Polycyclic aromatic hydrocarbons(PAHs)are one of the most important groups in oil,and re sponsible for major toxic and/or carcinogenic impact on humans and wildlife.It is important to understand the behavior of PAHs i...Polycyclic aromatic hydrocarbons(PAHs)are one of the most important groups in oil,and re sponsible for major toxic and/or carcinogenic impact on humans and wildlife.It is important to understand the behavior of PAHs in marine environment after an oil-spill incident.However,interaction between petroleum PAHs and microbial communities in a marine environment remains unclear.Therefore,a series of mesocosm experiments were conducted.in which water-accommodated fraction(WAF)of oil was generated to simulate an oil-spill scenario and to analyze the transport and behavior of marine oil spill containing PAHs with and without dispersants.Results indicate that the application of dispersant could increase the concentration of total PAHs in water column due mainly to significant increase in the concentration of highmolecular weight(HMW)PAHs at a lower removal rate.At the end of the 7-day experiment,significant amount of HMW PAHs were accumulated in sediment.In general,the application of dispersant did not increase the sediment uptake of PAHs but increased the PAHs concentration in water column.展开更多
The ecological suitability of marine resources and environmental conditions for marine ranching in Guangdong,South China was evaluated.Niche theory was used to establish an ecological suitability evaluation model for ...The ecological suitability of marine resources and environmental conditions for marine ranching in Guangdong,South China was evaluated.Niche theory was used to establish an ecological suitability evaluation model for marine ranching site selection,and suitability evaluation of marine ranching was conducted in.Results show that the ecological suitability index of marine ranching site selection was greater than 64.0 in 20 sites,including offshore Shantou Bay,offshore Zhanjiang Port,and Longdou Bay etc.,which are the priority areas for marine ranching.In other 13 sites,the ecological suitability index ranged between 8.0 and 32.0,including Houjiang Bay,Haimen Bay,and Jieshi Bay etc.,indicating the suitability for marine ranching.However,the ecological suitability index was 0 in Shantou Bay,Zhujiang(Pearl)River estuary,Huangmao Sea,Guanghai Bay,Zhanjiang Port,Qiongzhou Strait,and Anpu Port.These sites are thus unsuitable for marine ranching.This study provides a theoretical basis for site selection and planning of marine ranching in Guangdong Province.展开更多
Submarine volcanism is widely developed in the South China Sea(SCS).However,the characteristics,distribution,and genesis of submarine volcanoes in the southern margin of the SCS remain obscure.In this study,we analyze...Submarine volcanism is widely developed in the South China Sea(SCS).However,the characteristics,distribution,and genesis of submarine volcanoes in the southern margin of the SCS remain obscure.In this study,we analyzed the characteristics of submarine volcanoes and identified a total of 43 submarine volcanoes in the southern margin of the SCS,based on a newly acquired 310-km seismic reflection profile,along with previous 45 multi-channel seismic(MCS)profiles,petrological results from volcanic rocks sampled by dredging and drilling,nearby ocean bottom seismometer(OBS)wide-angle seismic profiles,and gravity and magnetic data.The study ascertains that most of these volcanoes are located in fault-block belts and graben-horst zones with strong crustal stretching and thinning.These volcanoes exhibit positive high-amplitude external seismic reflections,weak and chaotic internal seismic reflections,and are accompanied by local deformation of the surrounding sedimentary strata.Meanwhile,they have higher positive gravity anomalies and higher magnetic anomalies than the background strata.The petrological dating results show that volcanic ages are primarily in the Pliocene-Pleistocene,with geochemical characteristics indicating dominance of oceanic island basalt(OIB)-type alkali-basalts.Extensional faults have obviously spatial correspondence with post-spreading volcanism,suggesting these faults may provide conduits for submarine volcanism.The high-velocity bodies(HVBs)in the lower crust and magma underplating exist in the southern SCS,which could provide a clue of genesis for submarine volcanism.The inference is that the intensity of post-spreading volcanism in the southern margin might be affected by stretching faults,crustal thinning and magma underplating.展开更多
A new gravity sensor based on electromagnetic damping for the JMGrav marine gravimeter is presented.The new gravity sensor considered the advanced construction methods of the electromagnetic damping system of the grav...A new gravity sensor based on electromagnetic damping for the JMGrav marine gravimeter is presented.The new gravity sensor considered the advanced construction methods of the electromagnetic damping system of the gravimeter.The design features of the new system are discussed and the research survey data in the South China Sea are shown.Numerical simulations are applied to model the magnetic and mechanical characteristics of the system using finite element analysis and to evaluate the force distribution and the resulting damping effects.The performance characteristics of the system were tested on a motion simulator in laboratory,and the gravimeter was subjected to vertical accelerations of up to 100 Gal in 1-1000 s.It was found that the amplitude reduction of vertical accelerations in 3-15 s is 30-45 dB,with a time lag of 2-5 s,while the effect on gravity in period greater than 600 s is less than 0.5 dB,with a time lag of less than 100 s.The accelerations cause discrepancies of approximately only 1 mGal between the static value and the mean dynamic value.The sea tests were conducted in September 2020.Gravity measurements were taken with a JMGrav marine gravimeter onboard the R/V Dongfanghong 3,and the effective survey line exceeded 2000 km.Completely irregular accelerations with peaks up to 100 Gal yielded a reduction of approximately 40 dB in amplitude.The survey data were evaluated using ocean gravity field models and grid line tests.The results show that the accuracy of the gravity measurements is better than 2 mGal.展开更多
As one of the four largest bay areas with strong economic activities in the world,the Guangdong-Hong Kong-Macao Greater Bay Area(GHMGBA)is located in the zone of interaction between the South China Block(SCB)and the S...As one of the four largest bay areas with strong economic activities in the world,the Guangdong-Hong Kong-Macao Greater Bay Area(GHMGBA)is located in the zone of interaction between the South China Block(SCB)and the South China Sea(SCS).Under the influence of complex geologic evolution,basin-range structures,fault systems and hot springs are well developed here.However,the characteristics of geological structures and the genetic mechanism of these geological phenomena are still unclear.Therefore,we performed ambient noise tomography to obtain 3-D upper crust(0-7.5 km)S-wave velocity structures of the GHMGBA by using 40-day continuous waveform data from 130 seismic stations in the GHMGBA.Our results show that sedimentary basins in the GHMGBA are mainly characterized by low-velocity anomalies.S-wave velocities of sediment formation in basins are about 2.8-3.1 km/s.Rapid changes in velocity appear at the edges of the basins,which correspond to the NE-,NEE-,and NW-trending faults,indicating prominent basin-controlling effects of the faults.The Sanshui Basin(SSB),the largest in the GHMGBA,has a developmental depth of about 4 km,and there is a significant difference in velocity gradient between the east and west sides of the basin,indicating that SSB has experienced east-west asymmetric expansion.Moreover,there are prominent low-velocity anomalies at a depth of about 4.5 km beneath the hot springs at the west of the Zhujiang(Pearl)River estuary(ZRE).We infer that the low-velocity anomalies are fluid reservoirs of the hot springs,which lead to the development of the hot springs on the surface.In addition,the distribution of main cities in the GHMGBA shows a spatial correlation with low-velocity areas at shallow depths(<3 km).The population development trend in the GHMGBA in the past 20 years is also mainly concentrated in the structural province of relatively low-velocity.In combination with the GHMGBA basin structures and drainage distribution characteristics,we suggest that the basic geological environment to some extent affects the habitability of the human settlement and thus determines the distribution and development trend of the main urban context.We believe that the 3-D S-wave velocity structure of the upper crust of the GHMGBA obtained in this study,as well as the deep structural characteristics of the basins and hot springs,will provide support to urban construction planning and geological hazards research of the GHMGBA.展开更多
