Benthic assemblages of a temperate estuarine system in South America: Transition from a freshwater to an estuarine zone

The objectives of the present study were to describe the species composition, diversity and distribution of the zoobenthic assemblages, to estimate the abundance and biomass of the dominant species, and to identify the main environmental factors determining the distribution patterns of the invertebrates from a freshwater to an estuarine zone in a temperate estuary of South America. The Río de la Plata estuary is a microtidal system characterized by a high concentration of suspended solids. Fifty-three taxa of meso- and macro-invertebrates were identified in the samples collected during November and December 2001. Molluscs, annelids, crustaceans and nematodes were found at 90% of the sampling sites. Molluscs comprised up to about 90% of the total zoobenthos biomass: the remaining percentage corresponded mainly to annelids and less to nematodes and crustaceans. An ecocline along the salinity gradient could be observed for the benthic assemblages from the freshwater to the estuarine zone in Rio de la Plata. A Canonical Correspondence Analysis shows that results from sampling sites in the outer zone were strongly related to salinity, depth and pH and less to oxygen and percentage of clay. The results from stations in the inner zone, and part of the middle zone, were mainly related to the occurrence of sand and contents of NH₄⁺–N, NO₃⁻–N, and PO₄³⁻–P.     

水静得明独留巧思--访全国"三八"红旗手、CCS信息中心副总经理王立真

想采访王立真很久了。自本刊2002年第三期对她进行报道后,就一直期待着有机会再次做些深入采访。每次,王立真总是友好地与你交谈,然后是彬彬有礼地谢绝。 从2002年到2003年,从去年到今年,几乎每一期《中国船检》都将采访王立真列入选题。记者不断重复着一个同样的请求,王立真的友好依旧,谢绝依旧。 直到这期《中国船检》即将付印前夕,记者才在领导的帮助下,坐在了王立真的办公桌前。     

孕妇坠海生还记

意外坠海　　落难钻井平台　　　　2002年9月13日深夜,波涛汹涌的墨西哥湾上,一艘从墨西哥东海岸韦拉克鲁斯开往哈瓦那的客轮正全速航行在夜色深沉的大海上。28岁的单身女乘客琳达乘船去哈瓦那探望丈夫凯,凯常年在古巴做药品生意。琳达启程前故意没有通知凯,她要给丈夫一个惊喜     

The U.S. national marine sanctuary program: An analysis of the program's implementation and current issues

Abstract

The U.S. National Marine Sanctuary Program was established in 1972 by Title III of the Marine Protection, Research, and Sanctuaries Act (16 U.S.C. §1431 et seq.). In this article, we discuss the development of the sanctuary concept, and the original intent of Congress, and analyze how it was applied by the sanctuary program. Differences in interpretation of the program's purpose are examined, including discussion of the multiple‐use management concept, an important but controversial management technique used in the sanctuaries. The continuing efforts by Congress and the National Oceanic and Atmospheric Administration to clarify the program's purpose are investigated. The program's administrative history is explained and the current sanctuaries and active candidates are briefly described. In light of the 1988 reauthorization of the Marine Sanctuary Act, the current issues facing the program are analyzed. Finally, we draw conclusions and make recommendations for the program's future.     

旧船局域网的构建方案

从旧船的实际情况出发,介绍了一种全新的旧船局域网构建方案。它不同于传统的使用网线组网的方式,而是利用船舶中原有电话线连接微机组成局域网,不破坏船体,不需重新布线,有效地利用了船舶现有资源。该方案不但解决了旧船搭建局域网的问题,而且具有较好的经济效益。     

A box model approach for a long-term assessment of estuarine eutrophication, Szczecin Lagoon, southern Baltic

We develop a layered “box model” to evaluate the major effects of estuarine eutrophication of the Szczecin lagoon which can be compared with integrating measures (chlorophyll a (Chl a), sediment burial, sediment oxygen consumption (SOC), input and output of total nutrient loads) and use it to hindcast the period 1950–1996 (the years when major increase in nutrient discharges by the Oder River took place). The following state variables are used to describe the cycling of the limiting nutrients (nitrogen and phosphorus): phytoplankton (Phy), labile and refractory detritus (D_N, D_Nref, D_P, D_Pref), dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP), and oxygen (O₂). The three layers of the model include two water layers and one sediment layer. Decrease of the carrying capacity with respect to the increased supply of organic matter of the system with advancing eutrophication over the period studied is parameterized by an exponential decrease of the sediment nitrogen fluxes with increasing burial, simulating changing properties from moderate to high accumulating sediments. The seasonal variation as well as the order of magnitude of nutrient concentrations and phytoplankton stocks in the water column remains in agreement with recent observations. Calculated annual mean values of nutrient burial of 193 mmol N m⁻² a⁻¹ and 23 mmol P m⁻² a⁻¹ are supported by observed values from geological sediment records. Estimated DIN remineralization in the sediments between 100 and 550 mmol N m⁻² a⁻¹ corresponds to SOC measurements. Simulated DIP release up to 60 mmol P m⁻² a⁻¹ corresponds to recent measurements. The conceptual framework presented here can be used for a sequential box model approach connecting small estuaries like the Szczecin lagoon and the open sea, and might also be connected with river box models.     

