Sedimentary systems of the Oligocene Huagang Formation in the central anticline zone of the Xihu Depression,East China Sea Shelf Basin

The Xihu Depression is the largest hydrocarbon-bearing depression of the East China Sea Shelf Basin(also referred to as the ECSSB).However,the depositional systems and reservoir distribution of the Oligocene Huagang Formation in the Xihu Depression are still controversial.Under the guidance of sedimentology and stratigraphy,this study documented a marine-terrestrial transitional environment in the restricted bay setting of the Oligocene Huagang Formation through core description,well logging,and seismic data analysis.This study also revealed that the Oligocene Huagang Formation is dominated by tidal delta,estuary,and gravity flow deposits in the central anticline zone of the Xihu Depression.The new understanding of the sedimentary systems and the discovery of the transgressive gap in the eastern Diaoyu Islands uplift explain the origin of fine-grained sediments and the EW-trending sand bodies in the central depression and the sand bodies parallel to shoreline in the west slope belt,which cannot be explained by previous study results,such as southern transgression or fluvial deltas and even lacustrine deposition.Moreover,the tidal channels,tidal sand flats,and gravity flow sand bodies formed by the transgressive tides are high-quality reservoirs.The study will provide a basis for well placement and serve as guidance for the selection of favorable hydrocarbon exploration areas in the Xihu Depression.

Seasonal Variations of Several Main Water Masses in the Southern Yellow Sea and East China Sea in 2011

The seasonal variations of several main water masses in the southern Yellow Sea (SYS) and East China Sea (ECS) in 2011 were analyzed using the in-situ data collected on four cruises.There was something special in the observations for the Yellow Sea Warm Current (YSWC) ,the Yellow Sea Cold Water Mass (YSCWM) and the Changjiang Diluted Water (CDW) during that year.The YSWC was confirmed to be a seasonal current and its source was closely associated with the Kuroshio onshore intrusion and the northerly wind.It was also found that the YSCWM in the summer of 2011 occupied a more extensive area in comparison with the climatologically-mean case due to the abnormally powerful wind prevailing in the winter of 2010 and decaying gradually thereafter.Resulting from the reduced Changjiang River discharge,the CDW spreading toward the Cheju Island in the summer of 2011 was weaker than the long-term mean and was confined to flow southward in the other seasons.The other water masses seemed normal without noticeable anomalies in 2011.The Yellow Sea Coastal Current (YSCC) water,driven by the northerly wind,flowed southeastward as a whole except for its northeastward surface layer in summer.The Taiwan Warm Current (TWC) was the strongest in summer and the weakest in winter in its northward movement.The Kuroshio water with an enhanced onshore intrusion in autumn was stable in hydrographic features apart from the seasonal variation of its surface layer.

Distributions and sea-to-air fluxes of volatile halocarbons in the southern Yellow Sea and the East China Sea

Distributions and sea-to-air fluxes of five kinds of volatile halocarbons（VHCs） were studied in the southern Yellow Sea（SYS） and the East China Sea（ECS） in November 2007. The results showed that the concentrations of 1,1,1-trichloroethane（C2H3Cl3）, 1,1-dichloroethene（C2H2Cl2）, 1,1,2-trichloroethene（C2HCl3）, trichloromethane（CHCl3） and tetrachloromethane（CCl4） in the surface water were 0.31–4.81, 2.75–21.3, 1.21–17.1, 5.02–233 and 0.045–4.47 pmol/L, respectively, with the average values of 1.89, 12.20, 6.93, 60.90 and 0.33 pmol/L. On the whole, the horizontal distributions of C2H3Cl3, C2H2Cl2 and CCl4 were affected mainly by anthropogenic activities, while C2HCl3 and CHCl3 were influenced by biological factors as well as anthropogenic activities. In the study area, the concentrations of VHCs（except C2HCl3） exhibited a decreasing trend from inshore to offshore sites, with the higher values occurring in the coastal waters. The sea-to-air fluxes of C2H3Cl3, C2HCl3, CHCl3 and CCl4 were calculated to be-56.00–（-5.68）,-7.31–123.42, 148.00–1 309.31 and-83.32–（-1.53） nmol/（m2·d）, respectively, with the average values of-6.77, 17.14, 183.38 and-21.27 nmol/（m2·d）. Our data showed that the SYS and ECS in autumn was a sink for C2H3Cl3 and CCl4, while it was a source for C2HCl3 and CHCl3 in the atmosphere.

