Winter–spring dynamics in sea-ice carbon cycling in the coastal Arctic Ocean

An understanding of microbial interactions in first-year sea ice on Arctic shelves is essential for identifying potential responses of the Arctic Ocean carbon cycle to changing sea-ice conditions. This study assessed dissolved and particulate organic carbon (DOC, POC), exopolymeric substances (EPS), chlorophyll a, bacteria and protists, in a seasonal (24 February to 20 June 2004) investigation of first-year sea ice and associated surface waters on the Mackenzie Shelf. The dynamics of and relationships between different sea-ice carbon pools were investigated for the periods prior to, during and following the sea-ice-algal bloom, under high and low snow cover. A predominantly heterotrophic sea-ice community was observed prior to the ice-algal bloom under high snow cover only. However, the heterotrophic community persisted throughout the study with bacteria accounting for, on average, 44% of the non-diatom particulate carbon biomass overall the study period. There was an extensive accumulation of sea-ice organic carbon following the onset of the ice-algal bloom, with diatoms driving seasonal and spatial trends in particulate sea-ice biomass. DOC and EPS were also significant sea-ice carbon contributors such that sea-ice DOC concentrations were higher than, or equivalent to, sea-ice-algal carbon concentrations prior to and following the algal bloom, respectively. Sea-ice-algal carbon, DOC and EPS-carbon concentrations were significantly interrelated under high and low snow cover during the algal bloom (r values ≥ 0.74, p < 0.01). These relationships suggest that algae are primarily responsible for the large pools of DOC and EPS-carbon and that similar stressors and/or processes could be involved in regulating their release. This study demonstrates that DOC can play a major role in organic carbon cycling on Arctic shelves.     

A new regulation for the European public transport

Authority intervention in the public transport sector has a long history and has led to a growing corps of legal texts in European countries. These texts are often divergent, if not incompatible. This was no problem until the rather recent internationalization of the sector. With this internationalization, the European Commission decided to address this issue. This chapter describes what has led to the appearance of this new Regulation and the main steps on the 10-year long road that led to the adoption of the new Regulation. The chapter also formulates some comments on the results reached.     

从《欧盟宪法条约草案》看欧盟的性质

作为一个特殊的国际组织,欧洲联盟的性质问题一直被广泛讨论。随着欧盟一体化程度的不断加深以及欧盟宪法条约草案的出台,欧盟究竟是一个什么样的组织就更值得研究了。文章通过对欧盟宪法条约草案内容的分析,认为欧洲联盟是一个联邦与邦联的混合体,但更倾向于向联邦发展。     

基于欧洲标准的城市轨道交通车辆制动系统动态型式试验

介绍了基于欧洲标准的城市轨道交通车辆制动系统的动态型式试验内容,对制动系统动态型式试验内容进行了分析。参考城市轨道交通BS EN 13452-2:2003及BS EN 15595:2009等标准提出了车辆整车制动系统动态型式试验的评价标准及所需要进行的相关试验。     

Environmental causes of the fluctuations of red shrimp (Aristeus antennatus) landings in the Catalan Sea

The fluctuations of catches of the deep-sea shrimp Aristeus antennatus (Risso, 1816) were analysed in the 6 ports of Catalonia where production is concentrated, based on monthly landings from 1988 to 2004. The 6 selected ports produced 300 t of red shrimp in 2004, or 80% of the total production in Catalonia. The series for each port showed clear interannual variability, with peaks of production in the early 1990s and more recently from 2001 to 2003. The time periods of the monthly data series, estimated by frequency analysis based on Fourier transform, varied around 7–8 years in the four central ports and 12–13 years in the two northern ports. Additionally, the different curves were not in phase: even in nearby ports, the maximum production is observed in different years. Since the North Atlantic Oscillation (NAO) index is an excellent proxy for long-term series of environmental variables, we aimed to explore relationships between the fluctuation of the NAO index and A. antennatus landings in the Catalan Sea. The correlation between the mean annual NAO index and the annual catches in each port was positive and significant with some time lags (from 1 to 3 years). The existence of clear patterns linking the NAO with marine ecological processes has been demonstrated in many studies, but the underlying ecological mechanisms are far from being well understood. The variations in environmental parameters linked to the NAO may act on biological organisms at different levels (individual, population) through physiology (metabolic and reproductive processes) or through trophic relationships, including ecological cascade effects. We propose that NAO-induced environmental variability may enhance food supply to A. antennatus and hence strengthen the reproductive potential of particular year classes, which result in increased catches 1 to 3 years later, although other possible effects of environmental variability on the population dynamics of this species are worth investigating.     

