A Comparison of the Zooplankton Community in the Bay of Bengal and South China Sea During April-May, 2010

This study compares the structure of the zooplankton community in the Bay of Bengal(BoB) and South China Sea(SCS) during the period of spring inter-monsoon, 2010. A total of 215 species of zooplankton were identified, of which 187 species were present in the BoB and 119 in the SCS. Of the taxonomic groups recorded, Copepoda was the most diverse group in all samples followed by pelagic Tunicata, Siphonophorae and Chaetognatha. Flaccisagitta enflata, Cosmocalanus darwinii, Euchaeta larva, Macrura larva and Candacia truncata were predominant both in the BoB and SCS. Moreover, the distribution of some dominant species differed regionally, such as Cypridina dentata, Pleuromamma robusta and Mesosagitta decipiens only in the BoB, and Pleuromamma gracilis, Neocalanus gracilis and Eudoxoides spiralis in the SCS. The average zooplankton abundance was 33.37 ± 7.19 ind. m^(-3) in the BoB and 35.08 ± 2.07 ind. m-3 in the SCS. Copepoda was one of the most abundant groups in the Bo B and SCS. Based on multivariate analysis, it was possible to distinguish the zooplankton in the BoB and SCS communities at the similarity level of approximately 55%, and the dissimilarity was mainly due to C. dentata, P. robusta, M. decipiens, C. darwinii, N. gracilis and P. gracilis. The relationships between zooplankton and temperature, salinity and chlorophyll a were not statistically significant. Zooplankton community structure in the BoB and SCS was observed to be generally similar in terms of species composition and abundance, but the differences observed may be the result of species-specific geographical distribution and local hydrographic conditions.

Community structure and biodiversity of free-living marine nematodes in the northern South China Sea

A quantitative study on the community structure and biodiversity of free-living marine nematodes and their relationship with environmental factors in the northern South China Sea were carried out based on the samples collected at five stations in the deep sea （from 313 to 1 600 m） and one station in shallowwaters （87 m） during the cruise in September, 2010. Results showed that the abundance of marine nematodes ranged from 224 to 1 996 ind./（10 cm2）. A total of 69 free-living marine nematode genera, belonging to 26 families and three orders, were identified. The most dominant genera were Sabatieria, Linhystera, Aegialoalaimus and Daptonema according to SIMPER analysis. Results of CLUSTER analysis revealed four types of marine nematode community （or station groups） in the sampling area. In terms of trophic structure, non-selective deposit feeders （1B） and selective deposit feeders （1A） were the dominant trophic types with highest genera numbers and abundances, which implied that organic detritus was the main food source of marine nematodes in the northern South China Sea. The percentage of male nematode was low, ranging from 2.22% to 17.81%, while those of juvenile individuals ranged from 36.99% to 82.09%. For genera level diversity of marine nematodes, Shannon-Wiener diversity indices （H＇） ranged from 3.76 to 4.57 and had highly significant negative correlation with water depth. In general, diversity indices H＇ at the five stations in deep sea （over 200 m） were lower than that at the station in shallow waters （87 m）. BIOENV analysis showed that the most important environmental factor controlling marine nematode communities was water denth.

The profound influence of Kuroshio intrusion on microphytoplankton community in the northeastern South China Sea

To further understand the effect of Kuroshio intrusion on phytoplankton community structure in the northeastern South China Sea(NSCS,14°–23°N,114°–124°E),one targeted cruise was carried out from July to August,2017.A total of 79 genera and 287 species were identified,mainly including Bacillariophyta(129 species),Pyrrophyta(150 species),Cyanophyta(4 species),Chrysophyta(3 species)and Haptophyta(1 species).The average abundance of phytoplankton was 2.14×10~3 cells/L,and Cyanobacterium was dominant species accounting for 86.84%of total phytoplankton abundance.The abundance and distribution of dominant Cyanobacterium were obviously various along the flow of the Kuroshio,indicating the Cyanobacterium was profoundly influenced by the physical process of the Kuroshio.Therefore,Cyanobacterium could be used to indicate the influence of Kuroshio intrusion.In addition,the key controlling factors of the phytoplankton community were nitrogen,silicate,phosphate and temperature,according to Canonical Correspondence Analysis.However,the variability of these chemical parameters in the study water was similarly induced by the physical process of circulations.Based on the cluster analysis,the similarity of phytoplankton community is surprisingly divided by the regional influence of the Kuroshio intrusion,which indicated Kuroshio intrusion regulates phytoplankton community in the NSCS.

