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Corals are unique in the suite of proposed Anthropocene Global Boundary Stratotype Section and Point (GSSP) archives, as living organisms that produce aragonite exoskeletons preserved in the geological record that contain highly accurate and precise (, The Anthropocene Review, 10 (1), ISSN:2053-0196, ISSN:2053-020X

Oxygen isotope composition (δ18O) in Porites coral skeletons at the micrometer scale has been proposed to be uninfluenced by temperature in previous studies. Considering that temperature is the main controlling factor of coral δ18O at the macro scale, the effect of temperature on the δ18O variations at the micrometer scale should be evaluated carefully. To better understand the climatic and biological significance of high-resolution δ18O in coral skeletons, in situ δ18O values were analyzed in three modern Porites corals from the South China Sea and the Great Barrier Reef by a Cameca IMS 1280-HR secondary ion mass spectrometry (SIMS). A twice vacuum impregnation procedure for sample mount preparation and a subsection calibration method based on multiple controlling points for coral matrix effect correction were used for SIMS analysis. The derived SIMS coral δ18O time series exhibit consistent long-term variations with the monthly δ18O (measured by conventional gas isotope ratios mass spectrometry), monthly Sr/Ca, and daily sea surface temperature, first highlighting the dominant temperature control on micrometer-scale coral δ18O. The 1.5‰ fluctuation amplitude of SIMS coral δ18O at the scales of 400–800 μm can be explained by the combined SST effects of ~10-day variation and day–night fluctuation, whereas the effects of seawater δ18O and growth rate on SIMS coral δ18O seem not dominant. Some abnormally negative δ18O values possibly resulted from the primary ion bombardment on indistinguishable centers of calcification.

This bachelor’s essay aims to discuss breastfeeding and complications related to breastfeeding within archaeological contexts. Why complications have arisen when such a natural act is per- formed and how individuals have tried to manage them. By looking at different methods of recording breastfeeding patterns I aim to broaden the interpretations of breastfeeding in differ- ent time periods and locations. Isotope analysis will be an important part as well as paleopatho- logical analysis of human remains. Information from three completed studies from Öland and Västerhus in Sweden and Quarto Cappello del Prete in Rome will be presented and discussed. In conclusion I suggest that breastfeeding is a complex act surrounded by difficulties such as diseases and cultural norms. There is variation within populations regarding breastfeeding and weaning. People have been struggling as well as fighting for the survival of their children.

Transformation of aragonite, a mineral phase metastable at Earth’s surface, to calcite widely occurs in both sedimentary and metamorphic systems with the presence of an aqueous phase. The transformation process can affect geochemical signatures of aragonite (a protolith). This study focused on quantification of the retention of Mg/Ca and Sr/Ca ratios, and δ18O during the transformation process as well as evaluation of the transformation rate. To investigate the effect of transformation from aragonite to calcite on elemental and stable isotope ratios, we conducted a series of experiments in NaCl solutions at temperatures between 120 and 184 °C. Two additional experiments at 250 °C were conducted to estimate the transformation rate of aragonite to calcite. Protolith materials consist of (1) synthetic (Mg, Sr-bearing or non-Mg, Sr bearing) needle-shaped microcrystals of aragonite (&lt, 5 µm in size) and (2) larger chips (&gt, 100 µm in size) of natural aragonite. X-ray diffraction (XRD) showed that microcrystals successfully transformed to calcite within 30 h and scanning electron microscopy (SEM) yielded a change in the crystal size to &gt, 10 µm in rhombohedral shape. Electron backscatter diffraction (EBSD) of the larger aragonite chips showed that transformation to randomly oriented calcite occurred at the rims and along the cracks while the core retained an aragonite crystal structure. Isotope-ratio mass spectrometry (IRMS) analyses showed that calcite δ18O was controlled by temperature and δ18O of the solution. The obtained calibration curve of isotope fractionation factor versus temperature is consistent with other studies. Inductively coupled plasma optical emission spectroscopy (ICP-OES) analyses showed that calcite partially or completely retained Mg/Ca and Sr/Ca ratios through the transformation.

Constraining past variability in ocean conditions in the Western Pacific Warm Pool (WPWP) and examining how it has been influenced by the El-Niño Southern Oscillation (ENSO) is critical to predicting how these systems may change in the future. To characterize the spatiotemporal variability of the WPWP and ENSO during the past three decades, we analyzed climate proxies using coral cores sampled from Porites spp. from Kosrae Island (KOS) and Woleai Atoll (WOL) in the Federated States of Micronesia. Coral skeleton samples drilled along the major growth axis were analyzed for oxygen isotopes (δ18Oc) and trace element ratios (Sr/Ca), used to reconstruct sea surface salinity and temperature (SSS and SST). Pseudocoral δ18O time series (δ18Opseudo) were calculated from gridded instrumental observations and compared to δ18Oc, followed by fine-tuning using coral Sr/Ca and gridded SST, to produce age models for each coral. The thermal component of δ18Oc was removed using Sr/Ca for SST, to derive δ18O of seawater (δ18Osw), a proxy for SSS. The Sr/Ca, and δ18Osw records were compared to instrumental SST and SSS to test their fidelity as regional climate recorders. We found both sites display significant Sr/Ca-SST calibrations at monthly and interannual (dry season, wet season, mean annual) timescales. At each site, δ18Osw also exhibited significant calibrations to SSS across the same timescales. The difference between normalized dry season SST (Sr/Ca) anomalies from KOS and WOL generates a zonal SST gradient (KOSWOLSST), capturing the east-west WPWP migration observed during ENSO events. Similarly, the average of normalized dry season δ18Osw anomalies from both sites produces an SSS index (KOSWOLSSS) reflecting the regional hydrological changes. Both proxy indices, KOSWOLSST and KOSWOLSSS, are significantly correlated to regional ENSO indices. These calibration results highlight the potential for extending the climate record, revealing spatial hydrological gradients within the WPWP and ENSO variability back to the end of the Little Ice Age. Ministry of Education (MOE) Published version We also thank the crew of the M/V Alucia for assistance during the 2012 coral drilling expedition to FSM, funded by the Dalio Family Foundation through a WHOI Access to The Sea grant to KAH (#25110104). Geochemical analysis was funded by Singapore Ministry of Education Academic Research Fund Tier-2 (# MOE2016-T2-1016) to NFG and KAH, and by the WHOI Summer Student Fellowship Program (00450400) and Coastal Preservation Network 501c to IMS.

International audience

Bivalve shells serve as powerful high-resolution paleoclimate archives. However, the number of reliable temperature proxies is limited. It has remained particularly difficult to extract temperature signals from shell Sr/Ca, although Sr is routinely employed in other biogenic aragonites. In bivalves, Sr/Ca is linked to the prevailing microstructure and is sometimes affected by kinetics. Here, the hypothesis is tested that temperature can be reconstructed from shell Sr/Ca once microstructure and/or growth-rate-related bias has been mathematically eliminated. Therefore, the relationship between Sr/Ca and increment width, as well as biomineral unit size, has been studied in three different shell portions of field-grown Arctica islandica specimens. Subsequently, microstructure and/or growth-rate-related variation was removed from Sr/Ca data and residuals compared to temperature. As demonstrated, the hypothesis could not be verified. Even after detrending, Sr/Ca remained positively correlated to water temperature, which contradicts thermodynamic expectations and findings from inorganic aragonite. Any temperature signal potentially recorded by shell Sr/Ca is overprinted by other environmental forcings. Unless these variables are identified, it will remain impossible to infer temperature from Sr/Ca. Given the coupling with the biomineral unit size, a detailed characterization of the microstructure should remain an integral part of subsequent attempts to reconstruct temperature from Sr/Ca.

