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Strontium isotopes (87Sr/86Sr) are commonly used to assess the age of Cenozoic dolostones found on many isolated oceanic islands. The possible influence of Rubidium (Rb) content on the 87Sr/86Sr ratios, however, has generally been ignored. This critical issue is assessed by examining the 87Sr/86Sr ratios and elements (Rb, Sr, Al, Ti and K) of seventy‐one samples that came from a ca 339 m thick cored interval of Cenozoic dolomite on the Xisha Islands, South China Sea. For the dolomite from the upper Pliocene Yinggehai Formation (180.5 to 308.5 m; average 23% dolomite) there is a positive correlation between the 87Sr/86Sr ratios and Rb concentrations, whereas for the dolomite from the lower late Miocene Huangliu Formation (308.5 to 519 m; average >98% dolomite) such a correlation is not evident. Combined with high‐temperature experiments, correlation between Al, Ti, K, Rb and 87Sr/86Sr indicates that Rb containing old 87Rb from terrestrial materials modified the 87Sr/86Sr ratios of the Yinggehai dolomite, but not those from the Huangliu dolomite. This is mainly attributed to the different sources of terrestrial dust carried by different East Asian monsoon systems between the late Miocene and Pliocene, and probably also influenced by the dolomitization process to some extent. To test for 87Rb contamination, extrapolation of results from the Yinggehai dolomite and Huangliu dolomite indicate that concentrations of Rb < 1 ppm, Al < 1000 ppm, Ti < 15 ppm and K < 250 ppm in the dolomite indicates that terrestrial inputs are minimal and that the measured 87Sr/86Sr ratios can be used for determining the dolomitization age. Potentially, these concentration thresholds may serve as a screening criterion for assessing the reliability of Sr isotope chronostratigraphy of other island dolostones throughout the world. [ABSTRACT FROM AUTHOR]

Coral skeleton δ13C is a routinely measured indicator in modern insolation change research, but the knowledge of environmental and climatic signals recorded in its seasonality during geological time is sparse. In this study, we present eight Porites coral δ13C records from the mid‐late Holocene to the present from the northern South China Sea (NSCS). Compared with the main control factors for modern δ13C changes, coral δ13C seasonality in the NSCS since the mid‐Holocene shows a long‐term decreasing trend, which is consistent with the change trend as orbital‐induced (precession) insolation seasonal amplitude. By excluding other influencing factors, we speculate that the stronger coral δ13C seasonality (18.8%) over the mid‐Holocene than modern period is attributable to the metabolic effect, which predicts the stronger coral δ13C seasonality under stronger insolation seasonality. Our study has implications for coral δ13C seasonality as a potential indicator to record past insolation information under different climatic backgrounds. Plain Language Summary: Numerous studies have documented the seasonal features of fast‐growing modern coral skeleton δ13C in response to insolation variation. The environmental and climatic signals recorded by coral δ13C seasonality in the geological period remain unclear owing to the relatively short length of observation records. Here we present monthly resolved δ13C records in seven fossil Porites corals (5.6–3.6 ka BP, before 1950 CE) and one modern Porites coral (1987–2001 CE) from the northern South China Sea (NSCS). Compared with the widely accepted prevailing control factors for modern coral δ13C, our results indicated that the stronger coral δ13C seasonality (18.8%) over the mid‐Holocene compared to the modern period is consistent with the orbital‐induced (precession) insolation changes, which indicate a declining seasonality from the mid‐Holocene to present. By excluding other influencing factors, we infer that a tendency toward higher δ13C seasonality during the mid‐Holocene was primarily driven by the metabolic fractionation caused by the enhanced insolation seasonality. This study highlighted coral δ13C seasonality as a potential indicator for recording past insolation information. Key Points: The seasonal variation of modern coral skeleton δ13C in the northern South China Sea (NSCS) is primarily controlled by solar insolationCoral δ13C seasonality in the NSCS since the mid‐Holocene shows a long‐term decreasing trendThe decrease of orbital‐induced (precession) insolation seasonal amplitude led to the declining trend of δ13C seasonality [ABSTRACT FROM AUTHOR]

