Late-Quaternary changes in productivity of the Southern Ocean

Paleoceanographic records based on new proxies of export production have been constructed for the South Atlantic sector of the Southern Ocean. A radionuclide-ratio proxy of particle flux (¹⁰Be/²³⁰Th) and the accumulation rate of authigenic uranium, which responds to the flux of organic carbon to the sea bed, both indicate a dramatic increase, compared to the present, in the export production of the Subantarctic zone (approximately the region between the present-day positions of the Subtropical Convergence and the Antarctic Polar Front) during glacial periods. If the South Atlantic is representative of the entire Southern Ocean, then export production in the Southern Ocean during the Last Glacial Maximum was substantially greater than at present. Previous studies, focusing on the burial of biogenic opal, failed to recognize the glacial increase in export production of the Southern Ocean because of a strong non-linearity between accumulation rates of opal and of organic carbon.     

Modelling the silica pump in the Permanently Open Ocean Zone of the Southern Ocean

A coupled 1D physical–biogeochemical model has been built to simulate the cycles of silicon and of nitrogen in the Indian sector of the Permanently Open Ocean Zone of the Southern Ocean. Based on a simplified trophic network, that includes two size classes of phytoplankton and of zooplankton, and a microbial loop, it has been calibrated by reference to surface physical, chemical and biological data sets collected at the KERFIX time-series station (50°40′S–68°25′E). The model correctly reproduces the high nutrient low chlorophyll features typical of the studied area. In a region where the spring–summer mixed layer depth is usually deeper than 60 m, the maximum of chlorophyll never exceeds 1.5 mg m⁻³, and the annual primary production is only 68 g C m⁻² year⁻¹. In the surface layer nitrate is never exhausted (range 27–23.5 mmoles m⁻³) while silicic acid shows strong seasonal variations (range 5–20 mmoles m⁻³). On an annual basis 71% of the primary production sustained by nanophytoplankton is grazed by microzooplankton. Compared to North Atlantic, siliceous microphytoplankton is mainly prevented from blooming because of an unfavourable spring–summer light-mixing regime. Silicic acid limitation (high half saturation constant for Si uptake: 8 mmoles m⁻³) also plays a major role on diatom growth. Mesozooplankton grazing pressure excerpts its influence especially in late spring. The model illustrates the efficiency of the silica pump in the Southern Ocean: up to 63% of the biogenic silica that has been synthetized in the photic layer is exported towards the deep ocean, while only 11% of the particulate organic nitrogen escapes recycling in the surface layer.     

Life cycle strategies of epipelagic copepods in the Southern Ocean

Twelve epipelagic copepod species were reviewed to compare their adaptations to the short primary production season and low temperatures which characterise the Southern Ocean. The species show a spectrum of adaptations, but three broad life cycle strategies were defined: (1) herbivorous in summer, a short reproductive period and winter diapause at depth (Calanoides acutus and possibly Ctenocalanus citer); (2) predominantly omnivorous/detritivorous diet, an extended period of feeding, growth and reproduction and less reliance on diapause at depth (Metridia gerlachei, Calanus propinquus, Calanus simillimus, Oithona similis, Microcalanus pygmaeus, and possibly Oncaea curvata and Oithona frigida); (3) overwintering and feeding within sea ice as early nauplii or copepodids (Stephos longipes and Paralabidocera antarctica). The large species Rhincalanus gigas appears to be intermediate between strategies (1) and (2). Contrasting species from groups (1) and (2), namely C. acutus and O. similis, were selected for more detailed comparison. For C. acutus, maximum (probably food saturated) feeding and egg production rates are well below equivalent values for Calanus spp. at lower latitudes. Likewise, summer growth and moulting rates are slower, and the growth season of this herbivore is only 2–4 months. Therefore, both the low summer temperatures and short primary production season seem to dictate a long (1 year) life cycle for C. acutus. A collation of data on O. similis revealed that its abundance increases about tenfold from the Antarctic shelf northwards to the Polar Frontal Zone, where abundances are similar to those in temperate and tropical shelf seas. In contrast to C. acutus, O. similis appears to remain in the epipelagic and reproduce there year-round, although the food sources which sustain this are still uncertain.     