Variability of the circulation in the southern Huanghai Sea and East China Sea during the two investigative cruises in June 1999

On the basis of the hydrographic data obtained from June 17 to 25, 1999 on board R/V Eardo , Korea (hereafter'the second cruise'), the circulation in the southern Huanghai Sea and East China Sea is computed by using the modified inverse method. The comparison between the two computed results in the first cruise, which was carried out from June 4 to 19, 1999 on board R/V Xiangyanghong 14, China, and in the second cruise is made. The following results have been obtained. (1) Part of the Kuroshio flows northward through the eastern part of Section E, and its volume transport(VT) is about 6.2×106 m3/s,and its maximum velocity is about 93 cm/s.This shows that most of the Kuroshio flows northward through the region east of Section E.The VT of the offshore branch of Taiwan Warm Current west of the Kuroshio through Section E is about 0.4×106 m3/s. (2) There is the following variability between these two cruises, whose time difference is about two weeks:① The position of the Kuroshio in the second cruise is slightly more east than that in the first cruise; ②The high-density water (HDW) with a cold water occurs in the region south of Cheju Island between 125°30' and 127°E at Sections D and C. The circulation in the region of HDW is cyclonic. Comparing the position of HDW during the second cruise with that during the first cruise,it is found that its position in the second cruise moves slightly northward.(3) The cold and uniform mixing layer occurs in the layer from the 30 m level to the bottom of the middle part of Section A and in the layer from the 20 m level to the bottom of the middle part of Section B,respectively.They are both the southern part of the Huanghai Sea Cold Water Mass (HSCWM). (4) There are higher temperature and lower density with a weaker anticyclonic circulation in the southwestern part of the computed region.Its center is located at the westernmost point of Section E.

Linkages between the biomass of Scomber japonicus and net primary production in the southern East China Sea

Fish biomass is a critical component of fishery stock assessment and management and it is often estimated from ocean primary production（OPP）. However, the relationship between the biomass of a fish stock and OPP is always complicated due to a variety of trophic controls in the ecosystem. In this paper, we examine the quantitative relationship between the biomass of chub mackerel（Scomber japonicus） and net primary production（NPP） in the southern East China Sea（SECS）, using catch and effort data from the Chinese mainland large light-purse seine fishery logbook and NPP derived from remote sensing. We further discuss the mechanisms of trophic control in regulating this relationship. The results show a significant non-linear relationship exists between standardized CPUE（Catch-Per-Unit-Effort） and NPP（P〈0.05）. This relationship can be described by a convex parabolic curve, where the biomass of chub mackerel increases with NPP to a maximum and then decreases when the NPP exceeds this point. The results imply that the ecosystem in the SECS is subject to complex trophic controls. We speculate that the change in abundance of key species at intermediate trophic levels and/or interspecific competition might contribute to this complex relationship.

Thermal fronts and cross-frontal heat flux in the southern Huanghai Sea and the East China Sea

