Influence of the Mackenzie River plume on the sinking export of particulate material on the shelf

We examined the influence of the Mackenzie River plume on sinking fluxes of particulate organic and inorganic material on the Mackenzie Shelf, Canadian Arctic. Short-term particle interceptor traps were deployed under the halocline at 3 stations across the shelf during fall 2002 and at 3 stations along the shelf edge during summer 2004. During the two sampling periods, the horizontal patterns in sinking fluxes of particulate organic carbon (POC) and chlorophyll a (chl a) paralleled those in chl a biomass within the plume. Highest sinking fluxes of particulate organic material occurred at stations strongly influenced by the river plume (maximum POC sinking fluxes at 25 m of 98 mg C m^− 2 d^− 1 and 197 mg C m^− 2 d^− 1 in 2002 and 2004, respectively). The biogeochemical composition of the sinking material varied seasonally with phytoplankton and fecal pellets contributing considerably to the sinking flux in summer, while amorphous detritus dominated in the fall. Also, the sinking phytoplankton assemblage showed a seasonal succession from a dominance of diatoms in summer to flagellates and dinoflagellates in the fall. The presence of the freshwater diatom Eunotia sp. in the sinking assemblage directly underneath the river plume indicates the contribution of a phytoplankton community carried by the plume to the sinking export of organic material. Yet, increasing chl a and BioSi sinking fluxes with depth indicated an export of phytoplankton from the water column below the river plume during summer and fall. Grazing activity, mostly by copepods, and to a lesser extent by appendicularians, appeared to occur in a well-defined stratum underneath the river plume, particularly during summer. These results show that the Mackenzie River influences the magnitude and composition of the sinking material on the shelf in summer and fall, but does not constitute the only source of material sinking to depth at stations influenced by the river plume.     

On the distribution of dissolved lead in the Loire estuary and the North Biscay continental shelf, France

The dissolved lead was studied in the whole salinity gradient of the system composed of the Loire estuary and the North Biscay continental shelf. About 130 samples were collected in winter 2001 and spring 2002 during Nutrigas and Gasprod campaigns (Programme PNEC-Golfe de Gascogne, RV Thalassa) and metal measurements were conducted on board by Potentiometric Stripping Analysis. In the Loire estuary, levels of dissolved lead ranged from 0.15 to 0.24 nM and from 0.04 to 0.26 nM in winter and spring, respectively. Compared to the concentrations reported in 1987 and 1990 (0.4–1.7 nM; Boutier, B., Chiffoleau, J.F., Auger, D., Truquet, I., 1993. Influence of the Loire river on dissolved lead and cadmium concentrations in coastal waters of Brittany. Estuar. Coast. Shelf S., 36:133–143, Estuarine, Coastal and Shelf Science 36, 133–143) our study indicated much lower values. The fall in concentration in the estuary could be attributed to the stopping of activity of Octel, a big manufacturer of tetra alkyl lead. Discharge in dissolved metal to the continental shelf by the Loire river was assessed as 7.5 and 1.9 kg day^− 1 for winter and spring, respectively. On the continental shelf, levels of dissolved lead varied within 0.06 and 0.27 nM in winter (0.15 ± 0.06 nM, sd = 1.96, n = 49), whereas concentrations measured in spring were in the range 0.06–0.17 nM (0.09 ± 0.03 nM, sd = 1.96, n = 60). This difference in metal concentration was related to the amounts of rainfall that have fallen over the continental shelf: estimations of inputs by this way (74 and 32 kg day^− 1 in winter and spring, respectively) appeared to be significantly higher than inputs from the Loire river (7.5 and 1.9 kg day^− 1 in winter and spring, respectively). The distributions of dissolved metal in the surface waters highlighted the role of suspended particular matter (SPM) for a rapid “trapping” of lead near the mouth of the estuary. The vertical distributions showed, in the stratified area, a biological transfer of lead between winter and spring from surface waters to the halocline.     