Paleoceanographical reconstructions are often based on microfossil geochemical analyses. Coccoliths are the most ancient, abundant and continuous record of pelagic photic zone calcite producer organisms. Hence, they could be valuable substrates for geochemically based paleoenvironmental reconstructions but only Sr/Ca is exploited even if it remains poorly understood. For example, some murolith coccoliths species have very high Sr/Ca compared to the common 1-4 mmol/mol recorded in placolith coccoliths. In this study, we analyzed the elemental composition of the Middle Jurassic murolith Crepidolithus crassus by synchrotron-based nanoXRF (X-ray Fluorescence Spectroscopy) mapping focusing on Sr/Ca and compared the record to two placolith species, namely Watznaueria contracta and Discorhabdus striatus. In C. crassus, Sr/Ca is more than ten times higher than in both placoliths and seems higher in the proximal cycle. By comparison with the placoliths analyzed in the same analytical set-up and from the same sample, we exclude the impact of the diagenesis and seawater Sr/Ca to explain the high Sr/Ca in C. crassus. Based on comparisons to Pontosphaera discopora and Scyphosphaera apsteinii which also have high Sr/Ca, it seems more likely that high Sr/Ca in C. crassus is either due to the vertical elongation of the R-units of the proximal cycle or related to the action of the special polysaccharide controlling the growth of those vertically elongated R-units that may have affinities to Sr2+ . In order to apply the Sr/Ca proxy to muroliths, further investigations are needed on cultured coccoliths.

his project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 643084 (BASE-LiNE Earth), and was also supported by the collaborative research initiative CHARON (DFG Research Group 1644 – Phase II) funded by the German Research Foundation. Brachiopods present a key fossil group for Phanerozoic palaeo-environmental and palaeo-oceanographical reconstructions, owing to their good preservation and abundance in the geological record. Yet to date, hardly any geochemical proxies have been calibrated in cultured brachiopods and only little is known on the mechanisms that control the incorporation of various key elements into brachiopod calcite. To evaluate the feasibility and robustness of multiple Element/Ca ratios as proxies in brachiopods, specifically Li/Ca, B/Ca, Na/Ca, Mg/Ca, Sr/Ca, Ba/Ca, as well as Li/Mg, we cultured Magellania venosa, Terebratella dorsata and Pajaudina atlantica under controlled experimental settings over a period of more than two years with closely monitored ambient conditions, carbonate system parameters and elemental composition of the culture medium. The experimental setup comprised of two control aquariums (pH0 = 8.0 and 8.15, T = 10 °C) and treatments where pCO2−pH (pH1 = 7.6 and pH2 = 7.35), temperature (T = 16 °C) and chemical composition of the culture medium were manipulated. Our results indicate that the incorporation of Li and Mg is strongly influenced by temperature, growth effects as well as carbonate chemistry, complicating the use of Li/Ca, Mg/Ca and Li/Mg ratios as straightforward reliable proxies. Boron partitioning varied greatly between the treatments, however without a clear link to carbonate system parameters or other environmental factors. The partitioning of both Ba and Na varied between individuals, but was not systematically affected by changes in the ambient conditions. We highlight Sr as a potential proxy for DIC, based on a positive trend between Sr partitioning and carbonate chemistry in the culture medium. To explain the observed dependency and provide a quantitative framework for exploring elemental variations, we devise the first biomineralisation model for brachiopods, which results in a close agreement between modelled and measured Sr distribution coefficients. We propose that in order to sustain shell growth under increased DIC, a decreased influx of Ca2+ to the calcifying fluid is necessary, driving the preferential substitution of Sr2+ for Ca2+ in the crystal lattice. Finally, we conducted micro-computed tomography analyses of the shells grown in the different experimental treatments. We present pore space – punctae – content quantification that indicates that shells built under increased environmental stress, and in particular elevated temperature, contain relatively more pore space than calcite, suggesting this parameter as a potential novel proxy for physiological stress and even environmental conditions. Publisher PDF

This study presents subdaily resolved chemical records through fossil mollusk shell calcite. Trace element profiles resolve periodic variability across similar to 40-mu m-thin daily growth laminae in a Campanian Torreites sanchezi rudist bivalve. These high-resolution records are combined with seasonally resolved stable isotope and trace element records that allow shell-chemical variability to be discussed on both seasonal and daily scale. A combination of layer counting, spectral analysis of chemical cyclicity and chemical layer counting shows that the rudist precipitated 372 daily laminae per year, demonstrating that length of day has increased since the Late Cretaceous, as predicted by astronomical models. This new approach to determine the length of a solar day in geologic history through multiproxy chemical records at subdaily resolution yields considerably more control on the uncertainty of this estimate. Daily chemical variability exceeds seasonal variability in our records, and cannot be explained by diurnal temperature changes. Instead, we postulate that rudist shell chemistry is driven on a daily scale by changes in light intensity. These results together with those of stable isotope analyses provide strong evidence that Torreites rudists had photosymbionts. Bivalve shell calcite generally preserves well. Therefore, this study paves the way for daily-scale reconstructions of paleoenvironment and sunlight intensity on geologic time scales from bivalve shells, potentially allowing researchers to bridge the gap between climate and weather reconstructions. Such reconstructions improve shell chronologies, document environmental change in warm ecosystems, and widen our understanding of the magnitude of short-term changes during greenhouse climates.

Sr/Ca ratios recorded in the aragonite skeleton of massive coral colonies are commonly used to reconstruct seasonal‐ to centennial‐scale variability in sea surface temperature (SST). While the Sr/Ca paleothermometer is robust in individual colonies, Sr/Ca‐SST relationships between colonies vary, leading to questions regarding the utility of the proxy. We present biweekly‐resolution calibrations of Sr/Ca from five Porites spp. corals to satellite SST across 10° of latitude in the Red Sea to evaluate the Sr/Ca proxy across both spatial and temporal scales. SST is significantly correlated with coral Sr/Ca at each site, accounting for 69–84% of Sr/Ca variability (P ≪ 0.01). Intercolony variability in Sr/Ca‐SST sensitivities reveals a latitudinal trend, where calibration slopes become shallower with increasing mean annual temperature. Mean annual temperature is strongly correlated with the biweekly‐resolution calibration slopes across five Red Sea sites (r2 = 0.88, P = 0.05), while also correlating significantly to Sr/Ca‐SST slopes for 33 Porites corals from across the entire Indo‐Pacific region (r2 = 0.26, P < 0.01). Although interannual summer, winter, and mean annual calibrations for individual Red Sea colonies are inconsistently robust, combined multicoral calibrations are significant at summer (r2 = 0.53, P ≪ 0.01), winter (r2 = 0.62, P ≪ 0.01), and mean annual time scales (r2 = 0.79, P ≪ 0.01). Our multicoral, multisite study indicates that the Sr/Ca paleothermometer is accurate across both temporal and spatial scales in the Red Sea and also potentially explains for the first time variability in Sr/Ca‐SST calibration slopes across the Indo‐Pacific region. Our study provides strong evidence supporting the robustness of the coral Sr/Ca proxy for examining seasonal to multicentury variability in global climate phenomena. NRF (Natl Research Foundation, S’pore) MOE (Min. of Education, S’pore) Published version