Phytoplanktonic nutrient utilisation and nutrient signature in the Southern Ocean

The separation in Southern Ocean provinces of silicate excess at nitrate exhaustion and of nitrate excess at silicate exhaustion was already introduced by Kamykowski and Zentara (Kamykowski, D., Zentara, S.J., 1985. Nitrate and silicic acid in the world ocean: patterns and processes. Mar. Ecol. Prog. Ser. 26, 47–59; and Kamykowski, D., Zentara, S.J., 1989. Circumpolar plant nutrient covariation in the Southern Ocean: patterns and processes. Mar. Ecol. Prog. Ser. 58, 101–111) and our investigations of the silicate to nitrate uptake ratios confirm the earlier distinction. Oligotrophic antarctic waters mainly exhibit proportionally higher silicate removal what induces a potential for nitrate excess. The nitrogen uptake regime of such areas is characterised by low absolute as well as specific nitrate uptake rates throughout. Maximal values did not exceed 0.15 μM d⁻¹ and 0.005 h⁻¹, respectively. Corresponding f-ratios ranged from 0.39 to 0.86. This scenario contrasts strikingly to the more fertile ice edge areas. They showed a drastic but short vernal increase in nitrate uptake. Absolute uptake rates reached a maximum value of 2.18 μM d⁻¹ whereas the maximal specific uptake rate was 0.063 h⁻¹. In addition to an optimal physical environment for bloom development, accumulation of ammonium stimulated nitrate uptake in a direct or indirect way. Since ammonium build-up in surface waters traces enhanced remineralisation, release of other essential compounds during degradation of organic matter might have been the main trigger. This peak nitrate utilisation during early spring led to the observed potential for silicate excess. With increasing seasonal maturity the nitrate uptake became inhibited by the presence of enhanced ammonium availability (up to 8% of the inorganic nitrogen pool), however, and after a short period of intensive nitrate consumption the uptake rates drop to very low levels, which are comparable to the ones observed in the area of nitrate excess at silicate exhaustion.     

Fluxes of biogenic carbon in the Southern Ocean: roles of large microphagous zooplankton

The Southern Ocean is an extreme environment, where waters are permanently cold, a seasonal ice cover extends over large areas, and the solar energy available for photosynthesis is severely restricted, either by vertical mixing to considerable depths or, especially south of the Antarctic Circle, by prolonged seasonal periods of low or no irradiance. Such conditions would normally lead to low productivity and a water column dominated by recycling processes involving microbial components of pelagic communities but this does not seem to be the case in the Southern Ocean, where there is efficient export to large apex predators and deep waters. This paper investigates the role of large microphagous zooplankton (salps, krill, and some large copepods) in the partitioning of biogenic carbon among the pools of short- and long-lived organic carbon and sequestered biogenic carbon. Large microphagous zooplankton are able to ingest microbial-sized particles and thus repackage small, non-sinking particles into both metazoan biomass and large, rapidly sinking faeces. Given the wide spatio-temporal extent of microbial trophic pathways in the Southern Ocean, large zooplankton that are omnivorous or able to ingest small food particles have a competitive advantage over herbivorous zooplankton. Krill efficiently transfer carbon to a wide array of apex predators and their faecal pellets are exported to depth during occasional brief sedimentation episodes in spring time. Salps may be a significant link towards some fish (directly) and other apex predators (indirectly) and, at some locations (especially in offshore waters) and time, they may account for most of the downward flux of biogenic carbon. Large copepods are a trophic link towards fish and at least one whale species, and their grazing activity generally impedes the export of organic particles to depth. As a result, biogenic carbon is channelled mainly towards apex predators and episodically into the deep ocean. Without these original interactions, Antarctic waters might well be dominated by microbial components and recycling processes instead of active export from the generally small primary producers towards large apex predators.     

