pl-To) and attains the lowest values (~12.5‰)just prior to and within the T-OAE, followed by fluctuations and a moderately increasingtrend afterwards. The decline in δ11B coincides with decreasing bulk CaCO3 content, inparallel with the two-phase decline in carbonate production observed at global scales andwith changes in pCO2 derived from stomatal indices. Seawater pH had declined significantlyalready prior to the T-OAE, probably due to the repeated emissions of volcanogenicCO2. During the earliest phase of the T-OAE, pH increased for a short period, likely dueto intensified continental weathering and organic carbon burial, resulting in atmosphericCO2 drawdown. Subsequently, pH dropped again, reaching the minimum in the middle ofthe T-OAE. The early Toarcian marine extinction and carbonate collapse were thus driven,in part, by ocean acidification, similar to other Phanerozoic events caused by major CO2 emissions and warming. Publisher PDF

Highlights • Coral reef responses to slow-rate, low-amplitude, high-frequency sea-level changes. • Continuous reef development over the last 6000 years in optimal conditions. • Mid-late Holocene coral assemblages similar to their modern counterparts. • Facies distribution governed by variations in accommodation space. • Prominent role played by reef deposits in the formation and shaping of modern islands. Geological records of coastal system evolution during past higher and/or rising sea levels provide an important baseline for developing projections regarding the response of modern coastal systems to future sea-level rise. The mid-late Holocene corresponds to the most recent window into natural variability prior to the Anthropocene and involves slow-rate and low-amplitude sea-level changes that were mostly governed by a limited glacio-eustatic contribution, most likely sourced from Antarctica, and ‘glacial isostatic adjustment’ processes. This paper documents in unprecedented detail the response of coral reefs and coastal systems to changing accommodation space in relation to mid-late Holocene sea-level changes in French Polynesia. The sea-level curve that underpins this study has a global significance and documents a single short-lived sea-level highstand between 4.10 and 3.40 kyr BP. The amplitude of the highstand is less than one metre, within the range of the predicted sea level at the end of the current century. The reported relative sea-level changes are characterized by slow rates ranging from a few tens of millimetres per year to up to 2.5 mm/yr and by significant sea-level stability (stillstands) lasting more than a century and up to 250 years, defining a step-like pattern. Sea-level variability probably driven by climatic oscillations on interannual to millennial time scales is evidenced during the entire time window. The detailed reconstruction of reef development over the last 6000 years brings valuable information regarding coral reef dynamics and coastal processes during periods of higher sea level and wave energy regimes. The persistence of stable and optimal depositional environments over the last 6000 years is demonstrated by the constant overall composition and diversity of reef communities and the almost continuous development of coral microatolls. The facies distribution as well as the lateral extension and shift of facies belts have been governed by variations in accommodation space, which are controlled by relative sea-level changes and antecedent topography. The widespread development of mid-late Holocene reef deposits in coastal areas suggests that they have played a prominent role in global processes related to the formation and shaping of modern islands.

The Permian/Triassic boundary approximately 251.9 million years ago marked the most severe environmental crisis identified in the geological record, which dictated the onwards course for the evolution of life. Magmatism from Siberian Traps is thought to have played an important role, but the causational trigger and its feedbacks are yet to be fully understood. Here we present a new boron-isotope-derived seawater pH record from fossil brachiopod shells deposited on the Tethys shelf that demonstrates a substantial decline in seawater pH coeval with the onset of the mass extinction in the latest Permian. Combined with carbon isotope data, our results are integrated in a geochemical model that resolves the carbon cycle dynamics as well as the ocean redox conditions and nitrogen isotope turnover. We find that the initial ocean acidification was intimately linked to a large pulse of carbon degassing from the Siberian sill intrusions. We unravel the consequences of the greenhouse effect on the marine environment, and show how elevated sea surface temperatures, export production and nutrient input driven by increased rates of chemical weathering gave rise to widespread deoxygenation and sporadic sulfide poisoning of the oceans in the earliest Triassic. Our findings enable us to assemble a consistent biogeochemical reconstruction of the mechanisms that resulted in the largest Phanerozoic mass extinction. The end-Permian mass extinction was linked with ocean acidification due to carbon degassing associated with Siberian Trap emplacement, according to boron isotopes from fossil shells and reconstruction of the carbon cycle.

