Using remote sensing technology for water quality evaluation is an inevitable trend in marine environmental monitoring. However, fewer categories of water quality parameters can be monitored by remote sensing technolo...Using remote sensing technology for water quality evaluation is an inevitable trend in marine environmental monitoring. However, fewer categories of water quality parameters can be monitored by remote sensing technology than the 35 specified in GB3097-1997 Marine Water Quality Standard. Therefore, we considered which parameters must be selected by remote sensing and how to model for water quality evaluation using the finite parameters. In this paper, focused on Leizhou Peninsula nearshore waters, we found N, P, COD, PH and DO to be the dominant parameters of water quality by analyzing measured data. Then, mathematical statistics was used to determine that the relationship among the five parameters was COD〉DO〉P〉N〉pH. Finally, five-parameter, fourparameter and three-parameter water quality evaluation models were established and compared. The results showed that COD, DO, P and N were the necessary parameters for remote sensing evaluation of the Leizhou Peninsula nearshore water quality, and the optimal comprehensive water quality evaluation model was the four- parameter model. This work may serve as a reference for monitoring the quality of other marine waters by remote sensing.展开更多
Zhanjiang Bay is a major aquaculture area in China with many types of mariculture products(such as oysters,fish,and shrimp).The culture area and shrimp output in Zhanjiang Bay are ranked first in China.We investigated...Zhanjiang Bay is a major aquaculture area in China with many types of mariculture products(such as oysters,fish,and shrimp).The culture area and shrimp output in Zhanjiang Bay are ranked first in China.We investigated the total organic carbon(TOC),total nitrogen(TN),TOC/TN ratio,and stable isotopes(δ^(13)C and δ^(15)N) of the fish and shrimp feed,fish and shrimp feces,and sedimentary organic matter(SOM) in and around different aquaculture areas of northeastern Zhanjiang B ay to study the impact of aquaculture activities on SOM.The average TOC contents of fish and shrimp feed were 39.20%±0.91% and 39.29%±0.21%,respectively.The average TOC content in the surface sediments of the oyster culture area,the mixed(fish and shrimp) culture area,and the cage fish farm area were 0.66%,0.88%±0.10%,and 0.58%±0.19%,respectively,which may indicate that mixed culture had a greater impact on SOM.The relatively high TOC and TN contents and relatively low TOC/TN ratios,and δ^(15)N values in the upper layer of the core sediment in the mixed culture area could also support the significant influence of mixed culture.The average δ^(13)C and δ^(15)N values of fish and shrimp feed were -20.6‰±2.2‰ and 1.8‰±1.2‰,respectively,which were different from the isotopic values of SOM in the study area.δ^(13)C and δ^(15)N values for SOM in different aquaculture areas were different from those of nearby reference stations,probably reflecting the influence of aquaculture.The δ^(13)C and δ^(15)N values in the oyster culture area(-25.9‰ and6.0‰,respectively) seemed to have reduced δ^(13)C and enriched δ^(15)N relative to those of the reference station(-24.6‰ and 5.8‰,respectively).This may reflect the influence of organic matter on oyster culture.The δ^(15)N value of the station in the mixed culture area(7.1‰±0.4‰) seemed to be relatively enriched in δ^(15)N relative to that of the reference station(6.6‰).Sedimentation and the subsequent degradation of organic matter from mixed cultures may have contributed to this phenomenon.The surface sediment at the cage fish farm area seemed to be affected by fish feces and primary production based on the indication of δ^(13)C and δ^(15)N values.The sediment core at the mixed culture region(NS6) had lower TOC/TN ratios and more positive δ^(13)C and δ^(15)N values than the sediment core at the oyster culture area,suggesting a higher proportionate contribution of marine organic matter in the mixed culture area.In summary,oyster culture,mixed culture,and cage fish culture in northeastern Zhanjiang Bay had a certain degree of impact on SOM,and mixed culture had more significant influences on SOM based on the high TOC contents and the significant vertical variations of TOC/TN ratio and δ^(15)N value in the sediment of this area.This study provides new insights into the impact of aquaculture activities on SOM content.展开更多
Recent studies have revealed that two boreal spring sea surface temperature （SST） indices have potential to predict the number of western North Pacific （WNP） tropical cyclones （TCs） in the following peak typhoon...Recent studies have revealed that two boreal spring sea surface temperature （SST） indices have potential to predict the number of western North Pacific （WNP） tropical cyclones （TCs） in the following peak typhoon season （June-October）： the northern tropical Atlantic （NTA） SST, and the SST gradient （SSTG） between the southwestern Pacific and western Pacic warm pool. The interannua[ and interdecadal variations of NTA SST and SSTG and their relationships to the number ofWNP TCs during 1950-2013 were compared. On the interdecadal timescale, SSTG showed better correlation with the number of WNP TCs than NTA SST. The interdecadal variation of NTA SST was closely associated with the Atlantic Multidecadal Oscillation, while that of SSTG was anti-correlated with the Central Pacific （CP） El Nino index at the interdecadal timescale. On the interannual timescale, both NTA SST and SSTG were modulated by two types of El Nino. The NTA SST revealed significant correlations with the number of WNPTCs beginning from the early 1960s; by contrast, SSTG showed significant correlations after the mid-1970s. Co-variability of NTA SST and SSTG existed after the late 1980s, induced by modulation from CP El Nino.The co-variability of these two spring SST predictors increased their prediction skill after the late 1980s, with enhanced correlation between the number of WNPTCs and the two predictors.展开更多
The correlation between summertime Nino3.4 index and western North Pacific(WNP)summer monsoon index has strikingly enhanced since the early 1990 s,with nonsignificant correlation before the early1990 s but significant...The correlation between summertime Nino3.4 index and western North Pacific(WNP)summer monsoon index has strikingly enhanced since the early 1990 s,with nonsignificant correlation before the early1990 s but significant correlation afterward.This observed interdecadal change around the 1990 s may be associated with more frequent occurrences of central Pacific(CP)El Nino and the interdecadal changes in ENSO-associated SST anomalies.During the post-1990 s period(the pre-1990 s period),highly noticeable tropical Atlantic(Indian)Ocean SST anomalies tend to co-occur with the summertime Nino3.4 SST anomalies.The concurrent tropical Atlantic(Indian)Ocean SST anomalies could constructively reinforce(destructively mitigate)the WNP monsoon circulation anomalies induced by the summertime Nino3.4 SST,thus boosting(muting)the correlation between summertime Nino3.4 SST and WNP monsoon.In addition,the faster decaying pace of preceding-winter El Nino after the 1990 s,which may have been mainly induced by the influences from the spring tropical North Atlantic SST anomalies,could also have contributed to the enhanced correlation between the summertime Nino3.4 index and WNP monsoon.These results suggest that the enhanced influences from the tropical Atlantic SST may have triggered the intensified correlation between summertime ENSO and WNP monsoon since the early 1990 s.展开更多
Wave-current interaction and its effects on the hydrodynamic environment in the Beibu Gulf(BG) have been investigated via employing the Coupled Ocean–Atmosphere–Wave–Sediment Transport(COAWST) modeling system. The ...Wave-current interaction and its effects on the hydrodynamic environment in the Beibu Gulf(BG) have been investigated via employing the Coupled Ocean–Atmosphere–Wave–Sediment Transport(COAWST) modeling system. The model could simulate reasonable hydrodynamics in the BG when validated by various observations.Vigorous tidal currents refract the waves efficiently and make the seas off the west coast of Hainan Island be the hot spot where currents modulate the significant wave height dramatically. During summer, wave-enhanced bottom stress could weaken the near-shore component of the gulf-scale cyclonic-circulation in the BG remarkably, inducing two major corresponding adjustments: Model results reveal that the deep-layer cold water from the southern BG makes critical contribution to maintaining the cold-water mass in the northern BG Basin.However, the weakened background circulation leads to less cold water transported from the southern gulf to the northern gulf, which finally triggers a 0.2℃ warming in the cold-water mass area;In the top areas of the BG, the suppressed background circulation reduces the transport of the diluted water to the central gulf. Therefore, more freshwater could be trapped locally, which then triggers lower sea surface salinity(SSS) in the near-field and higher SSS in the far-field.展开更多
