南极夏季南设德兰群岛东部海域南极大磷虾的摄食策略

Euphausia superba is a key species in the Southern Ocean that serves as a link between primary production and higher trophic levels. To investigate the feeding strategies of E. superba from the eastern South Shetland Islands,fatty acid biomarkers, stable isotope signatures, and an incubation experiment were conducted. The results of the incubation experiment proved that adult E. superba mainly fed on 2–20 μm particles, demonstrating the importance of nanoplankton in their diet. Moreover, significant positive relationships between δ15 N and body size demonstrated that size-related dietary shifts were present in E. superba. Evidence from principal component analysis and the C16:1ω7/C18:4ω3 ratio showed that juveniles preferentially fed on dinoflagellates and adults were more likely to feed on diatoms. Fatty acid profiles in adult E. superba roughly mirrored the different trophic conditions and feeding strategies between stations. Adult E. superba at Stas D2-07, D5-07, DA-01 and DA-02 exhibited elevated levels of C16:1ω7, C18:4ω3, C18:1ω9 and C18:1ω9/C18:1ω7, indicating higher levels of feeding on both phytoplankton and higher trophic diets. In contrast, adult E. superba at Stas D1-03 and D1-04 were characterized by high levels of polyunsaturated fatty acids/saturated fatty acids ratios and low levels of C16:1ω7,C18:1ω7, C18:4ω3, C18:1ω9 and total fatty acids. We inferred that adult krill at Stas D1-03 and D1-04 still suffered from difficult dietary conditions after overwintering. The different dietary conditions between stations suggest a highly plastic feeding strategy of E. superba in the eastern South Shetland Islands.     

Shore-platform development in the South Shetland Islands,Antarctica

Shore platforms in the South Shetland Islands, Antarctica, display morphological differences from mid-latitude platforms that are explicable in terms of the morphogenetic environment. These differences include marked horizontality of the platform surface terminated abruptly by low-tide and high-tide gradient changes. Since the processes of ice freezing-on, quarrying by impact and abrasion are responsible for such horizontality the platforms are widest in areas of restricted fetch where ice persists longest. In exposed locations, wave quarrying and abrasion limit the development of horizontality. Stratigraphic evidence suggests that the shore platforms of the South Shetland Islands are inherited features that have been rapidly retrimmed by polar shore processes. Some suggestions for future research are made.     

Gas hydrate versus geological features: The South Shetland case study

A gas hydrate reservoir is hosted in marine sediments of an accretionary prism, located offshore the South Shetland Islands (Antarctic Peninsula), and affected by widespread deformations. To analyse gas hydrate distribution and fluid circulation inside sediments, available velocity models were used. Seismic velocities are translated in terms of hydrate porosity, which is the difference between the reference porosity (i.e., the porosity without gas hydrate) and the effective porosity (i.e., the porosity reduced by the gas hydrate presence). The pre-stack depth migration sections underlined the presence of several geological features, such as gentle and open folds, fractures and faults. In this paper, we observed a relationship between syncline–anticline structures and hydrate presence. In particular, a relationship is underlined between the hydrate porosity values and the distance from the hinge of the anticline: the hydrate porosity increases toward the limbs of anticline. The micro-fracturing model supports the idea that the syncline favours the hydrate formation, while the anticline favours the free gas accumulation below the bottom simulating reflector.     

Mesoscale features and phytoplankton biomass at the GoodHope line in the Southern Ocean during austral summer

Two sets of high-resolution subsurface hydrographic and underway surface chlorophyll a (Chl a) measurements are used, in conjunction with satellite remotely sensed data, to investigate the upper layer oceanography (mesoscale features and mixed layer depth variability) and phytoplankton biomass at the GoodHope line south of Africa, during the 2010–2011 austral summer. The link between physical parameters of the upper ocean, specifically frontal activity, to the spatially varying in situ and satellite measurements of Chl a concentrations is investigated. The observations provide evidence to show that the fronts act to both enhance phytoplankton biomass as well as to delimit regions of similar chlorophyll concentrations, although the front–chlorophyll relationships become obscure towards the end of the growing season due to bloom advection and ‘patchy’ Chl a behaviour. Satellite ocean colour measurements are compared to in situ chlorophyll measurements to assess the disparity between the two sampling techniques. The scientific value of the time-series of oceanographic observations collected at the GoodHope line between 2004 to present is being realised. Continued efforts in this programme are essential to better understand both the physical and biogeochemical dynamics of the upper ocean in the Atlantic sector of the Southern Ocean.     