Distribution of dinoflagellate cysts in surface sediments of the Mackenzie Shelf and Amundsen Gulf, Beaufort Sea (Canada)

In order to document long-term climate cycles and predict future climate trends for the Arctic, we need to look at the geological records to establish the link between historical and pre-historical sea-surface parameters. Dinoflagellate cysts (dinocysts) are used as proxy indicators of sea-surface parameters (temperature, salinity, sea-ice cover, primary productivity) jointly with transfer functions and a modern dinocyst reference database, to reconstruct the evolution of sea-surface conditions at decadal and millennial timescales. Here we present the surface distribution of recent dinocyst assemblages from 34 surface sediment samples collected on the Mackenzie Slope/Amundsen Gulf during the 2004 CASES (Canadian Arctic Shelf Exchange Study) cruise. Dinocyst concentrations in surface sediments are relatively high outside the Mackenzie plume area and increase gradually eastward toward Amundsen Gulf. The cysts of autotrophic dinoflagellates are dominant throughout the study area, while the maximum abundance of heterotrophic taxa is found within the Mackenzie plume. Hierarchical clustering analyses allowed defining two dinocyst assemblages. Assemblage I is located on the Mackenzie Slope and southern Amundsen Gulf, while Assemblage II is located within the Cape Bathurst Polynya area in northern Amundsen Gulf. Both assemblages are dominated by Operculodinium centrocarpum, but are distinguished on the basis of the relative abundance of Islandinium minutum, a taxon generally associated with sea ice. I. minutum is found in lower abundance in the Cape Bathurst Polynya.     

Seasonal upwelling underneath the Tsushima Warm Current along the Japanese shelf slope

Seasonal upwelling variations are examined in the eastward coastal boundary branches of the Tsushima Warm Current (TWC). The climatological pattern and the fundamental hydrographic structure of the seasonal appearance of cold water are revealed by analyzing the temperature profile data around the Japanese shelf area. Seasonal maps of temperature at the intermediate layer around 200 m depth show the rise of the main pycnocline along the Japanese coast due to seasonal subsurface cooling from May to September. The cold water areas appear around the strong curvature in the continental shelf break. These areas are confined to the south of the TWC thermal front, i.e., to the coastal boundary region. The seasonal appearance of the localized cooling areas implies that the seasonal upwelling is induced by horizontal variations in shelf topography and the intensifying TWC from May to September.     

欧标体系下码头打入桩施工前期策划及工作流程

码头打入桩施工前期的策划主要包括选择打桩设备、制定沉桩控制标准和现场试验等,是打入桩设计施工能否顺利实施的关键.而中、欧标准的差异会让熟悉国内标准的中国工程师对欧标体系下打入桩施工前的策划工作感到困扰.从规范条文出发,介绍欧标体系下码头打入桩施工前期的主要策划工作,并通过与中国规范相关内容的对比,总结中、欧标准的异同以...     

Swimming for survival: A role of phytoplankton motility in a stratified turbulent environment

We investigate a role for vertical migration in stratified coastal water, where the swimming speed is generally significantly less than the typical turbulent fluctuations in a tidally-mixed bottom layer. In our modelling approach we use a k- turbulence model to describe the physical forcing, a Lagrangian random walk model to describe the vertical displacement of individual cells in response to turbulence and due to cell motility, and a phytoplankton growth model to direct the swimming behaviour of the phytoplankton according to their light and nutrient requirements. The model results show how the cells form a stable subsurface chlorophyll maximum (SCM) at the base of the thermocline where episodic tidal turbulence causes erosion of part of the SCM biomass into the bottom mixed layer (BML). We then focus on the question of whether an ability to swim (weakly, compared to typical bottom layer turbulent intensities) provides any advantage by allowing return to the SCM. Our results show that tidal turbulence in the BML helps both motile and neutrally-buoyant cells by periodically pushing them into the base of the thermocline. Motile cells then have the advantage that they can swim further into the thermocline towards higher light which also reduces the likelihood of being re-mixed back into the BML.