深海爬游机器人概念及关键技术分析

  目的  针对可潜浮式沉积物捕获器（FST）的时变姿态会影响采样效率的问题,对全采样流程内FST的质心偏移规律及姿态角变化进行定量分析与评估。  方法  设计一种包含采样模块及浮力调节模块的FST,然后利用SolidWorks软件进行建模,建立坐标系;通过Matlab软件完成静力学分析,模拟得到全流程内各时刻FST质心相对于坐标原点的偏移量;基于力矩平衡公式,推导因质心偏移造成的机体姿态变化;运用平面射影定理,定量分析姿态变化对有效采集面积的影响。  结果  结果显示,质心偏移被限制在以载体坐标系原点为圆心、半径为$ 8 \\times {10^{ - 3}}\\;{\\text{m}} $的圆内,质心坐标域为${x_{\\text{g}}} \\in ( - 6 \\times {10^{ - 3}}\\;{\\text{m}}, 3 \\times {10^{ - 3}}\\;{\\text{m}})$,${y_{\\text{g}}} \\in ( - 1 \\times {10^{ - 3}}\\;{\\text{m}}, $ 7 \\times {10^{ - 3}}\\;{\\text{m}})$;姿态角变化域为俯仰角$ \\theta \\in ( - 1.5^\\circ , 16.6^\\circ ) $,横滚角$\\phi \\in ( - {2.6^ \\circ }, {16.8^ \\circ })$;当$ \\theta = 14.7^\\circ , \\phi {\\text{ = 13}}^\\circ $时,有效采集面积缩减为捕获装置面积的94.27%,为最小值,当其他条件相同时,捕获相同质量的沉降颗粒所需时间比100%实采面积所需捕获时间多0.0578倍。  结论  研究工作可为FST的稳性分析和浮力调节系统设计提供有益的参考。     

Primary productivity of the Palmer Long Term Ecological Research Area and the Southern Ocean

A major objective of the Palmer Long Term Ecological Research (Palmer LTER) project is to obtain a comprehensive understanding of the various components of the Antarctic marine ecosystem. Phytoplankton production plays a key role in this so-called high nutrient, low chlorophyll environment, and factors that regulate production include those that control cell growth (light, temperature, and nutrients) and those that control cell accumulation rate and hence population growth (water column stability, grazing, and sinking). Sea ice mediates several of these factors and frequently conditions the water column for a spring bloom which is characterized by a pulse of production restricted in both time and space. This study models the spatial and temporal variability of primary production within the Palmer LTER area west of the Antarctic Peninsula and discusses this production in the context of historical data for the Southern Ocean. Primary production for the Southern Ocean and the Palmer LTER area have been computed using both light-pigment production models [Smith, R.C., Bidigare, R.R., Prézelin, B.B., Baker, K.S., Brooks, J.M., 1987. Optical characterization of primary productivity across a coastal front. Mar. Biol. (96), 575–591; Bidigare, R.R., Smith, R.C., Baker, K.S., Marra, J., 1987. Oceanic primary production estimates from measurements of spectral irradiance and pigment concentrations. Global Biogeochem. Cycles (1), 171–186; Morel, A., Berthon, J.F., 1989. Surface pigments, algal biomass profiles and potential production of the euphotic layer—relationships reinvestigated in view of remote-sensing applications. Limnol. Oceanogr. (34), 1545–1562] and an ice edge production model [Nelson, D.M., Smith, W.O., 1986. Phytoplankton bloom dynamics of the western Ross Sea ice edge: II. Mesoscale cycling of nitrogen and silicon. Deep-Sea Res. (33), 1389–1412; Wilson, D.L., Smith, W.O., Nelson, D.M., 1986. Phytoplankton bloom dynamics of the Western Ross Sea ice edge: I. primary productivity and species-specific production. Deep-Sea Res., 33, 1375–1387; Smith, W.O., Nelson, D.M., 1986. Importance of ice edge phytoplankton production in the Southern Ocean. BioScience (36), 251–257]. Chlorophyll concentrations, total photosynthetically available radiation (PAR) and sea ice concentrations were derived from satellite data. These same parameters, in addition to hydrodynamic conditions, have also been determined from shipboard and Palmer Station observations during the LTER program. Model results are compared, sensitivity studies evaluated, and productivity of the Palmer LTER region is discussed in terms of its space time distribution, seasonal and interannual variability, and overall contribution to the marine ecology of the Southern Ocean.     