Intra-annual variability of distribution patterns and fluxes of dissolved trace metals in a subtropical estuary (Danshuei River,Taiwan)

Water samples were collected along salinity gradients and dissolved trace metal (Cd, Cu, Ni, Pb, and Zn) concentrations were determined in a macro-tidal, mountainous estuary (Danshuei River Estuary) in northern Taiwan. Bi-monthly surveys were conducted between March 2001 and June 2002, during both wet and dry seasons. This study investigated intra-annual variability, fluxes, and the extent of addition or removal of dissolved trace metals in the estuary, which is characterized by the fluctuation of redox interface according to river flow conditions. In sub-oxic and anoxic waters, the presence of reduced sulfur species led to the formation of metal-sulfide minerals that sequester metals out of the water column. Therefore, trace metal fluxes and removal/addition rates are seasonally variable, largely by the extent of estuarine hypoxia. In the 9 sampling expeditions over the 16-month period, fluxes of dissolved trace metals out of the Danshuei River Estuary were estimated as follows: Cd, ? 0.33–4.46 mol/day; Cu, ? 48–1112 mol/day; Ni, 1836–6586 mol/day; Pb, 2.47–11.59 mol/day; and Zn, 361–2656 mol/day. For elements such as Cd and Cu, the removal in the Danshuei River Estuary during dry seasons was so dramatic that there were net fluxes from the coast to the estuary (negative fluxes). Ni behaved near conservatively in this estuary, thus its river endmember concentrations directly determined Ni fluxes out of the estuary. Removal of Pb was effectively enhanced by the presence of higher suspended particulate matter concentrations in the upper estuary and the formation of Fe- and Mn-oxides and oxyhydroxides that precipitate out of the water column in mid-estuary, which generally leaves low effective river endmember Pb concentrations, thus low fluxes out of the estuary.     

长江口南港河段近期河床演变特征及航道整治策略*

长江口南港长期以来是一条上下贯通、水深条件良好的入海通道。长系列水沙、地形实测资料表明,近期南 港河段发生了一系列的河势变化,突出表现在瑞丰沙下沙体的冲刷和中部串沟的发展。在近期河床演变特征、演变趋势分 析,以及南港12.5 m深水航道回淤特性分析的基础上,研究南港航道的整治策略,并提出初步治理方案。     

长江口北港航道开发治理思路

随着长江口主航道通航压力的不断加大,北港航道治理工程已被列入《长江口航道发展规划》、《长江经济带综合立体交通走廊规划(2014—2020年)》等规划之中。在总体把握北港河势现状和碍航性质的基础上,结合当前长江口航道发展面临的内外部形势,全面分析北港航道开发的各种有利条件和约束因素,探讨其治理思路。分析表明,北港航道已基本具备可开发性,但同时面临崇明东滩鸟类国家级自然保护区、中华鲟自然保护区、青草沙水源地等约束限制。从分期推进的战略角度出发,初步形成的北港航道治理思路是先期开通6 m航道,再结合横沙深水新港建设等周边需求协同开发。     

长江口维护疏浚工程施工特点与控制

基于长江口12.5 m深水航道维护疏浚工程历年的施工经验,分析工程特点,针对疏浚施工与航道安全运营之间矛盾大、质量要求高、外部环境复杂、实际回淤量远远超过合同工程量等特点,提出了掌握航道回淤规律、加强施工过程控制、安全控制和外部协调等控制要点,满足工程要求。     

长江口12.5m深水航道运行状况及特点

基于海事部门船舶运输管理系统(VTS)资料及交通运输部长江干线货运量统计资料,对长江口12.5 m深水航道运行状况及特点进行分析,并探讨当前深水航道通航压力的缓解对策及建议。研究表明:长江口航道货物通过量快速增长,重进轻出态势进一步发展;通航船舶运营组织方式发生一定变化,船舶朝大型化方向发展,尤其船宽超过45 m以上大型船舶数量增加明显,长江口12.5 m主航道的双向通航能力尚显不足。为缓解当前乃至未来一段时间内长江口深水航道通航压力,宜加快长江口航道体系建设的实施步伐,并适时加强长江口主航道拓宽可能性的研究。     

A matter of consistency: A congressional perspective of oil and gas development on the outer continental shelf

Abstract

On April 27, 1981, the Department of the Interior (DOI) published the final notice of lease sale 53—the Santa Maria Basin off Central California. In the northern part of the basin are located 29 tracts (out of a total 111 offered) considered environmentally sensitive by many and politically explosive by all. As expected, the state of California sued the federal government and has twice prevailed. Consequently, the DOI appealed these earlier rulings to the Supreme Court and in January 1984 the Court ruled in favor of the DOI. This well publicized case (Watt v. California) represents a failure on the part of the Congress, the Reagan Administration, and the coastal states to reach an accord on the degree of state participation in the Outer Continental Shelf (OCS) development process. This article does not attempt to resolve this debate; rather, this paper presents the contrasting arguments in the U.S. government; and it illustrates how U.S. coastal policy is politicized and shaped from the national level.     

