Sources and degradation of organic matter in the surface sediments of the Chukchi Sea:insights from amino acids

In the context of global warming and rapid environment change in the Arctic,the supply of organic matter(OM)has increased significantly and a large amount of OM are buried on the Arctic shelf.Studying the fate of OM in Arctic shelf sediments is crucial to understanding the global carbon sink.As a marginal sea of the Arctic Ocean,the Chukchi Sea is one of the most critical areas where OM is buried.Based on the surface sediment samples collected during the sixth Chinese National Arctic Research Expedition in the summer of 2014 and the SinoRussian joint Arctic Research Expedition in the summer of 2016,this study takes amino acids(AAs)as the primary tool to explore the source and degradation of OM in the surface sediments of the Chukchi Sea.This study shows that total hydrolyzable amino acid(THAA)concentrations(dry weight)are high,with a mean value of(32.7±15.8)μmol/g.Their spatial distribution is related to primary productivity,hydrodynamic conditions,sediment properties and other factors.The source of OM in the surface sediments of the Chukchi Sea is dominated by diatom-dominated marine productivity,with some input from terrestrial sources.Bacteria,as the main source of the D-enantiomer of AA(D-AA),not only have transforming effect on OM,but their cell walls and remnants likewise supply the OM pool.Based on a series of diagenetic indicators,we conclude that the OM in the surface sediments of the Chukchi Sea has undergone extensive degradation[DI(degradation index)=-0.59±0.44],and the degradation degree in the slope is higher than that in the shelf.This study uses AA to explore the sources and degradation of OM in the sediments of the Chukchi Sea,which facilitates our understanding of OM transport and transformation on the Arctic shelf.

Recent Ventures in Interdisciplinary Arctic Research:The ARCPATH Project

This paper celebrates Professor Yongqi GAO's significant achievement in the field of interdisciplinary studies within the context of his final research project Arctic Climate Predictions: Pathways to Resilient Sustainable Societies-ARCPATH(https://www.svs.is/en/projects/finished-projects/arcpath). The disciplines represented in the project are related to climatology, anthropology, marine biology, economics, and the broad spectrum of social-ecological studies. Team members were drawn from the Nordic countries, Russia, China, the United States, and Canada. The project was transdisciplinary as well as interdisciplinary as it included collaboration with local knowledge holders. ARCPATH made significant contributions to Arctic research through an improved understanding of the mechanisms that drive climate variability in the Arctic. In tandem with this research, a combination of historical investigations and social, economic, and marine biological fieldwork was carried out for the project study areas of Iceland, Greenland, Norway, and the surrounding seas, with a focus on the joint use of ocean and sea-ice data as well as social-ecological drivers. ARCPATH was able to provide an improved framework for predicting the near-term variation of Arctic climate on spatial scales relevant to society, as well as evaluating possible related changes in socioeconomic realms. In summary, through the integration of information from several different disciplines and research approaches, ARCPATH served to create new and valuable knowledge on crucial issues, thus providing new pathways to action for Arctic communities.

Molecular identifi cation and population diff erentiation of Aurelia spp.ephyrae in sea cucumber aquaculture ponds of northern China

Aurelia spp.ephyrae have been reported to form blooms in sea cucumber aquaculture ponds in the Bohai and Yellow Seas.To identify the species,we carried out a genetic analysis of Aurelia spp.ephyrae and medusae based on mitochondrial 16 S rRNA gene.Samples offour Aurelia sp.ephyrae populations were collected in sea cucumber aquaculture ponds and samples offour Aurelia sp.medusae populations were collected in coastal waters.Using a BLASTn search,we found that both the ephyrae collected in the aquaculture ponds and medusae collected in coastal waters belong to Aurelia coerulea.Seventeen haplotypes were recovered from the 16 S rRNA gene.The overall haplotype diversity and nucleotide diversity of the 166 A.coerulea individuals were 0.686%and 0.329%,respectively,indicating high haplotype diversity and low nucleotide diversity.Moreover,the haplotype diversity of ephyrae populations were generally lower than that of medusae populations with close sampling points.The genetic differentiation between ephyrae populations collected in the sea cucumber aquaculture ponds and A.coerulea medusae collected in coastal waters was not significant,suggesting the ephyrae populations in the sea cucumber culture ponds were part of the same genetic group as the medusae populations in the coastal waters.Phylogeographic analysis of the 16 S rRNA region revealed that there was no significant correlation between the haplotypes and the geographic distribution of populations.Pairwise fixation index values showed significant genetic differentiation and limited gene flow between A.coerulea population of Weifang and other locations.