The Zengmu Basin located in the shallow water area of the southern South China Sea,is rich in oil and gas resources,within which faults and mud-diapir are developed,but it is unknown whether oil and gas migrate to the...The Zengmu Basin located in the shallow water area of the southern South China Sea,is rich in oil and gas resources,within which faults and mud-diapir are developed,but it is unknown whether oil and gas migrate to the seafloor surface.The newly collected multibeam data across the Zengmu Basin reveal a large number of depressions,with depths of 2-4 m,widths of several tens of meters,large distribution range of 1.8-8 km along survey line,up to~50 km,and their backscatter intensity(-26 dB)is much greater than that of the surrounding area(-38 dB).Combined with the developed mud-diapir and fracture structures,and abundant oil and gas resources within this basin,these depressions are presumed to be pockmarks.Furthermore,more than 110 mono-sized small circular pockmarks,with a depth of less than 1 m and a width of 5 m,are observed in an area of less than 0.03 km2,which are not obliterated by sediment infilling with high sedimentation rate,implying an existence of unit-pockmarks that are or recently were active.In addition,seismic profiles across the Zengmu Basin show characterization of upward migration of hydrocarbons,expressed as mud-diapir structures,bright spots in the shallow formation with characteristics of“low frequency increase and high frequency attenuation”.The subbottom profiles show the mud-diapir structures,as well as the gas-bearing blank zones beneath the seafloor.These features suggest large gas leaking and occurrence of large amounts of carbonate nodules on the seafloor.This indicates the complex and variable substrate type in the Zengmu Basin,while the area was once thought to be mainly silty sand and find sand.This is the first report on the discovery of pockmarks in the Zengmu Basin;it will provide basic information for submarine stability and marine engineering in China’s maritime boundaries.展开更多
To dampen periodic off-levelling motions within an inertial platform while undergoing horizontal accelerations of the same period and to achieve a levelling accuracy of a few tens of arcseconds with that system,an int...To dampen periodic off-levelling motions within an inertial platform while undergoing horizontal accelerations of the same period and to achieve a levelling accuracy of a few tens of arcseconds with that system,an internally damped inertial platform for a marine scalar gravity system was the developed.Methods for attenuating horizontal acceleration and reducing off-levelling error by a satisfactory gyro-levelling loop,which are fundamental to the internally damped inertial platform,were designed and implemented.In addition,phase delays are introduced by the levelling loop.The resulting off-levelling gravity errors were analyzed and modeled.A series of tests on a motion simulator were performed in laboratory for a variety of simulated sea conditions.We found that the motion of the platform is a function of the amplitude and period of the simulated ship motions and ranges between 10 and 40 arcseconds.In addition,the phase lag between platform motion and ship motion is not constant but ranges 180°-270°,depending on the period and amplitude of the motion.Then,the platform,on which a gravimeter was mounted,was installed on the R/V Shiyan 2 to conduct a gravity survey in the South China Sea.Despite rough sea conditions,it was shown that in short periods of 2-30 s,the off-levelling angle was less than 30 arcseconds,and the phase lagged the horizontal acceleration by 230°-260°.From a repeated survey line and intersecting survey points,the estimated errors of gravity measurements were between 1.3 and 1.7 mGal.The marine measurements results were compared with those of satellite altimetry data and show a mean value of 0.5 mGal in a standard deviation of 1.5 mGal.展开更多
The deep-sea clam Calyptogena marissinica is widely distributed in the Haima cold seep ecosystem on the northwes-tern slope of the South China Sea with low pH values,low temperature and high pressure.Limited informati...The deep-sea clam Calyptogena marissinica is widely distributed in the Haima cold seep ecosystem on the northwes-tern slope of the South China Sea with low pH values,low temperature and high pressure.Limited information is available on the biomineralization of this species.In this research,we generated a comprehensive transcript dataset of C.marissinica’s mantle tissue,and a total of 19821 unigenes were assembled.Fourteen shell matrix proteins(SMP)-related genes were identified.The qPCR results showed that four out of six prismatic matrix genes(MSP2,MSP5,prisilkin-39,and shematrin),four out of the six nacreous matrix genes(perlucin,pif,pif97,and papilin),and two extrapallial fluid proteins(SPARC and calmodulin)were significantly expressed in the mantle.Both the nacreous and the prismatic layers are chrysanthemum-shaped,which are stacked on the top of each other to form a laminated nacreous structure.The alignment and phylogenetic analysis of MSP-5,Prisilkin-39,Perlucin,and Pif homologues showed that some amino acids of C.marissinica that differed from those detected in other molluscs may cause the different shape of the nacreous and prismatic layers,but do not lead to a change in the species’evolutionary status.These results indicated the conservation of the functions of SMP-related genes in C.marissinica,and the specific shape of the prismatic and nacreous layers of this deep-sea mollusc,which will contribute to the research on the molecular regulation mechanisms of biomineralization in C.marissinica and provide a new perspective to investigate biomineralization in deep-sea clams in general.展开更多
Offshore carbon dioxide(CO_(2)) storage is an effective method for reducing greenhouse gas emissions. However, when using traditional seismic wave methods to monitor the migration of sequestration CO_(2) plumes, the c...Offshore carbon dioxide(CO_(2)) storage is an effective method for reducing greenhouse gas emissions. However, when using traditional seismic wave methods to monitor the migration of sequestration CO_(2) plumes, the characteristics of wave velocity changes tend to become insignificant beyond a certain limit. In contrast, the controllable source electromagnetic method(CSEM) remains highly sensitive to resistivity changes. By simulating different CO_(2) plume migration conditions, we established the relevant models and calculated the corresponding electric field response characteristic curves, allowing us to analyze the CSEM's ability to monitor CO_(2) plumes. We considered potential scenarios for the migration and diffusion of offshore CO_(2) storage, including various burial depths, vertical extension diffusion, lateral extension diffusion,multiple combinations of lateral intervals, and electric field components. We also obtained differences in resistivity inversion imaging obtained by CSEM to evaluate its feasibility in monitoring and to analyze all the electric field(Ex, Ey, and Ez) response characteristics. CSEM has great potential in monitoring CO_(2) plume migration in offshore saltwater reservoirs due to its high sensitivity and accuracy. Furthermore, changes in electromagnetic field response reflect the transport status of CO_(2) plumes, providing an important basis for monitoring and evaluating CO_(2)transport behavior during storage processes.展开更多
Variations of picoplankton groups were investigated over a one-month period in Daya Bay and Sanya Bay,in the northern South China Sea.The two coastal regions exhibited different variation patterns in physicochemical p...Variations of picoplankton groups were investigated over a one-month period in Daya Bay and Sanya Bay,in the northern South China Sea.The two coastal regions exhibited different variation patterns in physicochemical parameters.Moreover,the diel variations of picoplankton groups were different between the two bays.The abundance of the picoplankton in Sanya Bay displayed a pronounced diel variation,while it was not significant in Daya Bay.In addition,some similar patterns of picoplankton abundance were discovered.In the two bays,virioplankton exhibited the smallest fluctuation range,whereas picocyanobacteria fluctuated most markedly.The fluctuation range of picoplankton groups was larger in spring tide than in neap tide,especially in Sanya Bay.Random forest model analysis demonstrated that the variation of picoplankton groups was attributed to physical and chemical factors in Sanya Bay and Daya Bay,respectively.Therefore,our findings suggest that virioplankton abundance can persist more stably in response to changing environmental conditions compared to bacterioplankton and picophytoplankton.展开更多