CONNECTION OF THE SOUTH CHINA SEA SUMMER MONSOON TO MARITIME CONTINENT CONVECTION AND ENSO

The relationship between the intensity of the South China Sea summer monsoon (SCSSM) and the Nino3.4 index and anomalous atmospheric circulation patterns associated with a strong and weak SCSSM are investigated using the NCEP/NCAR reanalysis data, Extended Reconstructed Sea Surface Temperature (ERSST) data and Climate Prediction Center Merged Analysis of Precipitation (CMAP) data. The SCSSM is significantly positively correlated with the Nino3.4 index in the succeeding northern autumn and winter. In the strong minus weak SCSSM composite, a positive East Asia-Pacific teleconnection (EAP) pattern and a negative Europe-Asian-Pacific teleconnection (EUP) pattern appear in the 500 hPa height difference field; low-level cross-equatorial flows are strengthened over the Maritime Continent (MC) region; positive (negative) precipitation anomalies occur in the South China Sea and western north Pacific (MC). A possible mechanism through which SCSSM affects ENSO is proposed. A strong (weak) SCSSM strengthens (weakens) cross-equatorial flows over the MC. The anomalous cross-equatorial flows cool (warm) the SST around the MC through enhanced (reduced) surface latent heat fluxes. The cooling (warming) further leads to suppressed (enhanced) convection over the MC, and causes the anomalous westerly (easterly) in the equatorial western Pacific, which favors the onset of El Nio (La Nia) through modulating the positive air-sea feedback process.

SST effect on the pre-monsoon intraseasonal oscillation over the South China Sea based on atmospheric-coupled GCM comparison

The role of sea surface temperature(SST)variability in the pre-monsoonal(April to July)intraseasonal oscillation(ISO)over the South China Sea(SCS)is investigated using the Community Earth System Model Version 2(CESM2).An Atmospheric Model Intercomparison Project(AMIP)simulation forced by daily sea surface temperatures(SSTs)derived from a parallel coupled general circulation model(CGCM)run was compared with observations and the mother coupled simulation.In the coupled model,the SST warming leads the peak convection about 1/4 period as in observations.The paralell uncoupled model fails to simulate this phase relationship,implying the importance of air-sea coupling in reproducing realistic ISO.Due to the near-quadrature phase relationship between SST and precipitation ISOs during the ISO events,it is difficult to distinguish the active/passive role of SST from observations alone.Significant correlation in intraseasonal precipitation between the daily SST-forced AMIP and mother CGCM runs indicates that SST plays a role in driving the atmospheric ISO.

Response of Phytoplankton Community Structure and Size- Fractionated Chlorophyll a in an Upwelling Simulation Experiment in the Western South China Sea

The South China Sea(SCS), which is the largest marginal sea in the western tropical Pacific, plays an important role in regional climate change. However, the research on the phytoplankton community structure(PCS) response to the upwelling remains inadequate. In January 2014, the upwelling simulation experiment was performed in the western SCS. Results indicate that the nutrient-rich bottom water not only increased the total Chlorophyll a(Chl a) concentrations, but would potentially altered the PCS. Due to new nutrients added, microphytoplankton had more sensitivity response to nutrient uptake than other phytoplankton groups. The variation of nutrients induced by formation, weakening and disappearance of upwelling resulted in phytoplankton species succession from cyanophyta to bacillariophyta. It may be the leading factor of the changes in PCS and size-fractionated Chl a. The initial concentration of DIP less than 0.1 μmol L-1 could not sustain the phytoplankton growth. This indicates that phosphorus may be the limiting factor in the western SCS.

Geochemical and microbial characters of sediment from the gas hydrate area in the Taixinan Basin, South China Sea