浅议老港区再开发——兼谈大连港大港区再开发

港口再开发理念、港口再开发目标控制及大连港大港作业区再开发的主要思路。     

旅顺百年大坞的修复方案

旅顺大坞建于1883年，至今仍在使用。具有很高的使用价值和文物保护价值。但因年代太久，内部砼大部分已经老化，必须彻底修复。本文主要介绍大坞的历史、结构和修复方案。     

Nitrogenous discharges to the eastern Gulf of Finland, the Baltic Sea: Elemental flows, stable isotope signatures, and their estuarine modification

We studied the nutrient input to the Gulf of Finland via River Neva, the largest river discharging freshwater to the Baltic Sea, and characterised the isotopic signatures (¹⁵N, ¹⁸O, ¹³C) in dissolved and particulate substances (NO₃⁻, PON, POC, DIC) in the River Neva over two seasonal cycles, as well as in samples from St. Petersburg wastewater treatment plants (NO₃⁻, NH₄⁺, PON, POC). These riverine and municipal discharges account for 40% of terrestrial inorganic N loading to the Gulf of Finland, representing annually 7% of the total nitrogen pool in the water mass of the whole Gulf. To describe and evaluate the modification of these isotopic signals along a Gulf of Finland transect towards the Baltic Proper, two cruises were arranged, one in late spring after the annual maximum in River Neva runoff, and one in autumn, in the late phase of the annual growth season.River Neva nitrate signatures of ¹⁵N and ¹⁸O indicated major agricultural fertilizer origin of nitrogen, and the isotopic composition was clearly lighter (δ¹⁵N-NO₃⁻ mean of 2.4‰ air) than previously measured from more southern rivers discharging into the Baltic Sea. Because of the light composition of the River Neva N source, close to the ¹⁵N signatures of the open Gulf, as well as of the efficient depletion of the inorganic load already in the innermost estuary, straightforward end-member tracer analysis of the transport of N in the basin is problematic. St. Petersburg wastewater ammonium showed, however, high δ¹⁵N values (ca. 13‰), which gives a first estimate of 5.8‰ for δ¹⁵N of the easternmost estuarine total inorganic N source. The available sediment data from the basin (δ¹⁵N 6 to 8‰) somewhat exceeds the average source signature. This emphasizes the significance of biological transformation processes, most importantly assimilation of inorganic nitrogen, food web interactions and denitrification, which all involve isotopic fractionation, for the mass balance models describing the dynamics of the sources and sinks of the N cycle of the basin.     

Mixing in the surface boundary layer of a tropical freshwater reservoir

A combined observational-modeling study was conducted to investigate turbulence mixing, and the relation to surface forcing, in the surface boundary layer (SBL) of a tropical, high-altitude, freshwater reservoir. A suite of vertical profiles of temperature microstructure, collected at three different stations of one-day duration each, provided estimates of dissipation rates of turbulence kinetic energy, , and temperature variance, χ. Numerical simulations of and χ, using state-of-the-art, public domain, two-equation turbulence closure models, compared favorably with the observations and reproduced the dynamics of daytime wind mixing as well as the vertical and temporal turbulence structure during nighttime convective conditions.Two independent estimates of vertical eddy diffusivities in the stably stratified (daytime) SBL, computed from the microstructure measurements, agreed closely, and the near surface heat and buoyancy fluxes, computed from the diffusivities, were similar to those computed independently from surface meteorology. Model generated eddy diffusivities agreed closely with the observed values, except those generated by K profile parameterization (KPP) model simulations. The good agreement provides confidence that nutrient fluxes in the SBL may be accurately computed from the models when forced with regularly measured surface meteorological parameters. The consequences are important for estimation of daily primary productivity rates in the euphotic zone and the ability to predict algal blooms such as those observed in the present reservoir.     