Existing lithospheric velocity models exhibit similar structures typically associated with the first-order tectonic features,with dissimilarities due to different data and methods used in model generation.The quantifi...Existing lithospheric velocity models exhibit similar structures typically associated with the first-order tectonic features,with dissimilarities due to different data and methods used in model generation.The quantification of model structural similarity can help in interpreting the geophysical properties of Earth's interior and establishing unified models crucial in natural hazard assessment and resource exploration.Here we employ the complex wavelet structural similarity index measure(CW-SSIM)active in computer image processing to analyze the structural similarity of four lithospheric velocity models of Chinese mainland published in the past decade.We take advantage of this method in its multiscale definition and insensitivity to slight geometrical distortion like translation and scaling,which is particularly crucial in the structural similarity analysis of velocity models accounting for uncertainty and resolution.Our results show that the CW-SSIM values vary in different model pairs,horizontal locations,and depths.While variations in the inter-model CW-SSIM are partly owing to different databases in the model generation,the difference of tomography methods may significantly impact the similar structural features of models,such as the low similarities between the full-wave based FWEA18 and other three models in northeastern China.We finally suggest potential solutions for the next generation of tomographic modeling in different areas according to corresponding structural similarities of existing models.展开更多
To understand the acoustic and physical properties of piston core samples collected from the Sunda continental shelf and analyze their distribution patterns,the samples were analyzed in laboratory,from which three pro...To understand the acoustic and physical properties of piston core samples collected from the Sunda continental shelf and analyze their distribution patterns,the samples were analyzed in laboratory,from which three provinces were divided in sound speed,sound speed ratio,porosity,wet bulk density,and maximum shear strength.ProvinceⅠhad lower sound speed and sound speed ratio(<1.04),high porosity,and low wet bulk density.ProvinceⅡhad higher sound speed and sound speed ratio(>1.04),low porosity,and high wet bulk density.ProvinceⅢhad the lowest sound speed and sound speed ratio(0.99),highest porosity(81%),and lowest wet bulk density(1.34 g/cm^(3)).The distribution pattern indicates that sediment movement,sediment source,topography,and hydrodynamic conditions influenced the distribution of acoustic and physical properties.Furthermore,we investigated the relationship of the maximum shear strength to the porosity and wet bulk density,and found that the maximum shear strength was proportional to both the porosity and wet bulk density.This finding has significant implications for ocean engineering applications.展开更多
Mud diapirs are significant structures often associated with hydrocarbon migration and accumulation as well as gas hydrate formation in sedimentary basins.A total of 30 mud diapirs were observed in the northwestern Ze...Mud diapirs are significant structures often associated with hydrocarbon migration and accumulation as well as gas hydrate formation in sedimentary basins.A total of 30 mud diapirs were observed in the northwestern Zengmu Basin in the southern South China Sea based on 2D multichannel seismic data.The structures are distributed along an NW-SE trend near the shelf break of the Kangxi depression in the Zengmu Basin.The mud diapirs were divided into the following according to their vertical shapes,intrusion heights,and effusive activities:tortoise,piercing,and nozzle types,which represent different evolutionary stages of diapirism.The mud diapirs in the study area suggest that the driving forces behind the mud diapirs considerably exceed the rock rupture limit of the overlying strata.Diapir formation can be divided into two steps:the accommodation of a large amount of mud in the Zengmu Basin and the movement of plastic mud induced by gravity-driven flow and regional tectonic compression.Combining seismic interpretations with analyses of the regional geology and tectonic subsidence,the current study proposes that rapid subsidence in the Kangxi depression sufficiently accommodated the vast amount of sediments deposited since the Middle Miocene,which provided favorable conditions for the growth of mud diapirs.Furthermore,the N-S directional stress field in the Zengmu Basin and the gravity slide northward along the southern slope of the depression further facilitated the development of mud diapirs since the late Miocene.The mud diapirs in the southern South China Sea margins were accompanied by the accumulation and release of overpressured fluid.展开更多
Recently,methane seepage related to the dissociation of natural gas hydrates has attracted much attention,which has a significant impact on the study of the global carbon and nitrogen cycles.Based on the detailed geoc...Recently,methane seepage related to the dissociation of natural gas hydrates has attracted much attention,which has a significant impact on the study of the global carbon and nitrogen cycles.Based on the detailed geochemical analyses of sediments(core Q6)from the Qiongdongnan Basin,South China Sea,three methane seepage activities were identified and the exact horizons of anaerobic oxidation of methane(AOM)were defined.Furthermore,organic carbon isotopic(δ^(13)C_(TOC))levels ranged from−23.6‰–−20.6‰PDB;nitrogen isotopes(δ^(15)N_(TN))of the same sedimentary samples ranged from 1.8‰–5.3‰.We also found obvious simultaneous negative excursions of organic carbon isotopes(δ^(13)C_(TOC))and nitrogen isotopes(δ^(15)N_(TN))in the horizons of methane seepages.Compared with the normal sediments,their maximum negative excursions were 2.6‰and 2.5‰,respectively.We discuss in detail the various characteristics ofδ^(15)N_(TN) andδ^(13)C_(TOC) levels in sediments and their coupling responses to methane seepage activities.We believe that the methane seepage events changed the evolution trajectory ofδ^(15)N_(TN) andδ^(13)C_(TOC) levels in sediment records,which resulted in the simultaneous negative excursions.This phenomenon is of great significance to reveal the historical dissociation of natural gas hydrates and their influence on the deep-sea carbon and nitrogen pool.展开更多
An extraordinary and unprecedented heatwave swept across western North America(i.e.,the Pacific Northwest)in late June of 2021,resulting in hundreds of deaths,a massive die-off of sea creatures off the coast,and horri...An extraordinary and unprecedented heatwave swept across western North America(i.e.,the Pacific Northwest)in late June of 2021,resulting in hundreds of deaths,a massive die-off of sea creatures off the coast,and horrific wildfires.Here,we use observational data to find the atmospheric circulation variabilities of the North Pacific and Arctic-Pacific-Canada patterns that co-occurred with the development and mature phases of the heatwave,as well as the North America pattern,which coincided with the decaying and eastward movement of the heatwave.Climate models from the Coupled Model Intercomparison Project(Phase 6)are not designed to simulate a particular heatwave event like this one.Still,models show that greenhouse gases are the main reason for the long-term increase of average daily maximum temperature in western North America in the past and future.展开更多
Mirs Bay is a semi-enclosed bay neighboring the Zhujiang(Pearl)River estuary,one of the largest estuarine systems in the world.The long-term historical observational data(1994-2017)of temperature,salinity,dissolved ox...Mirs Bay is a semi-enclosed bay neighboring the Zhujiang(Pearl)River estuary,one of the largest estuarine systems in the world.The long-term historical observational data(1994-2017)of temperature,salinity,dissolved oxygen(DO),and biochemical parameters were used to examine the spatiotemporal distribution of hypoxia in Mirs Bay and adjacent coastal waters.Results show that bottom hypoxia varied seasonally and interannually.Hypoxia mainly occurred from June to September in Mirs Bay and the transition zone in the southern waters of Hong Kong,and the recorded hypoxia events have increased from 2007.The density difference between the bottom and surface layers was positively related to the bottom apparent oxygen utilization(AOU)(R=0.620,P<0.001)and negatively related to the bottom DO(R=0.616,P<0.001),indicating that water column stratification was an essential prerequisite for the formation of bottom hypoxia in summer.The bottom oxygen consumption and hypoxia had higher positive correlation with the seasonal thermocline(R=0.683,P<0.001)than the halocline(R=0.540,P<0.001),including in the area was affected by freshwater plume.The insignificant relationship between AOU and nutrients indicated that local eutrophication was not the only important factor in the formation of the hypoxic zone during summer.The decrease in phosphorous owing to the pollutant reduction policy and the increase in nitrate may have led to an increase in hypoxia events in the bay where waters therein are characterized by nitrogen-limitation.The increase in chemical oxygen demand in wastewater also promoted oxygen consumption.Compared to the adjacent coastal waters influenced by Zhujiang River plume water,the Mirs Bay experienced more hypoxia events.The high concentrations of ammonium and total Kjeldahl nitrogen in the sediment of Mirs Bay increased the oxygen depletion in the bottom water.The long residence time of the near-bottom water in Mirs Bay increased the risk of bottom hypoxia events,although the nutrient concentrations were lower than those in the transition zone.These factors lead to differences in hypoxia occurrence in Mirs Bay and adjacent coastal waters.展开更多