The Taixinan Basin is one of the most potential gas hydrate bearing areas in the South China Sea and abundant gas hydrates have been discovered during expedition in 2013. In this study, geochemical and microbial methods are combinedly used to characterize the sediments from a shallow piston Core DH_CL_11（gas hydrate free） and a gas hydrate-bearing drilling Core GMGS2-16 in this basin. Geochemical analyses indicate that anaerobic oxidation of methane（AOM） which is speculated to be linked to the ongoing gas hydrate dissociation is taking place in Core DH_CL_11 at deep. For Core GMGS2-16, AOM related to past episodes of methane seepage are suggested to dominate during its diagenetic process; while the relatively enriched δ18O bulk-sediment values indicate that methane involved in AOM might be released from the ＂episodic dissociation＂ of gas hydrate.Microbial analyses indicate that the predominant phyla in the bacterial communities are Firmicutes and Proteobacteria（Gammaproteobacteria and Epsilonproteobacteria）, while the dominant taxa in the archaeal communities are Marine_Benthic_Group_B（MBGB）, Halobacteria, Thermoplasmata, Methanobacteria,Methanomicrobia, Group C3 and MCG. Under parallel experimental operations, comparable dominant members（Firmicutes and MBGB） are found in the piston Core DH_CL_11 and the near surface layer of the long drilling Core GMGS2-16. Moreover, these members have been found predominant in other known gas hydrate bearing cores, and the dominant of MBGB has even been found significantly related to gas hydrate occurrence. Therefore,a high possibility for the existing of gas hydrate underlying Core DH_CL_11 is inferred, which is consistent with the geochemical analyses. In all, combined geochemical and microbiological analyses are more informative in characterizing sediments from gas hydrate-associated areas in the South China Sea.

Evidence of China's sea boundary in the South China Sea

According to a series of important historical maps,i.e.,the Location Map of the South China Sea Islands,the Nansha Islands,Zhongsha Islands,Xisha Islands,Yongxing Island and Shidao Island,and Taiping Island（archived by the Territorial Administration Division of the Ministry of Interior of Republic of China in 1946）,and the Administration District Map of the Republic of China published in 1948,the dashed line surrounding the South China Sea Islands represents China＇s sea boundary in the South China Sea at that time.It was both connected with,and an extension of,the land boundary of China.At that time the dashed line was used to represent the waters boundaries while the solid line was used to represent the land boundary—a universal method used in maps that was then recognized internationally.The above observation provides historical and scientific evidence of China＇s sea boundary in the South China Sea that is useful for the international maritime delimitation over the South China Sea area.

Striking taxonomic differences in summer zooplankton in the northern South China Sea: implication of an extreme cold anomaly

An extreme persistent cold anomaly was prevailing in the South China Sea in February 2008. In order to understand the effect of the cold anomaly on zooplankton community, the zooplankton composition, abundance and biomass were analyzed in the northern South China Sea in August 2007 and August 2008. A total of 467 zooplankton species representing 16 groups were identified, with 275 species in August 2007 and 351 in August2008. Copepods were the most dominant zooplankton group in the study area. Compared with 2007, a dramatic decline was observed in the abundance of four dominant copepod species： Subeucalanus subcrassus, Temora discaudata, Nannocalanus minor and Temora turbinata in 2008. Moreover, zooplankton abundance declined from 133.37 ind./m^3 in August 2007 to 75.49 ind./m^3 in August 2008. In contrast, the abundance of medusa, such as Diphyes chamissonis, and tunicate, such as Doliolum denticulatum and Dolioletta gegenbauri, increased during the same season. Cluster analysis showed that there was a difference in zooplankton community structure between the two years. These variations in zooplankton communities were indicative of an anomalous oceanographic condition along with the extreme cold event in 2008.

Plankton respiration in the northern South China Sea during summer and winter

Plankton respiration is an important part of the carbon cycle and significantly affects the balance of autotrophic assimilation and heterotrophic production in oceanic ecosystems. In the present study, respiration rates of the euphotic zone plankton community（CR_（eu））, size fractionated chlorophyll a concentration（Chl a）, bacterial abundance（BAC）, and dissolved oxygen concentration（DO） were investigated during winter and summer in the northern South China Sea（n SCS）. The results show that there were obvious spatial and temporal variations in CR_（eu） in the n SCS（ranging from 0.03 to 1.10 μmol/（L·h））, CR_（eu） in winter（（0.53±0.27） μmol/（L·h）） was two times higher than that in summer（（0.26±0.20） μmol/（L·h））, and decreased gradually from the coastal zone to the open sea. The distribution of CR_（eu） was affected by coupled physical-chemical-biological processes, driven by monsoon events. The results also show that CR_（eu） was positively correlated with Chl a, BAC, and DO, and that BAC contributed the highest CR_（eu） variability. Furthermore, the results of the stepwise multiple linear regression suggest that bacteria and phytoplankton were the dominant factors in determining CR_（eu）（R^2 = 0.82, p〈0.05） in the n SCS. Based on this relationship, we estimated the integrated water column respiration rate（CRint） within 100 m of the investigated area, and found that the relationship between the biomass of the plankton community and respiration may be nonlinear in the water column.

