Coral records of Mid-Holocene sea-level highstands and climate responses in the northern South China Sea

High-resolution sea-level data and high-precision dating of corals in the northern South China Sea(SCS)during the Holocene provide a reference and historical background for current and future sea-level changes and a basis for scientific assessment of the evolutionary trend of coral reefs in the SCS.Although sporadic studies have been performed around Hainan Island in the northern SCS,the reconstructed sea level presents different values or is controversial because the indicative meaning of the sea-level indicators were neither quantified nor uniform criteria.Here,we determined the quantitative relationship between modern living coral and sea level by measuring the top surfaces of 27 live Porites corals from the inner reef flat along the east coast of Hainan Island and assessed the accuracy of results obtained using coral as sea-level indicators.Additionally,three in situ fossil Porites corals were analyzed based on elevation measurements,digital X-ray radiography,and U-Th dating.The survey results showed that the indicative meanings for the modern live Porites corals is(146.09±8.35)cm below the mean tide level(MTL).It suggested that their upward growth limit is constrained by the sea level,and the lowest low water is the highest level of survival for the modern live Porites corals.Based on the newly defined indicative meanings,6 new sea-level index points(SLIPs)were obtained and 19 published SLIPs were recalculated.Those SLIPs indicated a relative sea level fluctuation between(227.7±9.8)cm to(154.88±9.8)cm MTL between(5393±25)cal a BP and(3390±12)cal a BP,providing evidences of the Mid-Holocene sea-level highstand in the northern SCS.Besides that,our analysis demonstrated that different sea-level histories may be produced based on different indicative meanings or criteria.The dataset of 276 coral U-Th ages indicates that coral reef development in the northern SCS comprised the initial development,boom growth,decline,and flourishing development again.A comparison with regional records indicated that synergistic effects of climatic and environmental factors were involved in the development of coral reefs in the northern SCS.Thus,the cessation of coral reef development during the Holocene in the northern SCS was probably associated with the dry and cold climate in South China,as reflected in the synchronous weakening of the ENSO and East Asian summer monsoon induced by the reduction of the 65°N summer insolation,which forced the migration of the Intertropical Convergence Zone.

U-Pb zircon geochronology of basaltic pyroclastic rocks from the basement beneath the Xisha Islands in the northwestern South China Sea and its geological significance

As one of the micro-blocks dispersed in the South China Sea(SCS), the basement of the Xisha Islands has rarely been drilled because of the thick overlying Cenozoic sediments, which has led to a confused understanding of the pre-Cenozoic basement of the Xisha Islands. Well CK-1, a kilometer-scale major scientific drill in the Xisha Islands in the northwestern SCS, penetrated thick reefal limestone(0–888.4 m) and the underlying basement rocks(888.4–901.4 m). In this study, we present the zircon U-Pb ages of basement basaltic pyroclastic rocks from Well CK-1 in the Xisha Islands of the northwestern SCS to investigate the basement nature of the Xisha microblock. The basement of Well CK-1 consists of basaltic pyroclastic rocks on the seamount. The zircon grains yielded apparent ages ranging from ca. 2 138.9 Ma to ca. 36 Ma. The old group of zircon grains from Well CK-1 was considered to be inherited zircons. Two Cenozoic zircons gave a weighted mean 206Pb/238U age of(36.3 ± 1.1) Ma,Mean Squared Weighted Deviations(MSWD) = 1.2, which may represent the maximum age of the volcano eruption. The Yanshanian inherited zircons(116.9–105.7 Ma and 146.1–130.2 Ma) from Well CK-1 are consistent with the zircons from Well XK-1, indicating that the basement of Chenhang Island may be similar to that of Well XK-1. We propose that the Xisha micro-block may have developed on a uniform Late Jurassic metamorphic crystalline basement, intruded by Cretaceous granitic magma.

