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Coral reef ecosystems supported by environmentally sensitive reef-building corals face serious threats from human activities. Our understanding of these reef threats is hampered by the lack of sufficiently sensitive coral environmental impact assessment systems. In this study, we established a platform for metabolomic analysis at the single-coral-polyp level using state-of-the-art mass spectrometry (probe electrospray ionization/tandem mass spectrometry; PESI/MS/MS) capable of fine-scale analysis. We analyzed the impact of the organic UV filter, benzophenone (BP), which has a negative impact on corals. We also analyzed ammonium and nitrate samples, which affect the environmental sensitivity of coral-zooxanthella (Symbiodiniaceae) holobionts, to provide new insights into coral biology with a focus on metabolites. The method established in this study breaks new ground by combining PESI/MS/MS with a technique for coral polyps that can control the presence or absence of zooxanthellae in corals, enabling functions of zooxanthellae to be assessed on a polyp-by-polyp basis for the first time. This system will clarify biological mechanisms of corals and will become an important model system for environmental impact assessment using marine organisms. [ABSTRACT FROM AUTHOR]

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) (~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 ~25–11 kyr BP. The resultant multicoral Sr/Ca‐ and δ18O‐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 ~5–5.5°C at Noggin Pass (~17°S) and ~7–8°C at Hydrographer's Passage (~20°S) (Sr/Ca‐derived) during the LGM, in line with previous estimates (Felis et al., 2014, https://doi.org/10.1038/ncomms5102). We focus on contextualizing the Younger Dryas Chronozone (YDC, ~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, https://doi.org10.1038/ncomms5102), 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. Key Points: Near‐modern sea surface temperatures were reached during the Younger Dryas Chronozone on the Great Barrier ReefSea surface temperature, reef assemblage, and sea level data provide an overview of the evolution of the Great Barrier Reef since the LGMIsopora‐based sea surface temperature calibrations can be applied to fossil Isopora to understand environmental change on coral reefs [ABSTRACT FROM AUTHOR]

ABSTRACT Radiocarbon (14C) dating is a widely used and powerful tool for determining the ages of samples in studies of palaeoclimatology, palaeoseismology and archaeology. 14C ages of marine samples often require correction for local reservoir age (Δ R). Although Δ R in the mid- to low latitudes has varied through time, few spatiotemporal reconstructions of Δ R have been published for those regions. Here we report on new and previously published Δ R data for the early 1900s to 1950 obtained from coral skeletons from the Kuroshio region off southern Japan. The data presented here show a marked positive-to-negative shift of Δ R from the early 1900s to the 1940s, which has important implications for calibration of radiocarbon ages in the region and for understanding the relationship of Δ R in the western Pacific with both the El Niño-Southern Oscillation and the Pacific Decadal Oscillation. [ABSTRACT FROM AUTHOR]

In this study, we report the acidification impact mimicking the pre-industrial, the present, and near-future oceans on calcification of two coral species ( Porites australiensis , Isopora palifera ) by using precise p CO 2 control system which can produce acidified seawater under stable p CO 2 values with low variations. In the analyses, we performed Bayesian modeling approaches incorporating the variations of p CO 2 and compared the results between our modeling approach and classical statistical one. The results showed highest calcification rates in pre-industrial p CO 2 level and gradual decreases of calcification in the near-future ocean acidification level, which suggests that ongoing and near-future ocean acidification would negatively impact coral calcification. In addition, it was expected that the variations of parameters of carbon chemistry may affect the inference of the best model on calcification responses to these parameters between Bayesian modeling approach and classical statistical one even under stable p CO 2 values with low variations. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: 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 [CO3 2−] effect. Here we studied how the growth rate influenced the skeletal oxygen and carbon isotope ratios (δ 18O and δ 13C) 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 δ 18O values during summer showed a negligible influence of the large intercolony variation in growth rate (2–10mmyr−1) on δ 18O variation, but δ 18O 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 δ 13C in slower growing corals, which we attributed to the kinetic behaviour of the calcification reaction. The seasonal fluctuation in δ 13C corresponded not to changes in light intensity nor to δ 13C 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 δ 18O 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. [Copyright &y& Elsevier]

