Effects of dissolved oxygen on intestinal bacterial community and immunity of Atlantic salmon Salmo salar

Dissolved oxygen(DO)is one of most important factors which affect wide range physiologic features of including immune responses and intestinal bacterial community.However,the underlying mechanisms remain enigmatic.To address this question,the intestinal bacterial community compositions and the immune features of Atlantic salmon(Salmo salar)grown in recirculating aquaculture systems(RAS)were characterized.Fish were reared under different DO saturation levels,e.g.,200% saturation named high group(H),100%saturation named control group(CK),and 60%saturation named lower group(L).Large variations in the operational taxonomic units(OTUs)frequency distribution for the intestinal bacterial community of Atlantic salmon were observed.The intestinal bacterial community of all groups was dominated mainly by three phyla,e.g.,Proteobacteria.Firmicutes,and Bacteroidetes.Interestingly,Acinetobacter baumannii,an opportunistic pathogen of salmon was increased significantly in L group.We further monitored the immunity features of fish under different DO levels.The results show that leucocyte number,cortisol level,the expressions of interleukin-1β(IL-1β),Toll-like receptor 4(TLR4),and nucleotide-binding oligomerization domain like protein 2(NOD2)were higher at significant levels in the L group than those in the other two groups.TLR4 and NOD2 are usually related with the bacterial infections;therefore,it is reasonable to believe that the stronger immune responses observed in the L group might be related with the higher abundance of A.baumannii in the inte stine of Atlantic salmon.Overall,these findings demonstrated that low DO level may induce stronger immunity responses in Atlantic salmon.

The impact of oceanic processes on the transient climate response: a tidal forcing experiment

In this study, the impact of oceanic processes on the sensitivity of transient climate change is investigated using two sets of coupled experiments with and without tidal forcing, which are termed ExpTide and ExpControl,respectively. After introducing tidal forcing, the transient climate response(TCR) decreases from 2.32 K to 1.90 K,and the surface air temperature warming at high latitudes decreases by 29%. Large ocean heat uptake efficiency and heat storage can explain the low TCR in ExpTide. Approximately 21% more heat is stored in the ocean in ExpTide(1.10×10^24 J) than in ExpControl(0.91×10^24 J). Most of the large ocean warming occurs in the upper 1 000 m between 60°S and 60°N, primarily in the Atlantic and Southern Oceans. This ocean warming is closely related to the Atlantic Meridional Overturning Circulation(AMOC). The initial transport at mid-and high latitudes and the decline in the AMOC observed in ExpTide are both larger than those observed in ExpControl. The spatial structures of AMOC are also different with and without tidal forcing in present experiments. The AMOC in ExpTide has a large northward extension. We also investigated the relationship between AMOC and TCR suggested by previous studies using the present experiments.

灾难救援的国际协调机制研究——以北约“欧洲大西洋灾难响应协调中心”为例

目的以欧洲大西洋灾难响应协调中心为例,探讨构建灾难救援的国际协调机制的意义,并为我国的相关实践提供借鉴和参考。方法通过查阅学术论文、官方文件、新闻报道等文献资料,研究北大西洋公约组织协调中心的历史、职能和成功经验,分析其对国际灾害救援事业的重要意义和启示。结果提炼出协调中心对国际灾害救援的3点重要借鉴意义:灾难救援是构建国际安全合作框架的重要环节,建设国际协调机制能够有效提升国际灾难响应能力;在灾难应急救援领域建立多边安全合作机制有助于保护人类生命财产安全,也将有效助力国际安全合作框架的构建。结论建立区域协调机制可以更加有效地提升灾害救援国际合作的效率;北约的协调机制可以为我国的相关实践提供借鉴和参考。