中全新世海南潭门滨珊瑚的生长率特征及其气候意义

珊瑚生长率是珊瑚古气候研究的重要指标,其反映珊瑚生长快慢,并提供高分辨率的海水表层温度变化信息。中全新世作为当前全球变暖的地质历史相似型,利用珊瑚生长率重建该时期的气候环境状况对于理解现代气候变化的过程及其机制具有重要的参考价值。文章对采自海南潭门珊瑚岸礁的23段中全新世(6143—4356 a BP)滨珊瑚进行生长率分析,并基于该区域现代(2005—2021 AD)滨珊瑚生长率与SST的关系重建了中全新世期间共406 a的年均SST序列。结果显示:1)中全新世滨珊瑚生长率的变化范围为0.607~1.670 cm/a,均值为1.079 cm/a,且存在明显的波动变化过程;2)基于生长率重建的中全新世平均SST为25.7±0.54℃,这与全球变暖程度加剧背景下的现代海温相近;中全新世年均SST的变化范围为24.7~26.8℃,其中5860、5660和5160 a BP为3个显著的低温期;3)对比现代与中全新世(5427—5394、5243—5209、4515—4456和4404—4356 a BP)珊瑚生长率的频谱周期,发现现代与中全新世珊瑚的生长率均存在显著的3~7 a ENSO周期,但中全新世ENSO主周期改变且频率显著降低,表明中全新世的ENSO活动总体偏弱;概率密度函数统计进一步显示中全新世期间ENSO变率存在逐渐增强的趋势。

Chemical diversity of scleractinian corals revealed by untargeted metabolomics and molecular networking

The chemical diversity of scleractinian corals is closely related to their physiological,ecological,and evolutionary status,and can be influenced by both genetic background and environmental variables.To investigate intraspecific variation in the metabolites of these corals,the metabolomes of four species(Pocillopora meandrina,Seriatopora hystrix,Acropora formosa,and Fungia fungites)from the South China Sea were analyzed using untargeted mass spectrometry-based metabolomics.The results showed that a variety of metabolites,including amino acids,peptides,lipids,and other small molecules,were differentially distributed among the four species,leading to their significant separation in principal component analysis and hierarchical clustering plots.The higher content of storage lipids in branching corals(P.meandrina,S.hystrix,and A.formosa)compared to the solitary coral(F.fungites)may be due to the high densities of zooxanthellae in their tissues.The high content of aromatic amino acids in P.meandrina may help the coral protect against ultraviolet damage and promote growth in shallow seawater,while nitrogen-rich compounds may enable S.hystrix to survive in various challenging environments.The metabolites enriched in F.fungites,including amino acids,dipeptides,phospholipids,and other small molecules,may be related to the composition of the coral's mucus and its life-history,such as its ability to move freely and live solitarily.Studying the chemical diversity of scleractinian corals not only provides insight into their environmental adaptation,but also holds potential for the chemotaxonomy of corals and the discovery of novel bioactive natural products.

El Ni?o/Southern Oscillation during the 4.2 ka event recorded by growth rates of corals from the North South China Sea

The 4.2 ka event that occurred during the period from 4 500–3 900 a BP was characterized by cold and dry climates and resulted in the collapse of civilizations around the world. The cause of this climatic event, however, has been under debate. We collected four corals(Porites lutea) from Yongxing Island, Xisha Islands, South China Sea, dated them with the U-series method, and measured the annual coral growth rates using X-ray technology. The dating results showed that the coral growth ages were from 4 500–3 900 a BP, which coincide well with the period of the4.2 ka event. We then reconstructed annual sea surface temperature anomaly(SSTA) variations based on the coral growth rates. The growth rate-based SSTA results showed that the interdecadal SSTA from 4 500–3 900 a BP was lower than that during modern times(1961–2008 AD). A spectral analysis showed that the SSTA variations from4 500–3 900 a BP were under the influence of El Nino-Southern Oscillation(ENSO) activities. From 4 500–4 100 a BP, the climate exhibited La Nina-like conditions with weak ENSO intensity and relatively stable and lower SSTA amplitudes. From 4 100–3 900 a BP, the climate underwent a complicated period of ENSO variability and showed alternating El Nino-or La Nina-like conditions at interdecadal time scales and large SSTA amplitudes. We speculate that during the early and middle stages of the 4.2 ka event, the cold climate caused by weak ENSO activities largely weakened social productivity. Then, during the end stages of the 4.2 ka event, the repeated fluctuations in the ENSO intensity caused frequent extreme weather events, resulting in the collapse of civilizations worldwide. Thus, the new evidence obtained from our coral records suggests that the 4.2 ka event as well as the related collapse of civilizations were very likely driven by ENSO variability.