For acoustic detection of internal waves, the core issue is to obtain the temporal and spatial distribution of the sound speed profile(SSP). In the inversion process, the SSP is usually expressed by a few parameters t...For acoustic detection of internal waves, the core issue is to obtain the temporal and spatial distribution of the sound speed profile(SSP). In the inversion process, the SSP is usually expressed by a few parameters through expansion. However, information about internal waves may sometimes be hard to read directly from the inversion results. The aim of this paper is to characterize the internal waves directly though expansion coefficients. By deducing the dynamic equations of the internal waves, an orthogonal basis called the hydrodynamic normal modes(HNMs) can be extracted from a certain number of SSP samples. Unlike the existing widely used empirical orthogonal functions(EOFs), the HNMs have a more explicit physical meaning that is directly related to internal wave activity. The HNMs are then used to expand the SSP time series, and the expansion coefficients are derived.Eventually, information about internal waves can be read directly from the time derivative of the expansion coefficients of the first two modes. In this study, this method is applied to thermistor string profiles from the northern shelf of the South China Sea, where the SSP shows evident spatial and temporal variations due to internal waves. The results show that the SSP can be described approximately by the first two modes with adequate precision. The special oscillation structure of the time derivative of the expansion coefficients can be used to detect internal solitary waves. The expansion coefficients can also give information on internal solitary wave amplitude and width. According to theoretical and experimental analysis, it can be concluded that the internal waves monitoring method introduced in this paper is effective. The HNMs method is simple to apply and depends less on sample data than EOFs. It could be used as an efficient alternative to EOFs to expand the use of the SSP in highly variable areas, where internal waves are intensive.展开更多
Analyses of the Tropical Rainfall Measuring Mission （TRMM） datasets revealed a prominent interannual variation in the convective-stratiform rainfall and latent heating over the southern South China Sea （SCS） durin...Analyses of the Tropical Rainfall Measuring Mission （TRMM） datasets revealed a prominent interannual variation in the convective-stratiform rainfall and latent heating over the southern South China Sea （SCS） during the winter monsoon between 1998 and 2010. Although the height of maximum latent heating remained nearly constant at around 7km in all of the years, the year-to- year changes in the magnitudes of maximum latent heating over the region were noticeable. The interannual variations of the convee- tive-stratiform rainfall and latent heating over the southern SCS were highly anti-correlated with the Nifio-3 index, with more （less） rainfall and latent heating during La Nifia （El Nifio） years. Analysis of the large-scale environment revealed that years of active rain- fall and latent heating corresponded to years of large deep convergence and relative humidity at 600hPa. The moisture budget diag- nosis indicated that the interarmual variation of humidity at 600hPa was largely modulated by the vertical moisture advection. The year-to-year changes in rainfall over the southern SCS were mainly caused by the interannual variations of the dynamic component associated with anomalous upward motions in the middle troposphere, while the interannual variations of the thermodynamic com- ponent associated with changes in surface specific humidity played a minor role. Larger latent heating over the southern SCS during La Nifia years may possibly further enhance the local Hadley circulation over the SCS in the wintertime.展开更多
There is a rainfall variability biennial relationship between Central America （CA） and equatorial South America （ESA） over the tropical western hemisphere, which is known to have arisen due to the combined effects...There is a rainfall variability biennial relationship between Central America （CA） and equatorial South America （ESA） over the tropical western hemisphere, which is known to have arisen due to the combined effects of ENSO and tropical North Atlantic （TNA） SST. Here, the authors report that this biennial rainfall relationship between CA and ESA has weakened remarkably since 2000, with weakening in both in-phase and out-of-phase rainfall transitions. The observed decadal changes in the biennial relationship between CA and ESA rainfall can be attributed to changes in the effects of ENSO and TNA SST since 2000, which may be associated with more frequent occurrences of the central Pacific or＇Modoki＇ type El Ni^o. The weakening of the association with ENSO for CA rainfall since 2000 might have given rise to the weakening of the in-phase rain transition from CA rainfall to the following ESA rainfall. The weakened linkage between boreal-winter ESA rainfall and the subsequent boreal-summer TNA SST since 2000 may have resulted in the weakening of the out- of-phase rainfall transition from boreal-winter ESA rainfall to the subsequent boreal-summer CA rainfall.展开更多
Recent studies suggest that the interannual variability in the tropical Pacific associated with the El Nino-Southern Oscillation has weakened since 2000. In this study, the authors report that the interannual variabil...Recent studies suggest that the interannual variability in the tropical Pacific associated with the El Nino-Southern Oscillation has weakened since 2000. In this study, the authors report that the interannual variability of the contrast in rainfall between the eastern equatorial Pacific and equatorial Atlantic has also weakened remarkably since 2000, attributable to the weakened interannual variability in the zonal sea surface temperature gradient between the eastern equatorial Pacific and equatorial Atlantic and in the associated equatorial low-level zonal wind across South America linking the two ocean basins. Diagnosis of a column-integrated moisture budget indicates that the weakening in the interannual variability of the contrast in rainfall is primarily attributable to the changes in moisture convergence associated with vertical motion. The results highlight the clear weakened interannual variability in the coupled equatorial Pacific-Atlantic climate system since 2000, including the Pacific El Nino, Atlantic Nino, equatorial zonal wind across South America, and rainfall over the eastern equatorial Pacific and equatorial Atlantic.展开更多
Sediment samples obtained from the South Mid-Atlantic Ridge were analyzed for the major and trace elements by inductively coupled plasma atomic emission spectroscopy and inductively coupled plasma mass spectrometry. R...Sediment samples obtained from the South Mid-Atlantic Ridge were analyzed for the major and trace elements by inductively coupled plasma atomic emission spectroscopy and inductively coupled plasma mass spectrometry. Results revealed that the contents of elements(e.g., Fe, Mn, Cu, Zn, V, Co) were high in samples 22V-TVG10 and 26V-TVG05 from the sites near the hydrothermal areas, and low in sample 22V-TVG14, which was collected far from the hydrothermal areas. The contents of Ca, Sr and Ba in the samples showed opposite trends. A positive correlation between the concentrations of metallic elements(Cu, Zn, Co, Ni, Pb, V) and Fe in the samples were observed. These results are consistent with chemical evolution of the dispersing hydrothermal plume.展开更多
The coupled ocean atmosphere wave sediment transport(COAWST)modeling system is employed to investigate the role of wave-mixing playing in the upwelling off the west coast of Hainan Island(WHU).Waves,tides and sea surf...The coupled ocean atmosphere wave sediment transport(COAWST)modeling system is employed to investigate the role of wave-mixing playing in the upwelling off the west coast of Hainan Island(WHU).Waves,tides and sea surface temperature(SST)are reproduced reasonably well by the model when validated by observations.Model results suggest the WHU is tidally driven.Further investigations indicate that inclusion of wave-mixing promotes the intensity of the WHU,making the simulated SST become more consistent with remote-sensed ones.Dynamically,wave-mixing facilitates the“outcrop”of more upwelled cold water,triggering stronger WHU and leading to a three-dimensional dynamical adjustment.From the perspective of time,wave-mixing contributes to establishing an earlier tidal mixing front strong enough to generate WHU and that is,WHU may occur earlier when taking wave-mixing into consideration.展开更多