Synoptic features in/around thermal fronts and cross-frontal heat fluxes in the southern Huanghai./Yellow Sea and East China Sea （HES） were examined using the data collected from four airborne expendable bathythermograph surveys with horizontal approxmately 35 km and vertical 1 m（from the surface to 400 m deep） spacings. Since the fronts are strongly affected by HES current system, the synoptic thermal features in/around them represent the interaction of currents with surrounding water masses. These features can not be obtained from climatological data. The identified thermal features are listed as follows ： （ 1 ） multiple boundaries of cold water, asymmetric thermocline intrusion, locally-split front by homogeneous water of approxmately 18 ℃, and mergence of the front by the Taiwan Warm Current in/around summertime southern Cheju - Changjiang/Yangtze front and Tsushima front; （2） springtime frontal eddy-like feature around Tsushima front; （3） year-round cyclonic meandering and summertime temperature-inversion at the bottom of the surface mixed layer in Cheju - Tsushima front; and （4） multistructure of Kuroshio front. In the Kuroshio front the mean variance of vertical temperature gradient is an order of degree smaller than that in other HES fronts. The southern Cheju- Changjiang front and Cheju -Tsushima front are connected with each other in the summer with comparable cross-frontal temperature gradient. However, cross-frontal heat flux and lateral eddy diffusivity are stronger in the southern Cheju - Changjiang front. The cross-frontal heat exchange is the largest in the mixing zone between the modified Huanghai Sea bottom cold water and the Tsushima Warm Current, which is attributable to enhanced thermocline intrusions.

The circulation in the southern Huanghai Sea and northern East China Sea in June 1999

On the basis of hydrographic data and current measurement (the mooring system, vessel-mounted ADCP and toward ADCP) data obtained in June 1999, the circulations in the southern Huanghai Sea (HS) and northern East China Sea (ECS) are computed by using the modified inverse method. The Kuroshio flows northeastward through eastern part of the investigated region and has the main core at Section PN, a northward flow at the easternmost part of Section PN, a weaker anti-cyclonic eddy between these two northward flows, and a weak cyclonic eddy at the western part of Section PN. The above current structure is one type of the current structures at Section PN in ECS. The net northward volume transport (VT) of the Kuroshio and the offshore branch of Taiwan Warm Current (TWCOB) through Section PN is about 26.2 x 10(6) m(3)/s in June 1999. The VT of the inshore branch of Taiwan Warm Current (TWCIB) through the investigated region is about 0.4 x 10(6) m(3)/s. The Taiwan Warm Current (TWC) has much effect on the currents over the continental shelf. The Huanghai Sea Coastal Current (HSCC) flows southeastward and enters into the northwestern part of investigated region, and flows to turn cyclonically, and then it flows northeastward, due to the influences of the Taiwan Warm Current and topography. There is a cyclonic eddy south of Cheju Island where the Huanghai Sea Coastal Current flows to turn cyclonically. It has the feature of high dense and cold water. The uniform and cold water is occurred in the layer from about 30 m level to the bottom between Stations C306 and C311 at the northernmost Section C3. It is a southern part of the Huanghai Sea Cold Water Mass (HSCWM).

Distribution of phytoplankton in the East China Sea and the southern Yellow Sea in spring in relation to environmental variables and dimethylsulfide compounds

The coastal ecosystems are highly sensitive to climate change and are usually influenced by variations in phytoplankton communities and water physiochemical factors.In the present study,the phytoplankton community,chlorophyll a(Chl a)and their relationships with environmental variables and dimethylsulfide(DMS)and dimethylsulfoniopropionate(DMSP)were investigated in spring 2017(March 24 to April 16)in the East China Sea(26.0°-33.0°N,120.0°-128.0°E)and southern Yellow Sea(31.0°-36.0°N,120.0°-125.0°E).The spatial distributions of phytoplankton species composition and cell density were investigated by qualitative and quantitative methods and were compared with historical data to study phytoplankton species succession in the survey area.The results showed that there were 275 phytoplankton species belonging to 90 genera and 6 phyla in the survey area,of which 208 species belonged to 62 genera of Bacillariophyta and 56 species belonged to 20 genera of Pyrrophyta.The dominant phytoplankton species were Skeletonema dohrnii,Chaetoceros vanheurckii and Prorocentrum donghaiense.The phytoplankton cell densities ranged from 0.06×10^(4)cells/L to 418.73×10^(4)cells/L,with an average value of 21.46×10^(4)cells/L.In spring,the average ratio of Bacillariophyta/Pyrrophyta was41.13 for the entire study area.The areas with high phytoplankton cell density were mainly distributed in the northern South Yellow Sea and offshore waters of the East China Sea.According to a canonical correspondence analysis among phytoplankton and environmental parameters,the water Chl a concentrations were notably consistent with phytoplankton cell density(P<0.001),and both showed significant negative correlations with salinity and nitrite(P<0.05)and significant positive correlations with dissolved oxygen and pH(P<0.001).There was a significant positive correlation between diatom(both in cell density and in dominant species)and DMS(P<0.05),which indicated that diatoms play a greater role in DMS production in this investigated area.