The ever-increasing deepwater oil and gas development in the Qiongdongnan Basin,South China Sea has initiated the need to evaluate submarine debris-flow hazard risks to seafloor infrastructures.This paper presents a c...The ever-increasing deepwater oil and gas development in the Qiongdongnan Basin,South China Sea has initiated the need to evaluate submarine debris-flow hazard risks to seafloor infrastructures.This paper presents a case study on evaluating the debris-flow hazard risks to the planned pipeline systems in this region.We used a numerical model to perform simulations to support this quantitative evaluation.First,one relict failure interpreted across the development site was simulated.The back-analysis modeling was used to validate the applicability of the rheological parameters.Then,this model was applied to forecast the runout behaviors of future debris flows originating from the unstable upslope regions considered to be the most critical to the pipeline systems surrounding the Manifolds A and B.The model results showed that the potential debris-flow hazard risks rely on the location of structures and the selection of rheological parameters.For the Manifold B and connected pipeline systems,because of their remote distances away from unstable canyon flanks,the potential debris flows impose few risks.However,the pipeline systems around the Manifold A are exposed to significant hazard risks from future debris flows with selected rheological parameters.These results are beneficial for the design of a more resilient pipeline route in consideration of future debris-flow hazard risks.展开更多
How coral reefs with high productivity and biodiversity can flourish in oligotrophic tropical oceans has inspired substantial research on coral reef ecosystems.Increasing evidence shows that similar to water in an oas...How coral reefs with high productivity and biodiversity can flourish in oligotrophic tropical oceans has inspired substantial research on coral reef ecosystems.Increasing evidence shows that similar to water in an oasis in the desert,there are stable nutrient supplies to coral reefs in oligotrophic oceans.Here,with emphasis on the fluxes of organic matter,we summarize at the ecosystem level(1)the multiple input pathways of external nutrients,(2)the storage of nutrients in reef organisms,(3)the efficient retaining and recycling of dissolved and particulate organic matter within coral reef ecosystems,(4)the distinctly high phytoplankton productivity and biomass inside and near oceanic coral reefs,and(5)the export of reef-related organic carbon to adjacent open oceans.These properties enable coral reefs to function as ecological“pumps”for gathering nutrients across ecosystems and space,retaining and recycling nutrients within the ecosystem,supporting high phytoplankton productivity,and exporting organic carbon to adjacent open oceans.Particularly,the high phytoplankton productivity and biomass make waters around coral reefs potential hotspots of carbon export to ocean depths via the biological pump.We demonstrate that organic carbon influx is vital for coral reef ecosystems’carbon budget and carbon export.The concept of the coral reef ecological pump provides a framework to improve the understanding of the functioning of the coral reef ecosystem and its responses to disturbance.Prospects of the coral reef ecological pump in coral reef studies are discussed in changing oceans driven by human activities and global change in the Anthropocene.展开更多
Understanding the nature of parental melts for pyroxenite veins in supra-subduction zone(SSZ)ophiolites provides vibrant constraints on melt infiltration processes operating in subduction zones.The Zedang ophiolitic m...Understanding the nature of parental melts for pyroxenite veins in supra-subduction zone(SSZ)ophiolites provides vibrant constraints on melt infiltration processes operating in subduction zones.The Zedang ophiolitic massif in the eastern Yarlung–Zangbo suture zone in Tibet consists of mantle peridotites and a crustal section of gabbro,diabase,and basalt.Veins of two pyroxenite varieties cut the southern part of the Zedang massif.These pyroxenite rocks have different geochemical characteristics,where the first variety(type-I)has relatively higher contents of SiO_(2)(51.82–53.08 wt%),MgO(20.08–23.23 wt%),andΣPGE(3.42–13.97 ppb),and lower Al_(2)O_(3)(1.59–2.28 wt%)andΣREE(1.63–2.94 ppm).The second pyroxenite variety(type-II)is characterized by SiO_(2)(45.44–49.61 wt%),Mg O(16.68–19.78 wt%),Al_(2)O_(3)(4.24–8.77 wt%),ΣPGE(14.46–322.06 ppb),andΣREE(5.82–7.44 ppm).Pyroxenite type-I shows N-MORB-like chondritenormalized REE patterns.Zircon U-Pb ages of pyroxenite type-I(194±10 Ma),associated ophiolitic gabbro(135.3±2.0 Ma),and plagiogranite(124.2±2.3 Ma)evidently imply episodic evolution of the Zedang ophiolites.The mineralogical and geochemical characteristics of the investigated pyroxenites can be explained by subduction-initiated hydrous melting of metasomatized sub-arc mantle,later overprinted by sub-slab mantle melting triggered by upwelling asthenosphere during the Jurassic–Early Cretaceous times.The geochemical variations in pyroxenite vein composition,coupled with age differences amongst the other ophiolite units,may correspond to intermittent emplacement of pyroxenite dikes and isotropic gabbroic intrusions where the geodynamic setting progressed from arc maturation and slab rollback to slab tearing and delamination.展开更多
Microplastics(MPs)are important exempla of the Anthropocene and are exerting an increasing impact on Earth’s carbon cycle.The huge imbalance between the MPs floating on the marine surface and those that are estimated...Microplastics(MPs)are important exempla of the Anthropocene and are exerting an increasing impact on Earth’s carbon cycle.The huge imbalance between the MPs floating on the marine surface and those that are estimated to have been introduced into the ocean necessitates a detailed assessment of marine MP sinks.Here,we demonstrate that cold seep sediments,which are characterized by methane fluid seepage and a chemosynthetic ecosystem,effectively capture and accommodate small-scale(<100μm)MPs,with 16 types of MPs being detected.The abundance of MPs in the surface of the sediment is higher in methane-seepage locations than in non-seepage areas.Methane seepage is beneficial to the accumulation,fragmentation,increased diversity,and aging of MPs.In turn,the rough surfaces of MPs contribute to the sequestration of the electron acceptor ferric oxide,which is associated with the anaerobic oxidation of methane(AOM).The efficiency of the AOM determines whether the seeping methane(which has a greenhouse effect 83 times greater than that of CO_(2)over a 20-year period)can enter the atmosphere,which is important to the global methane cycle,since the deep-sea environment is regarded as the largest methane reservoir associated with natural gas hydrates.展开更多
文摘Polycyclic aromatic hydrocarbons(PAHs)are one of the most important groups in oil,and re sponsible for major toxic and/or carcinogenic impact on humans and wildlife.It is important to understand the behavior of PAHs in marine environment after an oil-spill incident.However,interaction between petroleum PAHs and microbial communities in a marine environment remains unclear.Therefore,a series of mesocosm experiments were conducted.in which water-accommodated fraction(WAF)of oil was generated to simulate an oil-spill scenario and to analyze the transport and behavior of marine oil spill containing PAHs with and without dispersants.Results indicate that the application of dispersant could increase the concentration of total PAHs in water column due mainly to significant increase in the concentration of highmolecular weight(HMW)PAHs at a lower removal rate.At the end of the 7-day experiment,significant amount of HMW PAHs were accumulated in sediment.In general,the application of dispersant did not increase the sediment uptake of PAHs but increased the PAHs concentration in water column.