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2019; Aachen 1 Online-Ressource (XX, 177 Seiten) : Illustrationen, Diagramme, Karten (2019). = Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2019, In order to better understand natural and anthropogenically-induced climate variability, long records of tropical climate parameters covering the past hundreds to thousand years are needed. Usually, instrumental records are too short or lack spatial homogeneity. Only a few records provide continuous measurements of tropical climate parameters prior to 1950. Proxy archives, indirect climate indicators, can help to fill the gaps in the instrumental database. Tropical corals can constitute an ideal proxy archive to reconstruct seasonal, interannual and decadal tocentennial climate variations. They can be used to reconstruct past changes of environmental parameters such as sea surface temperature (SST) or rainfall by measuring Sr/Ca and d18O. In the past decades, the network of coral paleoclimate reconstructions has been growing. The tropical Indian Ocean has been underrepresented in this network. However, the Indian Ocean is of enormous relevance in terms of global warming as it is the largest contributor to global mean SST rise and has been warming faster than any other ocean basin during the last century. The Chagos Archipelago is located in the central Indian Ocean. It lies at the eastern margin of the Seychelles-Chagos thermocline ridge and features open ocean upwelling. In situ SST have been recorded by temperature loggers since 2006, which record upwelling-related cooling and is closely tracked by high-resolution satellite SST. Two modern Porites coral cores were collected from different colonies from a patch reef in the lagoon of Peros Banhos, which experiences low temperature variability and high mean SST. An open ocean Porites coral core was collected at the outer reef slope of Diego Garcia, a site characterized by large temperature fluctuations related to open ocean upwelling. The Sr/Ca record of the open ocean coral shows clear seasonal cycles that closely track the satellite SST. Between 2007 and 2010, Sr/Ca of both lagoon coral cores also tracks satellite SST. However, between 2003 and 2006 the Sr/Ca curves are almost flat and annual coral growth rates are low. For this period, warm SST and coral bleaching have been reported for Chagos. This suggests that observed reduction in coral growth rates is a response to prolonged warming events. Corals from the open ocean at Chagos are adapted to large temperature variability and appear to be unaffected by recent warm events, because upwelled water relieves corals from thermal stress. Based on that, it can be concluded that the temperature variability at a reef site is important to determine the sensitivity of a coral to thermal stress, with corals from sites with small temperature variations being more susceptible. Further, this study is the first to show that these Sr/Ca signatures are reproducible as they affect coral cores from different colonies. On interannual timescales, the dominant modes of climate variability in the tropical Indian Ocean are the El Niño Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD). Therefore, ENSO events also have a strong influence on the Chagos Archipelago. A stable ENSO-SST relationship between tropical Indian and Pacific Ocean is known for the period from the present back, but not prior, to 1950. Three monthly-resolved Sr/Ca records of sub-fossil coral samples from the Chagos Archipelago are used to reconstruct past SST covering the periods 1675-1716 (Maunder Minimum), 1836-1867 (late Little Ice Age) and 1870-1909 (early warming period). The records were combined with an additional record from the same site that was already published. All Sr/Ca records reveal typical ENSO periodicity between 3 and 8 years. Frequency and intensity of ENSO events vary between studied time periods. At Chagos, El Niño and La Niña events are more often recorded in modern corals (1965-1995) and satellite SST (1981-2018) reflecting the actual ENSO frequency compared to the coral covering the Maunder Minimum period. The results of this study suggest that the ENSO-SST teleconnection in the central Indian Ocean was stationary over the last centuries prior to 1950. The mid-Holocene (6 kyr BP) is a target period to study climate variability and its response to orbital forcing, because the latitudinal and seasonal distribution of insolation was different than today, whereas other climate parameters, such as ice volume and greenhouse gas concentrations, were similar to today. As rainfall in East Africa is coupled to changes in SST in the tropical Indian Ocean, it is a key region in which coral paleoclimatic reconstructions have to be conducted to better understand the complex interactions between atmosphere and ocean in the Indian Ocean. Three coral samples dated to the mid-Holocene and one modern coral from East Kenya were used to reconstruct past SST and d18O of the seawater. Both modern and mid-Holocene coral SST do not only follow solar radiation, but also reflect the monsoon circulation. The results further show a reduction of the mean annual SST cycle during the mid-Holocene compared to the present-day and a shift of the annual SST maxima between mid-Holocene and present-day, which can be related to orbital forcing. In addition to SST, coral d18O reflects rainfall, oceanic advection processes, or all three parameters. However, this signal is not as a clear as the signals in the Sr/Ca records. Overall, this study presents three modern and three sub-fossil coral Sr/Ca records from the central Indian Ocean (Chagos Archipelago) and three fossil coral Sr/Ca as well as one fossil and one modern coral d18O record from the western Indian Ocean / East Africa (Kenya), which are used to reconstruct SST and d18O of the seawater. Thus, this thesis contributes new records that help to further close the data gaps. Closing these gaps is needed to better understand the Indian Ocean’s climate system., Published by Aachen

International audience; In contrast to Li/Ca and Mg/Ca, Li/Mg is strongly anticorrelated with temperature in aragonites precipitated by the benthic foraminifer Hoeglundina elegans and a wide range of scleractinian coral taxa. We propose a simple conceptual model of biomineralization that explains this pattern and is consistent with available abiotic aragonite partition coefficients. Under this model the organism actively modifies seawater within its calcification pool by raising its [Ca2+], using a pump that strongly discriminates against both Li+ and Mg2+. Rayleigh fractionation during calcification effectively reverses this process, removing Ca2+ while leaving most Li+ and Mg2+ behind in the calcifying fluid. The net effect of these two processes is that Li/Mg in the calcifying fluid remains very close to the seawater value, and temperature-dependent abiotic partition coefficients are expressed in the biogenic aragonite Li/Mg ratio. We further show that coral Sr/Ca is consistent with this model if the Ca2+ pump barely discriminates against Sr2+. In H. elegans the covariation of Sr/Ca and Mg/Ca requires either that the pump more strongly discriminates against Sr2+, or that cation incorporation is affected by aragonite precipitation rate via the mechanism of surface entrapment. In either case Li/Mg is minimally affected by such ‘vital effects’ which plague other elemental ratio paleotemperature proxies.

Standard methods of reconstructing past sea surface temperatures with coral skeletal Sr/Ca ratios assume that the seawater Sr/Ca ratio is constant. However, data to support this assumption are sparse in coral reef environments, in part because analytical techniques capable of determining seawater Sr/Ca with sufficient accuracy and precision are time-consuming and not widely available. This work presents a new method to measure seawater Sr/Ca based on inductively coupled plasma atomic emission spectrometry that can be easily adopted by many coral paleothermometry laboratories. The work also presents a spatially gridded study of summer and winter seawater Sr/Ca from the middle Florida Keys Reef Tract. The results indicate that seawater Sr/Ca in nearshore waters influenced by the Florida Bay varies by ~0.1 mmol/mol. The observed variation could lead to errors of ~2°C in temperature reconstructions and suggests that corals growing in waters influenced by Florida Bay are less suited for paleoclimate studies.

DOI:10.17014/ijog.2.1.43-51Indonesia is an interesting and important location for a climate study, because it is located in the centre of a warm pool and adjacent to Pacific and Indian Oceans. Long records of climate data are required from this region to more understand the climate variability and the response of global warming. Geochemical proxies derived from Porites corals are believed to be an excellent climate recorder. Sr/Ca content in Porites corals from Kendari, Southeast Sulawesi shows that seasonal variability of SST is resolved by coral Sr/Ca from this region. The monsoon strongly influences reconstructed SST from coral Sr/Ca. Coral SST shows strong power spectrum at the 2.75 year period. Annual to interannual coral SST signal is stronger than the decadal to interdecadal signal. Both ENSO and IOD influence coral SST at two-month and three-month lags respectively.

International audience; Early-life stages of reef-building corals are vital to coral existence and reef maintenance. It is therefore crucial to study juvenile coral response to future climate change pressures. Moreover, corals are known to be reliable recorders of environmental conditions in their skeletal materials. Aposymbiotic Acropora millepora larvae were cultured in different seawater temperature (27 and 29 • C) and pCO 2 (390 and 750 µatm) conditions to understand the impacts of "end of century" ocean acidification (OA) and ocean warming (OW) conditions on skeletal morphology and geochemistry. The experimental conditions impacted primary polyp juvenile coral skeletal morphology and growth resulting in asymmetric translucent appearances with brittle skeleton features. The impact of OA resulted in microstructure differences with decreased precipitation or lengthening of fasciculi and disorganized aragonite crystals that led to more concentrations of centers of calcifications. The coral skeletal δ 11 B composition measured by laser ablation MC-ICP-MS was significantly affected by pCO 2 (p = 0.0024) and water temperature (p = 1.46 × 10 −5). Reconstructed pH of the primary polyp skeleton using the δ 11 B proxy suggests a difference in coral calcification site and seawater pH consistent with previously observed coral pH up-regulation. Similarly, trace element results measured by laser ablation ICP-MS indicate the impact of pCO 2. Primary polyp juvenile Sr/Ca ratio indicates a bias in reconstructed sea surface temperature (SST) under higher pCO 2 conditions. Coral microstructure content changes (center of calcification and fasciculi) due to OA possibly contributed to the variability in B/Ca ratios. Our results imply that increasing OA and OW may lead to coral acclimation issues and species-specific inaccuracies of the commonly used Sr/Ca-SST proxy.