珠江口区域海上溢油动态预测信息系统的开发与应用

为了对《珠江口区域溢油应急计划》提供决策支持,在国内外相关研究成果基础上,针对珠江口海域的特点,研究开发了先进实用的"珠江口区域海上溢油动态预报信息系统",综合了三维潮流模型、三维溢油扩散模型、溢油风化模型、应急反应模型、以及电子海图、地理信息系统(GIS)、数据库等关键技术。该系统可以预测模拟并可视化显示海上溢油的漂移扩散和性质变化过程,同时显示环境敏感区和应急人员设备分布等相关信息。实际溢油应用案例表明,该系统的预报模拟结果与现场实际情况完全相符,能有效地提高海上溢油污染事故的应急决策效率。     

长江口水域高精度水文测量四维无缝基准的建立及应用

在宽阔的潮汐河段,由于潮汐和地形的影响,大范围的同步水文测验的精度和可靠性受到了很大的限制。为了得到高精度的水文测量成果,使同步观测资料和时间序列资料具备良好的可比性,需要建立高精度的平面基准、高程基准和速度基准。理论和实践表明,建立大范围内的高精度的GNSS(global navigation satellite system)控制网,基于RTK(real-time kinematic)测量方式进行三维水深测量、基于RTK的速度参考进行流量测量,是在大范围条件下开展高精度同步水文观测的有效途径。     

Spatial distribution patterns of demersal and epibenthic communities on the Galician continental shelf (NW Spain)

Spatial distribution patterns of epibenthic communities on the Galician continental shelf were studied using multivariate methods. Data came from 5 surveys carried out in 2002, 2003 and 2004. Beam trawls and otter trawls were used to study epibenthic communities along 8 transects perpendicular to the coastline. The role of depth, season, latitude and sediment characteristics was examined. Seven habitats were described according to bathymetry and sediment characteristics. There were weak linear relationships between environmental variables and species richness, biomass and species diversity. However, the canonical analysis showed that depth and sediment characteristics greatly influence smaller epibenthic communities sampled by beam trawl. Six assemblages were obtained for beam trawls: inner shelf mud, very fine sands, and fine sands, middle shelf sands, and outer shelf very fine sands, and fine sands. Five assemblages were identified for larger-sized and swimming epibenthos sampled with otter trawls. These assemblages were also determined according to depth and sediment type but sediment characteristics were less important. Otter trawl assemblages were the same as the beam trawl ones, except for on the outer shelf where no differences between sediment type were detected. For both gears, inner and outer shelf assemblages displayed a higher biotic variability than the middle shelf, as a consequence of a higher environmental heterogeneity. Typifying species were mainly eurytopic in the middle shelf, whereas eurytopic and stenotopic species characterised the inner and outer shelves.     

海平面上升对长江口涨落潮历时差的影响

针对近年来全球变暖,海平面上升影响河口地区水文特性的问题,对海平面上升对长江口涨落潮历时差的影响进行研究。采用二维潮流数学模型的方法,模拟在长江口上游大通的洪枯季及年平均径流量条件下,海平面上升100 cm对涨落潮历时的影响。结果表明:海平面上升减小了长江口北支上半段、南支和南北港等中上游区域的涨落潮历时差,对靠近外海的北支末段和南北槽的涨落潮历时差影响很小。海平面上升加大了河口地区的涨潮动力,使长江口的涨落潮历时差有所减小,由此对长江口地区的盐水入侵和泥沙输运带来的影响必须引起重视。     