Serum calcium (Ca), bone biomarkers, and radiological imaging do not allow accurate evaluation of bone mineral balance (BMB), a key determinant of bone mineral density (BMD) and fracture risk. We studied naturally occurring stable (non-radioactive) Ca isotopes in different body pools as a potential biomarker of BMB. 42 Ca and 44 Ca are absorbed from our diet and sequestered into different body compartments following kinetic principles of isotope fractionation; isotopically light 42 Ca is preferentially incorporated into bone, whereas heavier 44 Ca preferentially remains in blood and is excreted in urine and feces. Their ratio (δ44/42 Ca) in serum and urine increases during bone formation and decreases with bone resorption. In 117 healthy participants, we measured Ca isotopes, biomarkers, and BMD by dual-energy X-ray absorptiometry (DXA) and tibial peripheral quantitative CT (pQCT). 44 Ca and 42 Ca were measured by multi-collector ionization-coupled plasma mass-spectrometry in serum, urine, and feces. The relationship between bone Ca gain and loss was calculated using a compartment model. δ44/42 Caserum and δ44/42 Caurine were higher in children (n = 66, median age 13 years) compared with adults (n = 51, median age 28 years; p < 0.0001 and p = 0.008, respectively). δ44/42 Caserum increased with height in boys (p < 0.001, R2 = 0.65) and was greatest at Tanner stage 4. δ44/42 Caserum correlated positively with biomarkers of bone formation (25-hydroxyvitaminD [p < 0.0001, R2 = 0.37] and alkaline phosphatase [p = 0.009, R2 = 0.18]) and negatively with bone resorption marker parathyroid hormone (PTH; p = 0.03, R2 = 0.13). δ44/42 Caserum strongly positively correlated with tibial cortical BMD Z-score (n = 62; p < 0.001, R2 = 0.39) but not DXA. Independent predictors of tibial cortical BMD Z-score were δ44/42 Caserum (p = 0.004, β = 0.37), 25-hydroxyvitaminD (p = 0.04, β = 0.19) and PTH (p = 0.03, β = -0.13), together predicting 76% of variability. In conclusion, naturally occurring Ca isotope ratios in different body compartments may provide a novel, non-invasive method of assessing bone mineralization. Defining an accurate biomarker of BMB could form the basis of future studies investigating Ca dynamics in disease states and the impact of treatments that affect bone homeostasis. © 2020 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Background and Aims In CKD dysregulated calcium (Ca) homeostasis is common and causally associated with reduced bone mineral density (BMD) and vascular calcification. Currently available radiological measures and biomarkers do not allow accurate evaluation of BMD. The aim of our study was to determine the sensitivity and specificity of stable Ca isotopes in determining bone mineral content. Method We measured stable Ca isotopes 44Ca and 42Ca by plasma-ionization mass-spectrometry in blood and urine. The relationship between bone Ca gain and loss is calculated using a compartment model based on Ca kinetics, and expressed as δ44/42Ca. Ca absorption from bones increases δ44/42CaBlood and δ44/42CaUrine, and resorption decreases these fractions. 104 children in CKD4-5 and on dialysis (CKD4-5D), 40 matched controls and 100 adults underwent Ca isotope measurement, bone biomarkers, dual energy x-ray absorptiometry (DXA) and tibial peripheral quantitative CT scan (pQCT), an accurate measure of cortical BMD. Results In healthy children the δ44/42CaBlood and δ44/42CaUrine were higher than in adults (p In CKD2-5D δ44/42CaBlood positively correlated with cholecalciferol (p=0.01) and alfacalcidol (p=0.002) doses, implying increased bone Ca uptake when Ca bioavailability is increased. δ44/42CaBlood positively correlated with biomarkers of bone formation (alkaline phosphatase, p=0.05) and negatively with bone resorption markers (PTH, p=0.013; TRAP5b, p Conclusion Ca isotope ratios provide a novel, non-invasive method of assessing bone mineralization. Further studies are in progress to define optimal levels of δ44/42CaBlood that can guide safe and effective treatment to prevent Ca deficiency or overload.