基金Supported by the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(No.GML2019ZD0402)。
文摘The ecological suitability of marine resources and environmental conditions for marine ranching in Guangdong,South China was evaluated.Niche theory was used to establish an ecological suitability evaluation model for marine ranching site selection,and suitability evaluation of marine ranching was conducted in.Results show that the ecological suitability index of marine ranching site selection was greater than 64.0 in 20 sites,including offshore Shantou Bay,offshore Zhanjiang Port,and Longdou Bay etc.,which are the priority areas for marine ranching.In other 13 sites,the ecological suitability index ranged between 8.0 and 32.0,including Houjiang Bay,Haimen Bay,and Jieshi Bay etc.,indicating the suitability for marine ranching.However,the ecological suitability index was 0 in Shantou Bay,Zhujiang(Pearl)River estuary,Huangmao Sea,Guanghai Bay,Zhanjiang Port,Qiongzhou Strait,and Anpu Port.These sites are thus unsuitable for marine ranching.This study provides a theoretical basis for site selection and planning of marine ranching in Guangdong Province.
基金Supported by the National Key Research and Development Program of China(No.2022YFC3102200)the Guangdong Research Foundation(No.2019BT02H594)+3 种基金the National Natural Science Foundation of China(No.42076071)the Key Special Project for Introduced Talents Team of the Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(No.GML2019ZD0204)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA22020303)the Key Research Program of the Chinese Academy of Sciences(No.ZDRW-XH-2021-2-02)。
文摘Submarine volcanism is widely developed in the South China Sea(SCS).However,the characteristics,distribution,and genesis of submarine volcanoes in the southern margin of the SCS remain obscure.In this study,we analyzed the characteristics of submarine volcanoes and identified a total of 43 submarine volcanoes in the southern margin of the SCS,based on a newly acquired 310-km seismic reflection profile,along with previous 45 multi-channel seismic(MCS)profiles,petrological results from volcanic rocks sampled by dredging and drilling,nearby ocean bottom seismometer(OBS)wide-angle seismic profiles,and gravity and magnetic data.The study ascertains that most of these volcanoes are located in fault-block belts and graben-horst zones with strong crustal stretching and thinning.These volcanoes exhibit positive high-amplitude external seismic reflections,weak and chaotic internal seismic reflections,and are accompanied by local deformation of the surrounding sedimentary strata.Meanwhile,they have higher positive gravity anomalies and higher magnetic anomalies than the background strata.The petrological dating results show that volcanic ages are primarily in the Pliocene-Pleistocene,with geochemical characteristics indicating dominance of oceanic island basalt(OIB)-type alkali-basalts.Extensional faults have obviously spatial correspondence with post-spreading volcanism,suggesting these faults may provide conduits for submarine volcanism.The high-velocity bodies(HVBs)in the lower crust and magma underplating exist in the southern SCS,which could provide a clue of genesis for submarine volcanism.The inference is that the intensity of post-spreading volcanism in the southern margin might be affected by stretching faults,crustal thinning and magma underplating.
基金Supported by the National Natural Science Foundation of China(Nos.42192535,41876136)the Guangdong Special Support Program(No.2019BT02H594)。
文摘A new gravity sensor based on electromagnetic damping for the JMGrav marine gravimeter is presented.The new gravity sensor considered the advanced construction methods of the electromagnetic damping system of the gravimeter.The design features of the new system are discussed and the research survey data in the South China Sea are shown.Numerical simulations are applied to model the magnetic and mechanical characteristics of the system using finite element analysis and to evaluate the force distribution and the resulting damping effects.The performance characteristics of the system were tested on a motion simulator in laboratory,and the gravimeter was subjected to vertical accelerations of up to 100 Gal in 1-1000 s.It was found that the amplitude reduction of vertical accelerations in 3-15 s is 30-45 dB,with a time lag of 2-5 s,while the effect on gravity in period greater than 600 s is less than 0.5 dB,with a time lag of less than 100 s.The accelerations cause discrepancies of approximately only 1 mGal between the static value and the mean dynamic value.The sea tests were conducted in September 2020.Gravity measurements were taken with a JMGrav marine gravimeter onboard the R/V Dongfanghong 3,and the effective survey line exceeded 2000 km.Completely irregular accelerations with peaks up to 100 Gal yielded a reduction of approximately 40 dB in amplitude.The survey data were evaluated using ocean gravity field models and grid line tests.The results show that the accuracy of the gravity measurements is better than 2 mGal.
基金Supported by the National Natural Science Foundation of China(No.42076071)the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(No.GML2019ZD0204)+2 种基金the Guangdong Key Project(No.2019BT02H594)the Key Research and Development Plan of Hainan Province(No.ZDYF2020198)the Rising Star Foundation of the South China Sea Institute of Oceanology(No.NHXX2017DZ0101)。
文摘As one of the four largest bay areas with strong economic activities in the world,the Guangdong-Hong Kong-Macao Greater Bay Area(GHMGBA)is located in the zone of interaction between the South China Block(SCB)and the South China Sea(SCS).Under the influence of complex geologic evolution,basin-range structures,fault systems and hot springs are well developed here.However,the characteristics of geological structures and the genetic mechanism of these geological phenomena are still unclear.Therefore,we performed ambient noise tomography to obtain 3-D upper crust(0-7.5 km)S-wave velocity structures of the GHMGBA by using 40-day continuous waveform data from 130 seismic stations in the GHMGBA.Our results show that sedimentary basins in the GHMGBA are mainly characterized by low-velocity anomalies.S-wave velocities of sediment formation in basins are about 2.8-3.1 km/s.Rapid changes in velocity appear at the edges of the basins,which correspond to the NE-,NEE-,and NW-trending faults,indicating prominent basin-controlling effects of the faults.The Sanshui Basin(SSB),the largest in the GHMGBA,has a developmental depth of about 4 km,and there is a significant difference in velocity gradient between the east and west sides of the basin,indicating that SSB has experienced east-west asymmetric expansion.Moreover,there are prominent low-velocity anomalies at a depth of about 4.5 km beneath the hot springs at the west of the Zhujiang(Pearl)River estuary(ZRE).We infer that the low-velocity anomalies are fluid reservoirs of the hot springs,which lead to the development of the hot springs on the surface.In addition,the distribution of main cities in the GHMGBA shows a spatial correlation with low-velocity areas at shallow depths(<3 km).The population development trend in the GHMGBA in the past 20 years is also mainly concentrated in the structural province of relatively low-velocity.In combination with the GHMGBA basin structures and drainage distribution characteristics,we suggest that the basic geological environment to some extent affects the habitability of the human settlement and thus determines the distribution and development trend of the main urban context.We believe that the 3-D S-wave velocity structure of the upper crust of the GHMGBA obtained in this study,as well as the deep structural characteristics of the basins and hot springs,will provide support to urban construction planning and geological hazards research of the GHMGBA.
基金Supported by the Special Support Program for Cultivating High-level Talents in Guangdong Province(No.2019BT02H594)the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(No.GML2019ZD0104)+3 种基金the National Natural Science Foundation of China(Nos.41876052,42076218,U1901217,91855101,41773039)the Guangdong Basic and Applied Basic Research Foundation(Nos.2022A1515011836,2021A1515110851)the Science and Technology Planning Project of Guangzhou(No.202201010230)the Special Research Assistant Program of Chinese Academy of Sciences to Junhui YU。
文摘The Zengmu Basin located in the shallow water area of the southern South China Sea,is rich in oil and gas resources,within which faults and mud-diapir are developed,but it is unknown whether oil and gas migrate to the seafloor surface.The newly collected multibeam data across the Zengmu Basin reveal a large number of depressions,with depths of 2-4 m,widths of several tens of meters,large distribution range of 1.8-8 km along survey line,up to~50 km,and their backscatter intensity(-26 dB)is much greater than that of the surrounding area(-38 dB).Combined with the developed mud-diapir and fracture structures,and abundant oil and gas resources within this basin,these depressions are presumed to be pockmarks.Furthermore,more than 110 mono-sized small circular pockmarks,with a depth of less than 1 m and a width of 5 m,are observed in an area of less than 0.03 km2,which are not obliterated by sediment infilling with high sedimentation rate,implying an existence of unit-pockmarks that are or recently were active.In addition,seismic profiles across the Zengmu Basin show characterization of upward migration of hydrocarbons,expressed as mud-diapir structures,bright spots in the shallow formation with characteristics of“low frequency increase and high frequency attenuation”.The subbottom profiles show the mud-diapir structures,as well as the gas-bearing blank zones beneath the seafloor.These features suggest large gas leaking and occurrence of large amounts of carbonate nodules on the seafloor.This indicates the complex and variable substrate type in the Zengmu Basin,while the area was once thought to be mainly silty sand and find sand.This is the first report on the discovery of pockmarks in the Zengmu Basin;it will provide basic information for submarine stability and marine engineering in China’s maritime boundaries.
