Impact of the Aegean Sea oil spill on the subtidal fine sand macrobenthic community of the Ares-Betanzos Ria (Northwest Spain)     

Gesteira JL  Dauvin JC 《Marine environmental research》2005,60(3):289-316

Two sites located in the sublittoral fine-sand macrobenthic community of the Ares-Betanzos Ria were sampled over four years (December 1992-November 1996) in the wake of the Aegean Sea oil spill. This sampling revealed that the petroleum had affected the structure and abundance of this community, as well as the number of taxa present. In this context, the results of the biotic index and the biotic coefficient were insufficient; however, study of the synthetic parameters, particularly through multivariate analysis, showed that the community went through three successive and distinct phases over time. A short period of high mortality in some species, especially amphipods, was followed by a period of low abundance that lasted until the spring of 1995. A period of recovery began in the second half of 1995 and continued through to the end of 1996, when the survey ended. The community showed a gradual evolution back towards the conditions observed immediately after the spill, when abundance of the more resistant species was still high. Despite this similarity, the last period exhibits a new structure, clearly separate from the two previous periods. This study provides information about the short-term effects of the Aegean Sea oil spill on the fine sand bottoms of the sites surveyed in the Ares-Betanzos Ria. This information could also serve as a baseline for identifying the effects of a more recent accident, the Prestige oil spill, in which similar communities in other Galician rias were polluted in 2002-2003.  相似文献   

Experimental simulation of Titan's organic chemistry at low temperature     

de Vanssay E  Gazeau MC  Guillemin JC  Raulin F 《Planetary and Space Science》1995,43(1-2):25-31

A wide range of experiments has already been carried out to simulate the chemical evolution of Titan. Such experiments can provide useful information on the possible nature of minor constituents, mostly organic, likely to be present in Titan's atmosphere. Indeed, all but one of the organic compounds already detected in Titan's atmosphere have been identified in simulation experiments. The exception, C4N2, as well as other compounds expected in Titan from theoretical modeling, such as other N-organics, mainly CH2N2, and polyynes, namely C6H2, have never been detected in experimental simulation. It turned out that these compounds were thermally unstable, and the temperature conditions used during the simulation experiments (including conditions used for chemical analysis) were not appropriate. We have recently started a new program of simulation experiments using temperature conditions close to those of Titan's environment, more compatible with the build-up and detection of organics only stable at low temperature. Spark discharge of N2-CH4 gas mixtures was carried out at low temperature in the range of 100-150 K. The analysis of the obtained products was performed through FTIR, GC and GC-MS techniques. GC-peak identification was done owing to its mass spectrum and, in most cases, by comparison of the retention time and of the mass spectrum with standards. We report here the first detection in Titan's simulation experiments of C6H2. Its abundance is a few 10(-2) relative to C4H2. We also report a tentative identification of HC5N (to be confirmed by use of standard) with an abundance of a few 10(-2) relative to HC3N. The possible presence of HC5N suggested by our work provides the occurrence of very novel pathways in the formation of Titan's organic aerosols, involving not only C and H but also N atoms.  相似文献   

基于A-Train综合资料的云顶高度反演研究   总被引：1，自引：0，他引：1  

李冠林  严卫  王蕊  韩丁  陆文  万应虎  里巍 《气象》2016,42(8):971-979

提出一种适用性较强的云顶高度反演方法。利用2007年低纬地区(15°S~15°N)的A-Train综合资料反演云顶高度。首先以M0DIS通道31和通道32的亮温值为特征参数,基于SVM分类法,将云分为不透明云、半透明云和透明云三类,分类准确率达到90.6%。然后对三类云分别用核回归法反演云顶高度,将其与CloudSat的2B-GEOPROF-LIDAR产品对比,均方根误差分别为0.95、1.17和1.27 km。与未分类的核回归法结果相比,分类后三种云的反演误差都有所减小。最后分析了三个典型个例。该方法可推广至其他含有红外分裂窗通道的卫星上,发挥更多卫星资源的效用。  相似文献   

Does the Phaeocystis bloom affect the diel migration of the suprabenthos community?     