On the Tectonic Problems of the Southern East China Sea and Adjacent Regions:Evidence from Gravity and Magnetic Data

In this paper, two sets of gravity and magnetic data were used to study the tectonics of the southern East China Sea and Ryukyu trench-arc system： one data set was from the ＇Geological-geophysical map series of China Seas and adjacent areas＇ database and the other was newly collected by R/VKexue Ⅲ in 2011. Magnetic and gravity data were reorganized and processed using the software MMDP, MGDP and RGIS. In addition to the description of the anomaly patterns in different areas, deep and shallow structure studies were performed by using several kinds of calculation, including a spectrum analysis, upward-continuation of the Bouguer anomaly and horizontal derivatives of the total-field magnetic anomaly. The depth of the Moho and magnetic basement were calculated. Based on the above work, several controversial tectonic problems were discussed. Compared to the shelf area and Ryukyu Arc, the Okinawa Trough has an obviously thinned crust, with the thinnest area having thickness less than 14km in the southern part. The Taiwan-Sinzi belt, which terminates to the south by the NW-SE trending Miyako fault belt, contains the relic volcanic arc formed by the splitting of the paleo Ryukyu volcanic arc as a result of the opening of the Okinawa Trough. As an important tectonic boundary, the strike-slip type Miyako fault belt extends northwestward into the shelf area and consists of several discontinuous segments. A forearc terrace composed of an exotic terrane collided with the Ryukyu Arc following the subduction of the Philippine Sea Plate. Mesozoic strata of varying thicknesses exist beneath the Cenozoic strata in the shelf basin and significantly influence the magnetic pattern of this area. The gravity and magnetic data support the existence of a Great East China Sea, which suggests that the entire southern East China Sea shelf area was a basin in the Mesozoic without alternatively arranged uplifts and depressions, and might have extended southwestward and connected with the northern South China Sea shelf basin.

Reanalysis of the Atmospheric Flux of Nutrient Elements to the Southern Yellow Sea and the East China Sea

Based on the recent research results on dry and wet deposition of nutrient elements and sulphate, we estimate the atmospheric flux of nutrient elements and sulphate to the southern Yellow Sea and the East China Sea in each season. The results suggest that the concentrations of nutrient elements and sulphate in aerosol and precipitation show an apparent seasonal cycle with the maximum values in winter and the minimum values in summer. Depositions of nitrate and sulphate are dominated by wet deposition, while the deposition for phosphate is mainly dry deposition. Moreover, compared with the riverine inputs, the atmospheric deposition may be the main source of dissolved inorganic nutrients in the southern Yellow Sea and the East China Sea.

The Mesozoic Basin-Mountain Coupling Process of the Southern East China Sea Shelf Basin and its Adjacent Land Area

Basin-mountain coupling is a key issue for basin formation and evolution. The analysis of basin-mountain coupling process, as well as quantitative or semiquantitative restoration of prototype basin and the evolution of continental margin, can be used to interpret the geological process of basin-range conversion and reconstruct early prototype basins, which is a difficult and leadin~ scientific oroblem of basin research.

Distribution of heavy metals and nutrients in rainwater in coastal regions between the southern Yellow Sea and East China Sea

Rainwater samples were collected in series in Qianliyan Island (southern Yellow Sea) and Shengsi Archipelago (East China Sea) between May 2000 and May 2002, chemical analysis for pH values, concentrations of heavy metals (Cu, Pb, Zn and Cd) and nutrients (NH4+, NO3-, PO43-, SiO32-) were performed. Results indicate that concentrations of most of the heavy metals and nutrients in rainwater show clear seasonal variation, i.e. high level in winter and low level in summer. Regionally, concentrations are higher in the southern Yellow Sea than in the East China Sea, but the annual input of heavy metals into oceans by wet deposition is similar in both stations. However, the input of nutrients by wet deposition in the East China Sea is 2–3 times higher than that in the southern Yellow Sea. In individual, Pb and PO43- are input to the sea mainly by dry deposition; whereas Cu, Zn, Cd and N compounds are input dominantly by wet deposition, the N/P ratios in the rainwater from two stations are much higher than those in seawater, showing a significant impact of atmospheric wet deposition on marine production and biogeochemical circulation of nutrients in these sea regions.