基金Supported by the National Natural Science Foundation of China(Nos.42192535,41876136)the Guangdong Special Support Program(No.2019BT02H594)supported by the Key Special Projects of the Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(for Introduced Talents Team)(Nos.GML2021GD0810,GML2019ZD0602)。
文摘To dampen periodic off-levelling motions within an inertial platform while undergoing horizontal accelerations of the same period and to achieve a levelling accuracy of a few tens of arcseconds with that system,an internally damped inertial platform for a marine scalar gravity system was the developed.Methods for attenuating horizontal acceleration and reducing off-levelling error by a satisfactory gyro-levelling loop,which are fundamental to the internally damped inertial platform,were designed and implemented.In addition,phase delays are introduced by the levelling loop.The resulting off-levelling gravity errors were analyzed and modeled.A series of tests on a motion simulator were performed in laboratory for a variety of simulated sea conditions.We found that the motion of the platform is a function of the amplitude and period of the simulated ship motions and ranges between 10 and 40 arcseconds.In addition,the phase lag between platform motion and ship motion is not constant but ranges 180°-270°,depending on the period and amplitude of the motion.Then,the platform,on which a gravimeter was mounted,was installed on the R/V Shiyan 2 to conduct a gravity survey in the South China Sea.Despite rough sea conditions,it was shown that in short periods of 2-30 s,the off-levelling angle was less than 30 arcseconds,and the phase lagged the horizontal acceleration by 230°-260°.From a repeated survey line and intersecting survey points,the estimated errors of gravity measurements were between 1.3 and 1.7 mGal.The marine measurements results were compared with those of satellite altimetry data and show a mean value of 0.5 mGal in a standard deviation of 1.5 mGal.
基金supported by the Major Project of Basic and Applied Basic Research of Guangdong Province(No.2019B030302004)the Guangdong Basic and Applied Basic Research Foundation(No.2023A1515030295)the Science and Technology Planning Project of Guangdong Province,China(No.2020B1212060058).
文摘The deep-sea clam Calyptogena marissinica is widely distributed in the Haima cold seep ecosystem on the northwes-tern slope of the South China Sea with low pH values,low temperature and high pressure.Limited information is available on the biomineralization of this species.In this research,we generated a comprehensive transcript dataset of C.marissinica’s mantle tissue,and a total of 19821 unigenes were assembled.Fourteen shell matrix proteins(SMP)-related genes were identified.The qPCR results showed that four out of six prismatic matrix genes(MSP2,MSP5,prisilkin-39,and shematrin),four out of the six nacreous matrix genes(perlucin,pif,pif97,and papilin),and two extrapallial fluid proteins(SPARC and calmodulin)were significantly expressed in the mantle.Both the nacreous and the prismatic layers are chrysanthemum-shaped,which are stacked on the top of each other to form a laminated nacreous structure.The alignment and phylogenetic analysis of MSP-5,Prisilkin-39,Perlucin,and Pif homologues showed that some amino acids of C.marissinica that differed from those detected in other molluscs may cause the different shape of the nacreous and prismatic layers,but do not lead to a change in the species’evolutionary status.These results indicated the conservation of the functions of SMP-related genes in C.marissinica,and the specific shape of the prismatic and nacreous layers of this deep-sea mollusc,which will contribute to the research on the molecular regulation mechanisms of biomineralization in C.marissinica and provide a new perspective to investigate biomineralization in deep-sea clams in general.
基金Supported by Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory (2019BT02H594)Sanya Technology Innovation Special Project (2022KJCX08)。
文摘Offshore carbon dioxide(CO_(2)) storage is an effective method for reducing greenhouse gas emissions. However, when using traditional seismic wave methods to monitor the migration of sequestration CO_(2) plumes, the characteristics of wave velocity changes tend to become insignificant beyond a certain limit. In contrast, the controllable source electromagnetic method(CSEM) remains highly sensitive to resistivity changes. By simulating different CO_(2) plume migration conditions, we established the relevant models and calculated the corresponding electric field response characteristic curves, allowing us to analyze the CSEM's ability to monitor CO_(2) plumes. We considered potential scenarios for the migration and diffusion of offshore CO_(2) storage, including various burial depths, vertical extension diffusion, lateral extension diffusion,multiple combinations of lateral intervals, and electric field components. We also obtained differences in resistivity inversion imaging obtained by CSEM to evaluate its feasibility in monitoring and to analyze all the electric field(Ex, Ey, and Ez) response characteristics. CSEM has great potential in monitoring CO_(2) plume migration in offshore saltwater reservoirs due to its high sensitivity and accuracy. Furthermore, changes in electromagnetic field response reflect the transport status of CO_(2) plumes, providing an important basis for monitoring and evaluating CO_(2)transport behavior during storage processes.
基金Supported by the National Natural Science Foundation of China(Nos.42176116,41576126,41890851,U21A6001)the Natural Science Foundation of Guangdong Province(No.2017A030306020)+4 种基金the Guangdong Major Project of Basic and Applied Basic Research(No.2019B030302004)the Rising Star Foundation of the South China Sea Institute of Oceanology(No.NHXX2019ST0101)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2018377)the Science and Technology Planning Project of Guangdong Province of China(No.2021B1212050023)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA19060503)。
文摘Variations of picoplankton groups were investigated over a one-month period in Daya Bay and Sanya Bay,in the northern South China Sea.The two coastal regions exhibited different variation patterns in physicochemical parameters.Moreover,the diel variations of picoplankton groups were different between the two bays.The abundance of the picoplankton in Sanya Bay displayed a pronounced diel variation,while it was not significant in Daya Bay.In addition,some similar patterns of picoplankton abundance were discovered.In the two bays,virioplankton exhibited the smallest fluctuation range,whereas picocyanobacteria fluctuated most markedly.The fluctuation range of picoplankton groups was larger in spring tide than in neap tide,especially in Sanya Bay.Random forest model analysis demonstrated that the variation of picoplankton groups was attributed to physical and chemical factors in Sanya Bay and Daya Bay,respectively.Therefore,our findings suggest that virioplankton abundance can persist more stably in response to changing environmental conditions compared to bacterioplankton and picophytoplankton.
基金supported by the National Natural Science Foundation of China(Nos.42174063,92155307,41976046)Guangdong Provincial Key Laboratory of Geophysical High-resolution Imaging Technology under(No.2022B1212010002)Project for introduced Talents Team of Southern Marine Science and Engineering Guangdong(Guangzhou)(No.GML2019ZD0203)。
文摘Existing lithospheric velocity models exhibit similar structures typically associated with the first-order tectonic features,with dissimilarities due to different data and methods used in model generation.The quantification of model structural similarity can help in interpreting the geophysical properties of Earth's interior and establishing unified models crucial in natural hazard assessment and resource exploration.Here we employ the complex wavelet structural similarity index measure(CW-SSIM)active in computer image processing to analyze the structural similarity of four lithospheric velocity models of Chinese mainland published in the past decade.We take advantage of this method in its multiscale definition and insensitivity to slight geometrical distortion like translation and scaling,which is particularly crucial in the structural similarity analysis of velocity models accounting for uncertainty and resolution.Our results show that the CW-SSIM values vary in different model pairs,horizontal locations,and depths.While variations in the inter-model CW-SSIM are partly owing to different databases in the model generation,the difference of tomography methods may significantly impact the similar structural features of models,such as the low similarities between the full-wave based FWEA18 and other three models in northeastern China.We finally suggest potential solutions for the next generation of tomographic modeling in different areas according to corresponding structural similarities of existing models.
