Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER GEOPHYSICAL UNION  

The Great Barrier Reef (GBR) is an internationally recognized and widely studied ecosystem, yet little is known about its sea surface temperature (SST) evolution since the Last Glacial Maximum (LGM) (similar to 20 kyr BP). Here, we present the first paleo-application of Isopora coral-derived SST calibrations to a suite of 25 previously published fossil Isopora from the central GBR spanning similar to 25-11 kyr BP. The resultant multicoral Sr/Ca- and delta O-18-derived SST anomaly (SSTA) histories are placed within the context of published relative sea level, reef sequence, and coralgal reef assemblage evolution. Our new calculations indicate SSTs were cooler on average by similar to 5-5.5 degrees C at Noggin Pass (similar to 17 degrees S) and similar to 7-8 degrees C at Hydrographer's Passage (similar to 20 degrees S) (Sr/Ca-derived) during the LGM, in line with previous estimates (Felis et al., 2014, ). We focus on contextualizing the Younger Dryas Chronozone (YDC, similar to 12.9-11.7 kyr BP), whose Southern Hemisphere expression, in particular in Australia, is elusive and poorly constrained. Our record does not indicate cooling during the YDC with near-modern temperatures reached during this interval on the GBR, supporting an asymmetric hemispheric presentation of this climate event. Building on a previous study (Felis et al., 2014, ), these fossil Isopora SSTA data from the GBR provide new insights into the deglacial reef response, with near-modern warming during the YDC, since the LGM.

DOI： 10.1029/2020PA003962

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This data article describes data of magnetic stratigraphy and anisotropy of isothermal remanent magnetization (AIRM) from "Magnetic properties of early Pliocene sediments from IODP Site U1467 (Maldives platform) reveal changes in the monsoon system" [1]. Acquisition of isothermal magnetization on pilot samples and anisotropy of isothermal remanent magnetization are reported as raw data; magnetostratigraphic data are reported as characteristic magnetization (ChRM). (C) 2019 The Authors. Published by Elsevier Inc.

DOI： 10.1016/j.dib.2019.104666

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We report a study of the magnetic stratigraphy and the anisotropy of isothermal remanent magnetization of Pliocene sediments from International Ocean Discovery Program (IODP) Site U1467 drilled in the Maldives platform (Indian Ocean) during Exp. 359. Magnetic stratigraphy gives a precise record of geomagnetic reversals of the early Pliocene from approximately 5.3 Ma to 3.1 Ma providing a detailed age model in an interval where the biostratigraphic record is scarce. We use the anisotropy of isothermal remanent magnetization (AIRM) to investigate the statistical orientation of fine magnetic particles and provide data on the strength and direction of bottom currents during the early Pliocene. The strength of bottom currents recorded by the AIRM, shows a prominent increase at the top of Chron C3n.1n (about 4.2 Ma), and the current direction (NE - SW) is consistent with that of modern instrumental measurements. Since bottom currents in the Maldives are driven by the monsoon, we speculate that the 4.2 Ma increase of bottom currents could mark the onset of the present-day setting, probably related to the coeval uplift phase of the Himalayan plateau.

DOI： 10.1016/j.palaeo.2019.109283

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This paper reports on the newly discovered occurrence of thick sequences (similar to 100 m) of Late Oligocene and Early Miocene (similar to 24.9 to similar to 20 Ma) interbedded organic-rich sediments (sapropels) and pelagic (organic poor) carbonates at Sites 01466 and U1468 drilled in the Maldives archipelago during the International Ocean Discovery Program (IODP) Expedition 359. This occurrence is unusual in that this sequence is located > 1000 m above the surrounding ocean floor within an inter-atoll basin and not linked to any known global oceanic events. Total organic content reaches as high as 35% in the darker layers, while the interbedded carbonates have concentrations of less than 0.1%. Trace elements characteristic of anoxic waters, such as Mo, V, Cr, U, and Pb, correlate positively with concentrations of organic carbon. Nitrogen isotopic data show no evidence that the intervals of high total organic carbon are related to enhanced productivity driven by upwelling. Instead, high organic carbon is associated with intervals of anoxia. We propose that sea-level fluctuations linked to changes in Antarctic ice volume restricted exchange with the open ocean causing bottom waters of the inter-atoll basin to become anoxic periodically. The architecture of the platform at the end of the Oligocene, combined with the global sea-level highstand, set the stage for orbitally-driven sea-level changes producing cyclic deposition of sapropels. The proposed mechanism may serve as an analogue for other occurrences of organic carbon rich sediments within carbonate platform settings. (C) 2019 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.epsl.2019.05.019

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Language：English   Publisher：SPRINGEROPEN  

In the original version of this article (Kunkelova et al. 2018), published on 18 December 2018, there was 1 error in the author name of Dr. Yu.

DOI： 10.1186/s40645-019-0259-0

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The CO2 concentration of air has increased over the last two centuries and recently surpassed 400ppm. Carbon cycle models project CO2 concentrations of 720 to 1000ppm for the IPCC intermediate scenario (RCP 6.0), resulting in an increase in global mean temperature of similar to 2.6 degrees C and a decrease in seawater pH of similar to 0.3. Together, global warming and ocean acidification are often referred to as the evil twins of climate change, potentially inducing severe threats in the near future. In this paper, our discussion is focused on the response of two major calcifiers, foraminifera and corals, which contribute much to the global carbonate burial rate. Photosymbiosis is regarded as an adaptive ecology for living in warm and oligotrophic oceans, especially for reef-building corals and larger reef-dwelling benthic foraminifera. As a consequence of global warming, bleaching may be a global threat to algal symbiont-bearing marine calcifying organisms under conditions of high temperature and light intensity. If CO2 is dissolved in seawater, the partial pressure of CO2 in seawater (pCO(2)) and dissolved inorganic carbon (DIC) increases while pH and the saturation state of carbonate minerals decreases without any change in total alkalinity. Generally, marine calcifying organisms show decreases in calcification rates in response to acidified seawater. However, the response often differs depending on situations, species, and life-cycle stage. Some benthic foraminifera showed a positive response to low pH conditions. The Acropora digitifera coral calcification of adult branches was not reduced markedly at higher pCO(2) conditions, although calcification tended to decrease versus pCO(2) in both aposymbiotic and symbiotic polyps. New analytical technologies help identify important constraints on calcification processes. Based upon Ca isotopes, the transport path of Ca2+ and the degree of its activity would predominantly control the carbonate precipitation rate. Visualization of the extracellular pH distribution shows that proton pumping produces the high internal pH and large internal-external pH gap in association with foraminiferal calcification. From the perspective of a long-term change in the Earth's surface environment, foraminifera seem to be more adaptive and robust than corals in coping with ocean warming and acidification but it is necessary to further understand the mechanisms underlying variations in sensitivity to heat stress and acidified seawater for future prediction. Since CO2 is more soluble in lower temperature seawater, ocean acidification is more critical in the polar and high-latitude regions. Additionally, older deep-water has enhanced acidity owing to the addition of CO2 from the degradation of organic matter via a synergistic effect with high pressure. With current ocean acidification, pH and the saturation state of carbonate minerals are decreasing without any change in total alkalinity. However, in the Earth's history, it is well known that alkalinity has fluctuated significantly. Therefore, it is necessary to quantitatively reconstruct alkalinity, which is another key factor determining the saturation state of carbonate minerals.The rapid release of anthropogenic CO2 (in the present day and at the Paleocene/Eocene boundary) induces severe ocean acidification, whereas in the Cretaceous, slow environmental change, even at high levels of pCO(2), could raise alkalinity, thereby neutralizing ocean acidification.