Characteristics of Water Type Distribution and Seasonal Variations in the Southern East China Sea

By using the data of Summer and Winter 1987, Spring and Autumn 1988 obtained by the R/V " Shijian" during the China-Japan Joint Research Program on Kuroshio, the paper makes an analysis and research on the water type distribution and its variations in the studied sea area. Trie results of which are mainly as follows: (1) The Class IV mixing water whose property is similar to that of the continental coastal water is located in the northeast sea area, along the coast of the continent in autumn and winter while extending to the open sea in spring and summer. (2) The boundary between the Kuroshio water and the shelf mixing water (called the left boundary of the Kroshio water) is approximately located in between the 100m and 200m isobaths in various seasons and various layers, and mostly near the 200m isobath. In the sea area northeast of Taiwan, the Kuroshio water is to the west most in spring and then in winter. In summer, it is to the east most while, in autumn, it is in between its positions in summer

SIMPLE ECOSYSTEM MODEL OF THE CENTRAL PART OF THE EAST CHINA SEA IN SPRING

This paper’s simple ecological model to simulate the ecosystem variation and the vertical carbon flux in the central part of the East China Sea in spring, inter-reated the phytoplankton, zooplankton,autotrophic and heterotrophic bacterioplankton, nitrate, and dissolved organic carbon (DOC) in a run lasting 90 days. Except for DOC, because of poor observation precision,the major seasonal features of the vertical distribution for these components can be simulated by this model. The results show that spring bloom is just a short period of 1-2 weeks and that deposit carbon flux at the bottom interface is about 200 mg /m2 ·d in the first 20 days and then reaches its maximum of 1500mg/m2·d about 2 months later after the spring bloom.

Dynamics of the Eukaryotic Microbial Community at the Breeding Sites of the Large Yellow Croaker Pseudosciaena crocea in the Southern East China Sea

Clarifying eukaryotic microbial spatial distribution patterns and their determinants is an important idea in ecological research.However,information on the distribution patterns of eukaryotic microbial community structures(EMCSs)within oceans remains unclear.In this study,surface water samples from the southern East China Sea(SECS)were collected to investigate the spatiotemporal variation in EMCSs by using 18S rRNA high-throughput sequencing technology and the impact of this variation on Pseudosciaena crocea during the breeding season.The results indicated that the distribution patterns of the eukaryotic microbial community structure were different among the Sansha Bay,Mindong and Wentai reserves and the offshore East China Sea.In addition,there were notable potential effects of EMCSs on fishery activities.The variation partitioning analysis showed the environmental and spatial factors caused 53.4%of the variation in the EMCSs,indicating that spatially structured environmental factors were the key determinants of the EMCSs spatial heterogeneity in the SECS and may have contributed to the general distribution of P.crocea.In addition,all the environmental factors were the main factors driving the distribution of eukaryotic microbes except for total phosphorus.Furthermore,it was noted some phytoplankton such as Poterioochromonas and Rhizophydium of fungi in Sansha Bay can effectively prevent Cyanobacteria blooms.Chrysophyceae are natural high-quality baits for juvenile fish distributed in Sansha Bay,Mindong and Wentai reserves.This study provides a part of the insight into potential eukaryotic community distributions in large water bodies and how they are affected by environmental factors.