Summary: Environmental conditions between the outer reef slope (ORS) and lagoon in tropical atolls are significantly different, but the variations of juvenile coral‐microbiomes in the two environments and their relationship with coral thermal acclimatization are poorly understood. We explored this issue based on local water conditions and the microbiome of juvenile corals in the ORS and lagoon in the central South China Sea. Coral‐symbiotic Symbiodiniaceae showed significant differences among coral species; Pocillopora verrucosa and Pachyseris rugosa in the ORS, and Acropora formosa in the lagoon were dominated by Durusdinium, but other corals were dominated by Cladocopium. Although A. formosa in the ORS were dominated by Cladocopium (C3u), they were dominated by Durusdinium (D1/D1a) and Cladocopium (C50) in the lagoon. Other coral species were both dominated by Cladocopium in the lagoon and ORS. The relative abundance of bacteria in the Deinococcus–Thermus was generally higher in the lagoon corals than in the ORS corals. Our study indicates that P. verrucosa, P. rugosa and Porites lutea may have high thermal tolerance based on the relatively high abundance of heat‐tolerant Durusdinium and Thermus scotoductus. Likewise, A. formosa in the lagoon may acclimatize to the thermal environment based on a high relative abundance of heat‐tolerant Durusdinium. [ABSTRACT FROM AUTHOR]

Aim: In this study, we investigated whether environmental factors can effectively control the spatial distribution of various benthic algae and examined the critical ecological impacts of algae on corals across the South China Sea (SCS). Relationships between benthic algae and environmental factors were assessed, and potential ecological impacts of algae on coral communities were evaluated across spatial scales. Location: A total of 104 sites at 12 coral reefs in four coral reef regions (CRRs) of the SCS (latitude range of 9–22° N). Taxa: Turf algae, macroalgae (including fleshy macroalgae and Halimeda), crustose coralline algae (CCA), coral and juvenile coral. Methods: Using diver‐based surveys (2015–2018), we investigated four CRRs with different reef distance to mainland (RDM) across the SCS. We obtained field data on benthic algal composition and cover, coral cover and diversity, and juvenile coral density. We also measured and collected the environmental factors (including seawater environmental parameters and reef fish diversity). Results: The cover of turf algae and CCA gradually decreased and increased, respectively, with an increase in RDM, which had a strong relationship with the gradually changing environmental factors. Random forest models suggested that nutrients, reef fish diversity, seawater transparency and temperature were the most important factors for predicting turf algae and CCA cover. Linear regression analyses showed a significant relationship between the turf algae, macroalgae, and CCA covers, and juvenile coral density. Main conclusions: Our results showed that gradually changing environmental factors were correlated with the spatial distributions of turf algae and CCA. However, the natural biophysical relationships between macroalgae and environmental factors may be disrupted by turf algal overgrowth and nutrient subsidies. Increases in all benthic algal groups significantly impacted coral recruitment, highlighting the critical role of benthic algae in determining the recovery trajectory of the Indo‐Pacific reefs that are threatened by human activities. [ABSTRACT FROM AUTHOR]

As one of the microcontinents dispersed in the South China Sea (SCS), the Xisha microcontinent lacks the petrological evidence of the Cenozoic magmatic activity and basement. Well CK‐2, as a full‐coring kilometre‐scale major scientific drilling in Xisha Islands in the northwestern SCS, drilled through the thick reefal limestone and into the underlying basaltic pyroclastic rocks basement. This paper presents zircon U–Pb age and mineral chemistry of clinopyroxenes from the basaltic pyroclastic rocks. Mineral composition of the clinopyroxenes suggests that most of the clinopyroxenes are composed of diopside, which contains relatively high Al(w (Al2O3) = 5.03%–10.25%) and Ti(w (TiO2) = 2.2%–4.95%). The clinopyroxene discrimination diagrams show that the primary magma is alkaline basalt and likely generated in an intraplate tectonic setting. U–Pb dating of zircons by LA‐ICP‐MS yielded a wide range of ages: 36–33, 116–104, 148–140, 207–196, 255–236, 440, 808–749, and 2,440–1185 Ma. The youngest group has an average age of 35.5 ± 0.9 Ma, which is considered as the maximum age of the basalt eruption. The 2440 ± 19 Ma, which is the oldest zircons in the SCS, are firstly found in the basaltic pyroclastic rocks from the SCS, suggesting that the SCS may contain very old materials. The ages of the inherited zircons are comparable to magmatic activities that occurred around the SCS, implying that they were probably once linked and an integrated part of Gondwana. The ancient continental basement has experienced multistages magmatic events. [ABSTRACT FROM AUTHOR]