Features of physical oceanography in the oceans near the Prydz Bay during the 1998/1999 austral summer

1Introduction The Prydz Bay has its open water in the northadjacent to the Indian Ocean sector of the SouthernOcean.It borders on the ice shelf to its south,andthe Antarctic Continent to its east and west.It is thelargest water stretching southward into t…     

Basin-scale distribution of prokaryotic phylotypes in the epipelagic layer of the Central South Pacific Ocean during austral summer

In the present study, we used catalyzed reporter deposition-fluorescence in situ hybridization to quantify the abundance of five bacterial (Alphaproteobacteria, SAR11, Gammaproteobacteria, SAR86, and Bacteroidetes) and two archaeal (Crenarchaeota and Euryarchaeota) phylotypes in the epipelagic layer (0–200 m) of the Central South Pacific Ocean along 170°W from 0° to 40°S. We found that the distribution patterns of these phylotypes differed from each other. All phylotypes except Gammaproteobacteria were particularly abundant at the surface water of the equatorial region, whereas Gammaproteobacteria was relatively abundant in the area from the southern part of the South Pacific Ocean. SAR11, affiliated with Alphaproteobacteria was the dominant phylotype at all depths, throughout the study area. The abundance of SAR11 significantly increased with chlorophyll a concentration, suggesting that phytoplankton could affect their distribution pattern. There was a positive correlation between Bacteroidetes abundance and water temperature, suggesting that the temperature gradient could be a critical factor determining their distribution in the South Pacific Ocean. Crenarchaeota and Euryarchaeota were more abundant at the equatorial region than in other study areas. Euryarchaeota abundance significantly decreased with depth, and increased with chlorophyll a concentration. This suggests that there was ecological interaction between Euryarchaeota and phytoplankton in the equatorial surface. Our data indicate that distinct hydrographic properties such as seawater temperature, salinity, and the concentrations of chlorophyll a and nutrients can principally control the basin-scale distribution of different prokaryotic phylotypes in the epipelagic layer of the Central South Pacific Ocean.     

The distribution of chlorophyll a in the tropical eastern Indian Ocean in austral summer

To study the effect of hydrographic factors on the spatial distributions of chlorophyll a (Chl a), an investigation was carried out in the tropical eastern Indian Ocean (80 -100 E along 7 S, and 7 -18 S along 80 E) in December 2010. The fluorescent method was used to obtain total Chl a and size-fractioned Chl a at the 26 stations. The results show that surface Chl a concentration averaged at (0.168 ± 0.095) mg/m 3 s.d. (range: 0.034-0.475 mg/m 3 ), concentrations appeared to be higher in the west for longitudinal variations, and higher in the north for latitudinal variations. Furthermore, the surface Chl a concentration was lower (0.034-0.066 mg/m 3 ) in the region to the south of 16 S. There was a strong subsurface Chl a maximum layer at all stations and the depth of the Chl a maximum increased towards to the east and south along with the respective nitracline. The spatial variation of Chl a was significant: correlation and regression analysis suggests that it was primarily affected by PO 3 4 , N(NO 3 -N+NO 2 -N) and temperature. Size-fractionated Chl a concentration clearly showed that the study area was a typical oligotrophic open ocean, in which picophytoplankton dominated, accounting for approximately 67.8% of total Chl a, followed by nanophytoplankton (24.5%) and microphytoplankton (7.6%). The two larger fractions were sensitive to the limitation of P, while picophytoplankton was primarily affected by temperature.     