Early-life stages of reef-building corals are vital to coral existence and reef maintenance. It is therefore crucial to study juvenile coral response to future climate change pressures. Moreover, corals are known to be reliable recorders of environmental conditions in their skeletal materials. Aposymbiotic Acropora millepora larvae were cultured in different seawater temperature (27 and 29°C) and pCO2 (390 and 750 μatm) conditions to understand the impacts of “end of century” ocean acidification (OA) and ocean warming (OW) conditions on skeletal morphology and geochemistry. The experimental conditions impacted primary polyp juvenile coral skeletal morphology and growth resulting in asymmetric translucent appearances with brittle skeleton features. The impact of OA resulted in microstructure differences with decreased precipitation or lengthening of fasciculi and disorganized aragonite crystals that led to more concentrations of centers of calcifications. The coral skeletal δ11B composition measured by laser ablation MC-ICP-MS was significantly affected by pCO2 (p = 0.0024) and water temperature (p = 1.46 × 10−5). Reconstructed pH of the primary polyp skeleton using the δ11B proxy suggests a difference in coral calcification site and seawater pH consistent with previously observed coral pH up-regulation. Similarly, trace element results measured by laser ablation ICP-MS indicate the impact of pCO2. Primary polyp juvenile Sr/Ca ratio indicates a bias in reconstructed sea surface temperature (SST) under higher pCO2 conditions. Coral microstructure content changes (center of calcification and fasciculi) due to OA possibly contributed to the variability in B/Ca ratios. Our results imply that increasing OA and OW may lead to coral acclimation issues and species-specific inaccuracies of the commonly used Sr/Ca-SST proxy.

In present day paleoclimate research one of the most pressing challenges is the reconstruction of atmospheric CO2 concentrations. A variety of proxies for several components of the marine inorganic carbon system have been developed in this context (e.g. B isotopes, B/Ca, U/Ca) to allow reconstruction of past seawater pH, HCO3 − and CO3 2− and thereby facilitate estimates of past atmospheric pCO2. Based on culture experiments using the benthic foraminifera Ammonia sp. we describe a positive correlation between Sr/Ca and the carbonate system, namely DIC/bicarbonate ion concentration. Foraminiferal Sr/Ca ratios provide potentially additional constraints on the carbonate system proxy, because the analysis of foraminiferal carbonate Sr/Ca is straightforward and not easily contaminated. Applying our calibration to a published dataset of paleo-Sr/Ca suggests the validity of Sr/Ca as a carbonate system proxy. Furthermore, we explore how our data can be used to advance conceptual understanding of the foraminiferal biomineralization mechanism.

DOI: 10.17014/ijog.v6i3.121Sea surface temperature (SST) is one of the important parameters for (paleo) climate studies. The long time series of SST data are required to understand more the climate change. Coral geochemical proxy such as Sr/Ca overcomes this problem. Coral can provide long time series of climate data continuously from present till hundreds years ago, even fossil (dead) coral can do it till thousand years ago. In this study, Sr/Ca content of Porites coral within 10 m deep from Labuan Bajo, Simeulue Island was analyzed to reconstruct SST. Coral Sr/Ca shows a strong correlation with local SST in seasonal scale as well as in the annual mean scale. Reconstructed SST data show that the monsoon between 1993 2007 strongly influence the SST variation in the Simeulue region. It supposed that the seasonal variation signal strongly influence local SST than the annual mean signal such as El Nino.

Caribbean sea surface temperatures (SSTs) have increased at a rate of 0.2°C per decade since 1971, a rate double that of the mean global change. Recent investigations of the coral Siderastrea siderea on the Belize Mesoamerican Barrier Reef System (MBRS) have demonstrated that warming over the last 30 years has had a detrimental impact on calcification. Instrumental temperature records in this region are sparse, making it necessary to reconstruct longer SST records indirectly through geochemical temperature proxies. Here we investigate the skeletal Sr/Ca and Li/Mg ratios of S. siderea from two distinct reef zones (forereef and backreef) of the MBRS. Our field calibrations of S. siderea show that Li/Mg and Sr/Ca ratios are well correlated with temperature, although both ratios are 3 times more sensitive to temperature change in the forereef than in the backreef. These differences suggest that a secondary parameter also influences these SST proxies, highlighting the importance for site- and species-specific SST calibrations. Application of these paleothermometers to downcore samples reveals highly uncertain reconstructed temperatures in backreef coral, but well-matched reconstructed temperatures in forereef coral, both between Sr/Ca-SSTs and Li/Mg-SSTs, and in comparison to the Hadley Centre Sea Ice and Sea Surface Temperature record. Reconstructions generated from a combined Sr/Ca and Li/Mg multiproxy calibration improve the precision of these SST reconstructions. This result confirms that there are circumstances in which both Li/Mg and Sr/Ca are reliable as stand-alone and combined proxies of sea surface temperature. However, the results also highlight that high-precision, site-specific calibrations remain critical for reconstructing accurate SSTs from coral-based elemental proxies.

Conflicting results have been reported for the stable Sr isotope fractionation, specifically with respect to the influence of temperature. In an experimental study we have investigated the stable Sr isotope systematics for inorganically precipitated and biogenic (coral) aragonite (natural and laboratory-cultured). Inorganic aragonite precipitation experiments were performed from natural seawater using the CO2 diffusion technique. The experiments were performed at different temperatures and different carbonate ion concentrations. Sr-88/Sr-86 of the inorganic aragonite precipitated in the experiments are 0.2% lighter than seawater, but showed no correlation to the water temperature or to CO32- concentration. Similar observations are made in different coral species (Cladocora caespitosa, Porites sp. and Acropora sp.), with identical fractionation from the bulk solution and no correlation to temperature or CO32- concentration. The lack of Sr-88/Sr-86 variability in corals at different environmental parameters and the similarity to the Sr-88/Sr-86 fractionation in inorganic aragonite may indicate a similar Sr incorporation mechanism in corals skeleton and inorganic aragonite, and therefore the previously proposed Rayleigh-based multi element model (Gaetani et al., 2011) cannot explain the process of Sr incorporation in the coral skeletal material. It is proposed that the relatively constant Sr-88/Sr-86 fractionation in aragonite can be used for paleo reconstruction of seawater Sr-88/Sr-86 composition. The seawater Sr-88/Sr-86 ratio reconstruction can be further used in calcite samples to reconstruct paleo precipitation rates. (C) 2016 Elsevier Ltd. All rights reserved.

International audience; The Sr/Ca and Ba/Ca ratios in inorganic apatite are strongly dependent on the temperature of the aqueous medium during precipitation. If valid in biogenic apatite, these thermometers would offer the advantage of being more resistant to diagenesis than those calibrated on biogenic calcite and aragonite. We have reared seabreams (Sparus aurata) in tanks with controlled conditions during experiments lasting for more than 2 years at 13, 17, 23 and 27 degrees C, in order to determine the variations in Sr and Ba partitioning relative to Ca (D(Sr) and D(Ba), respectively) between seawater and fish apatitic hard tissues (i.e. teeth and bones), as a function of temperature. The sensitivity of the Sr and Ba thermometers (i.e. partial derivative D(Sr)/partial derivative T and partial derivative D(Ba)/partial derivative T, respectively), are similar in bone (partial derivative D(b-w)(Sr)/partial derivative T = 0.0036 +/- 0.0003 and partial derivative D(b-w)(Ba)/partial derivative T = 0.0134 +/- 0.0026, respectively) and enamel (partial derivative D(e-w)(Sr)/partial derivative T = 0.0037 +/- 0.0005 and partial derivative D(e-w)(Ba)/partial derivative T = 0.0107 +/- 0.0026, respectively). The positive values of partial derivative D(Sr)/partial derivative T and partial derivative D(Ba)/partial derivative T in bone and enamel indicate that D(Sr) and D(Ba) increase with increasing temperature, a pattern opposite to that observed for inorganic apatite. This distinct thermodependent trace element partitioning between inorganic and organic apatite and water highlights the contradictory effects of the crystal-chemical and biological controls on the partitioning of Ca, Sr and Ba in vertebrate organisms. Taking into account the diet Sr/Ca and Ba/Ca values, it is shown that the bone Ba/Ca signature of fish can be explained by Ca-biopurification and inorganic apatite precipitation, whereas both of these processes fail to predict the bone Sr/Ca values. Therefore, the metabolism of Ca as a function of temperature still needs to be fully understood. However, the biogenic Sr thermometer is used to calculate an average seawater temperature of 30.6 degrees C using the Sr/Ca compositions of fossil shark teeth at the Cretaceous/Tertiary boundary, and a typical seawater Sr/Ca ratio of 0.02. Finally, while the present work should be completed with data obtained in natural contexts, it is clear that Sr/Ca and Ba/Ca ratios in fossil biogenic apatite already constitute attractive thermometers for marine paleoenvironments.