The decadal variability of ocean primary productivity (PP) has mainly been studied using relatively short term satellite data, limiting its in‐depth analysis. Here, by removing the influence of the 13C Suess effect, we extract the PP signal on decadal timescales using a record of coral δ13C values from the northern South China Sea (NSCS), where the physical‐biogeochemical conditions are influenced largely by the winter monsoon. Our results show that the PP in the NSCS increased from 1851 to the 1920s and decreased from the 1920s to 2007, and large superimposed decadal‐scale changes were observed. The in‐phase relationship observed between the PP reconstruction and winter monsoon records suggests that the changes in the PP in the NSCS are linked to decadal‐scale changes in the winter monsoon. Considering that the winter monsoon intensity may weaken in the future under global warming, the PP in the NSCS might decrease in the coming decades. Plain Language Summary: Marine phytoplankton contributes roughly half of the global primary production and thus constitutes a vital component of the marine ecosystem that serves as the foundation of the marine food web. Due to the relatively short length of observation records, evaluations of the long‐term changes in ocean primary productivity (PP) have suffered from large uncertainties, which have hampered further discussion of the decadal variability of PP in a long‐term context. To discuss the decadal variability of the PP beyond the range of satellite observations, we present a coral‐based PP reconstruction since 1851 CE from the northern South China Sea (NSCS), where the physical‐biogeochemical conditions are influenced largely by the winter monsoon. Our results show considerable decadal variability of the PP in the NSCS superimposed on a pre‐1920s increase and a post‐1920s decrease. We also found an in‐phase relationship between the decadal variability of the reconstructed PP and the winter monsoon records over the past 150 years, indicating that the PP in the NSCS is linked to changes in the winter monsoon forcing on decadal timescales. Considering that the winter monsoon intensity may weaken in the future under global warming scenarios, the PP in the NSCS might decrease in the coming decades. Key Points: The decadal variability of primary productivity was extracted from a coral δ13C record by removing the influence of the 13C Suess effectThe coral‐based primary productivity reconstruction for the past 150 years showed a pre‐1920s increase and a post‐1920s decreaseThe primary productivity of the northern South China Sea varied in phase with the intensity of the winter monsoon on decadal timescales [ABSTRACT FROM AUTHOR]

To date, the decadal variability of the Global Monsoon (GM) has been mainly studied using instrumental data collected over the last 50 years, and further discussion has been hampered by the limited data length. Here, we present a coral δ18O record from the northern South China Sea, where the hydrology is related to the seasonal Intertropical Convergence Zone (ITCZ) migration, and we use this record to reconstruct the decadal migration of the ITCZ since 1851 A.D. Combining our record with a synthesis of monsoon records reveals an anti‐phase inter‐hemispheric variability of the GM over the last 150 years, indicating that the decadal‐scale hydrologic variability in the tropics is modulated by the meridional migration of the ITCZ. The plausible relationship observed between the decadal variability of the GM and the Atlantic Multidecadal Oscillation suggests that the decadal variability of tropical hydrological changes is likely linked to the climate perturbations in the North Atlantic. Plain Language Summary: The prediction of monsoon variability in the coming decades will be of great importance for policy‐making and socio‐economic development. The Global Monsoon (GM) is the global‐scale seasonal atmospheric overturning associated with the migration of the Intertropical Convergence Zone (ITCZ). The variability and dynamics of the GM on decadal timescales are still unclear due to the limited length of the instrumental data (< 50 years). Here, we integrated a synthesis of the monsoon and the ITCZ records, including published records and our new coral record, and found that the GM varied in an anti‐phase inter‐hemispheric mode on decadal timescales associated with the ITCZ migration over the past 150 years, suggesting that the simultaneous intensification of the monsoons in both hemispheres since the ~1980s was unusual in a long‐term context. The linkage between the decadal variability of GM and the Atlantic Multidecadal Oscillation/Variability indicated that the North Atlantic has been driving the anti‐phase inter‐hemispheric variability of the GM on decadal timescales. Key Points: The coral δ18O record from the northern South China Sea captures the migration of the regional ITCZ on decadal timescalesThe Global Monsoon varied in an anti‐phase inter‐hemispheric mode on decadal timescales associated with the ITCZ migration since 1851 A.DThe decadal variability of the Global Monsoon was found to be linked to the Atlantic Multidecadal Oscillation [ABSTRACT FROM AUTHOR]