Highly productive estuaries facilitate intense decomposition of dissolved organic matter(DOM) as a carbon source.However,the specific impacts of typhoons on DOM decomposition in eutrophic bays remain unclear.To addres...Highly productive estuaries facilitate intense decomposition of dissolved organic matter(DOM) as a carbon source.However,the specific impacts of typhoons on DOM decomposition in eutrophic bays remain unclear.To address this issue,we investigated the spectral characteristics of DOM before and after Typhoon Ewiniar in Zhanjiang B ay,a eutrophic semi-enclosed bay in the northwestern South China Sea.The results revealed that intense microbial decomposition of DOM occurred during the pre-typhoon period because high nutrient inputs facilitated the mobilization of DOM in the bay.However,the intrusion of external seawater induced by the typhoon diluted the nutrient levels in Zhanjiang B ay,reducing the impact of microbial decomposition on DOM during the post-typhoon perio d.Nevertheless,the net addition of DOM occurred in Zhanjiang Bay during the post-typhoon period,possibly because of the decomposition of particulate organic matter(POM) and desorption of particulate matter.In addition,an increase in apparent oxygen utilization,a decrease in DO saturation and the reduced level of Chl a indicated that organic matter(OM) decomposition was enhanced and OM decomposition shifted to POM decomposition in Zhanjiang Bay after the typhoon.Overall,our study highlighted the shift in the intense OM decomposition from DOM to POM decomposition before and after typhoons in eutrophic bays,providing new insights into the response of typhoons to biogeo chemistry.展开更多
Eutrophication in coastal waters has been increasing remarkably,severely impacting the water quality in mariculture bays.In this study,we conducted multiple isotopic measurements on suspended particulate nitrogen(δ^(...Eutrophication in coastal waters has been increasing remarkably,severely impacting the water quality in mariculture bays.In this study,we conducted multiple isotopic measurements on suspended particulate nitrogen(δ^(15)N-PN) and dissolved nitrate(δ^(15)N-NO_(3)^(-)and δ^(18)O-NO_(3)^(-)) in Zhanjiang Bay,a typical mariculture bay with a high level of eutrophication in South China,to investigate the changes in nitrogen sources and their cycling between the rainy and dry seasons.During the rainy season,the study found no significant relation between δ^(15)NPN and δ^(15)N-NO_(3)^(-)due to the impact of heavy rainfall and terrestrial erosion.In the upper bay,a slight nitrate loss and slightly higher δ_(15)N-NO_(3)^(-)and δ^(18)O-NO_(3)^(-)values were observed,attributed to intense physical sedimentwater interactions.Despite some fluctuations,nitrate concentrations in the lower bay mainly aligned with the theoretical mixing line during the rainy season,suggesting that nitrate was primarily influenced by terrestrial erosion and that nitrate isotopes resembled the source.Consequently,the isotopic values of nitrate can be used for source apportionment in the rainy season.The results indicated that soil nitrogen(36%) and manure and sewage(33%) were the predominant nitrogen sources contributing to nitrogen loads during this period.In contrast,the dry season saw a deficient ammonium concentration(<0.2 μmol/L) in the bay,due to nearly complete consumption by phytoplankton during the red tide period.Additionally,the significant loss of nitrate and simultaneous increase in the stable isotopes of dissolved and particulate nitrogen suggest a strong coupling of assimilation and mineralization during the dry season.More active biogeochemical processes during the dry season may be related to decreased runoff and increased water retention time.Overall,our study illustrated the major seasonal nitrogen sources and their dynamics in Zhanjiang B ay,providing valuable insights for formulating effective policies to mitigate eutrophication in mariculture bays.展开更多
Using the occurrence characteristics of bubble plumes in the South China Sea as a reference, this paper continues to study the seismic responses produced by bubble plumes in the cold seepage active region. To make the...Using the occurrence characteristics of bubble plumes in the South China Sea as a reference, this paper continues to study the seismic responses produced by bubble plumes in the cold seepage active region. To make the plume modelling scheme more reasonable, we modified the original modelling scheme and reconstructed a plume water body model based on the variation of its radius as bubbles rise in seawater. The plume seismic records of shot gathers were obtained by forward simulation. The seismic records of single shot show obvious characteristics of a scattering wave field and the periodic characteristics of the model. Seismic records of shot gathers were processed using prestack depth migration. The boundary of its imaging section has a good convergence effect. The migration sections can be imaged distinctly with higher accuracy. The aforementioned studies once again laid a foundation for the further study of the seismic responses produced by plumes. They also gradually probed a more suitable seismic data processing method for plumes and provided a theoretical guidance for the identification of plumes.展开更多
Huguangyan Maar Lake is a typical maar lake in the southeast of China. It is well preserved and not disturbed by anthropogenic activities. In this study, microbial community structures in sediment and water samples fr...Huguangyan Maar Lake is a typical maar lake in the southeast of China. It is well preserved and not disturbed by anthropogenic activities. In this study, microbial community structures in sediment and water samples from Huguangyan Maar Lake were investigated using a high-throughput sequencing method. We found significant differences between the microbial community compositions of the water and the sediment. The sediment samples contained more diverse Bacteria and Archaea than did the water samples. Actinobacteria, Betaproteobacteria, Cyanobacteria, and Deltaproteobacteria predominated in the water samples while Deltaproteobacteria, Anaerolineae, Nitrospira, and Dehalococcoidia were the major bacterial groups in the sediment. As for Archaea, Woesearchaeota (DHVEG-6), unclassified Archaea, and Deep Sea Euryarchaeotic Group were detected at higher abundances in the water, whereas the Miscellaneous Crenarchaeotic Group, Thermoplasmata, and Methanomicrobia were significantly more abundant in the sediment. Interactions between Bacteria and Archaea were common in both the water column and the sediment. The concentrations of major nutrients (NO^3-, PO4^3-, SiO3^2- and NH4^+) shaped the microbial population structures in the water. At the higher phylogenetic levels including phylum and class, many of the dominant groups were those that were also abundant in other lakes;however, novel microbial populations (unclassified) were often seen at the lower phylogenetic levels. Our study lays a foundation for examining microbial biogeochemical cycling in sequestered lakes or reservoirs.展开更多
The Canada Basin （CB） is the largest sub-basin in the Arctic, with the deepest abyssal plain of 3 850 m. The double-diffusive process is the possible passage through which the geothermal energy affects the above iso...The Canada Basin （CB） is the largest sub-basin in the Arctic, with the deepest abyssal plain of 3 850 m. The double-diffusive process is the possible passage through which the geothermal energy affects the above isolated deep waters. With the temperature-salinity-pressure observations in 2003, 500-m-thick transition layers and lower 1 000-m-thick bottom homogenous layers were found below 2 400 m in the central deep CB. Staircases with downward-increasing temperature and salinity are prominent in the transition layers, suggesting the double- diffusive convection in deep CB. The interface of the stairs is about 10 m thick with 0.001-0.002℃ temperature difference, while the thicknesses of the homogenous layers in the steps decrease upward from about 60 to 20 m. The density ratio in the deep central CB is generally smaller than 2, indicating stronger double-diffusive convection than that in the upper ocean of 200-400 m. The heat flux through the deepest staircases in the deep CB varies between 0.014 and 0.031 W/m2, which is one-two orders smaller than the upper double-diffusive heat flux, but comparable to the estimates of geothermal heat flux.展开更多