长江口南支南港的北槽枯季水体中混合、层化与潮汐应变*

2010年1月1日至10日在长江口南支南港北槽航道弯道段内3个水文测站位CS1、CSW和CS8,观测得到大、中、 小潮的潮位、流速、盐度和含沙量的时间序列。这些资料揭示了由盐度和含沙量引起的垂向层化的大、小潮和涨、落潮的 潮周期变化特性。为定量了解航道弯道段水体的垂向混合程度,采用考虑含沙量后的水体密度来估算其梯度Richardson数 (Ri)。在转流时刻,CS1和CSW站位的量级为101 ~ 102,水体呈现层化状态;在涨急、落急时,Ri量级为10-2 ~ 10-1,水体呈 现强混合状态。CS8站位涨潮时的Ri在0.25~5,落潮时平均为10-2量级。3个水文测站位,涨潮时的层化均强于落潮时;大潮 时的层化程度最强,而小潮时的层化持续时间最长; 均存在潮汐应变的现象,且以非持久性的SIPS层化为主。采用Simpson 等[2]的公式,估算了长江口北槽航道弯道段内水体由河口环流、潮汐应变和潮汐搅动引起的势能变化率。潮汐应变是水体 层化的主要动力机制,而河口环流引起的势能变化率比潮汐应变和潮汐搅动引起的小102 ~ 103量级。     

联手下好“一盘棋” 合力推进长江口南槽航道治理工程

3月29日,随着长江口南槽航道96座导助航标志调整和设置工作的结束,该航道治理一期工程的第一阶段航海保障工程圆满收官,这是继长江口12.5米深水航道治理工程后,按照长江口"一主两辅一支"航道体系的总体规划实施的又一重大航道整治工程。     

长江口深水航道南导堤上段整治建筑物损坏原因及对策

在长江口航道养护工作中,为查找南导堤上段局部整治建筑物损坏的原因,通过对现场的详细调查和对损坏区段的地形状况、水动力特征、水动力模型进行分析,得知损坏的主要原因,即在河势条件及水动力因素综合作用下,近堤边坡不断变陡,从而导致了损坏。据此编制修复设计方案,并完成修复,取得良好的效果。     

Intrusions of eastern North Atlantic central waters and phytoplankton in the north and northwestern Iberian shelf during spring

The influence of intrusions of eastern North Atlantic central water (ENACW) in the north and northwestern Iberian shelf on phytoplankton composition and abundance and on particle-size distributions of seston was analyzed using data collected on three extensive cruises during spring 1991 and 1992. Water with temperature and salinity values between 12.20 and 13.86 °C and between 35.66 and 35.98 psu, respectively, characteristics of the subtropical type of ENACW (ENACW_t), was detected in the upper 100 m of the water-column in all cruises, but particularly in the western coast in 1992. The highest salinity values of this water were found near the surface (0–100-m depth) and in early spring 1992, while minimum salinity values, and also minimum geographical extension, were found in late spring in both years. Phytoplankton blooms concentrated in frontal areas between different water types, with maximum intensity and extension in early spring.Using temperature and salinity characteristics, samples were classified in four groups corresponding to the major water types found in the region: Bay of Biscay central water (BBCW), two segments of ENACW of different salinity and surface water influenced by continental runoff. This classification was significantly confirmed by three independent discriminant analyses using hydrographic and chemical (dissolved nutrients and chlorophyll) variables, phytoplankton species abundance variables and particle-size concentration of seston variables. Phytoplankton blooms related to the presence of saline waters were characterized by the dominance of either chain-forming diatoms or a mixture of diatoms and phytoflagellates and high concentrations of seston. The diatom species dominating in saline waters were typical of upwelling-induced blooms occurring generally during summer. Blooms occurring in waters influenced by runoff also contained diatoms but in lower numbers than those of saline waters. Nutrients were not exhausted in the region, suggesting that phytoplankton populations were still in active growth. These results are interpreted taking into account the known variability in water-mass formation and in the poleward current driving ENACW_t along the shelf, and indicate that saline intrusions are a major feature affecting the distribution and composition of plankton in the spring in the southern Bay of Biscay, thus enlarging to a wider spatial scale their reported influence on the pelagic ecosystem.     