DOI： 10.1186/s40645-018-0239-9

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Indian-Asian monsoon has oscillated between warm/wet interglacial periods and cool/dry glacial periods with periodicities closely linked to variations in Earth's orbital parameters. However, processes that control wet versus dry, i.e. aridity cyclical periods on the orbital time-scale in the low latitudes of the Indian-Asian continent remain poorly understood because records over millions of years are scarce. The sedimentary record from International Ocean Discovery Program (IODP) Expedition 359 provides a well-preserved, high-resolution, continuous archive of lithogenic input from the Maldives reflecting on low-latitude aridity cycles. Variability within the lithogenic component of sedimentary deposits of the Maldives results from changes in monsoon-controlled sedimentary sources. Here, we present X-ray fluorescence (XRF) core-scanning results from IODP Site U1467 for the past two million years, allowing full investigation of orbital periodicities. We specifically use the Fe/K as a terrestrial climate proxy reflecting on wet versus dry conditions in the source areas of the Indian-Asian landmass, or from further afield. The Fe/K record shows orbitally forced cycles reflecting on changes in the relative importance of aeolian (stronger winter monsoon) during glacial periods versus fluvial supply (stronger summer monsoon) during interglacial periods. For our chronology, we tuned the Fe/Kcycles to precessional insolation changes, linking Fe/K maxima/minima to insolation minima/maxima with zero phase lag. Wavelet and spectral analyses of the Fe/K record show increased dominance of the 100kyr cycles after the Mid Pleistocene Transition (MPT) at 1.25Ma in tandem with the global ice volume benthic O-18 data (LR04 record). In contrast to the LR04 record, the Fe/K profile resolves 100-kyr-like cycles around the 130kyr frequency band in the interval from 1.25 to 2 million years. These 100-kyr-like cycles likely form by bundling of two or three obliquity cycles, indicating that low-latitude Indian-Asian climate variability reflects on increased tilt sensitivity to regional eccentricity insolation changes (pacing tilt cycles) prior to the MPT. The implication of appearance of the 100kyr cycles in the LR04 and the Fe/K records since the MPT suggests strengthening of a climate link between the low and high latitudes during this period of climate transition.

DOI： 10.1186/s40645-018-0238-x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Light-enhanced calcification of reef-building corals, which eventually create vast coral reefs, is well known and based on coral-algal symbiosis. Several controversial hypotheses have been proposed as possible mechanisms for connecting symbiont photosynthesis and coral calcification, including pH rise in the internal pool, role of organic matrix secretion, and enzyme activities. Here, based on the skeletal chemical and isotopic compositions of symbiotic and asymbiotic primary polyps of Acropora digitifera corals, we show a simple pH increase in the calcification medium as the predominant contribution of symbionts to calcification of host corals. We used the symbiotic and asymbiotic primary polyps reared for 10 days at four temperatures (27, 29, 31, and 33 degrees C), five salinities (34, 32, 30, 28, and 26), and four pCO(2) levels (<300, 400, 800, and 1000)(atm). As a result of analyzing multiple geochemical tracers (U/Ca, Mg/Ca, Sr/Ca, delta O-18, delta C-13, and 8 44 Ca), a clear and systematic decrease in skeletal U/Ca ratio (used as a proxy for calcification fluid pH) was observed, indicating a higher pH of the fluid in symbiotic compared to asymbiotic polyps. In contrast, Mg/Ca ratios (used as a tentative proxy for organic matrix secretion) and 8 44 Ca (used as an indicator of Ca2+ pathway to the fluid) did not differ between symbiotic and asymbiotic polyps. This suggests that organic matrix secretion related to coral calcification is controlled mainly by the coral host itself, and a transmembrane transport of Ca2+ does not vary according to symbiosis relationship. Skeletal delta O-18 values of both symbiotic and asymbiotic polyps showed offsets between them with identical temperature dependence. Based on a newly proposed model, behavior of delta O-18 in the present study seems to reflect the rate of CO2 hydration in the calcifying fluid. Since CO2 hydration is promoted by enzyme carbonic anhydrase, the offset of delta O-18 values between symbiotic and asymbiotic polyps is attributed to the differences of enzyme activity, although the enzyme is functional even in the asymbiotic polyp. Symbiotic delta C-13 values in the temperature and salinity experiments were higher compared to those in the asymbiotic polyps due to photosynthesis, although photosynthetic delta C-13 signals in the pCO(2) experiment were masked by the dominant delta C-13 gradient in dissolved inorganic carbon in seawater caused by C-13-depletd CO2 gas addition in the higher pCO(2) treatments. Sr/Ca ratios showed a negligible relationship according to variation of temperature, salinity, and pCO(2), although it might be attributed to relatively large deviations of replicates of Sr/Ca ratios in the present study. Overall, only the U/Ca ratio showed a significant difference between symbiotic and asymbiotic polyps throughout all experiments, indicating that the critical effect on coral calcification caused by symbiotic algae is the increase of pH of the calcifying fluid by photosynthesis. (C) 2018 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.gca.2018.05.016

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Based on high-resolution reflection seismic and core data from IODP Expedition 359 we present a new channel related drift type attached to a carbonate platform slope, which we termed delta drift. Like a river delta, it is comprised of several stacked lobes and connected to a point source. The delta drifts were deposited at the exit of two gateways that connect the Inner Sea of the Maldives carbonate platform with the open ocean. The channels served as conduits focusing and accelerating the water flow; Entrained material was deposited at their mouth where the flows relaxed. The lobe-shaped calcareous sediment drifts must have formed under persistent water through flow. Sediment supply was relatively high and continuous, resulting in an average sedimentation rate of 17 cm ka(-1). The two delta drifts occupy 342 and 384 km(2), respectively; with a depositional relief of approximately 500 m. They have a sigmoidal clinoform reflection pattern with a particular convex upward bending of the foresets. In the Maldives the drift onset marks the transition from a sea-level controlled to a progressively current dominated depositional regime. This major event occurred in the Serravallian about 13 Ma ago, leading to the partial drowning of the carbonate platform and the creation of shallow seaways. The initial bank-enclosed topography resembles an "empty bucket" geometry which is rapidly filled by the drift sediments that aggrade and prograde into the basin. Thereby the depositional environment of the delta drifts changes from deep water (> 500) to shallow-water conditions at their topsets, indicated by the overall coarsening upward trend in grain size and the presence of shallow water large benthic foraminifers at their top.