Glioma-derived ANXA1 suppresses the immune response to TLR3 ligands by promoting an anti-inflammatory tumor microenvironment

A highly immunosuppressive tumor microenvironment(TME)and the presence of the blood‒brain barrier are the two major obstacles to eliciting an effective immune response in patients with high-grade glioma(HGG).Here,we tried to enhance the local innate immune response in relapsed HGG by intracranially injecting poly(I:C)to establish a robust antitumor immune response in this registered clinical trial(NCT03392545).During the follow-up,12/27(44.4%)patients who achieved tumor control concomitant with survival benefit were regarded as responders in our study.We found that the T-cell receptor(TCR)repertoire in the TME was reshaped after poly(I:C)treatment.Based on the RNA-seq analysis of tumor samples,the expression of annexin A1(ANXA1)was significantly upregulated in the tumor cells of nonresponders,which was further validated at the protein level.In vitro and in vivo experiments showed that ANXA1 could induce the production of M2-like macrophages and microglia via its surface receptor formyl peptide receptor 1(FPR1)to establish a Treg cell-driven immunosuppressive TME and suppress the antitumor immune response facilitated by poly(I:C).The ANXA1/FPR1 signaling axis can inhibit the innate immune response of glioma patients by promoting an anti-inflammatory and Treg-driven TME.Moreover,ANXA1 could serve as a reliable predictor of response to poly(I:C),with a notable predictive accuracy rate of 92.3%.In light of these notable findings,this study unveils a new perspective of immunotherapy for gliomas.

Linking coral fluorescence phenotypes to thermal bleaching in the reef-building Galaxea fascicularis from the northern South China Sea

Coral fluorescence phenotypes have been suggested as an adaptation to a broad range of environmental conditions,yet the mechanisms linking thermal bleaching tolerance in reef-building coral populations,associated with fluorescence phenotypes due to GFP-like proteins,remains unclear.In this study,the relationship between the thermal sensitivity and phenotypic plasticity of corals was investigated using two phenotypes of Galaxea fascicularis,green and brown.The results reveal that brown G.fascicularis was more susceptible to bleaching than green G.fascicularis when exposed to a higher growth temperature of 32℃.Both phenotypes of G.fascicularis were associated with the thermotolerant Symbiodiniaceae symbiont,Durusdinium trenchii.However,the brown G.fascicularis showed a significant decrease in Symbiodiniaceae cell density and a significant increase in pathogenic bacteria abundance when the growth temperature was raised from 29 to 32℃.The physiological traits and transcriptomic profiles of Symbiodiniaceae were not notably affected,but there were differences in the transcriptional levels of certain genes between the two phenotype hosts of G.fascicularis.Under heat stress of 32℃,the gene encoding green fluorescent protein(GFP)-like and chromosome-associated proteins,as well as genes related to oxidative phosphorylation,cell growth and death showed lower transcriptional levels in the brown G.fascicularis compared to the green G.fascicularis.Overall,the results demonstrate that the green form of G.fascicularis is better able to tolerate ocean warming and defend against pathogenic bacteria,likely due to higher gene transcription levels and defense ability.