Evolution of Cenozoic sedimentary architecture in Central and Southern South China Sea basins

The Central and Southern South China Sea(CSSCS) has a complex tectonic dynamic background and abundant oil and gas resources, which has always been a hot topic of academic and industrial attention.However, systematic analyses are still lacking regarding its sediment filling structure and evolution, mostly due to limited borehole penetration and poor quality of seismic reflection data for deeply buried sequences. No consensus has been reached yet on the sedimentary infilling processes, which impeded the reconstruction of the palaeogeography of Southeast Asia and the oil-and-gas exploration undertakings. Here, we illustrate the Cenozoic sedimentary evolution of the CSSCS region by synthesizing relevant data from previous literature and our own observations and displaying the evolution of depositional systems in sequential reconstructions. Besides, the controlling factors of preferred sedimentary scenarios in the CSSCS incorporate the latest interpretations of the spreading of South China Sea(SCS) as well as the demise of the hypothetical Proto-South China Sea(PSCS). The results show that there are three types of sedimentary basins in the CSSCS(foreland,strike-slip, and rift basins) with different sedimentary filling structures. The foreland basins formed a depositional pattern of ‘transition from deep water to shallow water environments', dominated by deep-water depositional systems which were formed before the Early Oligocene with submarine fans developed. Later,the foreland basins were gradually dominated by shallow-water depositional systems with deltas and shallow marine facies. The strike-slip basins showed the depositional architecture of ‘transition from lake to marine environments', i.e. the basins were dominated by lacustrine deposits during the Eocene and evolved into the marine depositional environment since Oligocene with delta developed in the western part of the basin. The depositional evolution of rift basins illustrated the characteristics of 'transition from clastic to carbonate deposits', i.e., the rift basins were dominated by Eocene-Oligocene shallow marine clastic depositional systems, while carbonate platforms started to develop since the Early Oligocene from east to west. The above-mentioned differences of depositional architecture in the CSSCS were controlled by the scissor-style closure of the PSCS and the progressive-style expansion of the SCS. Specifically, the early-period deep-water sedimentary environment of CSSCS basins was controlled by the distribution of PSCS in the Eocene. As the scissor-style closure of PSCS progressed from west to east during the Oligocene to Early Miocene, the northwest of Borneo continued to rise, providing a great number of clastic materials to the basins and gradually developing large-scale deltas from west to east. The distribution of early-period lacustrine sedimentation of strike-slip basins was affected by paleo uplift, and the basins transgressed from the northeast and gradually evolved into marine sedimentary environment due to the expansion of SCS. The expansion of SCS also controlled the sedimentary filling evolution of the rift basins, which broke away from the South China continent and drifted southward. Thus, the rift basins lacked the supply of terrigenous clastic sediments which hindered the development of large-scale deltas and formed a clear water environment conducive to the development of carbonate platforms from east to west.

Seasonal variations in planktonic foraminiferal flux and the chemical properties of their shells in the southern South China Sea

Results from sediment trap experiments conducted in the southern South China Sea from May 2004 to March 2006 revealed significant monsoon-induced seasonal variations in flux and shell geochemistry of planktonic foraminifera. The total and species-specific fluxes showed bimodal pattern, such as those of Globigerinoides ruber, Globigerinoides sacculifer, Neoglobo-quadrina dutertrei, Globigerinita glutinata, and Globigerina bulloides. Their high values occurred in the prevailing periods of the northeast and southwest monsoons, and the low ones appeared between the monsoons. Pulleniatina obliquiloculata had high flux rates mainly during northeast monsoon, with exceptional appearance in August 2004. These fluxes changed largely in accord with those of total particle matter and organic carbon, following chlorophyll concentration and wind force. It is inferred that the biogenic particle fluxes are controlled essentially by primary productivity under the influence of East Asian monsoon in the southern SCS. Shell stable oxygen isotope and Mg/Ca data correspond with seasonal variation of sea surface temperature. Shell δ18O values are affected primarily by sea water temperature, and the δ18O changes of different-depth dwelling species indicate upper sea water temperature gradient. Besides, the low carbon isotope values occurred in the periods of East Asian monsoon in general, whereas the high ones between the monsoons. The pattern is in contrary to chlorophyll concentration change, which indicates that the variation of the carbon isotope could probably reflect the change of sea surface productivity.