Evidence of increasing concentrations of dissolved carbon dioxide, especially in the surface ocean and its associated impacts on calcifying organisms, is accumulating. Among these organisms, benthic and planktonic foraminifera are responsible for a large amount of the globally precipitated calcium carbonate. Hence, their response to an acidifying ocean may have important consequences for future inorganic carbon cycling. To assess the sensitivity of benthic foraminifera to changing carbon dioxide levels and subsequent alteration in seawater carbonate chemistry, we cultured specimens of the shallow water species Ammonia tepida at two concentrations of atmospheric CO2 (230 and 1900 ppmv) and two temperatures (10 °C and 15 °C). Shell weights and elemental compositions were determined. Impact of high and low pCO2 on elemental composition are compared with results of a previous experiment were specimens were grown under ambient conditions (380 ppvm, no shell weight measurements of specimen grown under ambient conditions are, however, available). Results indicate that shell weights decrease with decreasing [CO32−], although calcification was observed even in the presence of calcium carbonate under-saturation, and also decrease with increasing temperature. Thus both warming and ocean acidification may act to decrease shell weights in the future. Changes in [CO32−] or total dissolved inorganic carbon do not affect the Mg distribution coefficient. On the contrary, Sr incorporation is enhanced under increasing [CO32−]. Implications of these results for the paleoceanographic application of foraminifera are discussed.

Foraminiferal calcite Mg/Ca (Mg/CaCC) is used in paleoceanographic studies to reconstruct temperature. Furthermore, the Mg/CaCC is influenced by different seawater Mg/Ca (Mg/CaSW). Foraminiferal calcite Sr/Ca (Sr/CaCC) can potentially be used to reconstruct Sr/Ca ratios of seawater (Sr/CaSW). As these elements are the most abundant of all elements incorporated into the calcium carbonate of the foraminiferal tests, they potentially might affect each other's incorporation. To investigate the effects of the Mg concentration in the test on Sr incorporation, we conducted a culture study with two species of benthic foraminifera producing carbonate tests with different Mg content. Foraminifers grew under controlled conditions in different Mg/CaSW, whereas Sr/CaSW was kept constant. By analyzing Sr/CaCC of cultured specimens with laser ablation�inductively coupled plasma�mass spectrometry (LA�ICP�MS), we show that Sr/CaCC increases with increasing Mg/CaCC. We explain this observation by a stress in the crystal lattice, caused by elevated Mg/CaCC, which may be compensated for by the additional incorporation of Sr. We discuss this finding in the context of biomineralization and evaluate the reliability of Sr/CaCC as a possible Sr/CaSW proxy.

The Pacific Ocean is the place of interannual and multi-decadal climate variabilities, namely the El Niño Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO). There can have globals impacts via teleconnections. Major impacts on populations, economic and environmental activitieshave been attributed to ENSO. It is therefore essential to improve our understanding of the Pacificdynamic, particularly ENSO activity and its evolution under recent climate change.Geochemical measurements (Sr/Ca and 818O) performed on corals are relevant paleoclimatic records for studying the evolution of ENSO and are essential to put into perspective the current climatedynamic in comparison to past climate.After an evaluation of the robustness of the coral geochemical paleothermometer (Sr/Ca), we present the reconstruction of sea surface temperature (SST) from Eastern tropical Pacific coral (Clippertonatoll) and central tropical Pacific coral (Marquesas archipelago) covering several parts of the last millennium. Our results suggest that ENSO spatial pattern was relatively stable over the past two centuries, mainly indicating an eastern Pacific ENSO pattern (canonical) in comparison to the centralPacific ENSO (Modoki). Although still debated, this spatial pattern could have recently changed dueto global climate change (and this could continue in the future). At the decadal timescale, both studiedareas (central and eastern Pacific) are influenced by the PDO.The results of this Phd thesis also suggest that the present day ENSO activity (under the influence ofanthropogenic forcing) is not atypical throughout the last millennium. The intensity and frequency of ENSO were stronger in the early Little Ice Age (LIA, 16th century). These results are compared withan ensemble of climate simulations (PMIP3) and indicate that ENSO variability is correctly reproduced by numerical climate models but that these models fail to correctly reproduce the mean temperature state of the Pacific., L’océan Pacifique est le siège de variabilités climatiques interannuel et multi-décennale, El Niño Southern Oscillation (ENSO) et la Pacific Decadal Oscillation (PDO), dont les répercussions (via des téléconnections) peuvent être mondiales. Des impacts importants sur les populations, les activités socio-économiques et sur l’environnement ont été attribuées à ENSO. Il est alors primordial d’améliorer notre compréhension de la dynamique Pacifique et notamment du phénomène ENSO ainsique son évolution sous l’effet du changement climatique.Les mesures géochimiques (Sr/Ca et 818O) réalisées sur les coraux constituent des enregistrements paléoclimatiques de choix pour l’étude de l’évolution d’ENSO et sont essentielles pour mettre en perspective la dynamique actuelle du climat par rapport à sa dynamique passée. Après avoir évaluer la robustesse du paléothermomètre géochimique corallien (Sr/Ca), cette thèse a permis la reconstruction de température de surface océanique (SST) à partir de coraux de l’atoll de Clipperton (Pacifique tropical Est) et de l’archipel des Marquises (Pacifique tropical centre) couvrantplusieurs parties du dernier millénaire. Nos résultats suggèrent que la structure spatiale d’ENSO étaitplutôt stable au cours des deux derniers siècles, montrant majoritairement une structure de type ENSOcanonique (Est Pacifique) par opposition à l’ENSO Modoki (centre Pacifique). Bien qu’encore débattue, cette structure spatiale pourrait avoir évoluée très récemment, en liaison avec le changement climatique global (et cela pourrait continuer dans le futur). A l’échelle décennale, nos deux zones d’étude (centre et Est Pacifique) sont influencées par la PDO.Les résultats de cette thèse tendent également à suggérer que l’activité d’ENSO actuelle (sous l’effet du forçage anthropique) n’est pas atypique à l’échelle du dernier millénaire. En effet, son intensité et sa fréquence étaient plus fortes au début du petit âge glaciaire (LIA, 16ème siècle). La comparaison deces résultats avec un ensemble de simulations climatiques (PMIP3) montre que la variabilité ENSO estbien reproduite par ces modèles climatiques mais qu’ils échouent à reproduire correctement l’état moyen des températures du Pacifique.

Basin-scale calcification rates are highly important in assessments of the global oceanic carbon cycle. Traditionally, such estimates were based on rates of sedimentation measured with sediment traps or in deep sea cores. Here we estimated CaCO3 precipitation rates in the surface water of the Red Sea from total alkalinity depletion along their axial flow using the water flux in the straits of Bab el Mandeb. The relative contribution of coral reefs and open sea plankton were calculated by fitting a Rayleigh distillation model to the increase in the strontium to calcium ratio. We estimate the net amount of CaCO3 precipitated in the Red Sea to be 7.3 ± 0.4·10(10) kg·y(-1) of which 80 ± 5% is by pelagic calcareous plankton and 20 ± 5% is by the flourishing coastal coral reefs. This estimate for pelagic calcification rate is up to 40% higher than published sedimentary CaCO3 accumulation rates for the region. The calcification rate of the Gulf of Aden was estimated by the Rayleigh model to be ∼1/2 of the Red Sea, and in the northwestern Indian Ocean, it was smaller than our detection limit. The results of this study suggest that variations of major ions on a basin scale may potentially help in assessing long-term effects of ocean acidification on carbonate deposition by marine organisms.