Effects of currents on winter wind waves in the tide-dominated Qiongzhou Strait(QS)were numerically evaluated via employing the coupled ocean-atmosphere-wave-sediment transport(COAWST)modeling system.Validations showe...Effects of currents on winter wind waves in the tide-dominated Qiongzhou Strait(QS)were numerically evaluated via employing the coupled ocean-atmosphere-wave-sediment transport(COAWST)modeling system.Validations showed satisfactory model performance in simulating the intense tidal currents in the QS.Different effects of sea level variations and tidal currents on waves were examined under the maximum eastward(METC)and westward(MWTC)tidal currents.In the east entrance area of the QS,the positive sea levels under the MWTC deepened the water depth felt by waves,benefiting the further propagation of wave energy into the inner strait and causing increased wave height.The METC and the MWTC could both enhance the wave height in the east entrance area of the QS,mainly through current-induced convergence and wavenumber shift,respectively.By current-induced refraction,the METC(MWTC)triggered counterclockwise(clockwise)rotation in peak wave directions in the northern part of the QS while clockwise(counterclockwise)rotation in the southern part.展开更多
From November 24 to 26, 2014, a red tide event occurred in the offshore water off the Hailing Island located at the western Guangdong coast. The red tide appeared as pink strips distributed within 3 km in the offshore...From November 24 to 26, 2014, a red tide event occurred in the offshore water off the Hailing Island located at the western Guangdong coast. The red tide appeared as pink strips distributed within 3 km in the offshore water and extended for about 10 km along the shoreline. During the flood tide, the pink seawater rushed to the beach with breaking waves, forming foam strips on the beach. Guangdong Province Key Laboratory for Coastal Ocean Variation and Disaster Prediction Technologies, Guangdong Ocean University, emergently responded to the event and organized three-dimensional observations from the air, onboard and on beach. The preliminary analyses of the cruise data and water samples indicate that the event was induced by non- toxic Noctiluca scintillans, of which the concentration reaches as high as 4 200 cells/L near the surface and 2600 cells/L at the bottom.展开更多
Fungi outperformed bacterial in maintaining the microbial co-occurrence networks.Fungi showed different elevational network co-occurrence pattern from bacteria.Distinct biotic/abiotic factors influenced bacterial and ...Fungi outperformed bacterial in maintaining the microbial co-occurrence networks.Fungi showed different elevational network co-occurrence pattern from bacteria.Distinct biotic/abiotic factors influenced bacterial and fungal network dynamics.The interplay between soil micro-organisms in mountain ecosystems critically influences soil biogeochemical cycles and ecosystem processes.However,factors affecting the co-occurrence patterns of soil microbial communities remain unclear.In an attempt to understand how these patterns shift with elevation and identify the key explanatory factors underpinning these changes,we studied soil bacterial and fungal co-occurrence networks on Mt.Seorak,Republic of Korea.Amplicon sequencing was used to target the 16S rRNA gene and ITS2 region for bacteria and fungi,respectively.In contrast to bacteria,we found that fungi were predominantly situated in the core positions of the network,with significantly weakened co-occurrence with increasing elevation.The different co-occurrence patterns of fungal and bacterial communities could be resulted from their distinct responses to various environments.Both abiotic and biotic factors contributed significantly to shaping co-occurrence networks of bacterial and fungal communities.Fungal richness,bacterial community composition(indicated by PCoA1),and soil pH were the predominant factors influencing the variation in the entire microbial co-occurrence network.Biotic factors,such as the composition and diversity of bacterial communities,significantly influenced bacterial co-occurrence networks.External biotic and abiotic factors,including climatic and vegetative conditions,had a significant influence on fungal co-occurrence networks.These findings enhance our understanding of soil microbiota co-occurrences and deepen our knowledge of soil microbiota responses to climatic changes across elevational gradients in mountain ecosystems.展开更多
To investigate the relationship between the alkenone unsaturation index(U^(K′)_(37)) and sea surface temperature(SST) in coastal and continental shelf waters, 58 surface sediment samples were collected from the South...To investigate the relationship between the alkenone unsaturation index(U^(K′)_(37)) and sea surface temperature(SST) in coastal and continental shelf waters, 58 surface sediment samples were collected from the South China Sea(SCS), Taiwan Strait,and East China Sea(ECS). We combined the new results with the previously published 71 data points from the SCS, the shallow water areas of the Yellow Sea(YS) and northern ECS, to form a dataset with sample sites spanning across 6°N and 37°N(including annual SST calibration between 14.3℃ and 28.6℃). With this dataset, we examined the U^(K′)_(37)-SST relationship based on 129 samples from the Western North Pacific(WNP) margin as well as using 85 samples from specific WNP shallow water.The U^(K′)_(37)index from the low-mid latitudinal WNP margin demonstrated a good correlation with the surface annual mean SST(0–50 m water depth;R^(2)=0.89). The slope of linear regression(U^(K′)_(37)-SST) based on the coastal-continental shelf samples with water depth less than 200 m is similar to that of the published global open ocean regression equation. These results confirm that U^(K′)_(37)can be used as a shallow sea water SST proxy in mid-low latitudes of the WNP marginal seas. In addition, our reintegrated U^(K′)_(37)-SST results based on 172 global shallow water samples are similar(similar slopes and intercepts) to the shallow ocean results in the WNP marginal seas. However, the similarity of the regression formula to the open ocean does not imply that the formula is applicable. For example, of the 85 data in the shallow waters from the marginal sea in this study, the majority of data points lie above the regression line, showing positive residuals for U^(K′)_(37). This regression bias appears to be caused by specific marine environments, such as warm ocean currents and/or high nutrient conditions that result in positive U^(K′)_(37)residuals. Taken together,considering the specific temperature and environmental factors in the shallow waters of the low-mid-latitude WNP margin, we propose a nonlinear U^(K′)_(37)-SST regression formula: U^(K′)_(37)=-1.2488+0.1740×SST-0.0035×(SST)2, R2=0.93, N=85, specifically for the environments with SST below 24℃.展开更多
基金The Science and Technology Project of Guangdong Province under contract No.2014A010103030the Postdoctoral Science Foundation of Zhejiang under contract No.BSH1301015the Supported by Foundation for Distinguished Young Talents in Higher Education of Guangdong Province No.GDOU2013050233
文摘Using remote sensing technology for water quality evaluation is an inevitable trend in marine environmental monitoring. However, fewer categories of water quality parameters can be monitored by remote sensing technology than the 35 specified in GB3097-1997 Marine Water Quality Standard. Therefore, we considered which parameters must be selected by remote sensing and how to model for water quality evaluation using the finite parameters. In this paper, focused on Leizhou Peninsula nearshore waters, we found N, P, COD, PH and DO to be the dominant parameters of water quality by analyzing measured data. Then, mathematical statistics was used to determine that the relationship among the five parameters was COD〉DO〉P〉N〉pH. Finally, five-parameter, fourparameter and three-parameter water quality evaluation models were established and compared. The results showed that COD, DO, P and N were the necessary parameters for remote sensing evaluation of the Leizhou Peninsula nearshore water quality, and the optimal comprehensive water quality evaluation model was the four- parameter model. This work may serve as a reference for monitoring the quality of other marine waters by remote sensing.