The trade winds cause strong upwelling in the eastern equatorial Pacific, and create the eastern Pacific Cold Tongue (EPCT) that has far‐reaching impacts on global climate. However, large discrepancies persist in quantifying 20th‐century EPCT sea surface temperature (SST) changes across different instrumental data sets. Here we synthesize four coral Sr/Ca‐SST records from the tropical central‐eastern Pacific to develop a Cold Tongue Index (CTI) reconstruction for 1887–1997. The coral CTI record shows a rapid 20th century warming of the EPCT, suggesting an underestimation of warming trends in instrumental CTI records. The decadal to multidecadal changes in reconstructed EPCT SST show an association with the Walker Circulation. Our reconstruction indicates that recent EPCT cooling during the global warming hiatus is not unusual in the context of the 20th century. Our results provide new evidence for 20th century EPCT SST changes and an observational constraint for predicting future tropical climate changes. Plain Language Summary: The tropical Pacific exhibits an asymmetric pattern of sea surface temperatures (SST) along the equator, with a warm pool in the west and a cold tongue in the east. The Eastern Pacific Cold Tongue (EPCT) plays a crucial role in influencing global climate. To date, however, considerable disagreement persists about changes and causes of the EPCT SST over the 20th century due to the sparse instrumental observations before ∼1960. Here we synthesize published coral Sr/Ca‐SST records from the tropical central‐eastern Pacific to develop a coral Cold Tongue Index (CTIcoral) for the period 1887–1997. The CTIcoral record correlates significantly with instrumental data since 1960, and thus allows reliable assessment of 20th century EPCT SST changes. Our record exhibits a rapid 20th century warming trend of the EPCT, indicating an underestimation of warming trends in instrumental CTI records. The decadal to multidecadal changes in CTIcoral also show an association with the Walker Circulation. Comparing the magnitude of the 1992–2011 trend in instrumental CTI with our reconstruction reveals that recent EPCT cooling during the global warming hiatus is not anomalous in the context of 20th century. Our findings have implications for predicting future EPCT SST changes by offering a constraint for model simulations. Key Points: Synthesizing coral Sr/Ca‐SST records yields robust estimates of 20th century warming trend in the eastern Pacific Cold Tongue (EPCT)A coral‐based reconstruction indicates an underestimation of 20th century EPCT warming trends in instrumental SST recordsRecent EPCT cooling during the global warming hiatus is not anomalous in the context of the 20th century [ABSTRACT FROM AUTHOR]

BACKGROUND β‐Glucosidases (3.2.1.21) play essential roles in the removal of nonreducing terminal glucosyl residues from saccharides and glycosides. However, the full potential and different applications of recombinant high‐yield microbial β‐glucosidase‐producing systems remain to be tackled. RESULTS: A β‐glucosidase gene designated as Mg132 was isolated from a coral microorganism by high‐throughput sequencing and functional screening. The deduced amino acid sequences of Mg132 showed a highest identity of 97% with β‐glucosidase predicted in the GenBank database. This gene was cloned and overexpressed in Escherichia coli BL21 (DE3) for the first time. The optimal pH and temperature of purified recombinant Mg132 were 8.0 and 50 °C respectively. It exhibited a high level of stability at high concentration of glucose and ethanol, and glucose concentrations below 300 mmol L–1 distinctly stimulated p‐nitrophenyl‐β‐d‐glucopyranoside hydrolysis, reaching 200% at 15% ethanol. The Km and Vmax values were 0.293 mmol L–1 and 320 μmol min−1 mg−1 respectively while using p‐nitrophenyl‐β‐d‐glucopyranoside as a substrate. Wine treated with Mg132 had an obvious positive catalytic specificity for glycosides, which give a pleasant flavor of temperate fruity and floral aromas. The total concentration of fermentative volatiles was 201.42 ± 10.22 μg L−1 following Mg132 treatment and 99.21 ± 7.72 μg L−1 in control samples. CONCLUSION: Good tolerance of winemaking and aroma fermentative properties suggest that Mg132 has potential application in aroma enhancement in wine and warrants further study. © 2021 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

The growing threat of global warming on coral reefs underscores the urgency of identifying heat‐tolerant corals and discovering their adaptation mechanisms to high temperatures. Corals growing in intertidal rock pools that vary markedly in daily temperature may have improved heat tolerance. In this study, heat stress experiments were performed on scleractinian coral Porites lutea from subtidal habitat and intertidal rock pool of Weizhou Island in the northern South China Sea. Thermotolerance differences in corals from the two habitats and their mechanisms were explored through phenotype, physiological indicators, ITS2, 16S rRNA, and RNA sequencing. At the extremely high temperature of 34°C, rock pool P. lutea had a stronger heat tolerance than those in the subtidal habitat. The strong antioxidant capacity of the coral host and its microbial partners was important in the resistance of rock pool corals to high temperatures. The host of rock pool corals at 34°C had stronger immune and apoptotic regulation, downregulated host metabolism and disease‐infection‐related pathways compared to the subtidal habitat. P. lutea, in this habitat, upregulated Cladocopium C15 (Symbiodiniaceae) photosynthetic efficiency and photoprotection, and significantly increased bacterial diversity and coral probiotics, including ABY1, Ruegeria, and Alteromonas. These findings indicate that rock pool corals can tolerate high temperatures through the integrated response of coral holobionts. These corals may be 'touchstones' for future warming. Our research provides new insights into the complex mechanisms by which corals resist global warming and the theoretical basis for coral reef ecosystem restoration and selection of stress‐resistant coral populations. [ABSTRACT FROM AUTHOR]