We observe a strong kinetic effect on Ca incorporation in aragonite. This effect is observed in both inorganic aragonite and in corals. As the rate of precipitation increases the isotope fractionation decreases (44Ca/40Ca). At high precipitation rates above ~104.0 μmol·m-2·h-1 the fractionation becomes constant in a minimum fractionation point. Since corals calcify at high rates of 103.9 μmol·m-2·h-1 and above, no rate effect on Ca isotopes fractionation is expected. Ionic strength appears to have insignificant effect on Ca incorporation of inorganic aragonite. We hypothesize that Ca isotope fractionation in corals is controlled by the saturation state in the extracellular fluid and the rate of calcification.

Sr/Ca has been analyzed from coral core from the Seribu Islands reef complex i.e Jukung Island. SST from ERSST dataset and air temperature measured at Jakarta is used for Sr/Ca calibration. The results show that Jukung Island coral Sr/Ca correlates better with SST than with air temperature. A comparison between the Sr/Ca records with the Nino 3.4 index shows that Jukung coral sites indicate warming sea surface temperatures during the beginning of El Nino events followed by cooling temperatures at the end of El Nino years.

Recently, calcareous cyst producing dinoflagellates, and especially the species Thoracosphaera heimii, have gained more interest in paleoenvironmental and paleoclimatic studies. This PhD thesis focuses on the stable oxygen isotope composition (d18O) and minor element to calcium ratios (Mg/Ca and Sr/Ca) of T. heimii shells from surface sediments in different oceanographic regions. An attempt was made to link d18O, Mg/Ca and Sr/Ca of T. heimii shells with environmental parameters of the upper water column, especially temperature and the carbonate chemistry of the seawater.

The shallow water benthic foraminiferal species Ammonia tepida was cultured in controlled temperature conditions (20 °C) at three different salinities (29.8, 32.2, and 35.5). The calcite shells of single individuals of different sizes that calcified entirely in controlled experimental conditions were analysed for their magnesium and strontium concentrations (LA-ICP-MS) as well as for their oxygen and carbon isotopic composition (pooled individuals). The approach used in this study allows us to investigate the effect of seawater salinity, inter-test variability and test size on the studied parameters. Inter-test Mg/Ca variability is large (24–28%) in each salinity experiment. The size of the individuals seems to have an effect on Mg/Ca only in the lowest salinity experiment (29.8 salinity units). In contrast, Sr/Ca ratios show a strong size dependency in all salinity experiments, with Sr/Ca ratios decreasing with the size of the individuals. There is no response of Mg/Ca and Sr/Ca ratios to a 5 unit salinity increase. The carbon isotopic composition of cultured A . tepida shows an important size dependency with the smallest individuals (~ 200 μm) being around 1‰ 13 C-depleted compared to the largest individuals (~ 600 μm). Interestingly, the oxygen isotopic composition of A . tepida , which does not show an ontogenetic effect, is ~ 0.30–0.45‰ enriched relative to the corresponding δ 18 O eq . values. We hypothesise that heavier than predicted δ 18 O values may be the result of depleted carbonate ion concentrations in the microenvironment surrounding the foraminiferal shell during calcification (i.e., food cyst).

International audience; The chemical composition of past oceans records the combined effects of the evolution of life, climate changes and solid Earth dynamics. Variations in the rate of hydrothermal alteration of the oceanic crust, continental weathering input and burial of marine carbonates are thought to drive the seawater Sr/Ca ratio. Several methods exist for reconstructing past seawater Sr/Ca ratio which are based on the partitioning of Sr between biogenic and inorganic carbonates, and seawater. A compilation of reconstructed seawater Sr/Ca ratios shows that results at variance with each other are obtained for the last 100 My, leaving the question of the Sr/Ca composition of seawater over this period unresolved. Here, a new method for reconstructing the Sr/Ca ratio of past seawater based on the partitioning of Sr between tooth apatite of fossil fish enamel and seawater is proposed. Previously reported values of Sr/Ca and δ18OPO4 for a collection of fish teeth and new data allow the reconstruction of the seawater Sr/Ca ratio evolution for the last 70 My using a new thermometer based on the Sr/Ca ratio in fish teeth. Calculated Sr/Ca ratios decrease from ~ 14 mmol*mol− 1 at 70 Ma to ~ 8 mmol*mol− 1 at 50 Ma and further increase to present day values during the Pliocene. The results are in agreement with values calculated from Cenozoic benthic foraminifera obtained from ODP and DSDP sites. Once the biological offsets of the partitioning of Sr between apatite and water are determined, fossil fish tooth bioapatite represents a material of choice for reconstructing the past seawater Sr/Ca considering its better resistance to diagenetic alteration than for calcite and aragonite.

Knowledge about climate variability is essentially based on observational climate data that are often too short to fully understand the underlying mechanisms with sufficient accuracy. Instrumental records of climate are sparse and become spatiotemporally incomplete before the middle of the 20th century thus, limiting our understanding of the Earth s climate system prior to the instrumental data period. Recent changes in climate are often attributed to anthropogenic global warming. However, to validate such an assumption, patterns of climate variability must be firmly established for periods of reduced anthropogenic forcing. The reconstruction of key climate parameters, such as sea surface temperature (SST) and salinity (SSS), in records extending beyond the relatively short instrumental period are a prerequisite. Additionally, since the reconstructions from climate archives usually focused on the long-term changes (i.e., centennial to millennial scales), there is a clear need to better understand the patterns of short-term (i.e., seasonal to multidecadal scales) climate variability, which are often overlooked in paleoclimatology but relevant for the predictability of hazardous climate phenomena. The aim of the present study is to document the natural range of short-term climate variability in the tropical Atlantic during periods of reduced human activity. Analyses were conducted on several annually-banded Diploria strigosa (Dana, 1846) fossil coral colonies of Holocene age found in the coastal deposits on Bonaire (southern Caribbean Sea).

DOI: 10.17014/ijog.v5i2.96Sr/Ca content ratio in coral is a promising tool for a sea surface temperature reconstruction. In this study, Sr/Ca was analyzed from the top core of fossil coral from Central Mentawai, Indonesia (BLS). The dating of U/Th is used for the age determination of the fossil coral. Based on the U/Th dating, the fossil coral used in this study was deposited in 14th century which approximately has a time range 11 years. The result of this study shows that in the 14th century, the sea surface temperature increased by 3.20 C during 11 years period.