DOI： 10.1016/j.margeo.2018.04.011

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGEROPEN  

International Ocean Discovery Program (IODP) Expedition 359 cored sediments from eight borehole locations in the carbonate platform of the Maldives in the Indian Ocean. The expedition set out to unravel the timing of Neogene climate changes, in particular the evolution of the South Asian monsoon and fluctuations of the sea level. The timing of these changes are assessed by dating resultant sedimentary alterations that mark stratigraphic turning points in the Neogene Maldives platform system. The first four turning points during the early and middle Miocene are related to sea-level changes. These are reliably recorded in the stratigraphy of the carbonate sequences in which sequence boundaries provide the ages of the sea-level lowstand. Phases of aggradational platform growth give precise age brackets of long-term sea-level high stands during the early Miocene and the early to middle Miocene Climate Optimum that is dated here between 17 to 15.1 Ma. The subsequent middle Miocene cooling coincident with the eastern Antarctic ice sheet expansion resulted in a long-term lowering of sea level that is reflected by a progradational platform growth. The change in platform architecture from aggradation to progradation marks this turning point at 15.1 Ma.& para;& para;An abrupt change in sedimentation pattern is recognized across the entire archipelago at a sequence boundary dated as 12.9-13 Ma. At this turning point, the platform sedimentation switched to a current-controlled mode when the monsoon-wind-driven circulation started in the Indian Ocean. The similar age of the onset of drift deposition from monsoon-wind-driven circulation across the entire archipelago indicates an abrupt onset of monsoon winds in the Indian Ocean. Ten unconformities dissect the drift sequences, attesting changes in current strength or direction that are likely caused by the combined product of changes in the monsoon-wind intensity and sea level fluctuations in the last 13 Ma. A major shift in the drift packages is dated with 3.8 Ma that coincides with the end of stepwise platform drowning and a reduction of the oxygen minimum zone in the Inner Sea.& para;& para;The strata of the Maldives platform provides a detailed record of the extrinsic controlling factors on carbonate platform growth through time. This potential of carbonate platforms for dating the Neogene climate and current changes has been exploited in other platforms drilled by the Ocean Drilling Program. For example, Great Bahama Bank, the Queensland Plateau, and the platforms on the Marion Plateau show similar histories with sediment architectures driven by sea level in their early history (early to middle Miocene) replaced by current-driven drowning or partial drowning during their later history (Late Miocene). In all three platform systems, the influence of currents on sedimentations is reported between 11 and 13 Ma.

DOI： 10.1186/s40645-018-0165-x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人日本地球化学会  

<p>本研究ではサンゴの骨格成長における褐虫藻の役割を明らかにするために、褐虫藻有りと無しのポリプ試料を作成し、温度、塩分、pCO2を調整した水槽で飼育した。飼育実験の後、ポリプ骨格について6種類の化学成分を分析した。その結果、海水のpH指標とされているU/Ca比についてのみ、褐虫藻有りと無しの間に有意な差が見られた。これは、褐虫藻有りのサンゴ体内のpHが上昇していることを示しており、これにより褐虫藻と共生関係にあるサンゴは骨格成長が早いことが分かった。</p>

DOI： 10.14862/geochemproc.65.0_23

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

Recent studies have revealed an intensification of the Indian Summer Monsoon (ISM) over the past 700 years, but its influence on the sediments in the northern Andaman Sea is unclear. To examine this influence, we used radiocarbon-dated sediment core StMY6, acquired 100km offshore in the northern Andaman Sea from the Ayeyarwady River mouth, and obtained a 700-year-long record of the grain-size distribution and geochemistry of the sedimentary sequence. The ISM influences precipitation surrounding the Ayeyarwady River, and thus the river water and sediment discharges to the northern Andaman Sea near the river mouth in the Ayeyarwady River and the weathering intensity in the river catchment. Based on the system, we propose that higher sedimentation rates and larger modal grain size (the most abundant size in the grain-size distribution of sediments) and lower carbonate concentrations after about AD 1600 can be attributed to higher ISM intensity. Profiles of total organic carbon (TOC) content and carbon/nitrogen (C/N) ratios, however, did not show any trends after about AD 1600, which suggests that the ISM has had little influence on these proxies at this site.

DOI： 10.1002/jqs.2947

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

Corals build their skeletons using extracellular calcifying fluid located in the tissue-skeleton interface. However, the mechanism by which corals control the transport of calcium and other ions from seawater and the mechanism of constant alkalization of calcifying fluid are largely unknown. To address these questions, we performed direct pH imaging at calcification sites (subcalicoblastic medium, SCM) to visualize active pH upregulation in live aposymbiotic primary coral polyps treated with HCl-acidified seawater. Active alkalization was observed in all individuals using vital staining method while the movement of HPTS and Alexa Fluor to SCM suggests that certain ions such as H+ could diffuse via a paracellular pathway to SCM. Among them, we discovered acid-induced oscillations in the pH of SCM (pH(SCM)), observed in 24% of polyps examined. In addition, we discovered acid-induced pH up-regulation waves in 21% of polyps examined, which propagated among SCMs after exposure to acidified seawater. Our results showed that corals can regulate pHSCM more dynamically than was previously believed. These observations will have important implications for determining how corals regulate pHSCM during calcification. We propose that corals can sense ambient seawater pH via their innate pH-sensitive systems and regulate pHSCM using several unknown pH-regulating ion transporters that coordinate with multicellular signaling occurring in coral tissue.

DOI： 10.1038/srep40324

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier  

Calcification processes are largely unknown in scleractinian corals. In this study, live confocal imaging was used to elucidate the spatiotemporal dynamics of the calcification process in aposymbiotic primary polyps of the coral species Acropora digitifera. The fluorophore calcein was used as a calcium deposition marker and a visible indicator of extracellular fluid distribution at the tissue-skeleton interface (subcalicoblastic medium, SCM) in primary polyp tissues. Under continuous incubation in calcein-containing seawater, initial crystallization and skeletal growth were visualized among the calicoblastic cells in live primary polyp tissues. Additionally, the distribution of calcein-stained SCM and contraction movements of the pockets of SCM were captured at intervals of a few minutes. Our experimental system provided several new insights into coral calcification, particularly as a first step in monitoring the relationship between cellular dynamics and calcification in vivo. Our study suggests that coral calcification initiates at intercellular spaces, a finding that may contribute to the general understanding of coral calcification processes.

DOI： 10.1016/j.bbrep.2017.01.006

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Other Link： http://orcid.org/0000-0002-8894-1977

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER GEOPHYSICAL UNION  

Symbiotic algae of primary polyps play an important role in calcification of coral skeletons. However, the function of the symbiotic algae, including the way they influence the physical features of their host skeleton under various conditions, is not well understood. We used X-ray microcomputed tomography to observe skeletal shape characteristics in symbiotic and aposymbiotic primary polyps of Acropora digitifera that were cultured at various temperature and pCO(2) levels (temperature 27, 29, 33 degrees C; pCO(2) 400, 800, 1000 mu atm). Symbiotic polyps had a basal plate with a well-developed folding margin supporting the branched skeleton, whereas aposymbiotic ones did not. The features of the folding margin suggest that it might be the initial growth stage of the epitheca. In addition, three-dimensional (3-D) morphological measurements made by X-ray microcomputed tomography show that the branched skeletons of symbiotic primary polyps were taller than those of aposymbiotic ones, suggesting that zooxanthellae in coral primary polyps play a critical role in the height growth of skeletal branches. Furthermore, results of the temperature- and pCO(2)-controlled experiments suggest that global warming might greatly affect the activity of zooxanthellae, whereas ocean acidification might reduce calcification by damaging the coral host itself. Our findings provide new knowledge about the role of zooxanthellae in coral calcification.

DOI： 10.1002/2016GC006536

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

The South Asian Monson (SAM) is one of the most intense climatic elements yet its initiation and variations are not well established. Dating the deposits of SAM wind-driven currents in IODP cores from the Maldives yields an age of 12.9 Ma indicating an abrupt SAM onset, over a short period of 300 kyrs. This coincided with the Indian Ocean Oxygen Minimum Zone expansion as revealed by geochemical tracers and the onset of upwelling reflected by the sediment's content of particulate organic matter. A weaker 'proto-monsoon' existed between 12.9 and 25 Ma, as mirrored by the sedimentary signature of dust influx. Abrupt SAM initiation favors a strong influence of climate in addition to the tectonic control, and we propose that the post Miocene Climate Optimum cooling, together with increased continentalization and establishment of the bipolar ocean circulation, i.e. the beginning of the modern world, shifted the monsoon over a threshold towards the modern system.