Sea-surface distribution of coccolithophores,diatoms, silicoflagellates and dinoflagellates in the South Atlantic Ocean during the late austral summer 1995

The sea-surface distribution of four selected fossilizable phytoplankton groups (coccolithophores, diatoms, silicoflagellates and dinoflagellates) has been studied along a transect from Cape Town (34°S) to South Sandwich Islands (57°S) during the late austral summer. The observed distribution of these groups shows that their biogeographical distribution is significantly constrained by the water masses and associated frontal systems of the Southern Ocean. Coccolithophores are the dominant group and show cell abundances up to 51×10³ cells/l down to 57°S. Three restricted areas are marked by particularly high cell densities: the continental shelf of South Africa, the area between the Sub-Tropical Convergence and the Sub-Antarctic Front, and the southern border of the Antarctic Polar Front, where the highest abundances are recorded (>650×10³ cells/l). The species composition of the various assemblages representative of the four groups defines distinct biogeographical zones bounded by marked sea-surface temperature gradients. This biogeographical distribution is confirmed by factor analysis of the coccolithophore (5 factors, 85% of the total variance) and diatom and silicoflagellate (7 factors, 87.5% of the total variance) populations. When compared with the distribution pattern of siliceous fossil assemblages in surface sediments, our data show a more accurate coupling between the various water-masses of the South Atlantic Ocean and the living siliceous population.     

中沙群岛附近海域沉积物中的轻矿物分区及物质来源

海底沉积物中的碎屑矿物(粒级为0.063~0.125 mm)的特征及分布样式对于鉴别沉积物的源区具有重要的指示意义.对取自南海中沙群岛附近海域114个表层沉积物样品的轻矿物含量、分布特征和矿物组合进行了研究,在此基础上将本区划分为以下三个矿物组合区:生物碎屑矿物区(Ⅰ)、火山碎屑矿物区(Ⅱ)、混合矿物区(Ⅲ).生物碎屑矿物区(Ⅰ)的矿物组合单一,为生物骨屑矿物.生物骨屑矿物主要来源于中沙环礁,极少量的陆源物质及火山物质可通过悬浮或风等途径搬运进入此区.火山碎屑矿物区(Ⅱ)的轻矿物以褐色火山玻璃为主,火山渣、无色火山玻璃等火山碎屑矿物含量也较高.风化碎屑及陆源碎屑矿物(如石英等)的含量较低.火山渣在本区呈点源式扩散分布.本区矿物组合为褐色火山玻璃-火山渣.此区的物质来源相对复杂,主要来源于原地海山岩石剥蚀风化以及区内可能存在的正在喷发的小型火山物质的风化,周边岛弧火山对其贡献极小.混合矿物区(Ⅲ)的物源丰富,包括生物源、火山源及陆源,该区又可分为两个矿物亚区:东北部混合矿物区(Ⅲ-1),主要的矿物组合包括生物骨屑矿物、褐色火山玻璃、石英、长石等,陆源物质来自于我国大陆,陆源物质基本上位于17°N以北;东南部混合矿物区(Ⅲ-2),矿物组合为生物骨屑矿物、褐色火山玻璃、石英以及风化碎屑矿物,其中陆源物质可能来自南海南部及西南部大陆中的碎屑矿物,通过发源于大河口的海底峡谷搬运进深海盆.     

A quantitative analysis of sources for summertime phytoplankton variability over 18 years in the South Shetland Islands (Antarctica) region

Eighteen years of summertime hydrographic and chlorophyll-a (Chl-a) data (～2700 stations) from the South Shetland Islands (Antarctica) region show that a “bell-shaped” (unimodal) distribution of phytoplankton biomass results annually when plotted against the inshore to offshore gradient in surface salinity. The maximum for this unimodal Chl-a distribution corresponds with a shallow upper mixed layer (UML) in iron-rich waters that occurs at salinities ～34. Methods of gradient analysis are used to distinguish sources of variability for bloom development among years. The control of phytoplankton biomass is resolved across the salinity gradient that separates the co-limiting conditions of deep UML depths and low-iron concentrations as opposing end-members. Chlorophyll-fluorescence yield data (a proxy for Fe-stress) showed that at salinities ～34, phytoplankton biomass was unlikely to be limited by Fe. Instead, blooming at salinities ～34 (1.3±1 mg Chl-a m^?3) co-varied with shallow UML depths (41±19 m) that occurred as a function of higher UML temperature (1.5±0.5 °C) among years, and is evidence that atmospheric climate variability impacts summertime phytoplankton biomass and production in this Southern Ocean seascape.     