On the dense water spreading off the Ross Sea shelf (Southern Ocean)

In this study, current meter and hydrological data obtained during the X Italian Expedition in the Ross Sea (CLIMA Project) are analyzed. Our data show a nice agreement with previous data referring to the water masses present in this area and their dynamics. Here, they are used to further analyze the mixing and deepening processes of Deep Ice Shelf Water (DISW) over the northern shelf break of the Ross Sea. In more detail, our work is focused on the elementary mechanisms that are the most efficient in removing dense water from the shelf: either classical mixing effects or density currents that interact with some topographic irregularity in order to drop to deeper levels, or also the variability of the Antarctic Circumpolar Current (ACC) which, in its meandering, can push the dense water off the shelf, thus interrupting its geostrophic flow. We also discuss in detail the (partial) evidence of dramatic interactions of the dense water with bottom particulate, of geological or biological origin, thus generating impulsive or quasi-steady density-turbidity currents. This complex interaction allows one to consider bottom particular and dense water as a unique self-interacting system. In synthesis, this is a first tentative analysis of the effect of bottom particulate on the dense water dynamics in the Ross Sea.     

Size-fractionated phytoplankton biomass and species composition in the Indian sector of the Southern Ocean during austral summer

During the late austral summer of 1994, Antarctic waters were characterized by low phytoplankton biomass. Along the 62°E meridian transect, between 49°S and 67°S, chlorophyll (Chl.) a concentration in the upper 150 m was on average 0.2 mg m⁻³. However, in the Seasonal Ice Zone (SIZ) chlorophyll a concentrations were higher, with a characteristic deep chlorophyll maximum. The highest value (0.6 mg Chl. a m⁻³) was measured at the Antarctic Divergence, 64°S, corresponding to the depth of the temperature minimum (100 m). This deep biomass maximum decreased from South to North, disappeared in the Permanently Open Ocean Zone (POOZ) and reappeared with less vigour in the vicinity of the Polar Front Zone (PFZ). In the SIZ, the upper mixed layer was shallow, biomass was higher and the >10 μm fraction was predominant. In this zone the >10 μm, 2–10 μm and <2 μm size fractions represented on the average 46%, 25.1% and 28.9% of the total integrated Chl. a stock in the upper 100 m, respectively. The phytoplankton assemblage was diverse, mainly composed of large diatoms and dinoflagellate cells which contributed 42.7% and 33.1% of the autotrophic carbon biomass, respectively. Moving northwards, in parallel with the decrease in biomass, the biomass of autotrophic pico- and nanoflagellates (mainly Cryptophytes) increased steadily. In the POOZ, the picoplanktonic size fraction contributed 47.4% of the total integrated Chl. a stock. A phytoplankton community structure with low biomass and picoplankton-dominated assemblage in the POOZ contrasted with the relatively rich, diverse and diatom-dominated assemblage in the SIZ. These differences reflect the spatial and temporal variations prevailing in the Southern Ocean pelagic ecosystem.     

Glacial–interglacial changes in the accumulation rates of major biogenic components in Southern Indian Ocean sediments

In this study we compare major biogenic components (opal-A, carbonate, and organic carbon) and authigenic uranium accumulation rates from the southeastern Indian Ocean for both Holocene and glacial periods. Integrated accumulation rates across the whole Indian sector of the Southern Ocean indicate that the burial of organic carbon which is held approximately constant, contrasts with lower biogenic silica and carbonate burial rates during glacial intervals. In addition, higher glacial accumulation rates of authigenic uranium are found in the sediments of the Polar Front Zone (PFZ) and the Sub-Antarctic zone (SAZ) than anywhere in the modern Southern Ocean. This suggests more reducing conditions in the PFZ and SAZ during the last glacial maximum. The simplest explanation of a northward shift of the PFZ cannot explain such changes. Glacial sediment burial changes result probably from deep water decrease in oxygen levels and increase in CO₂ due to combination of two processes: (1) hydrologic changes and (2) continuous organic carbon export fluxes to the seafloor. Such shifts in chemical conditions could have enhanced the dissolution of carbonates and better preserved the organic carbon in sediments, leading in significant changes of biogenic silica/C_org and CaCO₃/C_org flux ratios.     