DOI： 10.1038/srep29838

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Language：English   Publisher：NATURE PUBLISHING GROUP  

DOI： 10.1038/ncomms12006

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

In this study, the Ca-44/Ca-40 ratios of Porites australiensis grown under three different culture experiments composed of temperature, pH and light controlled culture experiments are measured. The temperature dependent isotope fractionation of 0.02 parts per thousand/degrees C deduced from this study is similar to inorganic aragonite, but the degree of isotope fractionation is about +0.4 parts per thousand offset in corals. These observations agree with earlier results on different coral species, suggesting Ca isotope fractionation during Ca transmembrane transport in corals. While in cultured corals a significant temperature dependence of delta Ca-44 is observed, the relationships between calcium isotope fractionation and pH as well as light intensity are negligible. Therefore variation of delta Ca-44 in Porites corals is mainly controlled by temperature. A combination of delta Ca-44 and Sr/Ca of corals in temperature controlled experiments cannot be explained by Rayleigh type fractionation directly from a fluid, which is seawater-like in terms of delta Ca-44 and Sr/Ca. Through coral-specific biomineralization processes, overall mean delta Ca-44 of scleractinian corals including previous studies are different from biogenic aragonites secreted by sclerosponges and pteropods, but are comparable with those of bivalves as well as calcitic coccolithophores and foraminifers. These findings are important for better understanding biomineralization in corals and in order to constrain the Ca isotopic composition of oceanic Ca sinks in response to climate changes and associated with shifts of calcite and aragonite seas. (C) 2015 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.gca.2015.06.009

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

The interactive effects of nutrient availability and ocean acidification on coral calcification were investigated using post-settlement juvenile corals of Acropora digitifera cultured in nutrient-sufficient or nutrient-depleted seawater for 4 d and then exposed to seawater with different partial pressure of carbon dioxide (P-CO2) conditions (38.8 or 92.5 Pa) for 10 d. After the nutrient pretreatment, corals in the high nutrient condition (HN corals) had a significantly higher abundance of endosymbiotic algae than did those in the low nutrient condition (LN corals). The high abundance of endosymbionts in HN corals was reduced as a result of subsequent seawater acidification, and the chlorophyll a per algal cell increased. The photosynthetic oxygen production rate by endosymbionts was enhanced by the acidified seawater regardless of the nutrient treatment, indicating that the reduction in endosymbiont density in HN corals due to acidification was compensated for by the increase in chlorophyll a per cell. Though the photosynthetic rate increased in the acidified conditions for both LN and HN corals, the calcification rate significantly decreased for LN corals but not for HN corals. The acquisition of nutrients from seawater, rather than the increase in alkalinity caused by photosynthesis, might effectively alleviate the negative response of coral calcification to seawater acidification, suggesting that the response of corals and their endosymbionts to ocean acidification can be influenced by nutrient conditions.

DOI： 10.4319/lo.2014.59.5.1468

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

To investigate the effect of nutrient concentrations on coral-algal symbiosis under thermal stress, the abundance and release of zooxanthellae in the coral Acropora tenuis were quantified under laboratory conditions. The coral fragments were first cultured in either low-nutrient (LN) or high-nutrient (HN) seawater condition at 27 degrees C for 25 days and the seawater temperature was then elevated and kept at 31 degrees C for 1 week for both nutrient conditions. Nutrient enrichment at 27 degrees C increased the densities of symbiotic algae and chlorophyll a and the algal release rates (AR) from the host coral to the ambient seawater. The percentage of algal release rate to the standing stock (AR%) was approximately 0.015%h(-1) for both nutrient conditions at 27 degrees C. After the seawater temperature was elevated to 31 degrees C, the densities of zooxanthellae in the corals decreased by 21-61%, and AR and AR% increased. The corals in HN lost more zooxanthellae per unit surface area than those in LN, but the lost percentages were not significantly different between LN and HN. AR% was also not significantly different between LN and HN at 31 degrees C. These results indicated that the percentage rate of symbiotic algal loss was not affected by the nutrient condition, implying that nutrient incorporation itself would not accelerate coral bleaching susceptibility. (C) 2014 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jembe.2014.04.019

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER GEOPHYSICAL UNION  

We investigated temperature and growth-rate dependency of skeletal oxygen and carbon isotopes in primary polyps of Acropora digitifera (Scleractinia: Acroporidae) by culturing them at 20, 23, 27, or 31 degrees C. Calcification was most rapid at 27 and 31 degrees C. We obtained a delta O-18-temperature relationship (-0.18 parts per thousand degrees C-1) consistent with reported ranges for Porites, indicating that juvenile Acropora polyps can be used for temperature reconstruction. A growth-rate dependency of skeletal isotopes was detected in the experimental polyps cultured at lower water temperatures, when the skeletal growth rate of these polyps was also low. The estimated upper calcification flux limit for a kinetic isotope effect to be observed in the delta O-18-growth rate relationship (similar to 0.4-0.7 g CaCO3 cm(-2) yr(-1)) was similar to the calcification flux in Porites corresponding to a linear extension rate of 5 mm yr(-1), the maximum rate at which the kinetic isotope effect is evident. This result suggests that the calcification flux can be used as a measure of growth rate-related isotope fractionation, that is, the kinetic isotope effect, in corals of different genera and at different growth stages.

DOI： 10.1002/2014GC005322

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Manganese (Mn) and iron (Fe) concentrations were measured in coral skeletons (Porites spp.) collected from the Todoroki River on Ishigaki Island, Japan, to reconstruct the history of land use in the river catchment area. We prepared (1) five bulk samples to investigate the present spatial distribution and (2) micro-samples from two long cores to study the temporal variability of sediment loading from the Todoroki River. The existing state of the elements Mn and Fe in bulk coral skeleton samples was examined by a chemical cleaning experiment. The results of the experiment suggested that Fe was not incorporated into the crystal lattice of the coral skeleton but that Mn was incorporated, as previously reported. The bulk sample data, with and without chemical cleaning, indicated that the spatial distribution of both elements in corals collected along a sampling line from the river mouth toward the reef crest was complex and most likely reflected salinity changes and the amount of suspended particulate matter. The temporal variation of Mn and Fe, in particular the variation of baseline/background levels, mainly reflected the history of land development on Ishigaki Island. In addition, Mn showed clear seasonal variability that appeared to be controlled by a combination of temperature, primary productivity, and precipitation. The results of the present study suggest that Mn may be a useful proxy for river discharge or biological activity depending on local marine conditions, if the specific behavior of Mn at the coral growth site is known.

DOI： 10.1007/s00338-014-1128-3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

Tropical south-western Pacific temperatures are of vital importance to the Great Barrier Reef (GBR), but the role of sea surface temperatures (SSTs) in the growth of the GBR since the Last Glacial Maximum remains largely unknown. Here we present records of Sr/Ca and delta O-18 for Last Glacial Maximum and deglacial corals that show a considerably steeper meridional SST gradient than the present day in the central GBR. We find a 1-2 degrees C larger temperature decrease between 17 degrees and 20 degrees S about 20,000 to 13,000 years ago. The result is best explained by the northward expansion of cooler subtropical waters due to a weakening of the South Pacific gyre and East Australian Current. Our findings indicate that the GBR experienced substantial meridional temperature change during the last deglaciation, and serve to explain anomalous deglacial drying of northeastern Australia. Overall, the GBR developed through significant SST change and may be more resilient than previously thought.