As a major green house gas, CO2 causes global warming which further induces changes in other climate parameters like precipitation and salinity. Additionally as about one-third of the atmospheric CO2 is absorbed by surface waters, the oceans become acidified. Bivalve shell production is costly and should therefore be sensitive to environmental stress. Water pCO2, salinity and temperature changes may be factors that increase physiological stress and thus, can reduce fitness, muscle strength, shell growth, shell stability and finally the bivalves’ ecological performance. The improvement of climate models requires a better understanding of climate history. The ratios of stable Ca isotopes and of divalent substituents of Ca (e.g. Mg and Sr) in bivalve shells depend on seawater temperatures and can therefore theoretically be used as archives of past seawater climates. In two 2-factorial experimental approaches (temperature vs. salinity, temperature vs. pCO2), this work investigates the influence of water temperature, salinity and pCO2 on shell growth, mortality, condition index (Ci = soft tissue weight / shell weight), lipofuscin content in the soft tissue (by fluorometry), shell stability (with a texture analyzer), shell Mg / Ca and Sr / Ca ratios (by optical emission spectrometry) and shell Ca isotope fractionation (Δ44/40Ca, by mass spectrometry) of the two bivalve species Arctica islandica and Mytilus edulis. Additionally, in a feeding assay, we tested the defence capability of M. edulis towards predation by starfish Asterias rubens. Lipofuscin accumulation, growth rates and mortalities indicate that M. edulis is rather an estuarine than a fully marine species. Independent of the respective salinity, however, condition and growth of this species are strongly controlled by temperature. In the Baltic Sea, a positive temperature effect on shell stability will presumably be stronger than a negative salinity effect. A. islandica is a species adapted to high salinity and low temperatures. This could be shown by mortalities and growth rates (salinity) on the one hand and by lipofuscin accumulation, condition index and shell stability (temperature) on the other hand. Both bivalve species that were under investigation in this thesis are largely insensitive to acidifications up to a water pCO2 of about 1400 μatm. Also, the starfish A. rubens did not change its feeding behaviour on M. edulis that were cultured under acidic conditions. Increasing temperature and decreasing salinity, in summary, will most likely shift distributions of M. edulis and A. islandica in the Baltic Sea towards the higher-saline and cooler North-Western areas. It became obvious that most of the shell chemistry characteristics investigated in this study can only be explained by a tightly biologically controlled shell formation. The DSr proxy for seawater Sr / Ca ratios (M. edulis) respectively for salinity (A. islandica) is applicable in both species. The Ca isotope (Δ44/40Ca)-temperature proxy in A. islandica has a shallow slope but is independent of salinity. Δ44/40Ca in M. edulis shells, with regard to our results cannot be used as a temperature proxy. Mg / Ca in M. edulis calcite, however, increases very consistently and exponentially with temperature, though Mg / Ca is influenced by salinity and water pCO2, too. Als bedeutendes Treibhausgas verursacht CO2 globale Klimaerwärmung, die wiederum Veränderungen von anderen Klimaparametern wie Niederschlag und Salinität nach sich zieht. Zusätzlich versauern die Meere, da etwa ein Drittel des atmosphärischen CO2 vom Oberflächenwasser absorbiert wird. Für Muscheln ist die Schalenbildung ein ressourcenaufwändiger Prozess, der folglich empfindlich auf umweltbedingten Stress reagieren sollte. Veränderung des pCO2 , der Salinität und der Temperatur des Wassers könnten als physiologische Stressoren wirken und Fitness, Muskelstärke, Schalenwachstum und -stabilität, also letztendlich die ökologische Performance der Muschel verringern. Zur Verbesserung von Klimamodellen muss die Klimageschichte verstanden werden. Das Verhältnis stabiler Kalzium (Ca)-Isotope und divalenter Ca-Substituenten (z.B. Mg und Sr) in Muschelschalen ist abhängig von Wassertemperaturen und könnte deshalb theoretisch als Archiv vergangener Meerwasserklimata genutzt werden. In zwei 2-faktoriellen Experimenten (Temperatur vs. Salinität, Temperatur vs. pCO2) wurde in dieser Arbeit der Einfluss von Wassertemperatur, Salinität und pCO2 auf Schalenwachstum, Mortalität, Verfassung (Condition Index = Weichkörpergewicht / Schalengewicht), Lipofuszingehalt des Weichkörpers (per Fluorometrie), Schalenstabilität (per Texture Analyzer) sowie auf das Verhältnis von Mg / Ca und Sr / Ca (per optischer Emissionsspektrometrie) und Kalziumisotopenfraktionierung (Δ44/40Ca, per Massenspektrometrie) in Muschelschalen der beiden Arten Arctica islandica und Mytilus edulis untersucht. Zudem wurde die Verteidigungsfähigkeit von M. edulis gegen Prädation durch den Seestern Asteria rubens in einem Fütterungsexperiment getestet. Lipofuszinakkumulation, Wachstums- und Sterblichkeitsraten zeigen an, dass es sich bei M. edulis eher um eine Brackwasserart handelt. Unabhängig von der jeweiligen Salinitätsstufe hängen Verfassung und Wachstum dieser Art aber stark von der Temperatur ab. Bezüglich der Schalenstabilität von M. edulis wird in der Ostsee voraussichtlich ein positiver Temperatureffekt über einen negativen Salinitätseffekt überwiegen. A. islandica ist eine an hohe Salinitäten und niedrige Temperaturen angepasste Art. Dies konnte einerseits durch Mortalität und Wachstumsraten (Salinität) und Lipofuszinakkumulation, Verfassung und Schalenstabilität (Temperatur) gezeigt werden. Beide in dieser Arbeit untersuchten Muschelarten sind äußerst unempfindlich gegenüber Versauerung bis zu einem pCO2 von etwa 1400 μatm. Zudem änderte der Seestern A. rubens sein Fraßverhalten gegenüber unter sauren Bedingungen gehälterten Muscheln nicht. In der Summe werden steigende Temperaturen und sinkende Salinitäten voraussichtlich die Verbreitungsgrenzen von M. edulis und A. islandica in Richtung stärker saliner und kälterer Bereiche in der westlichen Ostsee verschieben. Die meisten in dieser Arbeit untersuchten Muschelschalen-Charakteristika können nur mit einer streng biologisch kontrollierten Schalenbildung erklärt werden. Der DSr-Proxy für Meerwasser Sr / Ca -Verhältnisse (M. edulis) bzw. für Salinitäten (A. islandica) ist bei beiden Arten anwendbar. Der Δ44/40Ca-Temperaturproxy weist bei A. islandica eine flache Steigung auf, jedoch unabhängig von der Salinität. Δ44/40Ca in M. edulis Schalen kann unseren Ergebnissen zu Folge nicht als Temperaturproxy verwendet werden. Das Mg / Ca-Verhältnis im Kalzit von M. edulis steigt sehr stetig und exponentiell mit steigender Temperatur an, wird aber zusätzlich von Salinität und pCO2 des Wassers beeinflusst.

Well-preserved low-Mg calcite tests of modern benthic foraminifera from a depth transect off SW Norway show decreasing Sr/Ca with increasing water depth (r = –0.84). The Mg/Ca ratios also decrease with increasing water depth, although in a curvilinear fashion. Moreover, the inter- and intra-species scatter is apparently larger than for Sr/Ca. A majority of the analysed specimens have Mn/Ca < 200 μmol/mol, and show Sr/Ca, Mg/Ca that fall within published ranges for benthic foraminiferal calcite, indicating that pristine biogenic calcite has been analysed. The uniform temperature and salinity of bottom waters below ~800 m moreover indicate that neither temperature nor salinity can explain the observed Me/Ca trends. The Sr/Ca and Mg/Ca depth trends cannot be explained by dissolution since bottom waters are generally supersaturated with respect to calcite, and dissolution is only observed in a few specimens. Moreover, a regular increase in sedimentary organic content with depth needed to invoke a decrease in porewater pH and concomittant calcite dissolution is not observed. We tentatively ascribe the decreasing Sr/Ca and Mg/Ca trends to depthrelated physiological phenomena. The relatively small intra- and interspecies scatter at a given water depth, as well as the linear decrease in Sr/Ca ratios with increasing water depth observed in modern oceans, may render the Sr/Ca in calcitic benthic foraminifera a potential water-depth proxy for fossil deposits. publishedVersion

We report on a reconnaissance analysis of the geochemical composition of authigenic carbonates and sediment samples collected from various seepage sites on the Niger deep-sea fan. Our aim has been to investigate whether evidence for the presence of authigenic carbonates and gas hydrates within sediments is discernible from solid-phase sediment geochemistry. We show that sedimentary Sr/Ca and Mg/Ca ratios can be used to infer the presence of authigenic aragonite (Sr-rich) and Mg-rich carbonate phases (high-Mg calcite, dolomite) in cold seep settings. Using Sr/Ca and Mg/Ca ratios, the proportion (wt.%) of authigenic carbonates in Niger Fan sediments can be calculated from a mixing model between sediment fractions of terrigenous material, biogenic calcite, aragonite and high-Mg calcite. This approach was applied to high-resolution geochemical profiles along sediment cores recovered from various cold seep settings (mud volcano, diapirs, pockmarks, gas-hydrate bearing sediments). Our data reveal that authigenic carbonates occur as discrete phases in sediments from gas-hydrate-bearing areas, suggesting that such carbonate-rich sediment layers may represent paleo-indicators for ancient methane seepage in marine sediments, possibly associated to gas-hydrate reservoirs. (C) 2007 Elsevier B.V. All rights reserved.