Model for Predicting the Transport and Dispersal of Contaminants Incoming with Submarine Groundwater: Case Study for the Southwestern Taiwan Coastal Zone

As was recognized recently, the submarine groundwater transports a significant amount of various contaminants into the coastal ocean. An assessment of the impact of intruded pollutants in the coastal ecosystems requires understanding fate of the pollutants and processes of their dispersal in ambient waters. In this paper, we proposed a 3-D coupled ocean circulation/particle-tracking model for predicting the transport and dispersal of pollution-containing groundwater discharged into a coastal environment of the southwestern Taiwan. The particle-tracking model takes currents and turbulent diffusivities predetermined by the ocean circulation model and uses the Lagrangian approach to predict the motion of individual droplets, the sum of which constitutes a contaminant plume in result of discharge of contaminant-rich submarine groundwater. The ocean circulation model was forced by tides and seasonal favorable winds for the south-western coast of Taiwan. The initialization of the coupled model was set using field data obtained in 2009 on the Ping-tung shelf where shallow aquifer seepages were discovered. Several types of numerical experiment scenarios were set up to elucidate the transport and dispersal of conservative and nonconservative (nitrate) contaminants in the shallow coastal zone. The comparison of obtained numerical results with observations performed by other researches was discussed.

Morphology of Gametes and Insemination in the Vestimentiferan <i>Riftia pachyptila</i>

Ultrastructure of gametes (sperm and eggs) of vestimentiferan tubeworms and external-internal insemination by means of spermatozeugmata in Riftia pachyptila were described. The spermatozoa of Riftia are threadlike, about 130 μm long, and have a diameter of about 0.7 μm, narrowing to 0.2 μm in the apical portion of the macrodome, and pointed at the end of the tail. Oocytes are produced by the ovaries at the first meiotic prophase stage. The early oocytes are small, hardly exceeding 10 μm in diameter, spherical cells with a poorly differentiated cytoplasm and large nuclei with a nucleolus. Completely formed oocytes reaching up to 130 μm in diameter leave the ovary, their germinal vesicle is unresorbed and has a nucleolus. They are coated by a yolk membrane of 1.2 μm. The eggs enter the oviduct, move along, and accumulate in its expanded anterior portion, the ovisack. The sperm is released in seawater as sperm packages, each having the shape of a torch. Then sperm moves to females and sperm packages at the posterior end of the oviduct surrounding of eggs. Inside the female tube, spermatozoa and, possibly, yet unsplit sperm packages, invade the oviducts through genital openings, where the unfertilized eggs are already present in the terminal portion of the eggsack.

Comparison of linear and nonlinear extreme wave statistics

An extremely large（＂freak＂） wave is a typical though rare phenomenon observed in the sea. Special theories（for example, the modulation instability theory） were developed to explain mechanics and appearance of freak waves as a result of nonlinear wave-wave interactions. In this paper, it is demonstrated that the freak wave appearance can be also explained by superposition of linear modes with the realistic spectrum. The integral probability of trough-to-crest waves is calculated by two methods： the first one is based on the results of the numerical simulation of a wave field evolution performed with one-dimensional and two-dimensional nonlinear models.The second method is based on calculation of the same probability over the ensembles of wave fields constructed as a superposition of linear waves with random phases and the spectrum similar to that used in the nonlinear simulations. It is shown that the integral probabilities for nonlinear and linear cases are of the same order of values

地球电磁法研究新进展--“第19届国际地球电磁感应学术研讨会”专辑

1研讨会概况 地球电磁法是地球物理学的重要方法，它是通过观测自然的和人工产生的电场、磁场或电磁场研究自地表到地幔深处的电性结构和空间环境． 由IAGA I-2工作组主办的两年一届的＂国际地球电磁感应学术研讨会＂的目的是展示和交流各种电磁方法的最新研究成果和前沿研究课题．

New methods for processing and interpreting marine magnetic anomalies:Application to structure,oil and gas exploration,Kuril forearc,Barents and Caspian seas

New methods are presented for processing and interpretation of shallow marine differential magnetic data, including constructing maps of offshore total magnetic anomalies with an extremely high reso- lution of up to 1-2 nT, mapping weak anomalies of 5-10 nT caused by mineralization effects at the contacts of hydrocarbons with host rocks, estimating depths to upper and lower boundaries of anom- alous magnetic sources, and estimating thickness of magnetic layers and boundaries of tectonic blocks. Horizontal dimensions of tectonic blocks in the so-called ＂seismic gap＂ region in the central Kuril Arc vary from 10 to 100 km, with typical dimensions of 25-30 km. The area of the ＂seismic gap＂ is a zone of intense tectonic activity and recent volcanism. Deep sources causing magnetic anomalies in the area are similar to the ＂magnetic belt＂ near Hokkaido. In the southern and central parts of Barents Sea, tectonic blocks with widths of 30-100 kin, and upper and lower boundaries of magnetic layers ranging from depths of 10 to 5 km and 18 to 30 km are calculated. Models of the magnetic layer underlying the Mezen Basin in an inland part of the White Sea-Barents Sea paleorift indicate depths to the lower boundary of the layer of 12-30 km. Weak local magnetic anomalies of 2-5 nT in the northern and central Caspian Sea were identified using the new methods, and drilling confirms that the anomalies are related to concentrations of hydrocarbon. Two layers causing magnetic anomalies are identified in the northern Caspian Sea from magnetic anomaly spectra. The upper layer lies immediately beneath the sea bottom and the lower layer occurs at depths between 30-40 m and 150-200 m.