基金The National Natural Science Foundation of China under contract No.42276047the Guangdong Basic and Applied Basic Research Foundation under contract Nos 2023A1515110473 and 2021A1515110172+1 种基金the Program for Scientific Research Start-up Funds of Guangdong Ocean University under contract No.R17058the National College Student Innovation and Entrepreneurship Training Program Project under contract No.202310566007。
文摘Zhanjiang Bay is a major aquaculture area in China with many types of mariculture products(such as oysters,fish,and shrimp).The culture area and shrimp output in Zhanjiang Bay are ranked first in China.We investigated the total organic carbon(TOC),total nitrogen(TN),TOC/TN ratio,and stable isotopes(δ^(13)C and δ^(15)N) of the fish and shrimp feed,fish and shrimp feces,and sedimentary organic matter(SOM) in and around different aquaculture areas of northeastern Zhanjiang B ay to study the impact of aquaculture activities on SOM.The average TOC contents of fish and shrimp feed were 39.20%±0.91% and 39.29%±0.21%,respectively.The average TOC content in the surface sediments of the oyster culture area,the mixed(fish and shrimp) culture area,and the cage fish farm area were 0.66%,0.88%±0.10%,and 0.58%±0.19%,respectively,which may indicate that mixed culture had a greater impact on SOM.The relatively high TOC and TN contents and relatively low TOC/TN ratios,and δ^(15)N values in the upper layer of the core sediment in the mixed culture area could also support the significant influence of mixed culture.The average δ^(13)C and δ^(15)N values of fish and shrimp feed were -20.6‰±2.2‰ and 1.8‰±1.2‰,respectively,which were different from the isotopic values of SOM in the study area.δ^(13)C and δ^(15)N values for SOM in different aquaculture areas were different from those of nearby reference stations,probably reflecting the influence of aquaculture.The δ^(13)C and δ^(15)N values in the oyster culture area(-25.9‰ and6.0‰,respectively) seemed to have reduced δ^(13)C and enriched δ^(15)N relative to those of the reference station(-24.6‰ and 5.8‰,respectively).This may reflect the influence of organic matter on oyster culture.The δ^(15)N value of the station in the mixed culture area(7.1‰±0.4‰) seemed to be relatively enriched in δ^(15)N relative to that of the reference station(6.6‰).Sedimentation and the subsequent degradation of organic matter from mixed cultures may have contributed to this phenomenon.The surface sediment at the cage fish farm area seemed to be affected by fish feces and primary production based on the indication of δ^(13)C and δ^(15)N values.The sediment core at the mixed culture region(NS6) had lower TOC/TN ratios and more positive δ^(13)C and δ^(15)N values than the sediment core at the oyster culture area,suggesting a higher proportionate contribution of marine organic matter in the mixed culture area.In summary,oyster culture,mixed culture,and cage fish culture in northeastern Zhanjiang Bay had a certain degree of impact on SOM,and mixed culture had more significant influences on SOM based on the high TOC contents and the significant vertical variations of TOC/TN ratio and δ^(15)N value in the sediment of this area.This study provides new insights into the impact of aquaculture activities on SOM content.
基金funded by the Guangdong Natural Science Foundation[grant number 2015A030313796]the National Natural Science Foundation of China[grant numbers 41205026,41476009,41476010]+2 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences[grant number Xd A11010104]the National Program on Global Change and Air-Sea interaction[grant number GASi-i POVAi-04]the Knowledge innovation Program of the Chinese Academy of Sciences[grant number SQ201208]
文摘Recent studies have revealed that two boreal spring sea surface temperature （SST） indices have potential to predict the number of western North Pacific （WNP） tropical cyclones （TCs） in the following peak typhoon season （June-October）： the northern tropical Atlantic （NTA） SST, and the SST gradient （SSTG） between the southwestern Pacific and western Pacic warm pool. The interannua[ and interdecadal variations of NTA SST and SSTG and their relationships to the number ofWNP TCs during 1950-2013 were compared. On the interdecadal timescale, SSTG showed better correlation with the number of WNP TCs than NTA SST. The interdecadal variation of NTA SST was closely associated with the Atlantic Multidecadal Oscillation, while that of SSTG was anti-correlated with the Central Pacific （CP） El Nino index at the interdecadal timescale. On the interannual timescale, both NTA SST and SSTG were modulated by two types of El Nino. The NTA SST revealed significant correlations with the number of WNPTCs beginning from the early 1960s; by contrast, SSTG showed significant correlations after the mid-1970s. Co-variability of NTA SST and SSTG existed after the late 1980s, induced by modulation from CP El Nino.The co-variability of these two spring SST predictors increased their prediction skill after the late 1980s, with enhanced correlation between the number of WNPTCs and the two predictors.
基金supported by the National Key Research and Development Program of China [grant number2018YFC1506903]the National Natural Science Foundation of China [grant number 41776031]+2 种基金the Guangdong Natural Science Foundation [grant number 2015A030313796]the program for scientific research start-up funds of Guangdong Ocean Universitythe Foundation for Returned Scholars of the Ministry of Education of China
文摘The correlation between summertime Nino3.4 index and western North Pacific(WNP)summer monsoon index has strikingly enhanced since the early 1990 s,with nonsignificant correlation before the early1990 s but significant correlation afterward.This observed interdecadal change around the 1990 s may be associated with more frequent occurrences of central Pacific(CP)El Nino and the interdecadal changes in ENSO-associated SST anomalies.During the post-1990 s period(the pre-1990 s period),highly noticeable tropical Atlantic(Indian)Ocean SST anomalies tend to co-occur with the summertime Nino3.4 SST anomalies.The concurrent tropical Atlantic(Indian)Ocean SST anomalies could constructively reinforce(destructively mitigate)the WNP monsoon circulation anomalies induced by the summertime Nino3.4 SST,thus boosting(muting)the correlation between summertime Nino3.4 SST and WNP monsoon.In addition,the faster decaying pace of preceding-winter El Nino after the 1990 s,which may have been mainly induced by the influences from the spring tropical North Atlantic SST anomalies,could also have contributed to the enhanced correlation between the summertime Nino3.4 index and WNP monsoon.These results suggest that the enhanced influences from the tropical Atlantic SST may have triggered the intensified correlation between summertime ENSO and WNP monsoon since the early 1990 s.
基金The Program for Scientific Research Start-up Funds of Guangdong Ocean University under contract No.101302/R18001the Fund of Southern Marine Science and Engineering Guangdong Laboratory(Zhanjiang)under contract No.ZJW-2019-08+1 种基金the National Key Research and Development Program of China under contract No.2016YFC1401403the National Natural Science Foundation of China under contract Nos 41476009 and 41776034
文摘Wave-current interaction and its effects on the hydrodynamic environment in the Beibu Gulf(BG) have been investigated via employing the Coupled Ocean–Atmosphere–Wave–Sediment Transport(COAWST) modeling system. The model could simulate reasonable hydrodynamics in the BG when validated by various observations.Vigorous tidal currents refract the waves efficiently and make the seas off the west coast of Hainan Island be the hot spot where currents modulate the significant wave height dramatically. During summer, wave-enhanced bottom stress could weaken the near-shore component of the gulf-scale cyclonic-circulation in the BG remarkably, inducing two major corresponding adjustments: Model results reveal that the deep-layer cold water from the southern BG makes critical contribution to maintaining the cold-water mass in the northern BG Basin.However, the weakened background circulation leads to less cold water transported from the southern gulf to the northern gulf, which finally triggers a 0.2℃ warming in the cold-water mass area;In the top areas of the BG, the suppressed background circulation reduces the transport of the diluted water to the central gulf. Therefore, more freshwater could be trapped locally, which then triggers lower sea surface salinity(SSS) in the near-field and higher SSS in the far-field.