Ocean acidification may negatively impact the early life stages of some marine invertebrates including corals. Although reduced growth of juvenile corals in acidified seawater has been reported, coral larvae have been reported to demonstrate some level of tolerance to reduced pH. We hypothesize that the observed tolerance of coral larvae to low pH may be partly explained by reduced metabolic rates in acidified seawater because both calcifying and non-calcifying marine invertebrates could show metabolic depression under reduced pH in order to enhance their survival. In this study, after 3-d and 7-d exposure to three different pH levels (8.0, 7.6, and 7.3), we found that the oxygen consumption of Acropora digitifera larvae tended to be suppressed with reduced pH, although a statistically significant difference was not observed between pH conditions. Larval metamorphosis was also observed, confirming that successful recruitment is impaired when metamorphosis is disrupted, despite larval survival. Results also showed that the metamorphosis rate significantly decreased under acidified seawater conditions after both short (2 h) and long (7 d) term exposure. These results imply that acidified seawater impacts larval physiology, suggesting that suppressed metabolism and metamorphosis may alter the dispersal potential of larvae and subsequently reduce the resilience of coral communities in the near future as the ocean pH decreases. [ABSTRACT FROM AUTHOR]

Instrumental climate observations provide robust records of global land and ocean temperatures during the twentieth century. Unlike for temperature, continuous salinity observations in the surface ocean are scarce prior to 1970, and the magnitude of salinity changes during the twentieth century is largely unknown. Surface ocean salinity is a major component in climate dynamics, as it influences ocean circulation and water mass formation. Here we pre sent an annually resolved reconstruction of salinity variations in the surface waters of the western subtropical North Pacific Ocean since 1873, based on bimonthly records of δ18O, Sr/Ca, and U/Ca in a coral from the Ogasawara Islands. The reconstruction indicates that an abrupt regime shift toward fresher surface ocean conditions occurred between 1905 and 1910. Observational atmospheric data suggest that the abrupt freshening was associated with a weakening of the winds that drive the Kuroshio Current system and the associated subtropical gyre circulation. We note that the abrupt early-twentieth-century freshening in the western subtropical North Pacific precedes abrupt climate change in the northern North Atlantic by a few years. The potential for abrupt regime shifts in surface ocean salinity should be considered in climate predictions for the coming decades. [ABSTRACT FROM AUTHOR]

Abstract: The Meiwa Tsunami, one of the largest tsunamis recorded in historical documents in Japan struck Ishigaki Island and neighboring islands of the Ryukyu Arc in April 1771 AD, killing more than 12000 people. An enormous number of massive Porites coral boulders are scattered on the shore and in the reef moat of eastern Ishigaki Island. Although these boulders likely were cast ashore by the Meiwa Tsunami, a detailed examination has not yet been conducted. When the marine reservoir effect is taken into account, one of mode values of calibrated radiocarbon dates possibly corresponds to the time of the 1771 event. However, the range of calibrated radiocarbon ages indicates that the transport of the boulders cannot be ascribed solely to the tsunami. Oxygen isotope microprofiling, which indicates sea-surface temperature variation, was therefore conducted to further investigate the mechanism of transport. The results suggest that the skeletal growth of most coral colonies was interrupted in summer or autumn; hence, tropical storms and typhoons are also very likely to be agents of transport. Thus, by combining radiocarbon dating with oxygen isotope microprofiling to investigate Porites coral boulders, it is possible to separate paleotsunami boulders from those transported by storm events as far as tsunamis occurred during the non-storm season. [Copyright &y& Elsevier]

The composition of total hydrolysable amino acids (THAAs) in a skeleton of the coral Porites australiensis, collected from Ishigaki Island, Japan, was examined in order to determine whether amino acids (AA) can be used as biomarkers of past changes in coral physiology (metabolism). Micro-samples, corresponding to a time resolution of 1 month, were collected along the growth axis of the coral. Of the 20 AAs analyzed, aspartic acid (Asp) was the most abundant, and its mole concentration relative to the sum of all other AAs (mole%Asp) showed a clear seasonal pattern of low content during winters and high during summers. A growth disturbance in the coral skeleton during 1988-1990, shown by X-ray scans and oxygen and carbon stable isotope data, was marked by a high mole%Asp ratio. Variability in carbon isotope data has often been attributed to metabolic effects, or changes in the isotopic composition of seawater, or both. The changes in mole%Asp shown here suggest that metabolic effects are mainly responsible for sharp changes in carbon isotope profiles during periods of growth disturbance. [ABSTRACT FROM AUTHOR]