International audience; Trace elements in calcareous organisms have been widely used for paleoclimatic studies. However, the factors controlling their incorporation into mollusc shells are still unclear. We studied here the Sr, Mg, Ba and Mn serial records in the shells of two aragonitic marine bivalve species: Mesodesma donacium and Chione subrugosa from the Peruvian Coast. The elemental concentrations were compared to local temperature and salinity records. The relationships with crystal growth rate G were investigated thanks to well defined periodic growth structures providing a precise shell chronology. Our results show that for both species, environmental parameters only have minor influence, whereas crystal growth rate strongly influences trace elements concentrations, especially for Sr (explaining up to 74% of the variance). The relationship between G and Sr/Ca exhibits variability among the shells as well as inside the shells. For a same growth rate value, Sr/Ca values are higher in more curved shell sections, and the growth rate influence is stronger as well. We show that intercellular and Ca2+-pump pathways cannot support the calcification Ca2+ flux, leading us to propose an alternative mechanism for ionic transport through the calcifying mantle, implying a major role for calcium channels on mantle epithelial cell membranes. In this new calcification model, Sr/Ca shell ratios is determined by Ca2+-channel selectivity against Sr2+, which depends (i) on the electrochemical potential imposed by the crystallisation process and (ii) on the Ca2+-channel density per surface unit on mantle epithelia.

Paleoenvironmental changes in the Black Sea since the LGM were reconstructed using a multi-proxy approach. The hydrology and water chemistry of the Black Sea were significantly influenced by meltwater pulses originated from the Scandinavian Ice Sheet between 15.5 and 18 ka. The subsequent warming during Bölling/Alleröd and Early Holocene led to calcite precipitation, interrupted by the YD cold period. A steady increase in the d18O of Black Sea water was related to a higher d18O of the meteoric precipitation. Diverging d18O trends from different water depths indicate a stratification of the then lacustrine Black Sea. At 9.3 ka the inflow of Mediterranean water started as indicated by a drastic increase in the Mg/Ca and Sr/Ca of ostracod shells. High-frequent fluctuations in the river run-off of the Danube and Sakarya (Anatolia) rivers could be linked to the NAO. The data shows the persistence of the NAO-influence also during deglacial times and on millennial to decadal time scales.

This thesis investigates the response of two prominent coccolithophores, Coccolithus pelagicus and Calcidiscus leptoporus, to varying carbonate chemistry of seawater with special emphasis on calcification. The second issue of the present work is the assessment of coccolith-based proxies, in particular the Sr/Ca ratio and calcium isotope composition. This part focuses on Emiliania huxleyi.

International audience; Biogeochemistry is a powerful tool for dietary reconstruction, and mixing equations can be used to quantify the contribution of multiple sources to an individual's diet. The goals of this paper are: 1) to generalize the inverse method to dietary mixtures; and 2) to reconstruct the diet of the Saint-Césaire Neanderthal using Sr/Ca and Ba/Ca data of the mineral fraction of bone (hydroxylapatite), and with published δ13C and δ15N data of the associated organic fraction of bone (collagen). A new method is proposed to calculate the maximum diagenetic contribution of the Sr/Ba ratio, assuming that the soil soluble fraction is the diagenetic end-member and, for a given fraction of diagenesis, allows the restoration of the original Sr/Ba ratio. Considering the Saint-Césaire Châtelperronian mammalian assemblage as the meat source, and on the basis of available Sr, Ba, and Ca contents of plants, the results indicate that the percentage of plants in the Neanderthal's diet must have been close to zero for realistic Sr and Ba impoverishment between diet and hydroxylapatite. Contrary to previous studies, it is shown that fish could constitute a significant proportion (30%) of the diet of the Saint-Césaire Neanderthal. However, this mass balance solution is not supported by the zooarchaeological data. When the entire faunal assemblage is considered as the dietary source, the calculation shows that bovids (except reindeer) represent the greatest percentage of consumed meat (58%), followed by horses/rhinoceros (22%), reindeer (13%), and mammoths (7%). These respective percentages are in close accordance with zooarchaeological records, suggesting that the faunal assemblage associated with the Neanderthal of Saint-Césaire reliably reflects what he ate during the last few years of his life. In behavioral terms, this result supports the hypothesis that this Neanderthal carried the foodstuffs back to the Saint-Césaire shelter before their consumption.

Analizom koncentracije i omjera elemenata Ca, Mg, Sr i Mn u ljušturama gornjobadenskih ostrakoda okolice Pokupskog dobiveni su podaci koji mogu pomoći kod rekonstrukcije paleookoliša. Za geokemijsku analizu izdvojene su ljušture su ljušture marinskih rodova Aurila, Cytherella, Cytheridea, Bairdoppilata i Quadracythere.

Comprender mejor el sistema climático global depende de nuestra capacidad de extender los limitados registros instrumentales de la temperatura oceánica superficial (TOS) de regiones tropicales. Las razones elementales Sr/Ca y Mg/Ca contenidas en las bandas de crecimiento del coral han demostrado ser una herramienta muy precisa para reconstruir la variabilidad de la TOS. En este estudio presentamos la calibración obtenida a partir de la medición geoquímica estacional entre las razones molares Sr/Ca y Mg/Ca en el esqueleto de coral del género Porites de Isla San Benedicto, Archipiélago Revillagigedo, y la TOS. Las razones geoquímicas medidas (precisión ±0.2%, 2 #963;) mostraron una alta covariación estacional estrechamente relacionada con la TOS de la región. La ecuación de calibración calculada para la relación Sr/Ca-TOS (n = 52) fue Sr/Ca (mmol mol–1) = 10.467 (±0.067) – 0.0524 (±0.003) × TOS (r2 = 0.894) y para la relación Mg/Ca-TOS fue Mg/Ca (mmol mol–1) = 1.550 (±0.095) + 0.0956 (±0.0043) × TOS (r2 = 0.906). Comparando las series de tiempo de la TOS reconstruida a partir de las razones Sr/Ca y Mg/Ca con la TOS media de una malla espacial de 2º × 2º (longitud × latitud) que incluye Isla San Benedicto, encontramos una alta concordancia entre ambas, lo que demuestra la robustez del procedimiento. Un inconveniente del método es que no existe una calibración única para las relaciones Sr/Ca-TOS y Mg/Ca-TOS y las diferentes calibraciones publicadas generan una discrepancia hasta de 8ºC en la temperatura calculada, independientemente de que la sensitividad térmica (i.e. pendiente de la ecuación de paleotemperatura) de los corales sea muy similar. Por lo tanto, concluimos que los paleotermómetros de Sr/Ca y Mg/Ca son altamente confiables en esta región del Pacífico, siempre y cuando exista una ecuación específica para la zona de estudio en cuestión.

The Mg/Ca, Sr/Ca, δ18O and δ13C compositions are given for well-preserved specimens of ten belemnite species/genera from three stratigraphic intervals. The data help assess the use of these proxies for palaeo-oceanography. Samples are from Dorset, UK (Pliensbachian; 5 species); Cambridgeshire, UK (Callovian; 1 species); and the Vocontian Basin, SE France (Valanginian; 4 genera). In none of these belemnite populations (at species or genera level) does Mg/Ca correlate with δ18O. Neither do values of δ18O correlate with Mg/Ca along a microsampled radial profile across a single specimen of Cylindroteuthis puzosiana (Callovian). The use of Mg/Ca is therefore considered to be unreliable as a palaeo-temperature indicator for these belemnite species and genera.

In thermodynamic equilibrium with sea water the Sr/Ca ratio of aragonite varies predictably with temperature and the Sr/Ca ratio in coral have thus become a frequently used proxy for past Sea Surface Temperature (SST). However, biological effects can offset the Sr/Ca ratio from its equilibrium value. We report high spatial resolution ion microprobe analyses of well defined skeletal elements in the reef-building coral Porites lutea that reveal distinct monthly oscillations in the Sr/Ca ratio, with an amplitude in excess of ten percent. The extreme Sr/Ca variations, which we propose result from metabolic changes synchronous with the lunar cycle, introduce variability in Sr/Ca measurements based on conventional sampling techniques well beyond the analytical precision. These variations can limit the accuracy of Sr/Ca paleothermometry by conventional sampling techniques to about 2degreesC. Our results may help explain the notorious difficulties involved in obtaining an accurate and consistent calibration of the Sr/Ca vs. SST relationship.