基金The National Natural Science Foundation of China under contract No.41406041the Natural Science Foundation of Guangdong Province under contract No.2014A030310256+1 种基金the Project of Enhancing School with Innovation of Guangdong Ocean University under contract No.GDOU2016050246the Excellent Young Teachers Program of GDOU under contract No.HDYQ2015010
文摘For acoustic detection of internal waves, the core issue is to obtain the temporal and spatial distribution of the sound speed profile(SSP). In the inversion process, the SSP is usually expressed by a few parameters through expansion. However, information about internal waves may sometimes be hard to read directly from the inversion results. The aim of this paper is to characterize the internal waves directly though expansion coefficients. By deducing the dynamic equations of the internal waves, an orthogonal basis called the hydrodynamic normal modes(HNMs) can be extracted from a certain number of SSP samples. Unlike the existing widely used empirical orthogonal functions(EOFs), the HNMs have a more explicit physical meaning that is directly related to internal wave activity. The HNMs are then used to expand the SSP time series, and the expansion coefficients are derived.Eventually, information about internal waves can be read directly from the time derivative of the expansion coefficients of the first two modes. In this study, this method is applied to thermistor string profiles from the northern shelf of the South China Sea, where the SSP shows evident spatial and temporal variations due to internal waves. The results show that the SSP can be described approximately by the first two modes with adequate precision. The special oscillation structure of the time derivative of the expansion coefficients can be used to detect internal solitary waves. The expansion coefficients can also give information on internal solitary wave amplitude and width. According to theoretical and experimental analysis, it can be concluded that the internal waves monitoring method introduced in this paper is effective. The HNMs method is simple to apply and depends less on sample data than EOFs. It could be used as an efficient alternative to EOFs to expand the use of the SSP in highly variable areas, where internal waves are intensive.
基金funded by the Guangdong Natural Science Foundation (No.2015A030313796)the National Natural Science Foundation of China (No.41205026)+2 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences (No.XDA11010104)the Knowledge Innovation Program of Chinese Academy of Sciences (SQ201208)the foundation for returned scholars of Ministry of Education of China and the research fund for the doctoral program of Higher Education for Youths
文摘Analyses of the Tropical Rainfall Measuring Mission （TRMM） datasets revealed a prominent interannual variation in the convective-stratiform rainfall and latent heating over the southern South China Sea （SCS） during the winter monsoon between 1998 and 2010. Although the height of maximum latent heating remained nearly constant at around 7km in all of the years, the year-to- year changes in the magnitudes of maximum latent heating over the region were noticeable. The interannual variations of the convee- tive-stratiform rainfall and latent heating over the southern SCS were highly anti-correlated with the Nifio-3 index, with more （less） rainfall and latent heating during La Nifia （El Nifio） years. Analysis of the large-scale environment revealed that years of active rain- fall and latent heating corresponded to years of large deep convergence and relative humidity at 600hPa. The moisture budget diag- nosis indicated that the interarmual variation of humidity at 600hPa was largely modulated by the vertical moisture advection. The year-to-year changes in rainfall over the southern SCS were mainly caused by the interannual variations of the dynamic component associated with anomalous upward motions in the middle troposphere, while the interannual variations of the thermodynamic com- ponent associated with changes in surface specific humidity played a minor role. Larger latent heating over the southern SCS during La Nifia years may possibly further enhance the local Hadley circulation over the SCS in the wintertime.
基金funded by the National Natural Science Foundation of China[grant number 41776031]the Guangdong Natural Science Foundation[grant number 2015A030313796]+3 种基金the National Program on Global Change and Air-Sea Interaction[grant number GASI-IPOVAI-04]the Strategic Priority Research Program of the Chinese Academy of Sciences[grant number XDA11010104]the program for scientific research start-upfunds of Guangdong Ocean Universitythe Foundation for Returned Scholars of the Ministry of Education of China
文摘There is a rainfall variability biennial relationship between Central America （CA） and equatorial South America （ESA） over the tropical western hemisphere, which is known to have arisen due to the combined effects of ENSO and tropical North Atlantic （TNA） SST. Here, the authors report that this biennial rainfall relationship between CA and ESA has weakened remarkably since 2000, with weakening in both in-phase and out-of-phase rainfall transitions. The observed decadal changes in the biennial relationship between CA and ESA rainfall can be attributed to changes in the effects of ENSO and TNA SST since 2000, which may be associated with more frequent occurrences of the central Pacific or＇Modoki＇ type El Ni^o. The weakening of the association with ENSO for CA rainfall since 2000 might have given rise to the weakening of the in-phase rain transition from CA rainfall to the following ESA rainfall. The weakened linkage between boreal-winter ESA rainfall and the subsequent boreal-summer TNA SST since 2000 may have resulted in the weakening of the out- of-phase rainfall transition from boreal-winter ESA rainfall to the subsequent boreal-summer CA rainfall.
基金funded by the Guangdong Natural Science Foundation[grant numbers 2015A0303137962016A030310015+7 种基金2016A030312004]the National Natural Science Foundation of China[grant numbers 412050264147601041676008]the Strategic Priority Research Program of the Chinese Academy of Sciences[grant number XDA11010104]the National Program on Global Change and Air–Sea Interaction[grant number GASI-IPOVAI-04]the Foundation for Returned Scholars of the Ministry of Education of Chinathe Foundation for Visiting Scholars from the China Scholarship Council[grant number20153012]
文摘Recent studies suggest that the interannual variability in the tropical Pacific associated with the El Nino-Southern Oscillation has weakened since 2000. In this study, the authors report that the interannual variability of the contrast in rainfall between the eastern equatorial Pacific and equatorial Atlantic has also weakened remarkably since 2000, attributable to the weakened interannual variability in the zonal sea surface temperature gradient between the eastern equatorial Pacific and equatorial Atlantic and in the associated equatorial low-level zonal wind across South America linking the two ocean basins. Diagnosis of a column-integrated moisture budget indicates that the weakening in the interannual variability of the contrast in rainfall is primarily attributable to the changes in moisture convergence associated with vertical motion. The results highlight the clear weakened interannual variability in the coupled equatorial Pacific-Atlantic climate system since 2000, including the Pacific El Nino, Atlantic Nino, equatorial zonal wind across South America, and rainfall over the eastern equatorial Pacific and equatorial Atlantic.
基金the National Natural Science Foundation of China (No. 41306053)the Open Fund of the Key Laboratory of Marine Geology and Environment, Chinese Academy of Sciences (Nos. MGE 2015KG04 and MGE2015KG01)+2 种基金the Open Fund of the Key Laboratory of Submarine Geosciences, State Oceanic Administration, People’s Republic of China (No. KSLG 1503)the Special Fund for the Taishan Scholar Program of Shandong Province (No. ts201511061)The authors would like to thank the crews of the COMRA cruises (DY115-22 and DY115-26)
文摘Sediment samples obtained from the South Mid-Atlantic Ridge were analyzed for the major and trace elements by inductively coupled plasma atomic emission spectroscopy and inductively coupled plasma mass spectrometry. Results revealed that the contents of elements(e.g., Fe, Mn, Cu, Zn, V, Co) were high in samples 22V-TVG10 and 26V-TVG05 from the sites near the hydrothermal areas, and low in sample 22V-TVG14, which was collected far from the hydrothermal areas. The contents of Ca, Sr and Ba in the samples showed opposite trends. A positive correlation between the concentrations of metallic elements(Cu, Zn, Co, Ni, Pb, V) and Fe in the samples were observed. These results are consistent with chemical evolution of the dispersing hydrothermal plume.