Abstract: The skeletal oxygen isotope ratio of Porites corals is the most frequently used proxy of past seawater temperature and composition for tropical and subtropical oceans. However, field calibration of the proxy signals is often difficult owing to the dual dependence of skeletal oxygen isotope ratio on temperature and the oxygen isotope composition of water. We conducted tank experiments in which we grew Porites spp. colonies for 142 d in thermostated seawater at five temperature settings between 21°C and 29°C under moderate light intensity of 250 μmol m−2 s−1 with a 12:12 light:dark photoperiod. A skeletal isotope microprofiling technique applied along the major growth axis of each colony revealed that the oxygen isotope ratios of newly deposited skeleton in most colonies remained almost constant during tank incubation, thus providing an ideal situation for precise calibration of oxygen isotope ratio proxy signals. However, the oxygen isotope ratios displayed an unusually large intercolony variability (∼1‰) at each temperature setting although the mean slope (∼0.15‰ °C−1) obtained for the temperature–skeletal oxygen isotope ratio relationship was close to previous results. The intercolony variations in the oxygen isotope ratios were apparently caused by kinetic isotope effects related to variations in the skeletal growth rate rather than by species-specific variability or genetic differences within species. No correlation was found between skeletal carbon isotope ratios and temperature. The carbon isotope ratios showed significantly inverse correlation with linear growth rates, suggesting a kinetic isotope control at low growth rates. Observed intercolony variability in skeletal carbon isotope ratios (∼5‰) can be partly attributed to growth-rate-related kinetic isotope effects. [Copyright &y& Elsevier]

The CO2 concentration of air has increased over the last two centuries and recently surpassed 400 ppm. Carbon cycle models project CO2 concentrations of 720 to 1000 ppm for the IPCC intermediate scenario (RCP 6.0), resulting in an increase in global mean temperature of ~ 2.6 °C and a decrease in seawater pH of ~ 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 (pCO2) 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 pCO2 conditions, although calcification tended to decrease versus pCO2 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 pCO2, could raise alkalinity, thereby neutralizing ocean acidification. [ABSTRACT FROM AUTHOR]

• South China Sea Holocene large fluctuating marine reservoir ages >than 300 14C yr. • ΔR at South China Sea was controlled by Peruvian upwelling and East Asian Monsoon. • Abrupt shifts at 5.5 ka were similar to those from tropical East Pacific and GBR. Here, we report new estimates of local marine radiocarbon reservoir ages from northwestern Luzon Island in the Philippines, on the east side of the South China Sea. Data for two periods, through the 1940's and the mid-Holocene, were derived from modern and fossil corals. Our results from Luzon Island show variable ΔR values, from −39 ± 25 to 337 ± 27 14C yr over the past 6000 years and highlight the importance of understanding temporal ΔR changes to obtain accurate radiocarbon dates for mid-Holocene samples. An abrupt shift in ΔR at ∼5.5 ka BP, in the east side of the South China Sea, can be attributed to changes in the intensity of the upwelling, in the eastern Pacific, and to the East Asian Monsoon. Additional reservoir age data from the Pacific is likely to reveal details of oceanographic and climate changes at this time. [ABSTRACT FROM AUTHOR]

Sodium concentrations in biogenic CaCO 3 are several thousands of parts per million, and, on a molar basis, Na is among the most abundant constituent minor element in these carbonates. Nevertheless, the chemical form of Na in CaCO 3 is not well constrained. We used synchrotron X-ray spectroscopy to identify the dominant molecular host sites for Na in biogenic calcite and aragonite precipitated by corals, bivalves, and foraminifera. We also used the K -edge X-ray absorption near-edge structure to investigate the chemical environment of Na in biogenic calcium carbonates and identify the altervalent substitution of Na into Ca sites in the lattice structures of calcite and aragonite. Minor cation and anion concentrations in biogenic CaCO 3 suggest that the principal substitution mechanism involves charge compensation through the creation of CO 3 2− vacancies. The mostly homogeneous Na concentrations in the skeletal microstructures of the various biota we examined indicate that environmental and biological controls, such as temperature, skeletal microstructure, and calcification rates, have only minor influences on skeletal Na concentrations. A decrease of Na:Ca ratios with increasing age of foraminiferal shells picked from a Quaternary sediment core, indicates progressive release of Na, which suggests that structurally-substituted Na in biogenic CaCO 3 is readily leached during burial diagenesis. Whereas the sediment that undergo diagenesis release some Na back to the water column, sodium co-precipitation in biogenic CaCO 3 serves as a potential sink of Na for the ocean. [ABSTRACT FROM AUTHOR]

Abstract: We tested the hypothesis that foliose plates of Echinopora lamellosa (Esper, 1795) adjust their primary growth direction (or slope from the horizontal) when irradiance (light) is limiting. This hypothesis was tested at a coral-reef locality that is shaded daily by steep adjacent hills, restricting direct light to only a few hours each day (Iwayama Bay, Palau). The angle at which colonies received maximum light was measured using acetate film, and was compared with modeled estimates (using a simple global-light model). We show strong relationships between light and primary-colony gradients; with the foliose plates acting as parabolic antennae, predictably adjusting their primary gradients to optimize light capture. [Copyright &y& Elsevier]