日本福岛核废水排海情景下海洋生态环境影响与应对

2011年3月11日,太平洋海底9级大地震产生的海啸引发日本福岛核事故[1].福岛核事故后,大量的放射性核素泄漏进入环境,并通过大气环流和海洋环流对全球许多地区造成一定的影响[2~6].福岛核事故后,日本制定了福岛核电站中长期退役计划(30~40年),开展受损反应堆退役与周边环境修复措施,其中核废水处理、核燃料移除、其他废物处理是中长期退役计划的三大关键环节[7].

珊瑚礁区沉积物的极低放射性水平特征与成因

海洋沉积物作为放射性核素的归宿,在全球不同海区均有沉积物放射性核素的研究报道,然而珊瑚礁区却极少报道.本研究选取南海的岸礁和环礁两种类型的珊瑚礁区,采样站位跨越~1500 km(14°),系统开展南海9个不同珊瑚礁区沉积物中放射性核素研究.对比不同海区沉积物的放射性水平,本研究发现珊瑚礁区沉积物的总放射性水平(等当量镭指数)只有其他海区沉积物和全球土壤总放射性水平的1%~10%,环礁沉积物等当量镭指数平均值(3.97 Bq/kg)不到全球土壤平均值(108.70 Bq/kg)的5%,珊瑚礁区沉积物具有极低的总放射性水平特征.珊瑚礁区的沉积物同时具有低^(40)K、低^(226)Ra和^(228)Ra、低^(226)Ra/^(238)U活度比值的三大特征,该特征源于珊瑚礁区的生物矿化-破碎风化而形成的生源沉积物,显著不同于其他海区的岩石土壤风化-搬运而形成的陆源沉积物.这些特征可以作为新的地球化学指标,对传统元素(Al和Ti)、稀土元素、矿物组成等手段进行有益的补充,指示珊瑚礁区水体悬浮物/沉积物中不同物质来源的贡献.

Spatial variations in the trophic status of Favia palauensis corals in the South China Sea:Insights into their different adaptabilities under contrasting environmental conditions

Scleractinian corals exhibit a dual trophic pattern of autotrophic photosynthesis and heterotrophic predation.However,whether corals can adjust their trophic status under contrasting environmental conditions remains unclear.In our study,70 scleractinian corals(Favia palauensis)were collected from Sanya and the Xisha and Nansha Islands in the South China Sea.We measured the zooxanthellae density(ZD)andδ^(13)C of zooxanthellae(δ^(13)C_(z))and host tissue(δ^(13)C_(h))and analyzed the difference betweenδ^(13)C_(h) andδ^(13)C_(z)(i.e.,△^(h-z)^(13)C).The relatively high ZD andδ^(13)C_(z) values in the samples from Sanya indicate that these corals might have higher photosynthetic rates and autotrophic abilities than those from Xisha and Nansha.In contrast,the relatively lowδ^(13)C_(h) and△^(h-z)^(13)C values in the samples from Xisha and Nansha suggest that these corals might have a higher heterotrophic ability than those from Sanya.In addition,we tested the coral tissue biomass and skeletalδ^(13)C(δ^(13)C_(s))in the samples from Sanya and examined their correlations with△^(h-z)^(13)C.The results showed a negative correlation,indicating that the more the organic material produced by the coral,the stronger its heterotrophic ability.Our results show that corals can adjust their trophic status under different environmental and physiological conditions,which is essential for increasing their adaptability to different environmental conditions.