基金The Program for Scientific Research Start-up Funds of Guangdong Ocean University under contract No.101302/R18001the National Key Research and Development Program of China under contract No.2016YFC1401403the National Natural Science Foundation of China under contract Nos 41476009 and 41776034
文摘The coupled ocean atmosphere wave sediment transport(COAWST)modeling system is employed to investigate the role of wave-mixing playing in the upwelling off the west coast of Hainan Island(WHU).Waves,tides and sea surface temperature(SST)are reproduced reasonably well by the model when validated by observations.Model results suggest the WHU is tidally driven.Further investigations indicate that inclusion of wave-mixing promotes the intensity of the WHU,making the simulated SST become more consistent with remote-sensed ones.Dynamically,wave-mixing facilitates the“outcrop”of more upwelled cold water,triggering stronger WHU and leading to a three-dimensional dynamical adjustment.From the perspective of time,wave-mixing contributes to establishing an earlier tidal mixing front strong enough to generate WHU and that is,WHU may occur earlier when taking wave-mixing into consideration.
基金The National Natural Science Foundation of China under contract Nos 42276047, 92158201 and U1901213the Entrepreneurship Project of Shantou under contract No.2021112176541391the Scientific Research Start-Up Foundation of Shantou University under contract No.NTF20006。
文摘Highly productive estuaries facilitate intense decomposition of dissolved organic matter(DOM) as a carbon source.However,the specific impacts of typhoons on DOM decomposition in eutrophic bays remain unclear.To address this issue,we investigated the spectral characteristics of DOM before and after Typhoon Ewiniar in Zhanjiang B ay,a eutrophic semi-enclosed bay in the northwestern South China Sea.The results revealed that intense microbial decomposition of DOM occurred during the pre-typhoon period because high nutrient inputs facilitated the mobilization of DOM in the bay.However,the intrusion of external seawater induced by the typhoon diluted the nutrient levels in Zhanjiang B ay,reducing the impact of microbial decomposition on DOM during the post-typhoon perio d.Nevertheless,the net addition of DOM occurred in Zhanjiang Bay during the post-typhoon period,possibly because of the decomposition of particulate organic matter(POM) and desorption of particulate matter.In addition,an increase in apparent oxygen utilization,a decrease in DO saturation and the reduced level of Chl a indicated that organic matter(OM) decomposition was enhanced and OM decomposition shifted to POM decomposition in Zhanjiang Bay after the typhoon.Overall,our study highlighted the shift in the intense OM decomposition from DOM to POM decomposition before and after typhoons in eutrophic bays,providing new insights into the response of typhoons to biogeo chemistry.
基金The National Natural Science Foundation of China under contract Nos 42276047, 92158201 and U1901213the Entrepreneurship Project of Shantou under contract No.2021112176541391the Scientific Research Start-Up Foundation of Shantou University under contract No.NTF20006。
文摘Eutrophication in coastal waters has been increasing remarkably,severely impacting the water quality in mariculture bays.In this study,we conducted multiple isotopic measurements on suspended particulate nitrogen(δ^(15)N-PN) and dissolved nitrate(δ^(15)N-NO_(3)^(-)and δ^(18)O-NO_(3)^(-)) in Zhanjiang Bay,a typical mariculture bay with a high level of eutrophication in South China,to investigate the changes in nitrogen sources and their cycling between the rainy and dry seasons.During the rainy season,the study found no significant relation between δ^(15)NPN and δ^(15)N-NO_(3)^(-)due to the impact of heavy rainfall and terrestrial erosion.In the upper bay,a slight nitrate loss and slightly higher δ_(15)N-NO_(3)^(-)and δ^(18)O-NO_(3)^(-)values were observed,attributed to intense physical sedimentwater interactions.Despite some fluctuations,nitrate concentrations in the lower bay mainly aligned with the theoretical mixing line during the rainy season,suggesting that nitrate was primarily influenced by terrestrial erosion and that nitrate isotopes resembled the source.Consequently,the isotopic values of nitrate can be used for source apportionment in the rainy season.The results indicated that soil nitrogen(36%) and manure and sewage(33%) were the predominant nitrogen sources contributing to nitrogen loads during this period.In contrast,the dry season saw a deficient ammonium concentration(<0.2 μmol/L) in the bay,due to nearly complete consumption by phytoplankton during the red tide period.Additionally,the significant loss of nitrate and simultaneous increase in the stable isotopes of dissolved and particulate nitrogen suggest a strong coupling of assimilation and mineralization during the dry season.More active biogeochemical processes during the dry season may be related to decreased runoff and increased water retention time.Overall,our study illustrated the major seasonal nitrogen sources and their dynamics in Zhanjiang B ay,providing valuable insights for formulating effective policies to mitigate eutrophication in mariculture bays.
基金The National Natural Science Foundation under contract No.41306050the Science and Technology Project of Guangdong Province under contract No.2014A010103030+1 种基金the Natural Science Foundation of Guangdong Province under contract No.2015A030313617the National Marine Important Charity Special Foundation under contract No.201305019
文摘Using the occurrence characteristics of bubble plumes in the South China Sea as a reference, this paper continues to study the seismic responses produced by bubble plumes in the cold seepage active region. To make the plume modelling scheme more reasonable, we modified the original modelling scheme and reconstructed a plume water body model based on the variation of its radius as bubbles rise in seawater. The plume seismic records of shot gathers were obtained by forward simulation. The seismic records of single shot show obvious characteristics of a scattering wave field and the periodic characteristics of the model. Seismic records of shot gathers were processed using prestack depth migration. The boundary of its imaging section has a good convergence effect. The migration sections can be imaged distinctly with higher accuracy. The aforementioned studies once again laid a foundation for the further study of the seismic responses produced by plumes. They also gradually probed a more suitable seismic data processing method for plumes and provided a theoretical guidance for the identification of plumes.
基金Supported by the National Natural Science Foundation of China(Nos.41576123,41706129)the Guangdong Natural Science Foundation(Nos.2015A030313326,2016A030312004)+2 种基金the International Science and Technology Cooperation Project(No.GASI-IPOVI-04)the Project of Enhancing School with Innovation of Guangdong Ocean University(No.GDOU2016050243)the Program for Scientific Research Start-Up Funds of Guangdong Ocean University(No.E15030)
文摘Huguangyan Maar Lake is a typical maar lake in the southeast of China. It is well preserved and not disturbed by anthropogenic activities. In this study, microbial community structures in sediment and water samples from Huguangyan Maar Lake were investigated using a high-throughput sequencing method. We found significant differences between the microbial community compositions of the water and the sediment. The sediment samples contained more diverse Bacteria and Archaea than did the water samples. Actinobacteria, Betaproteobacteria, Cyanobacteria, and Deltaproteobacteria predominated in the water samples while Deltaproteobacteria, Anaerolineae, Nitrospira, and Dehalococcoidia were the major bacterial groups in the sediment. As for Archaea, Woesearchaeota (DHVEG-6), unclassified Archaea, and Deep Sea Euryarchaeotic Group were detected at higher abundances in the water, whereas the Miscellaneous Crenarchaeotic Group, Thermoplasmata, and Methanomicrobia were significantly more abundant in the sediment. Interactions between Bacteria and Archaea were common in both the water column and the sediment. The concentrations of major nutrients (NO^3-, PO4^3-, SiO3^2- and NH4^+) shaped the microbial population structures in the water. At the higher phylogenetic levels including phylum and class, many of the dominant groups were those that were also abundant in other lakes;however, novel microbial populations (unclassified) were often seen at the lower phylogenetic levels. Our study lays a foundation for examining microbial biogeochemical cycling in sequestered lakes or reservoirs.