东海北部和黄海南部细纹狮子鱼栖息地分布的季节变化

为了解细纹狮子鱼(Liparis tanakae)的生态学特征,根据2018—2019年4个季节在东海北部和黄海南部进行的渔业资源调查资料,利用同步采集的表层水温(SST)、表层盐度(SSS)、底层水温(SBT)、底层盐度(SBS)和水深等5个环境因子以及资源密度数据,开展了细纹狮子鱼栖息地适宜性的季节变化研究。利用提升回归树(boosted regression tree,BRT)模型确定各环境因子的权重,分别采用算术平均法(AMM)和几何平均法(GMM)建立各季节的栖息地适宜性指数模型,并通过交叉验证确定最优模型。结果表明:春夏秋3个季节,对细纹狮子鱼适宜栖息地影响最大的环境因子是底层水温,贡献率分别为84.05%、54.60%和60.74%;冬季影响最大的环境因子是表层水温,贡献率为34.71%。春季,细纹狮子鱼最适栖息底层水温9.60~11.37℃;夏季,最适栖息底层水温7.64~10.46℃;秋季,最适栖息底层水温8.92~9.92℃;冬季,最适栖息表层水温9.82~12.34℃。根据交叉验证评估结果,春季和夏季选取AMM算法、秋季和冬季选取GMM算法且赋予权重的HSI模型研究其栖息地适宜性。细纹狮子鱼的最适栖息地(HSI≥0.7)随季节表现出一定的变化,春夏秋3个季节面积较小,占研究海域面积的13.43%~23.53%,主要栖息地位于受黄海冷水团控制的南黄海中央深水海域;冬季,最适栖息地相对其他季节明显扩大,占研究海域面积的45.31%,从黄海南部向东海北部延伸,南端达长江口近海。

基于耳石地标点法的南黄海和东海小黄鱼种群关系研究

为比较不同地理群体的小黄鱼(Larimichthys polyactis)矢耳石形态特征,进一步明晰其种群划分问题,首次应用长于提取形态特征的地标点法探究了南黄海和东海小黄鱼群体的耳石形态学差异。2022年3—12月,于海州湾、吕泗、长江口和舟山渔场各采集30尾1龄小黄鱼,统一摘取其左矢耳石样本,在耳石外轮廓和耳石内听沟上分别提取了7和4个地标点,进行地标点法分析。结果显示:1)耳石听沟上的地标点8—11相对扭曲贡献率总计为91.88%,耳石外轮廓上的地标点1—7的总贡献率为8.12%,表明4个地理群体小黄鱼的耳石形态差异主要来源于耳石听沟;2)主成分分析散点图显示,部分海州湾群体明显可划分为1个类群,剩余海州湾群体和其他3个渔场所有群体高度重叠聚集为另一个类群,表明南黄海海域可能存在两个小黄鱼种群,即南黄海-东海群和北黄海-渤海群,同时也表明海州湾渔场存在着小黄鱼混栖群体。该现象可能是由于小黄鱼早期鱼卵、仔幼鱼阶段被动扩散和后期主动洄游造成的生境差异,从而诱导其耳石形态表型性状不同。研究结果证实了耳石地标点法在鱼类种间识别的可行性,从耳石形态学角度为中国近海小黄鱼的种群划分提供参考。

2011年春、夏季黄海、东海营养盐分布特征研究

利用2011年4月和8月的调查资料,分析讨论了春、夏季黄海、东海营养盐分布特征及影响因素。结果表明,在调查海域,春季的硅酸盐、硝酸盐的浓度较高;夏季磷酸盐、氨氮的浓度较高。受长江冲淡水影响,长江口-浙闽近海表层营养盐浓度较高,且夏季高值区向外海扩展;外海受黑潮表层水的影响营养盐浓度较低。南黄海营养盐主要受长江冲淡水、黄海冷水团、黄海暖流的共同影响,夏季形成强烈的温跃层,在底层维持着一个稳定的高盐、富营养盐的冷水团。