Effects of typhoon Roke and Haitang on phytoplankton community structure in northeastern South China sea

The influence of typhoon and Kuroshio intrusion process on the natural phytoplankton assemblages in the northeastern South China Sea(neSCS)was examined during a cruise in summer 2017.One hundred ninety-six seawater samples were collected and analyzed in the neSCS.In total,299 species were identified belonging to 82 genera,mostly dominated by Bacillariophyta(159),followed by Dinophyta(132),Cyanophyta(4)and Chrysophyta(4).Among all,Thalassionema nitzschioides,Thalassionema frauenfeldii,Thalassiosira minima,in Bacillariophyta,Prorocentrum lenticulatum,Prorocentrum compressum in Dinophyta,and Trichodesmium thiebautii,in the Cyanophyta were the most dominated species,respectively.Correlation analysis shows compared with other groups Bacillariophyta was mostly influenced by silicate,whereas,Dinophyta and Cyanophyta showed significant correlation with temperature,salinity,phosphate,and nitrate.After the typhoon,the higher abundance of Dinophyta was observed,whereas it was lower in case of Bacillariophyta and Cyanophyta,shows typhoon“Roke“and”Haitang”had a significant influence on the phytoplankton assemblages,which could be manifested by the variations of total phytoplankton abundance in the surface water of neSCS.Overall,our present study provides the latest in-depth information about how the environmental factors influencing the phytoplankton density and diversity in the neSCS during summer.

“中国海洋强国建设的重要成就与启示”笔谈

自党的十八大报告完整提出中国海洋强国战略以来,通过顶层设计、理论阐释、内涵拓展、布局实践,中国海洋强国建设成就斐然,为构建海洋命运共同体作出了重大贡献。但中国的海洋强国战略实施依然面临多种问题和挑战,需要不断增强主体自觉、理论自洽和文化自信,也需要在海权的发展进程中,结合实际,把握机遇,确保海洋强国战略目标如期实现,还需要消除南海问题对推进海洋强国建设的不利影响,合理处理影响南海问题的内外因素,确保中国海洋强国建设的顺利推进,为我国强国建设作出“海洋贡献”。

20世纪70年代以来域外国家介入南海问题研究:发展演变与未来趋势

域外各国对当代南海问题的关注和研究始于20世纪70年代,至今大致经历了《南海各方行为宣言》(DOC)达成前的早期阶段、DOC达成至“南海仲裁案”之间的阶段和中美竞争加剧后的新发展时期这3个阶段。在早期阶段,域外大国学界和智库虽然也对南海问题有不同的观点,但其立场和态度总体上是对中国有利的。第二阶段后期特别是中美竞争加剧后,其研究成果体现的对待南海问题的立场和态度逐渐多元化,研究方法也日益多元化,研究领域逐渐由传统领域向非传统领域扩展。与此同时,相关研究中对中国不利的结论和声音逐渐增多,这使得中国在国际舆论斗争和南海维权斗争中面临着更为严峻的挑战。上述变化受到各国研究人员代际更替、国际海洋法新发展和国际格局变迁的多重影响,但根本原因则是国际格局变迁及相关国家对本国利益的自我选择。中国应充分认识到国际规则和国际法的工具性作用,以平和的心态看待域外各国在南海问题各领域研究取向的变化,坚决反对歪曲或有选择地援引国际法来“抹黑”中国的行为;同时又要保持战略自信和战略耐心,努力加强和深化对国际法、国际政治和历史等不同学科交叉互融的研究,提高阐释运用国际法的能力,援引恰当的条款来维护中国的正当海洋权益。

新形势下中国与东盟国家共建“蓝色伙伴关系”:基础、挑战和路径

中国-东盟关系稳定发展、不断升级,为共建“蓝色伙伴关系”奠定了基础。但随着中国-东盟合作步入“深水区”,一些挑战难题近年愈发突显。美国等域外势力炒作南海争端并在经济和安全领域拉拢东盟国家,严重干扰地区合作深入推展。新形势下,中国与东盟国家共建“蓝色伙伴关系”,应坚持因国施策、双多边共同推进,可优先建立“蓝色经济伙伴关系”,以“海洋命运共同体”为指引推动开展务实的非传统安全领域合作,贡献更多“中国方案”引领地区治理规则建设。中国与东盟国家还当灵活运用二轨平台夯实“民心”基础,促进涉海文教领域合作不断深化。