浮动国土上的耕海人——记青岛远洋公司船长宿海山

金锚奖是中国海员工会全国委员会为表彰在艰苦航行工作中作出杰出贡献的海员,于1994年设立的一个专业大奖.本年度青岛远洋公司的宿海山船长获此殊荣.9月,记者在青岛采访期间,恰遇返航休假的宿船长,一番攀谈,让我对平素接触不多的远洋船长有了更多的认识.尽管坐在我眼前的宿船长,身着便装,沉默寡言,他军人般英挺的坐姿、威严的表情、锐利的目光和只有经历风霜才会有的紫铜般的肤色,无不鲜明地打上了职业的烙印.顿时让我对远洋船这一浮动的国土上的耕海人肃然起敬.     

"海洋权益":一个敏感而沉重的话题

2004年3月11日,正当十届人大二次会议和政协十届二次会议在北京召开,“两会”成为关注的焦点之际,当天的《参考消息》却以“中国渔民惹谁了”为主题,用了整整两个版面来报道周边国家对我渔民的驱赶和抓扣...... 2004年3月26日,经中国政府反复严正交涉,登上中国固有领土钓鱼岛后被日方非法扣留的7名中国公民,于当日晚离开日本,安全归来...... 媒体报道,中国国家海洋局所属“向阳红九号”海洋调查船最近在钓鱼岛附近海域进行调查活动,这是中方为搞清东海大陆架而进行的正常的调查活动,但日本不仅派出飞机进行监视,而且日本海上自卫队的舰船还强行驱赶“向阳红九号”...... 无论是外国对我渔民的驱赶和抓扣,还是日本对我保钓人士的无礼之举,在历史上都不是第一次,也绝不会是最后一次,而所有这一切,都事关中国的海洋权益。2     

青远航运：做好客户服务的大文章

“服务竞争”是未来企业竞争的一个核心领域。伴随着航运市场竞争的日益激烈，转变思维策略，跳出经验的窠臼，建立起现代客户服务管理的价值导向和宏观战略，成为大多数航运企业的探索和追求，以有效优质的服务满足客户需求是航运经营者最主要的目标之一。作为一家有着30多年航运经营历史的老牌航运企业，青远公司在变与不变中构思客户服务的大文章，用行动拭亮“青岛远洋”这块航运界的金字招牌。[编者按]     

中外理:港航价值链上的重要一环

中国外轮理货总公司(以下简称中外理总公司)成立于1961年,是经交通运输部批准,专门从事船舶理货业务的国有重要骨干企业,在上海、天津、青岛、广州、大连、宁波、深圳、厦门等主要港口设有70多家分支机构.经营国际、国内航线船舶的理货,国际、国内集装箱理箱,集装箱装、拆箱理货,货物的计量、丈量,监装、监卸,货损、箱损检定等业务.     

胡敦欣撩开海洋"神女"面纱

船舶安全与海洋环境、大洋环流等有着密不可分的关系.大海被称为神秘的“第六大陆“,无数科学家义无返顾踏进了这块“未知的蓝色土地“,决心撩开这位“神女“的面纱.中国科学院海洋研究所、海洋环流与气候环境联合研究中心主任胡敦欣院士,就是其中的一位.他从事海洋学研究40多年,在大洋环流、陆架环流和海洋通量研究等领域,有重大突破.他发现并命名了太平洋“棉兰老潜流“,并率先发现我国陆架中尺度涡“东海冷涡“;和确定我国“东海大气二氧化碳的弱汇区“.为船舶安全航行及国际海洋学的发展作出了杰出贡献.自上个世纪80年代中期至今,胡敦欣先后主持国家级重大科研项目8项,多次参与国际海洋前沿研究计划的设计和制定,并将有关研究引入中国,曾获得中国科学院重大成果一等奖等奖励.……     

Governance for Sustainability: Insights from Marine Resource Use in a Tropical Setting in the Western Indian Ocean

The last decade has seen a shift in the Natural Resource Management discourse, a shift from management to governance. Governance is held forward as a prime solution to problems associated with the sustainability of natural resources, including fisheries and other marine resources. Several countries in the Western Indian Ocean are framing governance solutions as a response to coastal/marine resource depletion and environmental degradation, but the challenges are huge and success stories remain few. This study provides an analysis of the governance situation in Chwaka Bay, Zanzibar, Tanzania. It presents the governance actors and how governance is expressed in terms of hierarchy (state), heterarchy (self-organized networks of resource users), and anarchy (market). The analysis illustrates the extreme difficulties of using governance approaches to steer human behavior to solve environmental problems and achieve sustainability. The study also provides some insights when considering the use of governance as a tool for the “designing” and/or “steering” social–ecological systems in subsistence contexts with weak formal institutions. These include the consideration of governance as an intrinsic part of complex societal processes, the idealization of governance as a template for redressing management failure and broader issues such as the importance of meta-governance.     