Abstract: To investigate the deteriorating health of coral reefs in Okinawa, Japan, natural sediment samples were analyzed for diuron, Irgarol 1051, chlorpyrifos, and bisphenol A (BPA) which are hazardous to corals. Samples were analyzed by solid-phase extraction (SPE) followed by high-performance liquid chromatography with tandem mass spectrometry (LC–MS–MS). Although diuron and chlorpyrifos usage is only well recorded for farms and not for cities, these chemicals were detected in both rural and urban areas. Additionally, diuron concentration in urban areas was in some cases higher than in rural areas, which might be caused by greater consumption of these chemicals in home gardens in city areas. Irgarol 1051 was detected in downstream river areas, which are situated far from the source sites such as pier or fishery harbor (0.6–3.2km). This result suggested that Irgarol 1051 could be transported from the river mouths to the sampling sites during flood tides. High BPA concentrations were associated with urban areas (<1.2–22.0μgkg−1), while low concentrations were associated with rural areas (nd–6.8μgkg−1). The river sediments under study are delivered to coral reefs in large quantity through runoff caused by typhoons and other heavy rains. The highly hazardous chemicals are carried into coral reefs on these sediments. Therefore, these hazardous chemical substances may already be influencing the coral reefs. [Copyright &y& Elsevier]

Coral skeletal P/Ca ratio has been developed as an indicator of temporal seawater dissolved inorganic phosphorus (DIP). The use of coral P/Ca proxy helps to assess oceanographic and climatic impacts such as upwelling, circulation, and continent runoffs on marine biogeochemical cycles. However, factors controlling skeletal P incorporation and elemental partitioning between seawater and coral skeletons remain elusive. We conducted temperature-controlled (∼21 to 29 °C) aquaria culture experiments using two colonies of Porites australiensis corals (here refer to B and C) with the only difference in zooxanthellae density (B > C). The coral growth rate ranges from 9.4 to 19.4 mg/day (B) and 0.7 to 14.1 mg/day (C). Only the growth rate of colony C significantly correlates to temperature, potentially reflecting physiological controls on the two colonies given the difference in the zooxanthellae density. We measured coral P/Ca ratios by Inductively coupled plasma mass spectrometry and determined skeletal P speciation through a synchrotron-based spectroscopic approach. Coral P/Ca ratio ranges from 6.5 to 18.6 μmol/mol (B) and 7.2 to 19.8 μmol/mol (C). The dominance of organic-P is confirmed, and the presence of inorganic-P cannot be excluded. Only colony C has a strong P/Ca dependence on temperature and both colonies show strong correlations between P/Ca and growth rate. Although growth rate and temperature are intercorrelated, the growth rate is more likely the direct controlling factor on coral P/Ca in our experiments. Combined laboratory data with field observations, we suggest that the validity of the Porites P/Ca proxy may be influenced by seawater DIP, coral species, and growth rate. • Cultured coral P/Ca ratio can be variable with relatively constant seawater chemistry. • Organic phosphorus is widely present in coral skeletons despite oxidative cleaning. • The validity of the P/Ca proxy could be influenced by seawater DIP, coral species, and growth rate. [ABSTRACT FROM AUTHOR]

Abstract: This study investigated the distribution of magnesium (Mg), phosphorus (P), sulfur (S) and strontium (Sr) using micro X-ray fluorescence (μ-XRF), and the speciation of S using X-ray absorption near edge spectroscopy (XANES) along the annual growth rings in the skeleton of Japanese red coral Paracorallium japonicum. The Mg, P and S distribution in μ-XRF mapping images correspond to the dark and light bands along the annual growth rings in microscopic images of the coral skeleton. The μ-XRF mapping data showed a positive correlation (r =0.6) between P and S distribution in the coral skeleton. A contrasting distribution pattern of S and Mg along the axial skeleton of P. japonicum indicates a weak negative correlation (r =−0.2) between these two elements. The distribution pattern of S, P and Mg in the axial skeleton of P. japonicum reveals linkage between the trace element distribution and the formation of dark/light bands along the annual growth rings. Sulfur and P were distributed in the organic matrix rich dark bands, while Mg was distributed in the light bands of the annual growth rings. XANES analysis showed that inorganic sulfate is the major species of S in the skeleton of P. japonicum with a ratio of 1:20 for organic and inorganic sulfate. [Copyright &y& Elsevier]