Metallothioneins and cytosolic metals in Neomysis integer exposed to cadmium at different salinities     

Erk M  Muyssen BT  Ghekiere A  Janssen CR 《Marine environmental research》2008,65(5):437-444

In the present study the induction of metallothioneins (MTs) and its relation to cytosolic metal concentrations (Zn, Cu and Cd) in the euryhaline crustacean Neomysis integer exposed to Cd at different salinities was studied. N. integer was exposed to the same free cadmium ion activity of 5.74 x 10(-9) mol l(-1) (i.e. 1/5 of the 96 h LC(50) value expressed as cadmium activity) in hypo-osmotic (5 psu), isosmotic (16 psu) and hyper-osmotic media (25 psu) for 7 days. In this way, the effect of salinity on cadmium speciation was eliminated and therefore the physiological effect of salinity on Cd accumulation and MT induction could be studied. The accumulation of cytosolic Cd in N. integer changed with salinity from 1.11+/-0.05 micromol l(-1) at 5 psu up to 1.43+/-0.17 micromol l(-1) at 25 psu. This could indicate that the physiological response of euryhaline estuarine invertebrates like N. integer to salinity changes can influence the rate of trace metal uptake from solution. While the salinity changes did not cause significant differences in cytosolic Zn concentrations (mean value of all tested salinities: 34.4+/-2.8 micromol l(-1)), an inverse relationship between salinity and cytosolic Cu concentration was observed. The highest concentration of 15.7+/-2.3 micromol Cul(-1) was determined at 5 psu and the lowest 10.9+/-1.4 micromol Cul(-1) at 25 psu. This could point to a possible relationship between the copper concentration and the hemocyanin metabolism in N. integer. This is the first time that differential pulse voltammetry method was applied to MT assays with N. integer. Although the exposure to Cd resulted in a higher Cd cytosolic concentration, no subsequent MT increase was detected. The significant positive correlation between MT levels and cytosolic Cu concentrations (Spearman correlation coefficient r(s)=0.356, p=0.009) implies a strong relationship between MT and Cu in N. integer.  相似文献   

菲律宾大马尼拉地区海水入侵研究分析     

王晖 《安徽地质》1995,(1)

本文阐述了菲律宾大马尼拉地区的地貌、气候、水文、地质等背景情况；介绍区内的地下水质水介质类型及含水层发育情况、富水性和导水性、地下水水力性质、水化学特征和补排条件以及地下水的开采情况和需求量，从而分析了大马尼拉地区海水的机理。  相似文献   

Mangos shale-associated alluvium     

Jonathan B. Laronne 《地球表面变化过程与地形》1981,6(6):541-552

Inquiry into the dissolution kinetics of naturally occurring geologic materials, rather than individual mineral species, has been relatively neglected. This is especially true of surface processes, the realm of surface water hydrology and geomorphology. This paper focuses attention at a laboratory study of the rate of such complex reactions. Functions defining the dissolution rates of saline (0.1–20 per cent salt content) Mancos Shale-associated alluvium in distilled water follow varying patterns. Dissolution is characterized by an initial (<5 min) high rate constant, by a following phase (20 min-57 h) where rates are reduced drastically, and by a final period of encroachment to equilibrium. Initial dissolution rates increase with increase in salt content and sediment: water ratio. The time necessary to approach equilibrium is, however, found to be directly proportional to the sediment; water ratio. The concentration of Na⁺, Mg²⁺, Ca²⁺, SC^2?₄ and HCO^?₃, and the relative abundance of Ca²⁺ and HCO^?₃ increase continuously with contact time, indicating that the hydrated sodium and magnesium sulphate minerals provide most of the initial solutes, though not necessarily most of the total solute bulk. The results obtained in this study indicate that the high initial dissolution rate of soluble minerals from alluvium, and particularly from shales in contact with aqueous solutions, is too short-lived to account for most of the solutes occurring in heavily sediment-laden surface flow. Excluding input from slower, usually supersaturated subsurface flow, dissolution from sediment in transport should be a major source of solutes in originally undersaturated and kinetically unequilibrated surface water in semiarid and arid regions.  相似文献   