The REMO Ocean Data Assimilation System into HYCOM(RODAS_H):General Description and Preliminary Results

The first version of the Brazilian Oceano- graphic Modeling and Observation Network （REMO） ocean data assimilation system into the Hybrid Coordi- nate Ocean Model （HYCOM） （RODAS H） has recently been constructed for research and operational purposes. The system is based on a multivariate Ensemble Optimal Interpolation （EnOI） scheme and considers the high fre- quency variability of the model error co-variance matrix. The EnOl can assimilate sea surface temperature （SST）, satellite along-track and gridded sea level anomalies （SLA）, and vertical profiles of temperature （T） and salinity （S） from Argo. The first observing system experiment was carried out over the Atlantic Ocean （78°S-50°N, 100°W-20°E） with HYCOM forced with atmospheric reanalysis from 1 January to 30 June 2010. Five integra- tions were performed, including the control run without assimilation. In the other four, different observations were assimilated： SST only （A SST）; Argo T-S profiles only （AArgo）; along-track SLA only （A_SLA）; and all data employed in the previous runs （A_All）. The A_SST, A_Argo, and A_SLA runs were very effective in improv- ing the representation of the assimilated variables, but they had relatively little impact on the variables that were not assimilated. In particular, only the assimilation of S was able to reduce the deviation of S with respect to ob- servations. Overall, the A_All run produced a good analy- sis by reducing the deviation of SST, T, and S with respect to the control run by 39%, 18%, and 30%, respectively, and by increasing the correlation of SLA by 81%.

Mixing in Shallow Waters: Measurements, Processing, and Applications

Microstructure profiling measurements taken on a shallow Black Sea shelf and in Lake Banyoles and Boadella reservoir （Both in Spain） are analyzed to investigate the influence of boundary-layer-induced turbulence of various sources on mixing in the water interior. The state of turbulence in shallow waters is examined and details of microstructure data processing and error analysis are discussed. The dependence between averaged activity parameter A6 and buoyancy Reynolds number Reb for the shelf turbulence indicates that for Reb 〈 1 the state of turbulence can be described by the fossil turbulence model, which postulates AG - Re b^1/2. For Reb 〉 1, however, the influence of Reb on Ao is weak, signifying that the buoyancy Reynolds number can no longer serve as the governing parameter for active turbulent mixing. The generation of turbulence by a one-minute long wind bursts （the Boadella reservoir） increases the averaged dissipation rate （ε） of the surface mixed layer by more than 5 times （up to 3 × 10^-6 W kg^-1）. The influence of the wind bursts was also traced below the thermocline, where turbulent patches with （ε） = （10^-7 - 10^-6） W kg^-1 were generated. It is shown that the geothermal convection in Lake Banyoles produces intermittent turbulent patches with characteristic dissipation rate （ε） = （2 × 10^-8- 3 × 10^-7） W kg^-1, which influences the overall vertical mixing in the basin.

南巴伦支海磁场异常及其与海底地质结构的对比(英文)

对1986—2001年间巴伦支海南部海洋磁力测量的数据处理结果进行了研究。南巴伦支海底的地磁测量揭示出其复杂多期的地质构造结构,其中以两期分离型的构造为主导:(1)具NW走向的里菲-文德期继承性裂谷构造;(2)NE向转换叠加断层正交系统。晚泥盆世碱性侵入体及其相关的金属矿化作用恰位于这些构造系统的交点上。

About ocean lithodynamics

The term 'lithodynamics' is suggested to denote processes of sediment transport due to exogenic factors and gravity, and also a branch of geosciences studying these processes. Integration of investigations, both of earth surface and of ocean, within one common branch of science is recommended. Basic notions and tasks of lithodynamics as applied to sediment transport processes are described.

Hard life in cold waters:Size distribution and gonads show that Greenland halibut temporarily inhabit the Siberian Arctic

The range of the Greenland halibut Reinhardtius hippoglossoides(Walbaum,1792)includes vast areas in the northern parts of the Atlantic and Pacific oceans,as well as the seas of the Arctic Ocean.Despite its commercial importance and decades of study,many aspects of its life cycle and reproduction remain poorly understood.Here,we evaluate the size distribution of Greenland halibut in the catches of research surveys in the Barents,Kara,and Laptev seas and conduct micro-and macroscopic studies of their gonads in the Laptev Sea.The size of Greenland halibut individuals increases from west to east,which is associated with the settling of pelagic juveniles and the subsequent residency of growing individuals near their settling sites.To the greatest extent,this size imbalance is manifested in the areas most remote from spawning grounds,i.e.the Kara and Laptev seas.The process of maturation in large individuals of Greenland halibut in the Arctic seas is characterized by a state of inhibitionwaiting in the early stages of gametogenesis(previtellogenesis).The data obtained indicate that Greenland halibut in the North Atlantic and the Siberian Arctic have a continuous range.The continental slope of the Barents Sea is a spawning and maturing ground,while the northern parts of the Barents and Kara seas,as well as the continental slope of the Laptev Sea,are feeding grounds for juveniles.The results of this study might serve as a necessary basis for monitoring condition of halibut stocks as well as for reallocation of the total allowable catch between countries that exploited them in the Norwegian and Barents seas.