Dauvin JC  Desroy N  Denis L  Ruellet T 《Marine pollution bulletin》2008,56(1):77-87

The suprabenthos comprises all bottom-dependent animals, mainly crustaceans (including decapods and peracarids), which perform--with varying amplitude, intensity and regularity--seasonal or daily vertical migrations above the sea floor. The presence of organisms in the Benthic Boundary Layer is determined by two general factors: (1) organism behaviour, which depends on the light penetration in the water column and (2) boundary-layer hydrodynamics. In the coastal zone of the eastern English Channel, during the spring Phaeocystis bloom, the presence of gelatinous colonies modifies the penetration of light in the water column, which may seriously affect the abundance and/or the behaviour of the suprabenthos community. To clarify this point, 19 suprabenthic hauls were taken with a modified Macer-GIROQ sledge both during the day and during the night, from March to June 2002 (i.e., before, during and after the bloom). Two sites, located in the coastal and offshore areas of the Ophelia medium sand macrobenthic community were investigated. The bloom had no effect on species richness and abundance in either site. However, the diel migrations of some dominant species--such as the cumaceans Pseudocuma longicornis and Pseudocuma similis, the mysid Gastrosaccus spinifer and the amphipod Stenothoe marina--were modified. During the bloom, diurnal and nocturnal suprabenthic abundances were similar, and in the absence of bloom, species remained benthic during the day. The permanent presence of suprabenthic species in the Benthic Boundary Layer could have a consequence on their predation by fish (mainly juveniles which preferentially consume small crustaceans in their diet), unless fish behaviour and predation efficiency--especially for visual predators--are also disturbed by changes in light intensity.  相似文献   

Effects of heavy metal contamination on the macrobenthic fauna in estuaries: the case of the Seine estuary   总被引：2，自引：0，他引：2  

Dauvin JC 《Marine pollution bulletin》2008,57(1-5):160-169

Heavy metal contamination levels are generally higher in estuaries than in the open sea. Some estuaries, the Seine estuary for example, have particularly high pollution levels of metals, yet continue to support a very high benthic biomass and remain quite productive. Measurements of sediment contamination are highly variable due to diverse chemical analysis methods, sediments origin and sources of contaminants found in the estuaries. Salinity appears to be the principal factor controlling contaminant distribution in the sediment and the overlying and/or interstitial waters; it also affects the bioavailability of contaminants in estuarine sediments. Of course, the response to contaminants varies greatly among species and assemblages. Trace metals explain only a small part of the variation in benthic community structure. Some species, such as the shrimp Crangon crangon, appears vulnerable to metal pollution, while other species, such as Scrobicularia plana, are able to tolerate quite high levels of cadmium in their tissue. This paper demonstrates the wide variability of benthic responses to contamination, which is probably due to the high spatio-temporal heterogeneity of the estuary. To reduce the problems due the heterogeneity and variability observed to date in the available results, it will be necessary to encourage integrated estuarine studies, in which sedimentologists, chemists, and biologists work together on the same campaigns at the same sites.  相似文献   

The glutathione antioxidant system as a biomarker suite for the assessment of heavy metal exposure and effect in the grey mangrove, Avicennia marina (Forsk.) Vierh   总被引：1，自引：0，他引：1  

Caregnato FF  Koller CE  MacFarlane GR  Moreira JC 《Marine pollution bulletin》2008,56(6):1119-1127

Alterations in the glutathione antioxidant system and lipid peroxidation in Avicennia marina were studied under laboratory and field conditions. The activity of glutathione peroxidase (GPx) was found to respond to Zn exposure, and a significant positive relationship between leaf Zn concentration and GPx activity was observed after 96 h and 8 weeks. Lipid hydroperoxides increased proportionally with increasing leaf Zn concentration after 2 and 8 weeks, while no changes in total glutathione were observed. Induction of GPx at 96 h predicted effects at the individual level at a later time interval (reduced biomass at 8 weeks). Results from the field revealed that increasing leaf metal concentration (Zn, Cu or Pb) produced a proportional increase in GPx activity whereas lipid hydroperoxides and total glutathione were not affected. The utility of GPx as an early warning biomarker is suggested, since GPx activity increases in a dose-dependant fashion in response to accumulated leaf metals, and is predictive of later effects on growth.  相似文献   