Mineral provinces and material provenance of the surficial sediments near the Zhongsha Islands in the South China Sea

1 IntroductionThe South China Sea is one of the northwesternPacific marginal basins, which is located atthe junc-tion region among Euro-Asia plate, Pacific plate andIndia plate. Owing to its unique geological charac-teristics, the South China Sea has beco…     

A comparison of primary production models in an area of high mesoscale variability (South Shetland Islands,Antarctica)

Three types of primary productivity (PP) models were evaluated in a mesoscale area around the South Shetland Islands (Antarctica). Input variables were: phytoplankton carbon biomass, Chlorophyll a, sea water temperature, daily irradiance, among others, collected in situ during an oceanographic cruise (COUPLING, January 2010). Models of the first type were based on Chl a measurements: the widely used model VGPM (Behrenfeld and Falkowski, 1997) and a derived version developed for the Western Antarctic Peninsula (Dierssen et al., 2000). The second type included two models based on phytoplankton carbon biomass: one developed for the whole Southern Ocean (Arrigo et al., 2008) and one based on the Metabolic Theory of Ecology developed by López-Urrutia et al. (2006), being the first time that a model with these features is used for Antarctic waters. The third type was an updated version of the carbon-based model CbPM (first described by Behrenfeld et al. (2005)) based on the Chl a/carbon biomass ratio modulation. The degree of agreement among the results between the different types of models turned out to be low (> 30% of difference), but high within models of the same type (< 10% of difference). Biomass-based model predictions differed the most from those estimated by the other two types. The differences in PP estimates were primarily attributed to the different ways these models treat the phytoplankton assemblage, along with the difference in input variables. Among the five models evaluated, the output from the modified version of the CbPM showed the lowest bias (0.55) being the most realistic. It made a special attempt to detect the factors controlling phytoplankton physiological state, showing a nutrient limitation towards the Drake area similar to the one observed for the in situ PP values.     

Glaciomarine sedimentation and palaeo-glacial setting of Maxwell Bay and its tributary embayment, Marian Cove, South Shetland Islands, West Antarctica

High-resolution (3.5 kHz and multi-channel) seismic profiles and piston cores were collected from Maxwell Bay and its tributary embayment, Marian Cove, in the South Shetland Islands, Antarctica, during the Korea Antarctic Research Program (1992/93 and 1995/96) to elucidate the glaciomarine sedimentation processes and recent glacial history of the area. Seismic data from Maxwell Bay reveal a rugged bay margin and flattened basin floor covered with well-stratified hemipelagic muds. On the base-of-slope, acoustically transparent debris flows occur, indicating downslope resedimentation of glaciomarine sediments. Despite the subpolar and ice-proximal settings of Marian Cove, the seafloor is highly rugged with a thin sediment drape, suggesting that much of the area has been recently eroded by glaciers. Sediment cores from the cove penetrated three distinct fining-upward lithofacies: (1) basal till in the lower part of the core, accumulated just seaward of the grounding line of the tidewater glacier; (2) interlaminated sand and mud in the middle part, deposited in ice-proximal zone by a combination of episodic subglacial meltwater inflow and iceberg dumping; and (3) pebbly mud in the upper part, deposited in ice-distal zone by both surface meltwater plume and ice-rafting from the glacier front. A reconstruction of the glacial history of these areas since the late glacial maximum shows an ice sheet filling Maxwell Bay in late Wisconsin time and grounding of the tidewater glacier in Marian Cove until about 1300 yr BP.     