Old laws for new risks at sea: mineral resources, climate change, sea lanes, and cables

Maritime security in a broad sense means more than piracy and terrorism. This paper concentrates on the risk potential of current and future resource-related activities on the seabed. The seabed mining of hard mineral resources??in addition to hydrocarbons??leads to new controversial maritime boundary claims of states in their effort to expand national access rights to raw materials. Outer continental shelf claims in the Arctic Ocean are today's test bench for law of the sea conflicts. Fiber-optic cables running through regional seas, straits, and land bridges may become another risky issue, while the pattern of maritime transport routes is moving from Northern to Southern waters. Under a medium-term perspective, the sea level rise will endanger ports and coasts. Borderlines of maritime zones will move and thus generate more injustice and conflicts among states. The tools to solve borderline conflicts and options for dispute settlement are available in UNCLOS. Some other legal gaps are covered by the 2005 SUA Convention and by bilateral agreements, while resolutions by the UN Security Council begin to broaden rights of intervention and interdiction. The need for new laws remains.     

The importance of estuarine gravitational circulation in the early life of the Bohai Penaeid Prawn

Estuaries along the southern shore of the Bohai Sea are the major habitat of the Bohai Penaeid Prawn (Penaeus chinensis). Since the 80's, however, many of the rivers have been dammed. Field observations, as well as laterally integrated 2-D numerical experiments, were conducted to understand both the role of estuarine gravitational circulation and the impact of the damming of the rivers on the early life of the Bohai Penaeid Prawn.For a river with runoff, especially for small discharge, the gravitational circulation tends to transport the planktonic larvae in their metamorphosis phase near the river mouth where condition is favorable for survival. The gravitational circulation inside the estuary tends to transport the mysis phase larvae towards the upstream end of the estuary when the most part of the larvae suspended in the bottom layer, and it transports the post larvae to the low salinity near upstream side of the estuary when the larvae become benthic, if the larvae enter the estuary.Damming causes long periods of zero runoff in the river, resulting in the alteration of the estuarine circulation and in the change of the estuarine environment. In addition, excess evaporation may prematurely transport the planktonic larvae into the estuary. On the other hand, sudden release of a large volume of freshwater from behind the dam may exert undesirable stress on the larvae.     

Hydrology, sediment yield, erosion and sedimentation rates in the estuarine environment of the Ria de Vigo, Galicia, Spain

The aim of this study is to provide a budget study with calculated erosion rates. Three methods have been used to calculate sediment yield and denudation rates in the Ria de Vigo: (1) measurements of sediment loads, (2) measurements of sediment accumulation rates at the coast, (3) theoretical calculations of potential denudation. Sediment loads and water discharge were measured over a period of 14 months from May 1997 to July 1998. Two of the tributaries entering the Ria de Vigo were monitored for 12 more months, from May 2000 to May 2001, to observe changes in discharge and sediment loads. This period corresponded with atypical precipitation, with peak monthly values (600 mm) three times higher than those on record.Water rating curves are typically exponential. Suspended and dissolved loads vary for different rivers, showing values of 1.5 to 130 mg/l during 1997/1998. For 2000/2001, these values are twice as high. Suspended load versus discharge relationships for 1997/1998 were logarithmic, but data from 2000/2001 does not fit the same equation. Dissolved loads are several times higher than suspended loads in almost all cases. Dissolved load concentrations vary more widely with discharge than suspended loads. This is probably due to local pollution and contamination from marine spray in areas closer to the sea.Second, erosion rates and bed load sediment yields were calculated from accumulation rates at the Ramallosa Complex. Well-preserved estuarine and tidal sediments, associated with the Minor River, have accumulated in this area during the Holocene. ¹⁴C ages allow calculation of sedimentation rates (SR) for two intervals. The lower interval extends from 2001 to 484 years BP and yields an SR of 1.12 mm/a. The upper interval extends from 484 years BP to the present and has an SR of 3.3–4.4 mm/a. These differences may be explained by basin dynamics as the beach progressively encloses the area and also by human interference. From sedimentary facies analysis it is concluded that 90% to 95% of the accumulated deposits were transferred to the basin as bed load. Muddy deposits (mostly marshes) are better developed at the upper part of the sediment pile, and inner areas, indicating a progressive shallowing and filling up of the basin. Most of suspended load is exported to the ria, whereas the Ramallosa Complex acts as a sediment sink for bed load derived material.Calculated potential erosion rates using Ahnert's [Am. J. Sci. 268 (1970) 243] equation show lower values than those estimated from river load concentrations. Potential erosion rates for the Minor River are higher than for the Lagares River which contrast with mechanical denudation rate values from river loads during 1997/1998 which are higher for the Lagares River. During 2000/2001 MDR values were higher than those of the potential erosion rates for both rivers, in line with the extremely high precipitation. Higher values in the Lagares could be in part due to human interference.     