The article talks about the geophysical method of natural gamma radiation applied in stratigraphic classification, counting the gamma photons emitted by natural radionuclides that originates from the interior of the Earth and its redistribution during the formation of rocks and minerals. It talks about the use of natural gamma radiation in search of uranium mine, to identify lithological profile, clay mineral typing and low energy resolution of gamma spectrometry.

Great efforts have been made to understand the impacts of the 1997 Indonesian wildfires on land ecology and human health, yet its influences on marine environments are poorly understood owing to sparse observations. Here we present weekly to monthly resolution coral δ13C records across the South China Sea in conjunction with a regional ocean general circulation model to study the effects of these cataclysmic wildfires on nearby oceans. Large and persistent negative δ13C excursions were found in corals from the interior South China Sea several months after the wildfires. This delay indicates that the 13C‐depleted ash fallout was distributed by ocean currents rather than direct atmospheric transport, which is supported by the results of our numerical model. Thus, the impacts of tropical wildfires on marine ecology may last for 1 year and extend thousands of kilometers from the burning center. Plain Language Summary: Tropical wildfires, intensified by extreme weather events and land use change, have continued to increase during this century, causing serious damage to the rainforests and local economies as well as human suffering and death. The threats of tropical wildfires to nearby oceans have been given little attention and are largely unknown because of limited observations. Here we use multiple coral records with weekly to monthly resolution from five sites near and around the South China Sea and a computer model to study the influences of the 1997 Indonesian wildfires on the ocean. We find a previously unrecognized ash fallout signal recorded in the corals in the interior of the South China Sea. Our model results indicate that the penetration of ash fallout into the South China Sea occurred through ocean currents rather than direct atmospheric transport. This study shows that the impacts of tropical wildfires on oceans may last for 1 year and can extend for thousands of kilometers from the source. We also show the potential for using coral records with computer modeling to identify and study the frequency and extent of past megafires. Key Points: A large negative excursion in δ13C values during summer–winter 1998 was detected in corals from the interior of the South China SeaModel shows that ash fallout from the 1997 Indonesian wildfires distributed by currents was responsible for the negative δ13C excursionNetworks of coral δ13C have great potential to record past pantropical wildfires [ABSTRACT FROM AUTHOR]

Widespread coral bleaching and mortality associated with global warming have occurred frequently since the phenomenon was first documented in the early 1980s. One such episode that occurred in 1991 over the tropical Pacific‐Indian Ocean region has been attributed to high summer sea surface temperatures. However, we found that sea surface temperature values from the South China Sea region do not provide a comprehensive explanation for the event. Our results, based on time series records of rare earth elements, trace element Al/Ca ratios, and microdomain images from corals in the South China Sea, suggest that this coral mortality event was exacerbated by heavy ash fallout from the cataclysmic 1991 volcanic eruption of Mount Pinatubo. Our findings highlight the profound impact of a volcanic eruption on the modern vulnerable coral reef ecosystems, already under the stress of global warming. Plain Language Summary: Intensive and frequent coral bleaching events have occurred under global warming conditions in recent decades. However, abrupt and extensive mortality episodes, such as which occurred in the South China Sea in mid‐1991, cannot be explained solely on the basis of high summer sea surface temperatures. Here we examine this event in the light of time series of rare earth elements, trace element Al/Ca ratios, and microdomain images for coral samples collected in the South China Sea region. Our results suggest that the second‐largest volcanic eruption of the 20th century, the 1991 Mount Pinatubo volcanic eruption, exacerbated this coral mortality event. The sensitive impacts of such a volcanic eruption on modern vulnerable coral reefs, associated with the stress of thermal conditions, are demonstrated. Key Points: This study reports that the mortality of modern coral reefs could be exacerbated by volcanic eruptionsThe anomalies of rare earth contents and Al/Ca ratios associated with microdomain images indicate an external impact from the 1991 PinatuboOur results highlight amplified responses of vulnerable coral reefs to environmental changes under global warming [ABSTRACT FROM AUTHOR]