DOI： 10.1038/ncomms5102

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PUBLIC LIBRARY SCIENCE  

Massive scleractinian corals of the genus Porites are important reef builders in the Indo-Pacific, and they are more resistant to thermal stress than other stony corals, such as the genus Acropora. Because coral health and survival largely depend on the interaction between a coral host and its symbionts, it is important to understand the molecular interactions of an entire "coral holobiont". We simultaneously sequenced transcriptomes of Porites australiensis and its symbionts using the Illumina Hiseq2000 platform. We obtained 14.3 Gbp of sequencing data and assembled it into 74,997 contigs (average: 1,263 bp, N50 size: 2,037 bp). We successfully distinguished contigs originating from the host (Porites) and the symbiont (Symbiodinium) by aligning nucleotide sequences with the decoded Acropora digitifera and Symbiodinium minutum genomes. In contrast to previous coral transcriptome studies, at least 35% of the sequences were found to have originated from the symbionts, indicating that it is possible to analyze both host and symbiont transcriptomes simultaneously. Conserved protein domain and KEGG analyses showed that the dataset contains broad gene repertoires of both Porites and Symbiodinium. Effective utilization of sequence reads revealed that the polymorphism rate in P. australiensis is 1.0% and identified the major symbiotic Symbiodinium as Type C15. Analyses of amino acid biosynthetic pathways suggested that this Porites holobiont is probably able to synthesize most of the common amino acids and that Symbiodinium is potentially able to provide essential amino acids to its host. We believe this to be the first molecular evidence of complementarity in amino acid metabolism between coral hosts and their symbionts. We successfully assembled genes originating from both the host coral and the symbiotic Symbiodinium to create a snapshot of the coral holobiont transcriptome. This dataset will facilitate a deeper understanding of molecular mechanisms of coral symbioses and stress responses.

DOI： 10.1371/journal.pone.0085182

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER GEOPHYSICAL UNION  

The Sr/Ca ratio of coral aragonite is used to reconstruct past sea surface temperature (SST). Twenty-one laboratories took part in an interlaboratory study of coral Sr/Ca measurements. Results show interlaboratory bias can be significant, and in the extreme case could result in a range in SST estimates of 7 degrees C. However, most of the data fall within a narrower range and the Porites coral reference material JCp-1 is now characterized well enough to have a certified Sr/Ca value of 8.838 mmol/mol with an expanded uncertainty of 0.089 mmol/mol following International Association of Geoanalysts (IAG) guidelines. This uncertainty, at the 95% confidence level, equates to 1.5 degrees C for SST estimates using Porites, so is approaching fitness for purpose. The comparable median within laboratory error is <0.5 degrees C. This difference in uncertainties illustrates the interlaboratory bias component that should be reduced through the use of reference materials like the JCp-1. There are many potential sources contributing to biases in comparative methods but traces of Sr in Ca standards and uncertainties in reference solution composition can account for half of the combined uncertainty. Consensus values that fulfil the requirements to be certified values were also obtained for Mg/Ca in JCp-1 and for Sr/Ca and Mg/Ca ratios in the JCt-1 giant clam reference material. Reference values with variable fitness for purpose have also been obtained for Li/Ca, B/Ca, Ba/Ca, and U/Ca in both reference materials. In future, studies reporting coral element/Ca data should also report the average value obtained for a reference material such as the JCp-1.

DOI： 10.1002/ggge.20230

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Symbiotic and aposymbiotic juvenile corals, which were grown in the laboratory from the gametes of the scleractinian coral Acropora digitifera and had settled down onto plastic culture plates, were observed with a microscope under different nutrient conditions. The symbiotic corals successfully removed the surrounding benthic microalgae (BMA), whereas the aposymbiotic corals were in close physical contact with BMA. The areal growth rate of the symbiotic corals was significantly higher than that of the aposymbiotic corals. The addition of nutrients to the culture seawater increased the chlorophyll a content in the symbiotic coral polyps and enhanced the growth of some of the symbiotic corals, however the average growth rate was not significantly affected, most likely because of the competition with BMA. The comparison between the symbiotic and aposymbiotic juvenile corals showed that the establishment of a symbiotic association could be imperative for post-settlement juvenile corals to survive in high-nutrient seawater. (C) 2012 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.marpolbul.2012.12.017

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

As application of coral-based climate reconstruction has become more frequent at tropical sites, increased attention is being paid to the potential ambiguities of coral thermometers that are intrinsic to the biomineralisation process, including the so-called vital effect, the growth-rate-related kinetic effect, and the [CO32- I effect. Here we studied how the growth rate influenced the skeletal oxygen and carbon isotope ratios (delta O-18 and delta C-13) and the Sr/Ca ratio in a common-garden experiment involving the long-term culture of Porites australiensis clone colonies. Comparison of the seasonal minimum delta O-18 values during summer showed a negligible influence of the large intercolony variation in growth rate (2-10 mm yr(-1)) on delta O-18 variation, but delta O-18 was relatively sensitive to temporary intracolony growth-rate changes related to colony health. In contrast, the Sr/Ca ratio was robust against both inter- and intracolony growth-rate variation. We found a positive shift in delta C-13 in slower growing corals, which we attributed to the kinetic behaviour of the calcification reaction. The seasonal fluctuation in delta C-13 corresponded not to changes in light intensity nor to delta C-13 of dissolved inorganic carbon in seawater, but to photosynthetic efficiency as measured by pulse-amplitude photometry. These findings support the inference that coral skeletal Sr/Ca and delta O-18 in a long-lived colony can function as a palaeoclimate archive by recording signals of clonal growth. We also propose practical guidelines for the proper interpretation of coral records. (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.epsl.2012.11.046

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DOI： 10.5194/bg-10-6807-2013

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER  

Although coral calcification is directly related to coral health, few studies have examined the responses of coral calcification to environmental stresses, with the exception of ocean acidification. In this study, we experimentally exposed aposymbiotic (lacking symbionts) and symbiotic primary polyps of the scleractinian coral Acropora digitifera to several seawater temperatures (27, 29, 31, and 33 degrees C) and salinities (26, 28. 30, 32, and 34) to investigate the effects of thermal and freshening stresses on coral calcification from the standpoint of coral-algal symbiosis. Calcification rates were higher for symbiotic versus aposymbiotic polyps in both sets of experiments, except for those reared at 31 degrees C and 33 degrees C. Calcification responses of symbiotic polyps were a non-linear function of temperature, and the threshold temperature affecting skeletal growth and bleaching was between 29 degrees C and 31 degrees C. Calcification rates of aposymbiotic polyps were also a non-linear function of temperature, with a maximum polyp weight at 31 degrees C, suggesting that thermal stress also did some damage to the coral host itself. In contrast, skeletal growth of both aposymbiotic and symbiotic polyps decreased linearly with increased salinity. Observations of the microstructure of polyp samples revealed a clearly cyclic feature of skeletal surfaces that was likely related to organo-mineral deposition of calcium carbonate even under lowered-salinity conditions. However, neither type of polyp reared at 33 degrees C evidenced this characteristic, suggesting that thermal stress had compromised the normal calcification process, which involves secretion of an organic matrix by the coral host. Our results suggest that the effects of future global warming will include a reduction in coral calcification itself and the collapse of coral-algal symbiosis, at least at the primary polyp stage. The present experiments showed that thermal stress would affect the host's physiological functionality, whereas freshening stress, which is simply the dilution of ambient seawater, would affect the mineralization process associated with coral calcification. (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.gloplacha.2012.05.001