Regulation of eutrophication susceptibility in oligohaline regions of a northern Gulf of Mexico estuary, Mobile Bay, Alabama   总被引：2，自引：0，他引：2  

Lehrter JC 《Marine pollution bulletin》2008,56(8):1446-1460

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利用全极化微波辐射计资料反演台风境内海面风场   总被引：3，自引：0，他引：3       下载免费PDF全文

王蕊  史顺文  严卫  陆文 《地球物理学报》2014,57(3):738-751

作为一种新兴的被动遥感技术,全极化微波辐射计不仅可以提供海面风速产品,还可以提供海面风向产品.以往利用全极化微波辐射计观测亮温进行海面风场反演仅在晴空条件下进行,本文通过对观测亮温结合台风区域海面风场的分布特征进行分析,验证了全极化微波辐射计具有在台风等恶劣天气条件下进行海面风场观测的能力.基于敏感性分析实验,确定使用6.8 GHz和10.7 GHz等低频通道组合可进行台风区域内海面风场反演.其中,海面风速反演使用基于统计的多元线性回归算法,同时对海面温度、大气水汽含量、云中液态水含量及降水强度等物理量进行反演计算,为海面风向反演做准备.海面风向反演使用物理统计法进行,借鉴散射计风向反演使用的最大似然估计法.通过在全极化辐射传输前向模型中加入降水对大气透过率的影响、设计第三和第四Stokes通道亮温环境影响修正函数,在实现台风区域内海面风向反演的同时减小了反演误差.通过对“云娜”台风境内海面风场进行数值计算,验证了本文反演算法的可行性,并对反演误差的空间分布特征进行了分析.将2004年各台风过程的海面风场反演结果与散射计风场产品进行对比,海面风速和海面风向反演的均方根误差分别为1.64 m·s^-1和18.02°.  相似文献   

A spreadsheet program for two-well tracer test data analysis     

Tang G  Watson DB  Parker JC  Brooks SC 《Ground water》2012,50(4):614-620

Two-well tracer tests are often conducted to investigate subsurface solute transport in the field. Analyzing breakthrough curves in extraction and monitoring wells using numerical methods is nontrivial due to highly nonuniform flow conditions. We extended approximate analytical solutions for the advection-dispersion equation for an injection-extraction well doublet in a homogeneous confined aquifer under steady-state flow conditions for equal injection and extraction rates with no transverse dispersion and negligible ambient flow, and implemented the solutions in Microsoft Excel using Visual Basic for Application (VBA). Functions were implemented to calculate concentrations in extraction and monitoring wells at any location due to a step or pulse injection. Type curves for a step injection were compared with those calculated by numerically integrating the solution for a pulse injection. The results from the two approaches are similar when the dispersivity is small. As the dispersivity increases, the latter was found to be more accurate but requires more computing time. The code was verified by comparing the results with published-type curves and applied to analyze data from the literature. The method can be used as a first approximation for two-well tracer test design and data analysis, and to check accuracy of numerical solutions. The code and example files are publicly available.  相似文献   

Contaminant concentrations, biochemical and hematological biomarkers in blood of West Indian manatees Trichechus manatus from Brazil     

Anzolin DG  Sarkis JE  Diaz E  Soares DG  Serrano IL  Borges JC  Souto AS  Taniguchi S  Montone RC  Bainy AC  Carvalho PS 《Marine pollution bulletin》2012,64(7):1402-1408

The West Indian manatee Trichechus manatus is threatened with extinction in Brazil, and this study focused on nondestructive blood samples analyzed for metals, polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs), as well as biochemical and hematological biomarkers. Studied manatees were kept at Projeto Peixe-Boi headquarters in Pernambuco State, and at two natural areas in estuaries where they are released to the wild. Manatees kept at the natural estuary in Paraiba State have blood concentrations of Al, Pb, Cd, Sn that are 11, 7, 8 and 23 times greater, respectively, than the concentrations found in blood of animals from the same species in Florida, USA. An inhibition of butyrylcholinesterase in manatees kept at the two reintroduction sites in Alagoas and Paraiba States indicated possible exposure of the animals to cholinesterase inhibitor insecticides. PCBs and OCPs were not detected. Results from this study will help delineate conservation efforts in the region.  相似文献