Impacts of tropical cyclones and anthropogenic activities on marine vanadium: A unique perspective from high resolution Porites coral record

As a typical contaminant in fossil fuels,vanadium has undergone dramatically increase due to the impacts from human activities.The excessive anthropogenic vanadium emissions have altered natural geochemical processes.However,research on vanadium geochemistry in the ocean,which is the major sink for vanadium mobilized on land,has lagged much behind relative to those of other contaminants.Here we reconstruct historical patterns of vanadium in surface seawater utilizing a high-resolution temporal record(1984–2015 CE)of geochemical proxies(vanadium/calcium(V/Ca),δ^(18)O,δ^(13)C,etc.)in a Porites coral colony from an offshore non-estuarine island in the northern South China Sea(SCS).We find a close association between the surface winds and the temporal patterns of coral V/Ca ratios,revealing great potential for documenting prehistoric changes in tropical cyclones.Moreover,the coral V/Ca record remarkably captured the temporal patterns of anthropogenic activities,offering a valuable and novel tool for testing the efficacy of specific legislation on pollution prevention.Combined with the other reported coral vanadium data,we recovered the historical changes in vanadium emissions in the northern SCS and identified that changing industrial practices should be responsible for the differences in anthropogenic vanadium emissions at each stage.Our results demonstrated that the coral V/Ca ratio at a high temporal resolution has great potential as a new and direct geochemical proxy for tropical cyclones after removing artificial disturbances in the ocean.

Interactions of fluoroquinolone antibiotics with sodium hypochlorite in bromide-containing synthetic water:Reaction kinetics and transformation pathways

Seven popular fluoroquinolone antibiotics(FQs)in synthetic marine aquaculture water were subject to sodium hypochlorite(NaClO)disinfection scenario to investigate their reaction kinetics and transformation during chlorination.Reactivity of each FQ to NaClO was following the order of ofloxacin(OFL)>enrofloxacin(ENR)>lomefloxacin(LOM)>ciprofloxacin(CIP)?norfloxacin(NOR)>>pipemedic acid(PIP),while flumequine did not exhibit reactivity.The coexisting chlorine ions and sulfate ions in the water slightly facilitated the oxidation of FQs by NaClO,while humic acid was inhibitable to their degradation.The bromide ions promoted degradation of CIP and LOM,but restrained oxidation of OFL and ENR.By analysis of liquid chromatography with tandem mass spectrometry(LC-MS/MS),eight kinds of emerging brominated disinfection byproducts(Br-DBPs)caused by FQ S were primarily identified in the chlorinated synthetic marine culture water.Through density functional theory calculation,the highest-occupied molecular orbital(HOMO)and the lowest-unoccupied molecular orbital(LUMO)characteristic as well as the charge distribution of the FQs were obtained to clarify transformation mechanisms.Their formation involved decarboxylation,ring-opening/closure,dealkylation and halogenation.Chlorine substitution occurred on the ortho-position of FQs's N4 and bromine substitution occurred on C8 position.The piperazine ring containing tertiary amine was comparatively stable,while this moiety with a secondary amine structure would break down during chlorination.Additionally,logK_(ow)and log BAF of transformation products were calculated by EPI-Suite^(TM)to analyze their bioaccumulation.The values indicated that Br-DBPs are easier to accumulate in the aquatic organism relative to their chloro-analogues and parent compounds.

Single-atom catalysts modified by molecular groups for electrochemical nitrogen reduction

Electrochemical nitrogen reduction reaction(eNRR)is one of the most important chemical reactions for the production of ammonia under ambient environment.However,the lack of in-depth understanding of the structure-activity relationship impedes the development of high-performance catalysts for ammonia production.Herein,the density functional theory(DFT)calculations are performed to reveal the structure–activity relationship for the single-atom catalysts(SACs)supported on g-C_(3)N_(4),which is modified by molecular groups(i.e.,H,O,and OH).The computational results demonstrate that the W-based SACs are beneficial to produce ammonia with a low limiting potential(UL).Particularly,the W-OH@g-C_(3)N_(4) catalyst exhibits an ultralow UL of−0.22 V for eNRR.And the competitive eNRR selectivity can be identified by the dominant*N2 adsorption free energy than that of*H.Our findings provide a theoretical basis for the synthesis of efficient catalysts to produce ammonia.