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

We investigated the effect of acidified seawater on calcification and symbiotic algae (zooxanthellae density, chlorophyll content per single algal cell, fluorescence yield (Fv/Fm)) on a massive coral, Porites australiensis, a common species in the Ryukyu Archipelago of Japan. We found that acidified seawater significantly decreased the calcification and fluorescence yield, but did not affect zooxanthellae density and chlorophyll content per single algal cell. This indicates low levels of photoacclimation to acidified seawater in this species, and this is contrary to the findings of previous studies of Acropora species. A significant correlation between calcification and fluorescence yield was observed, indicating the presence of a strong relationship between calcification and algal photosynthesis. Our results indicate that endosymbiont photosynthetic dysfunction may enhance the decrease of coral calcification in future acidified ocean conditions. Calcification and fluorescence yield among colonies clearly differed, showing that the response to acidified seawater is highly variable among colonies in natural coral populations. (C) 2011 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.marenvres.2011.10.008

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER HEIDELBERG  

High-precision Mg isotope measurements by multiple collector inductively coupled plasma mass spectrometry were applied for determinations of magnesium isotopic fractionation of biogenic calcium carbonates from seawater with a rapid Mg purification technique. The mean delta Mg-26 values of scleractinian corals, giant clam, benthic foraminifera, and calcite deep-sea corals were -0.87aEuro degrees, -2.57aEuro degrees, -2.34aEuro degrees, and -2.43aEuro degrees, suggesting preferential precipitation of light Mg isotopes to produce carbonate skeleton in biomineralization. Mg isotope fractionation in deep-sea coral, which has high Mg calcite skeleton, showed a clear temperature (T) dependence from 2.5 A degrees C to 19.5 A degrees C: 1,000 x ln(alpha) = -2.63 (+/- 0.076) + 0.0138 (+/- 0.0051) x T(R (2) = 0.82, p < 0.01). The delta Mg-26 values of large benthic foraminifera, which are also composed of a high-Mg calcite skeleton, can be plotted on the same regression line as that for deep-sea coral. Since the precipitation rates of deep-sea coral and benthic foraminifera are several orders of magnitude different, the results suggest that kinetic isotope fractionation may not be a major controlling factor for high-Mg calcite. The Mg isotope fractionation factors and the slope of temperature dependence from deep-sea corals and benthic foraminifera are similar to that for an inorganically precipitated calcite speleothem. Taking into account element partitioning and the calcification rate of biogenic CaCO3, the similarity among inorganic minerals, deep-sea corals, and benthic foraminiferas may indicate a strong mineralogical control on Mg isotope fractionation for high-Mg calcite. On the other hand, delta Mg-26 in hermatypic corals composed of aragonite has been comparable with previous data on biogenic aragonite of coral, sclerosponges, and scaphopad, regardless of species differences of samples.

DOI： 10.1007/s00216-011-5264-0

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER GEOPHYSICAL UNION  

The impact of ocean acidification caused by the increasing atmospheric CO2 has been studied in marine calcifiers, including hermatypic corals. However, the effect of elevated pCO(2) on the early developmental life-cycle stage of corals has been little studied. In this study, we reared polyps of Acropora digitifera in seawater at pH(T) 6.55, 7.31, 7.64, 7.77, and 8.03, controlled by CO2 bubbling. We measured the dry weights of polyp skeletons after the 40-d experiment to investigate the relationship between the seawater aragonite saturation state and polyp growth. In addition, we measured skeletal U/Ca ratio to estimate their pH dependence. Skeletal weights of coral polyps increased with the aragonite saturation state and reached an apparent saturation plateau above pH 7.77. U/Ca ratios had a strong inverse relationship with pH and a negligible relationship with skeletal growth rate (polyp weight), suggesting that skeletal U/Ca could be useful for reconstructing paleo-pH. Citation: Inoue, M., R. Suwa, A. Suzuki, K. Sakai, and H. Kawahata (2011), Effects of seawater pH on growth and skeletal U/Ca ratios of Acropora digitifera coral polyps, Geophys. Res. Lett., 38, L12809, doi:10.1029/2011GL047786.

DOI： 10.1029/2011GL047786

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER GEOPHYSICAL UNION  

We analyzed a 165 year delta(18)O coral record from Ishigaki Island, southwestern Japan, and compared our results with observed sea surface temperatures, as well as with the East Asian winter monsoon and El Nino Southern Oscillation. Coral skeletal delta(18)O fluctuations were consistent with other available SST information since the 1890s. The coral delta(18)O data indicated abrupt shift toward cooler condition during 1900-1905, consistent with the extremely cold winter air temperatures observed in Japan in 1902. The cold event was also supported by coral Sr/Ca data. Development of the Siberian High may have intensified the EAWM at this time, in association with active heat convection in the tropics and weak westerlies. This cooling may also have been related to surface ocean freshening in the Ogasawara Islands in the early 20th century. Thus, several phenomena were uniquely coupled during the first few years of the 20th century in the northwestern subtropical Pacific. Citation: Mishima, M., A. Suzuki, M. Nagao, T. Ishimura, M. Inoue, and H. Kawahata (2010), Abrupt shift toward cooler condition in the earliest 20th century detected in a 165 year coral record from Ishigaki Island, southwestern Japan, Geophys. Res. Lett., 37, L15609, doi: 10.1029/2010GL043451.

DOI： 10.1029/2010GL043451

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER GEOPHYSICAL UNION  

Riverine carbon transportation is an important carbon flux connecting reservoirs of the atmosphere, continents, and oceans. The flux is strongly related to the important roles of rivers such as regulation of climate change and buffering of ocean acidification. Here, to evaluate the linkage of such functions of rivers and geological characteristics of the watersheds, we present the results of a comparative hydrogeochemical study conducted on small subtropical watersheds of aluminosilicate-dominated Iriomote Island and carbonate-based Ishigaki Island, southwestern Japan. Rivers on Ishigaki Island exhibited much higher alkalinity than rivers on Iriomote Island, which was even higher than the mean value of major rivers in the world, such as the Saint Lawrence and the Mississippi. This high alkalinity was the result of carbonate dissolution enhanced by soil-originated CO2. As a result of this high inorganic carbon input, the ratio of inorganic carbon and nutrients of the river water was higher than that of marine organic matter such as the Redfield ratio, making the coastal seas a potential source of CO2 for the atmosphere.

DOI： 10.1029/2009JG001039

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER GEOPHYSICAL UNION  

The chronicles of the Ryukyu Kingdom describe at least four coastal inundation events at Ishigaki Island during the seventeenth through nineteenth centuries: the 1771 Meiwa earthquake tsunami, which killed 12,000 people; another earthquake tsunami (1687); and two events with unrecorded causes (1625 and 1714). We used a high-resolution U/Th method to date well-preserved surface parts of massive Porites spp. coral head boulders that had been cast ashore and found that the ages of two boulders correspond to the 1771 event. One large Porites boulder (diameter > 4 m) was dated to 1625, suggesting that that event was also a large inundation event. Calibrated C-14 ages, based on a newly estimated local value for the radiocarbon marine reservoir effect, clustered around 1625 and 1771, suggesting that these events were larger than the others. Our study demonstrated that Porites boulders have enormous potential value for studies of paleoinundation events such as tsunamis and extreme storms.