高纬度淡水强迫增强背景下大西洋经向翻转环流的响应及其机制

利用卑尔根海洋-大气-海冰耦合气候模式(Bergen Climate Model,简称BCM),研究在北冰洋及北欧海淡水强迫增强的背景下,大西洋经向翻转环流(Atlantic Meridional Overturning Circulation,简称AMOC)的响应及其机制,着重讨论了海表热力性质、北大西洋深层水(North Atlantic Deep Water,简称NADW)的生成率、海洋内部等密度层间的垂直混合(Diapycnal Mixing,简称DM)以及大气风场等物理过程随AMOC的响应所发生的时间演变特征。结果显示,在持续150年增强(强度为0.4 Sv)的淡水强迫下(淡水试验,FW1),AMOC的强度表现为前50年的快速减弱和在接下来100年中的逐渐恢复。同时,在淡水试验的前50年北大西洋高纬度海表盐度(Sea Surface Salinity,简称SSS)减小,海水密度降低,冬季对流混合减弱,导致NADW生成率快速减弱;在接下来的100年中,尽管增强的淡水强迫依然维持,由于海洋内部自身的调节和海气相互作用,导致了AMOC的逐渐恢复。恢复机制可以概括为:(1)随着向南的NADW的减少,大西洋中低纬度海水垂直层结逐渐减弱,DM随之逐渐增强,有利于中低纬度海盆内深层水的上升;(2)南半球西风应力增强与东风应力的减弱及北半球东风的增强使得大西洋向北的埃克曼体积通量净传输恢复;(3)大西洋向北的盐度传输逐渐恢复及次极地回旋区降水的减弱,导致SSS和NADW生成率的恢复,与之对应,AMOC逐渐恢复。研究还发现,淡水试验中,NADW的恢复主要以厄尔明格海(Irminger Sea)为主,冬季北大西洋海平面气压场(SLP)呈现类似正北大西洋涛动(NAO+)的模态,热带降水中心移到赤道以南,大西洋热带SSS增强。

热带大西洋对全球变暖的响应

与太平洋和印度洋不同,全球变暖下热带大西洋变化的研究较少。本文使用地球系统模型CESM(Community Earth System Model),发现全球变暖后热带大西洋在秋季的升温类似大西洋尼诺(Atlantic Ni?o)的正位相,即大西洋西部增暖幅度小于东部;在夏季类似大西洋尼诺的负位相,即大西洋西部增暖幅度大于东部。利用覆盖(overriding)技术,分离了风应力、风速和CO2的直接热效应对海洋升温的作用,探讨了大西洋尼诺本身和全球变暖作用下类似大西洋尼诺正位相(下文简称"类大西洋尼诺升温")的形成机制。结果表明,这两种情况下的形成机制基本相同,风应力的变化是导致大西洋东部暖异常的主要机制。但两者之间也存在区别:1)全球变暖下海表温度的季节变化振幅减小,而大西洋尼诺时变化不大;2)全球变暖下西风异常主要集中在大西洋东部,而大西洋尼诺时主要集中在大西洋中部;3)除风应力外, CO2的热效应对类尼诺升温的变化也有一定影响。

Dendrochronology and climatic signals in the wood of Nectandra oppositifolia from a dense rain forest in southern Brazil

Nectandra is one of the most representative genera of Lauraceae in the subtropical Atlantic Forest of Brazil. The objective of this work was to study the dendrochronological potential of Nectandra oppositifolia Nees and Mart. from two sites in Santa Catarina State in southern Brazil. A tree-ring chronology of 34 trees was developed. The time span ranged from 1843 to 2013. The oldest and youngest trees were 171 and 47 years-old and the average length of the series was 103 years. Average diameter and annual increment were 20.64 cm and0.74 mm a-1; diameter and age were unrelated. The species has good dendrochronological potential with an intercorrelation of 0.61 between sites, indicating the existence of a synchronous pattern in the development of the trees. The climate response of the species could be seen by negative tree growth effects for previous hot and current rainy growth seasons.

在原则与例外之间:油气因素对海洋划界的影响

国际海洋法法庭特别分庭于2017年判决的科特迪瓦与加纳之间的"大西洋划界案"对油气因素对海洋划界的影响进行了全面系统的检验,堪称教科书式的判例,受到了学界的广泛关注。在油气活动对海洋划界默示协议影响和油气因素对海洋划界主流方法影响方面,该案维护了海洋划界国际法原则,彰显了海洋划界国际法的可预见性,有利于法庭吸引潜在的海洋划界争端。但是,在油气活动对海洋划界国际责任影响方面,该案避开了对《联合国海洋法公约》第83条第3款实质义务的解释,而且对划界判决效力的阐述有鼓励争端当事国在争议海域不保持克制之嫌。中国应当依据东海和南海划界争端的不同情形,仔细评估油气活动现状,采取有针对性措施,切实维护中国的海洋权益,同时应当根据具体情形建议周边国家达成某种实际性临时安排,还应当警惕周边国家可能对中国就划界争端责任问题提起强制仲裁。