基金The National Natural Science Foundation of China under contract Nos 41476009,41106012 and 41506018the Science and Technology Program in Higher Education of Guangdong under contract No.2013KJCX0099
文摘The Canada Basin （CB） is the largest sub-basin in the Arctic, with the deepest abyssal plain of 3 850 m. The double-diffusive process is the possible passage through which the geothermal energy affects the above isolated deep waters. With the temperature-salinity-pressure observations in 2003, 500-m-thick transition layers and lower 1 000-m-thick bottom homogenous layers were found below 2 400 m in the central deep CB. Staircases with downward-increasing temperature and salinity are prominent in the transition layers, suggesting the double- diffusive convection in deep CB. The interface of the stairs is about 10 m thick with 0.001-0.002℃ temperature difference, while the thicknesses of the homogenous layers in the steps decrease upward from about 60 to 20 m. The density ratio in the deep central CB is generally smaller than 2, indicating stronger double-diffusive convection than that in the upper ocean of 200-400 m. The heat flux through the deepest staircases in the deep CB varies between 0.014 and 0.031 W/m2, which is one-two orders smaller than the upper double-diffusive heat flux, but comparable to the estimates of geothermal heat flux.
基金The Fund of Southern Marine Science and Engineering Guangdong Laboratory(Zhanjiang)under contract No.ZJW-2019-08the Program for Scientific Research Start-up Funds of Guangdong Ocean University under contract No.101302/R18001+1 种基金the National Natural Science Foundation of China under contract No.41776034the First-class Discipline Plan of Guangdong Province under contract No.CYL231419012。
文摘Effects of currents on winter wind waves in the tide-dominated Qiongzhou Strait(QS)were numerically evaluated via employing the coupled ocean-atmosphere-wave-sediment transport(COAWST)modeling system.Validations showed satisfactory model performance in simulating the intense tidal currents in the QS.Different effects of sea level variations and tidal currents on waves were examined under the maximum eastward(METC)and westward(MWTC)tidal currents.In the east entrance area of the QS,the positive sea levels under the MWTC deepened the water depth felt by waves,benefiting the further propagation of wave energy into the inner strait and causing increased wave height.The METC and the MWTC could both enhance the wave height in the east entrance area of the QS,mainly through current-induced convergence and wavenumber shift,respectively.By current-induced refraction,the METC(MWTC)triggered counterclockwise(clockwise)rotation in peak wave directions in the northern part of the QS while clockwise(counterclockwise)rotation in the southern part.
基金the National Natural Science Foundation of China under contract Nos 41106012,41476009,41276006,41476010 and 41476011
文摘From November 24 to 26, 2014, a red tide event occurred in the offshore water off the Hailing Island located at the western Guangdong coast. The red tide appeared as pink strips distributed within 3 km in the offshore water and extended for about 10 km along the shoreline. During the flood tide, the pink seawater rushed to the beach with breaking waves, forming foam strips on the beach. Guangdong Province Key Laboratory for Coastal Ocean Variation and Disaster Prediction Technologies, Guangdong Ocean University, emergently responded to the event and organized three-dimensional observations from the air, onboard and on beach. The preliminary analyses of the cruise data and water samples indicate that the event was induced by non- toxic Noctiluca scintillans, of which the concentration reaches as high as 4 200 cells/L near the surface and 2600 cells/L at the bottom.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korea Government(MSIP)(Grant Nos.NRF-2018R1C1B6007755 and NRF-2022R1F1A1066643)supported by a grant(No.20SCIP-C158976-01)from Construction Technology Research Program funded by Ministry of Land,Infrastructure and Transport of Korean Government+2 种基金the Guangxi Natural Science Foundation(Grant No.2018GXNSFDA281006)the National Natural Science Foundation of China(Grant No.41966005)the‘One Hundred Talents’Project of Guangxi(Grant No.6020303891251).
文摘Fungi outperformed bacterial in maintaining the microbial co-occurrence networks.Fungi showed different elevational network co-occurrence pattern from bacteria.Distinct biotic/abiotic factors influenced bacterial and fungal network dynamics.The interplay between soil micro-organisms in mountain ecosystems critically influences soil biogeochemical cycles and ecosystem processes.However,factors affecting the co-occurrence patterns of soil microbial communities remain unclear.In an attempt to understand how these patterns shift with elevation and identify the key explanatory factors underpinning these changes,we studied soil bacterial and fungal co-occurrence networks on Mt.Seorak,Republic of Korea.Amplicon sequencing was used to target the 16S rRNA gene and ITS2 region for bacteria and fungi,respectively.In contrast to bacteria,we found that fungi were predominantly situated in the core positions of the network,with significantly weakened co-occurrence with increasing elevation.The different co-occurrence patterns of fungal and bacterial communities could be resulted from their distinct responses to various environments.Both abiotic and biotic factors contributed significantly to shaping co-occurrence networks of bacterial and fungal communities.Fungal richness,bacterial community composition(indicated by PCoA1),and soil pH were the predominant factors influencing the variation in the entire microbial co-occurrence network.Biotic factors,such as the composition and diversity of bacterial communities,significantly influenced bacterial co-occurrence networks.External biotic and abiotic factors,including climatic and vegetative conditions,had a significant influence on fungal co-occurrence networks.These findings enhance our understanding of soil microbiota co-occurrences and deepen our knowledge of soil microbiota responses to climatic changes across elevational gradients in mountain ecosystems.
基金supported by the Guangzhou Science and Technology Plan Project(Grant No.202102080366)the Guangdong Academy of Sciences(Grant No.2016GDASRC-0209)+1 种基金the Research Grant Council of Hong Kong(Grant No.HKU17311816)the National Natural Science Foundation of China(Grant Nos.42106062,41706039&41606070)。
文摘To investigate the relationship between the alkenone unsaturation index(U^(K′)_(37)) and sea surface temperature(SST) in coastal and continental shelf waters, 58 surface sediment samples were collected from the South China Sea(SCS), Taiwan Strait,and East China Sea(ECS). We combined the new results with the previously published 71 data points from the SCS, the shallow water areas of the Yellow Sea(YS) and northern ECS, to form a dataset with sample sites spanning across 6°N and 37°N(including annual SST calibration between 14.3℃ and 28.6℃). With this dataset, we examined the U^(K′)_(37)-SST relationship based on 129 samples from the Western North Pacific(WNP) margin as well as using 85 samples from specific WNP shallow water.The U^(K′)_(37)index from the low-mid latitudinal WNP margin demonstrated a good correlation with the surface annual mean SST(0–50 m water depth;R^(2)=0.89). The slope of linear regression(U^(K′)_(37)-SST) based on the coastal-continental shelf samples with water depth less than 200 m is similar to that of the published global open ocean regression equation. These results confirm that U^(K′)_(37)can be used as a shallow sea water SST proxy in mid-low latitudes of the WNP marginal seas. In addition, our reintegrated U^(K′)_(37)-SST results based on 172 global shallow water samples are similar(similar slopes and intercepts) to the shallow ocean results in the WNP marginal seas. However, the similarity of the regression formula to the open ocean does not imply that the formula is applicable. For example, of the 85 data in the shallow waters from the marginal sea in this study, the majority of data points lie above the regression line, showing positive residuals for U^(K′)_(37). This regression bias appears to be caused by specific marine environments, such as warm ocean currents and/or high nutrient conditions that result in positive U^(K′)_(37)residuals. Taken together,considering the specific temperature and environmental factors in the shallow waters of the low-mid-latitude WNP margin, we propose a nonlinear U^(K′)_(37)-SST regression formula: U^(K′)_(37)=-1.2488+0.1740×SST-0.0035×(SST)2, R2=0.93, N=85, specifically for the environments with SST below 24℃.