DOI： 10.1029/2009GC002893

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Climate responses and changes in marine environments during the last deglaciation have been controversial and few paleoceanographic data are available from the tropical South Pacific, though this region is crucial in the investigations of ocean-atmosphere interactions. Integrated Ocean Drilling Program Expedition 310 was conducted to establish the time course of the postglacial sea-level rise at Tahiti in the South Pacific. A principal objective of this expedition was to examine the variation of marine environments during the last deglaciation. As fossil Porites coral is ideal for assessing past marine environments, we selected only Porites specimens from the many coral specimens retrieved, examined them by XRD, and dated them by the C-14 method. In all, we obtained 17 pristine Porites specimens composed of only aragonite with ages from 15 to 9 ka. Then, we measured Mg/Ca, Ba/Ca, and U/Ca ratios and Cd contents as proxies for upwelling and sea surface temperature. Higher Ba/Ca ratios and Cd content together with lower reconstructed SSTs using U/Ca ratios in the coral specimens between 12.6 and 9.8 cal ka compared to around 15 cal ka suggest that upwelling and/or entrainment of subsurface water into mixed layer was enhanced around Tahiti during this period. This finding is consistent with previous reports and supports the idea that the South Pacific was characterized by La Nina-like conditions at least from 12.6 to 9.8 cal ka. (C) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.margeo.2010.02.016

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

We conducted paired measurements of the Sr/Ca ratio and oxygen and carbon stable isotopes of a fossil Faviidae coral specimen (MYK90), age 16 ka, collected from near Miyako Island, the Ryukyus, southwestern Japan. Our study aimed to reconstruct the palaeoenvironment in the East China Sea at 16 ka by comparing the fossil sample with modern Faviidae corals. Our data with annual or longer time resolution may be very suitable for palaeoceanographic reconstruction, although no general calibration method for Faviidae corals has been reported. Our calibration showed that the annual mean sea surface temperature was approximately 5 degrees C lower and sea surface salinity (SSS) at the study site was locally higher at 16 ka than at present. Even though the mouths of the Yellow and Changjiang rivers were east of their present locations because sea level was much lower, our results suggest that the influence of the terrestrial water discharge may not have extended to Miyako Island. Weak summer monsoon activity during the last glacial, which decreased summer precipitation over the Asian continent, and an enhanced winter monsoon, which may have led to more evaporation, likely contributed to the inferred high SSS at the study site. Copyright (C) 2009 John Wiley & Sons, Ltd.

DOI： 10.1002/jqs.1268

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Unlike in the North Atlantic, no continuous record of anthropogenic lead (Pb) has been available in the western Pacific. We reconstructed historical changes in anthropogenic Pb on the basis of Pb isotope ratios recorded in annually-banded coral retrieved from Ogasawara Island, Japan. Whereas the predominant natural source of Pb to the surface of the western Pacific apparently is Chinese loess, anthropogenic Pb has affected the western Pacific at least since the late 19th century. From the late 19th to the early 20th century, Australian Pb used in Japan was an important source of anthropogenic Pb. During 1920-1940, Pb emitted from parts of the world other than Japan contributed somewhat to the western Pacific, and the amount of Pb imported from Australia declined. Alkyl Pb used in Japan became the main source from 1950 until the mid-1970s, when leaded gasoline began to be regulated in Japan. Since the mid-1980s, aerosols from China have been the predominant source of Pb in the western Pacific. During the 1990s, around 60% of Pb in the surface of the western Pacific was from Chinese aerosols. We also investigated the present spatial distribution and likely sources of Pb in the western Pacific by using coral samples. Enrichment in (208)Pb, which is a characteristic of Pb from China, was found in all coral samples except that from Pohnpei, Micronesia, suggesting that at present anthropogenic Pb is transported to the western Pacific mainly from China via westerly winds. (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.scitotenv.2008.07.032

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER GEOPHYSICAL UNION  

Coral strontium/calcium (Sr/Ca) and magnesium/ calcium (Mg/Ca) ratios might be useful for reconstructing past sea surface temperature (SST) in tropical oceans where instrumental data are limited. However, the link between coral skeletal trace elements and SST is disputed, and biological factors such as skeletal growth rate may also affect trace elements in a coral. We studied the relationships between growth rate and SST and Sr/Ca and Mg/Ca ratios using corals (Porites spp.) cultured in thermostated tanks. Sr/Ca was controlled primarily by SST, while Mg/Ca mainly reflected the growth rate with negligible contribution from species on both the variations. These relationships are consistent with modeled results of cation partitioning during aragonite crystal formation.

DOI： 10.1029/2007GL029628

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

We determined Pb contents together with Pb isotopic compositions in coral skeletons (Porites spp.) collected from the western Pacific and adjacent seas to examine distribution of Pb in sea surfaces. Temporal records of Pb were also investigated using coral skeletons from Hainan and Ogasawara Island, located in China and Japan, respectively. The spatial distribution of Pb showed a clear dilution pattern of Pb from Asian continent to the open ocean. Also the similar trend was found in the Java Sea from Jakarta to the offshore. In addition to the spatial distribution, Pb contents in Ogasawara coral have gradually increased during last 108 years. It may be attributed to Pb emission mainly from industrial activities in Asian countries. Hainan coral, which provided 10 years record of Pb, showed a remarkable decline around 1997 probably due to the partial introduction of unleaded gasoline in China. (c) 2006 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.envpol.2005.11.048

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

The delta O-18, delta C-13 and trace element composition of pearls collected from Ago Bay, Japan, were investigated in order to evaluate biomineralization in the cultured pearl oyster (Pinctada fucata martensii). The oxygen isotopic data suggest that the pearls were produced around 23-24 degrees C, mainly in June to early July, which is consistent with their occurrence in the field. Therefore the pearls were produced under or close to isotopic equilibrium conditions, although they showed high calcification rates (higher than 0.2-1.0 g cm(-2) yr(-1)) under which, for example, coral skeletons (calcification rate similar to 0.28 g cm(-2) yr(-1)) often show non-equilibrium isotope partitioning. The delta C-13 values were similar to-2.9 parts per thousand lower than those calculated for offshore waters under equilibrium conditions. This may be due to low-delta C-13 bottom waters resulting from the degradation of organic matter (OM) or to a contribution of low-delta C-13 food. In the latter case, a simple mass balance calculation gives a respiration component of 14%. Twelve trace elements of bulk pearl samples were classified into four groups on the basis of their enrichment/depletion patterns relative to seawater and inter-element relationships: group 1, Co, Cr, Ph; group 2, Ba, Cs, U; group 3, Cu, Sn, V, and group 4, Mn, Rb, Mo. Comparison with coral skeletons suggests that Ba and Mn (groups 2 and 4) were definitely much enriched in proteinaceous OM relative to aragonite crystals in pearls and that V (group 3) in pearls showed only slight enrichment in the organic-rich layer. By contrast, the other elements showed small differences between both layers (enrichment factor of < 3), suggesting that these elements occur largely in aragonite crystals.