The Ocean Shipping Reform Act: the trans-Atlantic cares

For many years, economists have pressed for the deregulation of the shipping industry, with studies purporting to show constant returns to scale in motor transport, and staggering losses inflicted on the economy by regulation. Deregulation is now the order of the day in the US, but during the deregulation process, the Federal Maritime Commission (FMC) struggled with strong pressure to remove anti-trust immunity historically enjoyed by ocean shipping conferences.

However, instead of entirely removing this anti-trust immunity, the US Congress passed the Ocean Shipping Reform Act (OSRA) in 1998. OSRA, which came into effect on 1 May 1999, represents a logical continuation of the trend toward deregulation established by the Shipping Act of 1984. Although the Act (OSRA) maintains anti-trust immunity, its creation also established confidential service contracts between shippers and individual lines.

Because the actual effect of this Act has yet to be researched and reported in the transportation literatures, this paper assesses the impact of OSRA on the market structure of the container shipping industry. Three major east- and westbound arterial routes, as determined by Drewry Shipping Consultants and Containerisation International, are examined in this study to ascertain whether the markets are competitive or not 1, 2. The trade imbalance existing in all three trade routes (trans-Atlantic, trans-Pacific, and from Asia to northern Europe) provides a basis from which to investigate the pricing structure in the container shipping market. The changing tariff structure of the trans-Atlantic lane in 1999 provides the foremost evidence of the impact of the Act to evaluate the new law's impact on the maritime industry. By examining the traffic volume and freight rates of inbound and outbound trades, this paper found that before the second quarter of 1999, the trans-Atlantic lane's market structure was non-competitive, but it became competitive after the third quarter of 1999. This paper concludes that OSRA did have substantial influence on the market structure of the trans-Atlantic lane since the Act came into effect on 1 May 1999. The Act laid a solid legal framework upon the industry that forced the carriers in the trans-Atlantic trade route to operate competitively.     

The Prince Edward Islands pelagic ecosystem, south Indian Ocean: a review of achievements, 1976–1990

This review summarizes the main research findings of the multi-year oceanographic and biological studies conducted in the vicinity of the Prince Edward Archipelago during the period 1976 to 1990. The Prince Edward Islands represent a flow-through system on the mainstream of the Antarctic Circumpolar Current. Although there are no taxonomic differences between the pelagic communities of the upstream, inter-island and downstream regions, these mesoscale subsystems may operate differently. The mesoscale oceanographic and biological processes appear to be affected by the position of the Subantarctic Front (SAF) in the vicinity of the islands. Both the rich benthic community, which is supported by the local enhancement of primary production, and the strong advection of zooplankton/micronekton from the upstream region provide the food resources necessary for the survival of the huge community of land-based predators present on the islands. Collectively this is termed the ‘life-support system'. Future studies should concentrate on the meridional shifts in the position of the SAF and its influence on background productivity upstream and downstream of the Prince Edward Archipelago.     

Modelling the ice-ocean-plankton interactions in the Souther Ocean

Our goal is the study of interactions between sea ice and ocean and of their influence on planktonic communities. We use a physical model which includes explicitly melting dynamics and mixed-layer physics. A one-dimensional model of the water column with a k-1 turbulent closure is applied. The sea-ice model is the one proposed by Semtner (1976); we add a parameterization of leads. We enlighten the importance, in this kind of model, of the sharing of the energy between lateral and basal meltings. The biological model comprises two state variables: phytoplankton and zooplankton biomasses. Melting induces a persistent shallow mixed layer and thus appropriate conditions for primary production. If ice melting is present, high biomasses are possible even with high losses. The absence of ice nearly forbids a massive bloom to form. Some sensitivity studies have shown that grazing pressure is a key factor governing the evolution of biomasses. The biomasses are also sensitive to little modifications of the photosynthetic production. The initial amount of phytoplankton or the presence of ice algae seems to be of lesser importance.