南海地区新局势、新挑战与新思路——2023年度“南海论坛”综述

2023年南海地区局势复杂多变,危机频发,南海问题依然是全球最为复杂的海洋争端和影响中国-东盟关系的重要因素。如何在中美战略博弈大背景下应对亚太海洋安全新形势,相关问题亟须深入的探讨与总结。在南京大学中国南海研究协同创新中心主办的2023年度“南海论坛”上,与会专家围绕南海维权维稳斗争的新形势与新问题、美国与小多边机制干涉南海的挑战与应对、南海岛礁主权与海洋权益的历史视角和法律斗争新态势与新挑战,以及增进南海合作的新思路新办法等议题进行了深入讨论。面对法律、认知、话语斗争等诸多形势变化,中国需要进一步强化证据链建设和话语权构建,结合具体条件重塑相关实践的规范性,增进南海合作和共同开发。

“南海行为准则”与区域海洋治理机制创新

《联合国海洋法公约》构建普遍性的全球海洋治理机制,但不是国际海洋法体系的上位法。国际法是多层级的立体系统,全球性海洋公约和区域性海洋法构成国际海洋法的双层次结构。区域性海洋法可能形成新的习惯国际海洋法,为《公约》提供更新的动力。“南海行为准则”构建南海的区域海洋治理机制,是对《公约》的扬弃,只要其有利于建立符合各方利益的南海秩序,同时没有违背公认的习惯海洋法原则,可以做出不同于《公约》的规定。“南海行为准则”的磋商困局有三个主因:南海的不对称格局、东盟对中国的不信任推定以及第三方国家的干预和介入。通过“南海行为准则”磋商构建区域海洋秩序应以搁置主权争议、规制当事方行为、反对第三方国家干预和介入、避免安全局势升级为主要内容。

日本强化东盟国家海上安保能力的政策及影响分析

利用东盟国家在南海问题上发难,是日本牵制中国、呼应美国的重要政策手段。基于这一地缘政治考虑,日本主要从海域态势感知、海上执法与海上防卫等三个方面为东盟强化海上安保能力提供支持。为了评估这一政策的具体落实及其对南海局势的实际影响,本文从地缘政治视角出发,对日本支持东盟强化海上安保能力进行了系统评估,并以南海争端中两个主要争议方越南、菲律宾为重点,分析了日本政策的演进及其特点。总体上看,日本的支持提高了相关东盟国家海上安保能力现代化的水平,增强了相关东盟国家对抗中国的信心,增加了南海冲突发生的机率,从而成为恶化南海局势的重要外部诱因。与此同时,日本政策及其影响受到东盟大国平衡立场以及不同成员国认知的限制。展望未来,日本在美国的鼓励与要求下还会进一步强化其对东南亚局势的介入,部分东盟国家特别是菲律宾与日本的互动可能进一步强化,中国维护南海的和平与稳定的努力也将面临更大的挑战。

北极海空搜救合作模式对建构南海搜救合作体系的借鉴与启示

南海作为重要的国际运输通道,面临日益增长的多元化海上安全威胁,搜救合作的制度化建构进程日益紧迫。北极海空搜救已经形成较为成熟的搜救合作机制,与其他半闭海水域海空搜救合作机制相比较,北极搜救模式经验借鉴更适用于南海。南海沿岸国需要考虑在“南海行为准则”磋商中加入区域性指导规范以夯实南海搜救合作法律基础,建立“南海合作理事会”以强化机构管理,建构海上搜救基金协同机制以保证基金供给稳定,辩证看待域外国家搜救参与以加强搜救效果。中国应当主动贡献中国力量,在搜救合作制度化建设中发挥南海区域大国的主导性作用。

泛南海海洋命运共同体建设中的人文交流思考

建设一个“同呼吸、共命运”的海洋命运共同体,是实现深化海洋治理,推动地区乃至全球共同发展的重要手段。立足于良好的区域政治经济环境,泛南海国家应当努力克服内部机制问题与域外因素的干扰,推进人文交流工程,从本源上实现“民心相通”,着力构建起泛南海海洋命运共同体。人文交流维度的泛南海命运共同体建设,既需要“顶层”的战略谋划,也需要来自政府、市场及社会力量的协同行动框架,还需要行之有效的技术路线。