DOI： 10.1007/s10872-006-0064-4

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Certain chemicals possess the potential to modulate endocrine systems, and thereby interfere with reproduction and developmental processes in the wild. We analyzed endocrine disrupters nonylphenol (NP) and bisphenol A (BPA) levels at various sites in Okinawa and Ishigaki Islands, Japan. River-water samples showed undetectable to low concentrations of NP and BPA at most of the sites investigated. However, an appreciable amount of BPA was detected in sediments at one coral reef site. In addition, significant numbers of river sediment samples showed appreciable amounts of NP and BPA. Most of the sampling sites for this study are located within a distance of I km from the coral reefs, which are under influence of river-waters to a variable extent. Therefore, influence of endocrine disrupters may have already begun on adjacent coral reefs. Both endocrine disrupters were positively correlated with human population densities, but not with the contents of red soil generated by farm land reformation. Therefore, it is concluded that NP and BPA pollution is a consequence of human waste discharge, both domestic and industrial, and not by agricultural activities. (c) 2004 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.chemosphere.2004.01.032

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

We present 40 year-long, skeletal chronologies of tin (Sri) and copper (Cu) from an annully-banded coral (Porites sp.) collected from Pohnpei Island. Micronesia (western equatorial Pacific). Both the elements are present in antifouling marine paints and are released inadvertently into ambient seawater. Especially, Sri has often been used in the form of tributyltin (TBT). Based on a stepwise pretreatment examination. Sri and Cu both inside and Outside the aragonite lattice of the coral skeleton show a potential for providing marine pollution indicators. High values of extra-skeletal Cu/Ca and Sn/Ca atomic ratios were found between late 1960s and late 1980s during a period of active use of TBT-based antifouling paints worldwide. However, a significant decrease in both the ratios in the beginning, of 1990s can be attributed to regulation Of the use of TBT oil cargo ships by Countries Such as the USA, Japan and Australia. (C) 2004 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.envpol.2003.11.009

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：GEOSTANDARDS  

Trace elements in the Geological Survey of Japan carbonate reference materials Coral JCp-1 and Giant Clam JCt-1 were determined by inductively coupled plasma-mass spectrometry after digestion with 2% v/v HNO3. A standard addition method was adopted in this determination in order to neutralise the Ca matrix effect. in addition, Sc, Y, In and Bi were used as internal standards to control the matrix effect and correct instrumental drift. Of the eighteen elements measured in JCp-1, precisions for fourteen elements, including Cu, Cd and Ba, were better than 10% RSD and concentrations ranged from 0.002 mu g g(-1) (Cs) to 8.02 mu g g(-1) (Ba). The concentrations of measured trace elements in JCt-1, except for Cu, were lower than those in JCp-1. Precisions for all elements with concentrations higher than 0.04 mu g g(-1) in JCt-1 were also better than 10% RSD and concentrations were found to be between 0.001 mu g g(-1) (Cs) and 4.84 mu g g(-1) (Ba). The concentrations of more than fifteen trace elements in the aragonite reference materials are reported here for the first time. Both reference materials are suitable for use in geochernical studies of environmental reconstruction based upon biogenic carbonate materials.

DOI： 10.1111/j.1751-908X.2004.tb00759.x

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Language：Japanese  

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Language：Japanese   Publisher：The Geochemical Society of Japan  

Components in biogenic carbonates have been recognized to be attractive tools for reconstructing past oceanographic and climatic changes. Although chemical components in coral aragonite are precipitated away from equilibrium, fluctuations of Sr/Ca ratio in coral skeletons have been empirically considered to be controlled by temperature. Thus, Sr/Ca ratio in coral skeletons has been applied for paleoclimate reconstruction. Recently, coupled measurements of coral skeletal δ¹⁸O, indicator of both SST and seawater δ¹⁸O, and Sr/Ca ratio are used to reconstruct seawater salinity as well as SST. On the other hand, it has been reported that Sr/Ca is also affected by growth rate of coral skeleton besides SST. However, the impact of skeletal growth rate on Sr/Ca ratio is a matter of debate and controversial results have been reported at the present. In this review, recent progress of studies on the topics and a mechanism of growth rate-related Sr/Ca variation based on a physiological model are summarized.

DOI： 10.14934/chikyukagaku.40.209

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Language：Japanese   Publisher：実業公報社  

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Publisher：The Japanese Coral Reef Society  

The distributions of sediments and its relation to reef water turbidities were investigated in three fringing reefs along the east coast of Ishigaki Island and a patch reef named &ldquo;Shimobishi&rdquo; in the lagoon of Sekisei Reef. In order to quantify fine particles in sediments, we employed &ldquo;SPSS (content of suspended particles in sea sediments)&rdquo; method, which was originally proposed by Ohmija (1987) for quick assessment of land-derived soil distribution in reef sediments. We found highest SPSS values in a moat and channel bottom of the Miyara Bay and along the northern coast of the Todoroki River mouth in Ishigaki Island. In contrast, SPSS values were low in other three reefs including Yasurazaki, Shiraho and Shimobishi areas. Reef water turbidities showed significant correlation with SPSS values, which suggests that the major cause of reef water turbidities is resuspension of fine particles in the sediments. Accuracy and precision of the measurements can be increased by using a portable turbidimeter in the original SPSS method. The modified method has the potential for applying to a study of under-water light environment, which may influence coral-algal competitions in degrading reef conditions.

DOI： 10.3755/jcrs.2004.1

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Language：Japanese   Publisher：The Geochemical Society of Japan  

The chemical composition of coral skeleton and clamshell is closely linked to the composition of surface sea water in which skeletal or shell calcium carbonate is precipitated. For this reason, several chemical components in coral and clam have been determined to be indicatrs of sea surface environmental conditions. However, there is no reference material having the same chemical composition as coral or clam. Therefore, GSJ/AIST has issued the reference materials JCp-1 (Coral <i>Porites</i> sp.) and JCt-1 (Giant Clam <i>Tridacna</i>), for the determination and evaluation of elements in coral, clam and other biogenic carbonates. In this study, collaborative analysis for the certification of reference materials JCp-1 and JCt-1 was carried out in ten laboratories. The analytical data were compiled for 9 components (CaO, Ba, Fe, K, Mg, Mn, Na, P and Sr). The ICP-AES and AAS were mainly used, and the analytical results agreed relatively well. In the statistical analysis, the reference values were mainly decided using the robust method. ISO typically recommends that data should be submitted from no fewer than 15 laboratories for deciding the certified values; the reference values given in this paper could be considered as preliminary certified values.

DOI： 10.14934/chikyukagaku.38.281

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Language：Japanese   Publisher：実業公報社  

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Language：Japanese   Publisher：The Geochemical Society of Japan  

Coral reefs are increasingly threatened by human activities (e.g., sewage discharge and industrial effluents). Composition of coral skeleton is expected to quantitatively record the change in marine environments in which skeletal calcium carbonate is precipitated. Recently, trace elements, particularly heavy metals, in the skeleton of massive and annually banded corals have been successfully used as a proxy of marine pollution at regional and local scale. Critical problems, however, exist due to lack of a well-established method for analyzing trace elements in coral skeleton. Large range in reported values for heavy metal concentrations in coral skeleton could be attributed to differences in pretreatment procedures of skeletal materials rather than the real extent of marine pollution. In this review, we summarize recent progress of studies on the topics and key factors for the further application of coral proxies in order to reconstruct the history of marine pollution.

DOI： 10.14934/chikyukagaku.36.65

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Language：Japanese   Publisher：The Society of Sea Water Science, Japan  

DOI： 10.11457/swsj1965.56.113

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