Effects of pollution on zooplankton abundance and distribution in two estuaries of the Basque coast (Bay of Biscay)     

Uriarte I  Villate F 《Marine pollution bulletin》2004,49(3):220-228

The abundance and spatial distribution of mesozooplankton were compared in the euhaline region of the polluted Bilbao estuary and the unperturbed Urdaibai estuary. The environmental variables measured were salinity, temperature, dissolved oxygen saturation, chlorophyll a, particulate organic matter and Secchi disk depth. Differences in the environmental variables and zooplankton between the estuaries and within the estuaries were tested statistically. Differences in the patterns of mesozooplankton abundance with salinity in each estuary indicated that they were affected by pollution in the Bilbao. Total mesozooplankton, and several mesozooplankton categories were more abundant in the Bilbao at higher salinities but in the Urdaibai at lower salinities. Therefore, we deduced that, in the Bilbao, zooplankton abundance was enhanced by the moderate pollution at the outer euhaline zone and limited by the poorer conditions of the inner zone. The response of the various zooplankton categories to the pollution is discussed.  相似文献   

Decadal-scale variations of water mass properties in the deep Weddell Sea   总被引：2，自引：0，他引：2  

Eberhard?FahrbachEmail author  Mario?Hoppema  Gerd?Rohardt  Michael?Schr?der  Andreas?Wisotzki 《Ocean Dynamics》2004,54(1):77-91

Data from cruises between 1989 and 2003 with FS Polarstern were used to construct section-wide potential temperature and salinity time series of the main water masses in the Weddell Gyre. In tandem with these CTD data, two time series between 1989 and 1995 are presented from moored instruments in the central Weddell Sea. The regional and methodological consistency of the dataset allows us to quantify variations which are not visible in less homogeneous datasets. The data reveal significant temperature and salinity variations of the Warm Deep Water and the Weddell Sea Bottom Water on a decadal time scale. The longest time series were obtained at the prime meridian. Here warming is observed in the Warm Deep Water from 1992 to 1998 followed by cooling. In the Weddell Sea proper, measurements of instruments moored in the Weddell Sea Bottom Water layer recorded a temperature increase over 6 years at a rate of 0.01 °C a^–1. After the mooring period, CTD casts in 1998 point to a weakening of the trend. The warming trend in the bottom water occurs over most of the Weddell Sea, as detected in the additional CTD surveys. The variations are close to the detection level in the voluminous Weddell Sea Deep Water. The initial warming trend of the Warm Deep Water is consistent with warming trends reported in literature of subsurface waters of the Antarctic Circumpolar Current. The reversal of the trend in the Weddell Sea seems to be related to variations of the atmospheric conditions which can affect both the intrusion of Circumpolar Deep Water from the north and the circulation of the Weddell Gyre. Because the Warm Deep Water is the major source water for the formation of deep and bottom water in the Weddell Sea, it is suggested that its increase in temperature and salinity is likely to at least partly cause the variations which were observed in the bottom water.Responsible Editor: Jörg-Olaf Wolff  相似文献   

Correlations and sequence stratigraphic model for Messinian carbonate platforms of the western and central Mediterranean   总被引：1，自引：0，他引：1  

Jean-Jacques?CornéeEmail author  Jean-Paul?Saint Martin  Gilles?Conesa  Philippe?Münch  Jean-Pierre?André  Simona?Saint Martin  Stefan?Roger 《International Journal of Earth Sciences》2004,93(4):621-633

Distance correlations of Late Tortonian–Messinian littoral carbonate complexes are proposed from the study of eight platforms in the western and central Mediterranean. Correlations are based on the identification of two major biological sedimentary cycles and of two index surfaces. Surface A is a maximum flooding surface during cycle 1 at around 6.7 Ma. Surface B is a regional marine planation surface at around 5.95 Ma, at the base of cycle 2 (Terminal Carbonate Complex). A general sedimentary model is proposed for the 7–5.6-Ma time-span. The boundary between cycles 1 and 2 is coincident with the onset of the Messinian Salinity Crisis, and appears to be related to major environmental–paleo-oceanographic changes in the Mediterranean, rather than to a major sea-level drop or to climatic change.  相似文献   