Bamboo corals are calcitic octocorals dwelling in a broad range of water depths and in all ocean basins. Their skeletons could give insight into the temporal variability of environmental parameters at their growth locations, in areas where long-time observations are often lacking. A thorough understanding of calcification mechanisms is essential to interpret the chemical composition of their high-magnesium calcite skeleton regarding environmental fluctuations of the deeper ocean. To address this issue, we employed electron microprobe analysis, confocal Raman spectroscopy, laser ablation-ICPMS and solution based multi collector-ICPMS that together provide insights into the fine-scale spatial heterogeneity of the coral chemical composition. We investigate the spatial distribution of Na, S, and Ca, as well as organic matter in skeletal sections of specimens of Keratoisis grayi (family Isididae) from the Atlantic Ocean. Two bamboo coral samples from the Atlantic and Pacific Ocean were further used to create laser ablation-based maps of δ11B and boron to carbon ratios (B/C) over the sample radii. These maps are compared with results obtained via solution based δ11B analyses on drilled samples.An inverse correlation between Na and S is observed while S seems to be positively correlated with organic matter. We will discuss the ability of a qualitative physicochemical model to explain the observed Na and S distribution and the potential role of organic matter and amorphous calcium carbonate. Our results indicate that skeletal Na/Ca in bamboo corals is largely driven by physiological processes rather than environmental salinity variability. The spatial distribution of δ11B shows a positive correlation with B/C. The observed range of bulk δ11B - partly falling below the theoretical borate fractionation curve in seawater - is larger than the conventional measured δ11B of the calcite fraction alone. The latter cannot be explained with a spatial smoothing of the distribution during sample drilling but is rather associated with a loss of an isotopically highly variable B fraction during sample bleaching. Potential reasons for the observed differences in B isotopic range and their implications will be presented. We conclude that skeletal δ11B as a proxy for pHSW is dependent on the applied technique and investigated material fraction.

Marine biogenic carbonate deposits are important climate archives as environmental conditions during mineral genesis are recorded chemically in the crystal lattice. When exposed to diagenetic alteration metastable carbonate phases as aragonite are prone to transform into more stable calcite, Mg-calcite or dolomite resulting in the loss of the original geochemical information. As diagenetic alteration is often heterogeneous, numerous carbonate archives are characterized by multi-phase compositions, including potentially unaltered remains of primary formation. Consequently, high-spatial-resolution identification of adjacent carbonate mineral phases is of key interest to constrain diagenetic fronts, as well as the degree and pattern of a carbonate archive alteration, and the deciphering of relevant geochemical proxy information.The aim of the present study is to contribute to the localization of potentially unaltered localities within heterogeneous carbonate samples, enhancing the retrieval of original geochronological and proxy information. Using natural tropical fossil coral samples as an example, we present an approach for the 3D-identification of multiple carbonate phases using µ-computed tomography scans with a resolution on a µm scale. The straightforward discrimination of aragonite, calcite, and dolomite from CT-imaging is principally hampered by the similar X-ray densities of these carbonate phases. To overcome this problem, reference material blocks for each of the three carbonate minerals were scanned together with the carbonate sample. Using the AVIZO 2019 software package in combination with a self-developed Tool command language (Tcl) script each of the carbonate reference blocks within the scanned volume was systematically subsampled for its voxel grey values. The obtained data set was statistically analysed and a robust mean voxel grey-value was calculated for each reference mineral. Subsequently, these mean grey values were used for the automated selection of seed points for subsequent image segmentation throughout the entire scanned volume based on a self-developed Tcl script. After seed point definition mineral identification was carried out throughout the volume using the watershed algorithm as a region-based image segmentation method. The final result yielded an approximation of the 3D-distribution of identified carbonate phases throughout the sample on a µm scale, which represents an excellent starting point for subsampling strategy development.

Brachiopods present a key taxon for Phanerozoic palaeo-climatic and palaeo-environmental reconstructions, owing to their good preservation and abundance in the geological record. Yet to date, only little is known on the mechanisms that control the incorporation of some key elements into their calcitic shells, as well as the mechanisms behind the biomineral formation itself, especially in thecideid brachiopods. To evaluate the distribution and controls on Mg, Ca, and Sr we examined the composition of natural Pajaudina atlantica Logan, 1988 (Thecideidae, Brachiopoda) originating from Canary Islands, Spain as well as specimens cultured experimentally under various pH-pCO2 and temperature conditions [1]. At a high-spatial resolution, electron microprobe analyses (EMP) revealed substantial intrashell and intraspecific Mg and Ca heterogeneities that seemed to be principally linked to growth features and different microstructures rather than changes in temperature. Strontium, on the other hand, appeared uniform across the shell and related to the culture medium or seawater Sr content. After almost two years of culturing, however, the new shell production was only minimal and cryptic, and difficult to evaluate by visual inspections. By combining culture-specific geochemical fingerprints with radiocarbon dating of natural samples, we estimated the growth rates to be on the order of several tens to few hundreds of µm per year, which may potentially suggest a large life span and slow growth of this species, and if true, would certainly make them a highly interesting archive for inferring past ocean variabilities. [1] Jurikova H., et al. (2019) Geochim. Cosmochim. Acta 248, 370–386.