淡水湖声速及千岛湖典型声速分布

在水声试验中,声速是影响声传播的一个重要因素,声速受水深、水温、含盐度等参数影响.本文分析了海水和抚仙湖的声速计算经验公式,并进行了同种条件下的声速剖面对比,在此基础上给出了千岛湖水域的典型声速剖面.     

预制插板在青岛港老码头改造中的应用

在青岛港老码头改造中,采用了预制插板技术。结合不同泊位的设计,对预制插板方案在设计计算、构造等方面进行了经验总结。     

巴基斯坦卡拉奇港OP-Ⅱ旧高桩码头群桩基础的拔除施工

今后，国内外均有大量的建筑物达到甚至超过其设计使用年限，拆除后重建的工程项目将呈上升趋势，而国内外对此类问题尚无较详细的报道。通过巴基斯坦卡拉奇港OP-Ⅱ旧高桩码头322根群桩基础的拔除施工，探索并总结出了一种成本费用较低、拔桩效率高的水上拔桩方法。     

The effect of precession-induced changes in the Mediterranean freshwater budget on circulation at shallow and intermediate depth

The Neogene marine sedimentary record of the Mediterranean basin is characterised by the regular occurrence of organic-rich layers or sapropels. These sapropels are known to correlate with the precession cycle: their deposition coincides with precession minima. This correlation is thought to be caused to a large extent by a precession-induced increase in the amount of freshwater reaching the Mediterranean Sea. In the literature, various sources of this extra freshwater have been identified and different mechanisms as to how this freshwater flux leads to sapropels have been proposed. In this study we investigate the effects of precession-induced changes in the freshwater budget using a regional ocean general circulation model of the Mediterranean Sea. Emphasis is on the effects at the surface and at intermediate depth. The forcing of the ocean model is adjusted to precession minimum conditions on a parameter by parameter basis. Novel to our approach is that the value of the required adjustments is taken from a global coupled climate model with which experiments have been performed for the present day (close to precession maximum) and precession minimum. With the ocean model we focus on the extent to which extra runoff from either south (specifically: the river Nile) or north and changes in net precipitation over the sea itself lead to a more stable stratification; this we judge by the associated reduction of the sea surface salinity and mixed layer depth in the regions of intermediate and deep water formation. Our main finding is that the effects of (1) increased discharge of the rivers coming from the north, and (2) the increase in net precipitation over the sea itself, are of equal or greater importance than that of increase in Nile discharge.     

碳纤维加固技术在旧厂房改建加固中的应用

碳纤维增强聚合物是一种新兴高强材料。以某旧厂房改建加固工程应用为例,介绍了碳纤维复合材料(CFRP)在结构加固中的计算方法和施工工艺。     

Impact of freshwater on a subarctic coastal ecosystem under seasonal sea ice (southeastern Hudson Bay, Canada). III. Feeding success of marine fish larvae

We monitored the feeding success (percent feeding incidence at length and mean feeding ratio at length) of Arctic cod (Boreogadus saida) and sand lance (Ammodytes sp.) larvae in relation to prey density, light, temperature and potential predator density under the ice cover of southeastern Hudson Bay in the spring of 1988, 1989 and 1990. Both prey density and light limited larval fish feeding. The relationship between feeding success and actual food availability (nauplii density X irradiance) was adequately described by an Ivlev function which explained 64 and 76% of the variance in Arctic cod and sand lance feeding success respectively. By affecting both prey density and irradiance, the thickness of the Great Whale River plume (as defined by the depth of the 25 isohaline) was the main determinant of prey availability. Arctic cod and sand lance larvae stopped feeding when the depth of the 25 isohaline exceeded 9 m. Limitation of feeding success attributable to freshwater inputs occurred exclusively in 1988, the only time when the depth of the 25 isohaline exceeded the 9 m threshold. The close dependence of larval fish feeding success on the timing of the freshet and plume dynamics suggests a direct link between climate and survival of Arctic cod and sand lance larvae. The actual impact of climate fluctuations and/or hydro-electric developments on recruitment will depend on the fraction of the larval dispersal area of the two species that is affected by river plumes.