A quantitative analysis of the desiccation and re-filling of the Mediterranean during the Messinian Salinity Crisis     

P.Th. Meijer  W. Krijgsman 《Earth and Planetary Science Letters》2005,240(2):510-520

Notwithstanding the great deal of attention that the Messinian evaporites of the Mediterranean region have received from an observational point of view, there is, to date, no consensus as to their mechanism of formation. We aim to contribute to the investigation through a quantitative analysis of the processes of desiccation and re-filling. These processes are thought to have played a role in particular during the deposition of the upper part of the evaporite sequence. We calculate the evolution of sea level and average salinity based on both the present-day geometry and a paleogeographic reconstruction and assess the sensitivity to variations in the freshwater budget. Our results support previous inferences that desiccation and re-filling are fast; desiccation occurs on a time scale of 3-8 kyr, re-filling probably even faster. Equilibrium sea levels imply that most water has gone from the western basin while a significant water column remains in the eastern basin. Whether or not the eastern basin reaches the level of halite saturation depends critically on, in particular, the freshwater budget. The fast rate of desiccation and re-filling imply that temporal differences in the onset of salt precipitation between western and eastern basin and between marginal basins and basin centres are below the resolution of (astronomical) dating. Also, when Atlantic sea level periodically varied from below to above the level of the intervening sill, the Mediterranean basin will have responded with repeated desiccation and re-filling. Fast re-filling is found to require only a small connection to the Atlantic Ocean. This, in combination with the previous results, suggests the Mediterranean is unlikely to attain stable intermediate water levels.  相似文献   

Première approche pour l'étude des bassins hydrogéologiques profonds du Sud-Ouest tunisien     

Moncef Chalbaoui 《Comptes Rendus Geoscience》2005,337(16):222

Due to their high cost, a small number of deep wells cannot give a satisfactory image of the architecture of deep geological formations and their continuity. However, it is very important at an early stage of research to recognize the relations that can exist between the different compartments of the underground formations. Generally speaking, we usually deduce that the hydrodynamic and geochemical parameters can be generated by geological discontinuity. In southwestern Tunisia, the seismic and diagraphic data make it possible to get a satisfactory insight into the underground layers so as to identify the hydrogeological basins and the extension of their parameters. To cite this article: M. Chalbaoui, C. R. Geoscience 337 (2005).  相似文献   

关于全球性水资源危机若干问题的探讨   总被引：2，自引：0，他引：2  

任世芳  牛俊杰 《世界地理研究》2006,15(2):31-35

本文以水资源的开发利用率作为评价指标,探讨和预测了全球以及10个人口大国水资源利用的现状和远景。作者认为:(1)日本、美国等发达国家,由于重视对水资源的规划、管理和节约,基本上已实现提取水量的零增长,水危机威胁得以解除;(2)孟加拉、印尼、俄罗斯和巴西4国水资源特别丰富,总体而言不存在危机;(3)印度、中国、尼日利亚和巴基斯坦4国是缺水国家,需要特别重视水资源的合理化利用,加强节水措施。  相似文献   

90年代发展中国家国际资本流入的新特点及其影响   总被引：1，自引：1，他引：0  

刘力 《世界地理研究》1998,(2)

从1992年起,流向发展中国家的证券资本以较大的优势超过了国际直接投资。在全球经济一体化、金融市场自由化和国际化的背景下,国际资本跨国流动呈现出规模巨大化、运作方式机构化、流动形式多样化的特点。庞大证券资本的注入在给新兴市场国家带来益处的同时,也可能造成伤害,这一点在墨西哥和东南亚金融危机中已经得到证实。因此防范和化解国际资本的流入所带来的金融风险,是新兴市场国家当前所面临的严峻课题。  相似文献