基金Supported by the National Key R&D Program of China(No.2021YFF0501202)the National Natural Science Foundation of China(Nos.12374428,42176191,U22A2012,12304507)+2 种基金the Guangdong Special Support Key Team Program(Nos.2019BT02H594,GML2021GD0810)the Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(No.SML2023SP232)the Fundamental Research Funds for the Central Universities,Sun Yat-sen University(No.24lgqb006)。
文摘To understand the acoustic and physical properties of piston core samples collected from the Sunda continental shelf and analyze their distribution patterns,the samples were analyzed in laboratory,from which three provinces were divided in sound speed,sound speed ratio,porosity,wet bulk density,and maximum shear strength.ProvinceⅠhad lower sound speed and sound speed ratio(<1.04),high porosity,and low wet bulk density.ProvinceⅡhad higher sound speed and sound speed ratio(>1.04),low porosity,and high wet bulk density.ProvinceⅢhad the lowest sound speed and sound speed ratio(0.99),highest porosity(81%),and lowest wet bulk density(1.34 g/cm^(3)).The distribution pattern indicates that sediment movement,sediment source,topography,and hydrodynamic conditions influenced the distribution of acoustic and physical properties.Furthermore,we investigated the relationship of the maximum shear strength to the porosity and wet bulk density,and found that the maximum shear strength was proportional to both the porosity and wet bulk density.This finding has significant implications for ocean engineering applications.
基金We thank the GMGS for permission to release the seismic data.The financial support was obtained from the National Natural Science Foundation of China(No.U1701245)the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(No.GML2019ZD0102)the project of the China Geological Survey(Nos.DD20190213,DD20211362).We thank Associate Prof.Jinwei Gao at the Institute of Deep-Sea Science and Engineering of the China Academy of Science,who spent valuable time providing constructive comments which markedly improved this manuscript.We benefited substantially from constructive reviews from the two anonymous reviewers,which considerably helped in improving the manuscript.
文摘Mud diapirs are significant structures often associated with hydrocarbon migration and accumulation as well as gas hydrate formation in sedimentary basins.A total of 30 mud diapirs were observed in the northwestern Zengmu Basin in the southern South China Sea based on 2D multichannel seismic data.The structures are distributed along an NW-SE trend near the shelf break of the Kangxi depression in the Zengmu Basin.The mud diapirs were divided into the following according to their vertical shapes,intrusion heights,and effusive activities:tortoise,piercing,and nozzle types,which represent different evolutionary stages of diapirism.The mud diapirs in the study area suggest that the driving forces behind the mud diapirs considerably exceed the rock rupture limit of the overlying strata.Diapir formation can be divided into two steps:the accommodation of a large amount of mud in the Zengmu Basin and the movement of plastic mud induced by gravity-driven flow and regional tectonic compression.Combining seismic interpretations with analyses of the regional geology and tectonic subsidence,the current study proposes that rapid subsidence in the Kangxi depression sufficiently accommodated the vast amount of sediments deposited since the Middle Miocene,which provided favorable conditions for the growth of mud diapirs.Furthermore,the N-S directional stress field in the Zengmu Basin and the gravity slide northward along the southern slope of the depression further facilitated the development of mud diapirs since the late Miocene.The mud diapirs in the southern South China Sea margins were accompanied by the accumulation and release of overpressured fluid.
基金supported by the National Key R&D Program of China(No.2017YFC0306703)the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(No.GML2019 ZD0201).
文摘Recently,methane seepage related to the dissociation of natural gas hydrates has attracted much attention,which has a significant impact on the study of the global carbon and nitrogen cycles.Based on the detailed geochemical analyses of sediments(core Q6)from the Qiongdongnan Basin,South China Sea,three methane seepage activities were identified and the exact horizons of anaerobic oxidation of methane(AOM)were defined.Furthermore,organic carbon isotopic(δ^(13)C_(TOC))levels ranged from−23.6‰–−20.6‰PDB;nitrogen isotopes(δ^(15)N_(TN))of the same sedimentary samples ranged from 1.8‰–5.3‰.We also found obvious simultaneous negative excursions of organic carbon isotopes(δ^(13)C_(TOC))and nitrogen isotopes(δ^(15)N_(TN))in the horizons of methane seepages.Compared with the normal sediments,their maximum negative excursions were 2.6‰and 2.5‰,respectively.We discuss in detail the various characteristics ofδ^(15)N_(TN) andδ^(13)C_(TOC) levels in sediments and their coupling responses to methane seepage activities.We believe that the methane seepage events changed the evolution trajectory ofδ^(15)N_(TN) andδ^(13)C_(TOC) levels in sediment records,which resulted in the simultaneous negative excursions.This phenomenon is of great significance to reveal the historical dissociation of natural gas hydrates and their influence on the deep-sea carbon and nitrogen pool.
基金supported by the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou) (GML2019ZD0306)National Natural Science Foundation of China (Grant Nos. 41731173 and 42192564)+5 种基金National Key R&D Program of China (2019YFA0606701)Strategic Priority Research Program of Chinese Academy of Sciences (XDB42000000 and XDA20060502)Innovation Academy of South China Sea Ecology and Environmental Engineering, Chinese Academy of Sciences (ISEE2021ZD01)Independent Research Project Program of State Key Laboratory of Tropical Oceanography (Grand No. LTOZZ2004)Leading Talents of Guangdong Province Programsupported by the High Performance Computing Division in the South China Sea Institute of Oceanology
文摘An extraordinary and unprecedented heatwave swept across western North America(i.e.,the Pacific Northwest)in late June of 2021,resulting in hundreds of deaths,a massive die-off of sea creatures off the coast,and horrific wildfires.Here,we use observational data to find the atmospheric circulation variabilities of the North Pacific and Arctic-Pacific-Canada patterns that co-occurred with the development and mature phases of the heatwave,as well as the North America pattern,which coincided with the decaying and eastward movement of the heatwave.Climate models from the Coupled Model Intercomparison Project(Phase 6)are not designed to simulate a particular heatwave event like this one.Still,models show that greenhouse gases are the main reason for the long-term increase of average daily maximum temperature in western North America in the past and future.
基金Supported by the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(Nos.GML2019ZD0302,GML2019ZD0303)the National Natural Science Foundation of China(No.31971480)the State Key Laboratory of Tropical Oceanology Independent Research Fund(No.LTOZZ2103)。
文摘Mirs Bay is a semi-enclosed bay neighboring the Zhujiang(Pearl)River estuary,one of the largest estuarine systems in the world.The long-term historical observational data(1994-2017)of temperature,salinity,dissolved oxygen(DO),and biochemical parameters were used to examine the spatiotemporal distribution of hypoxia in Mirs Bay and adjacent coastal waters.Results show that bottom hypoxia varied seasonally and interannually.Hypoxia mainly occurred from June to September in Mirs Bay and the transition zone in the southern waters of Hong Kong,and the recorded hypoxia events have increased from 2007.The density difference between the bottom and surface layers was positively related to the bottom apparent oxygen utilization(AOU)(R=0.620,P<0.001)and negatively related to the bottom DO(R=0.616,P<0.001),indicating that water column stratification was an essential prerequisite for the formation of bottom hypoxia in summer.The bottom oxygen consumption and hypoxia had higher positive correlation with the seasonal thermocline(R=0.683,P<0.001)than the halocline(R=0.540,P<0.001),including in the area was affected by freshwater plume.The insignificant relationship between AOU and nutrients indicated that local eutrophication was not the only important factor in the formation of the hypoxic zone during summer.The decrease in phosphorous owing to the pollutant reduction policy and the increase in nitrate may have led to an increase in hypoxia events in the bay where waters therein are characterized by nitrogen-limitation.The increase in chemical oxygen demand in wastewater also promoted oxygen consumption.Compared to the adjacent coastal waters influenced by Zhujiang River plume water,the Mirs Bay experienced more hypoxia events.The high concentrations of ammonium and total Kjeldahl nitrogen in the sediment of Mirs Bay increased the oxygen depletion in the bottom water.The long residence time of the near-bottom water in Mirs Bay increased the risk of bottom hypoxia events,although the nutrient concentrations were lower than those in the transition zone.These factors lead to differences in hypoxia occurrence in Mirs Bay and adjacent coastal waters.