Monitoring trace elements (Al, As, Cr, Cu, Fe, Mn, Ni and Zn) in deep and surface waters of the estuary of the Nerbioi-Ibaizabal River (Bay of Biscay, Basque Country)

Deep water samples (in contact with the sediment) were collected at eight different points of the estuary of the Nerbioi-Ibaizabal River (Bay of Biscay, Basque Country), both at low and high tides, during four sampling campaigns (May, September and December 2005 and March 2006). Superficial water was also sampled in March 2006. Temperature, pH, redox potential, dissolved oxygen and electrical conductivity corresponding to each sample were measured in situ at each sampling point using a multiparametric probe. The physico-chemical parameters found are typical of highly stratified estuaries, with an acceptable oxygenation level. After filtering and acidifying the samples, they were analysed by inductively coupled plasma/mass spectrometry (ICP/MS) to simultaneously determine the total concentration of Al, As, Cr, Cu, Fe, Mn, Ni and Zn. Concentrations in the μg kg^− 1 level were found in all cases (c_Cr and c_Ni, 1–10; c_Al, c_As and c_Zn, 10–50; c_Cu and c_Mn, 10–100 and c_Fe, 100–400 μg kg^− 1). A probable net input of Al, Cr, Mn and Zn via the main (Nerbioi-Ibaizabal) and some of the tributary rivers (Galindo, Asua and Gobela) was identified. Evidence of a common source of Al and Zn to the estuary was found. Correlation analysis of data revealed connections between variables (concentration of Cu, Fe and As with salinity, as well as c_Al with c_Zn, c_Cu with c_Fe, c_As with c_Fe, and c_As with c_Cu). Principal Component Analysis (PCA) of data allowed the samples to be grouped according to sampling campaign, with two principal components accounting for 62% of the total variance. In addition, plots of element concentration against salinity suggested a conservative behaviour for As, Cu and Fe and a non-conservative one for Cr. Not clear mixing behaviour was observed for the rest of elements.     

Benthic foraminifera in the surface sediments of the Beaufort Shelf and slope, Beaufort Sea, Canada: Applications and implications for past sea-ice conditions

This paper presents new data on distribution patterns of modern benthic foraminifera and other microfossils from the Canadian Arctic, specifically the Beaufort Shelf and slope. The material was collected in June to August of 2004 and is the first of its kind in this area to be collected since 1970. We examined the smaller sizes (45–63µm) as well as > 63µm and discovered that many species had been severely underrepresented in previous studies. Deep sea forms, that had been overlooked previously, were common on the shelf; two species (Elphidiella arctica and Ammotium cassis) appeared in preliminary results to be indicators of methane seepage; and it was possible to make determinations of sea-ice coverage using a combination of foraminifera and tintinnids (planktic ciliates). Our data indicated the presence of many of the same species as previous studies from this area, but improved techniques of sample processing greatly increased the number of specimens and species found (particularly the small deep sea arctic species Buliminella hensoni and Bolivina arctica) which provide much more reliable data for paleoceanographic determinations. One of the primary objectives for this work was to provide baseline data to help determine paleo-ice cover; these data cover a broad range of conditions on the Beaufort Shelf that make it possible to achieve this objective as well as improving what it is known about the assemblages on this shelf as compared to other arctic shelf areas, such as the Siberian Shelf).     

长江口南北港分汊口附近水域河势变化及航道格局调整

近些年,因新浏河沙头部的淤浅,长江口南北港分汊口河段宝山北航道的通航环境转差。为找到有效解决方案,利用地理信息系统(GIS)分析近10年该河段的河势变化,研究航道格局调整方案。结果表明,该水域河槽容积、深泓线平面及等深线变化比较明显,新浏河沙包收缩变小,新浏河沙头部逐渐淤浅并向航道方向移动的趋势仍在发展,现阶段可通过微调航道格局改善通航环境。     

未雨绸缪保长江汛期安全

2010年,长江流域出现罕见大洪水,长江三峡迎来了成库以来70000立方米/秒最大入库流量;2011年,长江迎来历史罕见的旱涝急转,9月中旬,嘉陵江、汉江分别遭遇30年一遇和20年一遇特大秋汛;2012年,长江上游先后形成4次洪峰,江津、坝上、坝下分别遭遇100年、50年和30年一遇的特大洪峰,创长江上游自1981年以来最大洪水……
　　每年春夏之际,长江都会迎来强降雨期,局部大雨、暴雨现象时有发生,水位陡涨陡落现象明显,长江洪峰的记录也不断被刷新。为了保证辖区船舶在长江汛期内航行安全,长江海事局提前部署,强化重点监管,以继续谱写抗洪抢险的辉煌篇章。