南海海域岛屿高程基准确定与计算

大陆与岛屿之间的高程传递是当前海洋测量急需解决的主要问题之一。本文研究了利用GPS定位技术，结合我国现有陆地和海洋重力资料以及其它重力场信息，并运用国内外确定大地水准面的严密理论和算法来确定高精度的局部大地水准面，最终将我国高程基准从大陆传递到南海海域的岛屿上。     

Meridional asymmetric distribution of the primary production in the Atlantic Sector of the Southern Ocean in the austral spring and summer

The spatial distribution of the phytoplankton productivity was investigated in the Atlantic Sector of the Southern Ocean in the austral summer of 2009?C2010 and the spring of 2010 on the basis of field measurements. In October?CNovember, the average integrated primary production and the concentration of surface and integrated (photosynthetic layer) chlorophyll ??a?? in the Subantarctic waters of the Drake Passage exceeded the similar values along the Greenwich meridian by 3, 2, and 1.5 times, respectively. Similar primary production was observed in December?CJanuary for the water column in the eastern and western sectors of the studied area. The chlorophyll ??a?? concentration in the surface water layer was higher by 1.7 times for the Greenwich meridian area compared to the deep layers, but the concentrations of this pigment in the deeper layers did not differ. During the spring, the average primary production in the water column (the chlorophyll ??a?? concentration in the surface and in the photosynthetic layer) differed in the Drake Passage and along the Greenwich meridian by 2.3, 1.6, and 1.7 times, respectively. The opposite pattern was observed during the summer period, when the parameters listed above were higher for the Greenwich meridian area by 1.9, 2.5, and 1.7 times, respectively. Therefore, the western Antarctic areas in the spring are characterized by higher production than the eastern ones, and an opposite pattern is observed in the summer. The possible reasons for the meridional zonation of the chlorophyll ??a?? and the primary production are discussed in regard to different seasons.     

夏季南极普里兹湾氮吸收受融冰调控

本研究将稳定同位素（¹⁵N）与放射性核素（²²⁶Ra）示踪相结合,探讨了2006年夏季南极普里兹湾融冰过程对氮吸收的调控作用。硝酸盐及铵盐的比吸收速率均与浓度呈正相关关系,表明底物浓度效应的存在。开阔洋区具有较高的f比值,而在埃默里冰架附近f比值低得多。f比值与冰融水份额之间存在负相关关系,暗示融冰过程在调控水体氮吸收方面起着重要作用。融冰改变了当地上层水体的层化条件,显著地影响南大洋的生物泵效率及对大气二氧化碳的吸收。本研究为南大洋上层水体碳、氮动力学的调控机制提供了新的认识,且有助于对历史记录的解读及对未来气候变化的预测。     

Geographical distribution and age composition of Euphausia superba larvae (Crustacea：Euphausiacea) in the South Shetland Islands region and southern Scotia Sea in relation to environmental conditions

Spatial distribution patterns of the different life stages of Euphausia superba in the region of the South Shet- land Islands and southern Scotia Sea （Antarctica） were assessed based on scientific survey data collected in lanuary and February of 2010. Adults, eggs, nauplii, metanauplii, calyptopis I-Ill, and furcilia I-II were found in the investigation. The abundance of larvae averaged 1 172.8 ind./mz, with calyptopis I and II as the dominant stages. Habitat occupancy patterns varied among Euphausia superba at different stages, and three sub-regions were identified by cluster analysis. The degree of larval development increased from west to east. Larvae were not observed north of the South Shetland Islands. Calyptopis I was predominant in the water between Elephant Island and the South Orkney Islands, which featured no thermocline. Older stages, including calyptopis II and III and furcilia I and II, were common in north and northeast of the South Orkney Islands, which were characterized by high temperature and high chlorophyll concentration. Distri- bution and abundance of the early life stages of E. superba were associated with specific environmental con- ditions. According to Biota-Environment matching （BIOENV）, the distributions of E. superba larvae were correlated with a combination of temperature at the surface and 200 m, and 0-100 m integrated chlorophyll a concentration.