基金The National Natural Science Foundation of China under contract Nos 42106198 and 41720104001the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)under contract No.GML2019ZD0210.
文摘The ever-increasing deepwater oil and gas development in the Qiongdongnan Basin,South China Sea has initiated the need to evaluate submarine debris-flow hazard risks to seafloor infrastructures.This paper presents a case study on evaluating the debris-flow hazard risks to the planned pipeline systems in this region.We used a numerical model to perform simulations to support this quantitative evaluation.First,one relict failure interpreted across the development site was simulated.The back-analysis modeling was used to validate the applicability of the rheological parameters.Then,this model was applied to forecast the runout behaviors of future debris flows originating from the unstable upslope regions considered to be the most critical to the pipeline systems surrounding the Manifolds A and B.The model results showed that the potential debris-flow hazard risks rely on the location of structures and the selection of rheological parameters.For the Manifold B and connected pipeline systems,because of their remote distances away from unstable canyon flanks,the potential debris flows impose few risks.However,the pipeline systems around the Manifold A are exposed to significant hazard risks from future debris flows with selected rheological parameters.These results are beneficial for the design of a more resilient pipeline route in consideration of future debris-flow hazard risks.
基金The Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou) under contract No.GML2019ZD0405the National Natural Science Foundation of China under contract Nos41506150 and 41130855+3 种基金the Guangdong Basic and Applied Basic Research Foundation under contract No.2019A1515011645the National Science and Technology Basic Work Program of the Ministry of Science and Technology of China under contract No.2015FY110600the Science and Technology Planning Project of Guangdong Province,China under contract No.2020B1212060058the Development Fund of South China Sea Institute of Oceanology of the Chinese Academy of Sciences under contract No.SCSIO202204。
文摘How coral reefs with high productivity and biodiversity can flourish in oligotrophic tropical oceans has inspired substantial research on coral reef ecosystems.Increasing evidence shows that similar to water in an oasis in the desert,there are stable nutrient supplies to coral reefs in oligotrophic oceans.Here,with emphasis on the fluxes of organic matter,we summarize at the ecosystem level(1)the multiple input pathways of external nutrients,(2)the storage of nutrients in reef organisms,(3)the efficient retaining and recycling of dissolved and particulate organic matter within coral reef ecosystems,(4)the distinctly high phytoplankton productivity and biomass inside and near oceanic coral reefs,and(5)the export of reef-related organic carbon to adjacent open oceans.These properties enable coral reefs to function as ecological“pumps”for gathering nutrients across ecosystems and space,retaining and recycling nutrients within the ecosystem,supporting high phytoplankton productivity,and exporting organic carbon to adjacent open oceans.Particularly,the high phytoplankton productivity and biomass make waters around coral reefs potential hotspots of carbon export to ocean depths via the biological pump.We demonstrate that organic carbon influx is vital for coral reef ecosystems’carbon budget and carbon export.The concept of the coral reef ecological pump provides a framework to improve the understanding of the functioning of the coral reef ecosystem and its responses to disturbance.Prospects of the coral reef ecological pump in coral reef studies are discussed in changing oceans driven by human activities and global change in the Anthropocene.
基金co-supported by Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(No.GML2019ZD0201)the Second Tibetan Plateau Scientific Expedition and Research Program(No.2019QZKK0801)+3 种基金the National Natural Science Foundation of China(NNSFCProject Nos.42272048,41720104009,42172069,92062215)the Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resources Fund(No.J1901-28)the China Geological Survey(CGS,Project Nos.DD20230340,DD20221630)。
文摘Understanding the nature of parental melts for pyroxenite veins in supra-subduction zone(SSZ)ophiolites provides vibrant constraints on melt infiltration processes operating in subduction zones.The Zedang ophiolitic massif in the eastern Yarlung–Zangbo suture zone in Tibet consists of mantle peridotites and a crustal section of gabbro,diabase,and basalt.Veins of two pyroxenite varieties cut the southern part of the Zedang massif.These pyroxenite rocks have different geochemical characteristics,where the first variety(type-I)has relatively higher contents of SiO_(2)(51.82–53.08 wt%),MgO(20.08–23.23 wt%),andΣPGE(3.42–13.97 ppb),and lower Al_(2)O_(3)(1.59–2.28 wt%)andΣREE(1.63–2.94 ppm).The second pyroxenite variety(type-II)is characterized by SiO_(2)(45.44–49.61 wt%),Mg O(16.68–19.78 wt%),Al_(2)O_(3)(4.24–8.77 wt%),ΣPGE(14.46–322.06 ppb),andΣREE(5.82–7.44 ppm).Pyroxenite type-I shows N-MORB-like chondritenormalized REE patterns.Zircon U-Pb ages of pyroxenite type-I(194±10 Ma),associated ophiolitic gabbro(135.3±2.0 Ma),and plagiogranite(124.2±2.3 Ma)evidently imply episodic evolution of the Zedang ophiolites.The mineralogical and geochemical characteristics of the investigated pyroxenites can be explained by subduction-initiated hydrous melting of metasomatized sub-arc mantle,later overprinted by sub-slab mantle melting triggered by upwelling asthenosphere during the Jurassic–Early Cretaceous times.The geochemical variations in pyroxenite vein composition,coupled with age differences amongst the other ophiolite units,may correspond to intermittent emplacement of pyroxenite dikes and isotropic gabbroic intrusions where the geodynamic setting progressed from arc maturation and slab rollback to slab tearing and delamination.
基金financially supported by the National Natural Science Foundation of China(42022046)the National Key Research and Development Program of China(2021YFF0502300)+1 种基金the Key Special Project for Introduced Talent Teams of the Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(GML2019ZD0403 and GML2019ZD0401)Guangdong Natural Resources Foundation(GDNRC[2022]45)。
文摘Microplastics(MPs)are important exempla of the Anthropocene and are exerting an increasing impact on Earth’s carbon cycle.The huge imbalance between the MPs floating on the marine surface and those that are estimated to have been introduced into the ocean necessitates a detailed assessment of marine MP sinks.Here,we demonstrate that cold seep sediments,which are characterized by methane fluid seepage and a chemosynthetic ecosystem,effectively capture and accommodate small-scale(<100μm)MPs,with 16 types of MPs being detected.The abundance of MPs in the surface of the sediment is higher in methane-seepage locations than in non-seepage areas.Methane seepage is beneficial to the accumulation,fragmentation,increased diversity,and aging of MPs.In turn,the rough surfaces of MPs contribute to the sequestration of the electron acceptor ferric oxide,which is associated with the anaerobic oxidation of methane(AOM).The efficiency of the AOM determines whether the seeping methane(which has a greenhouse effect 83 times greater than that of CO_(2)over a 20-year period)can enter the atmosphere,which is important to the global methane cycle,since the deep-sea environment is regarded as the largest methane reservoir associated with natural gas hydrates.
