Assessing food web dynamics and relative importance of organic matter sources for fish species in two Portuguese estuaries: a stable isotope approach     

França S  Vasconcelos RP  Tanner S  Máguas C  Costa MJ  Cabral HN 《Marine environmental research》2011,72(4):204-215

Stable carbon and nitrogen isotopes (δ13C, δ1?N) were used to analyse food web dynamics of two of the main estuaries of the Portuguese coast: Tejo and Mira. The ultimate sources of organic matter supporting production of some of the most abundant and commercially important fish species were determined; and seasonal, inter- and intra- estuarine differences in the trophic relations among producers and consumers were identified. Stable isotope analysis was performed in different producers, primary consumers (main prey items for fish) and fish species (Solea solea, Solea senegalensis, Pomatoschistus microps, Dicentrarchus labrax, Liza ramada, Diplodus vulgaris and Atherina presbyter) of two areas in each estuary, in July and October 2009. Model calculations showed that the main prey for the fish species in the Tejo estuary used mostly salt marsh-derived organic matter as nutritional sources, with no marked differences between the sampled months. Trophic levels of fish species from the same estuary differed at multiple scales: inter-species, seasonally and spatially (both between and within estuaries). Significant differences in isotopic composition of fish species were more pronounced spatially (between the two sampled areas in the estuary) than seasonally (between sampled months). Trophic relationships in both estuaries demonstrated that organic matter is transferred to higher trophic positions mainly through benthic pathways. This shows the flexibility of these species to share resources and to exploit temporary peaks in prey populations. The present results showed that extensive disturbance in intertidal habitats from both estuaries may potentially change the balance of organic matter in the base of these complex food webs.  相似文献   

Sediment-related distribution patterns of nematodes and macrofauna: two sides of the benthic coin?   总被引：1，自引：0，他引：1  

Vanaverbeke J  Merckx B  Degraer S  Vincx M 《Marine environmental research》2011,71(1):31-40

We investigated the sediment-related distribution of both nematodes and macrofauna on the Belgian part of the North Sea (Southern Bight of the North Sea) in order to evaluate whether both faunal groups reflect similar patterns in community composition and diversity. Fine-grained sediments (median grain size <200μm) were inhabited by nematode communities characterised by a low diversity and dominated by non-selective deposit-feeding nematodes. Nematode communities from coarser sediments were significantly different in terms of community composition and diversity. Moreover, all nematode feeding types were present in coarser sediments. These differences were explained by the contrasting biogeochemical processes prevailing in both sediment types, rather than granulometry and food availability per se. Macrofaunal distribution patterns were different from those of the nematode communities and seem to be related to water column processes (SPM loading, food availability, hydrodynamic stress) that promote the establishment of diverse communities in the coarser sediments but not in the finest sediments. This suggests that data on nematodes and macrofauna reveal different, complementary aspects of the factors structuring the benthic ecosystem that can be of importance in assessing the ecological status of the seafloor.  相似文献   

Ground-Based In Situ Measurements of Near-Surface Aerosol Mass Concentration over Anantapur: Heterogeneity in Source Impacts     

B. S. K. REDDY  K. R. KUMAR  G. BALAKRISHNAIAH  K. R. GOPAL  R. R. REDDY  V. SIVAKUMAR  S. Md. ARAFATH  A. P. LINGASWAMY  S. PAVANKUMARI  K. UMADEVI  Y. N. AHAMMED 《大气科学进展》2013,30(1):235-246

Surface measurements of aerosol physical properties were made at Anantapur(14.62°N,77.65 °E,331 m a.s.l),a semiarid rural site in India,during August 2008-July 2009.Measurements included the segregated sizes of aerosolsas as well as total mass concentration and size distributions of aerosols measured at low relative humidity(RH<75%) using a Quartz Crystal Microbalance(QCM) in the 25-0.05 μm aerodynamic diameter range.The hourly average total surface aerosol mass concentration in a day varied from 15 to 70 μg m-3,with a mean value of 34.02±9.05μgm-3 for the entire study period.A clear diurnal pattern appeared in coarse,accumulation and nucleation-mode particle concentrations,with two local maxima occurring in early morning and late evening hours.The concentration of coarse-mode particles was high during the summer season,with a maximum concentration of 11.81±0.98μgm-3 in the month of April,whereas accumulationmode concentration was observed to be high in the winter period contributed >68% to the total aerosol mass concentration.Accumulation aerosol mass fraction,A f(=Ma/Mt) was highest during winter(mean value of Af～0.80) and lowest(Af～0.64) during the monsoon season.The regression analysis shows that both R eff and R m are dependent on coarse-mode aerosols.The relationship between the simultaneous measurements of daily mean aerosol optical depth at 500 nm(AOD500) and PM 2.5 mass concentration([PM2.5]) shows that surface-level aerosol mass concentration increases with the increase in columnar aerosol optical depth over the observation period.  相似文献   

Inhibition of fish nodavirus by gymnemagenol extracted from Gymnema sylvestre     

V.Gopiesh Khanna  K.Kannabiran  V.Sarath Babu  A.S.Sahul Hameed 《中国海洋大学学报(英文版)》2011,10(4):402-408

Viral nervous necrosis(VNN)has emerged to become a major problem in the culture of larval and juvenile marine fish worldwide.Bioactive phytochemicals isolated from commonly available medicinal plants are often screened for their efficacy in controlling fish viral diseases.Occurrence of newer viral strains and resistance to existing antiviral drugs are problems currently as-sociated with treatment of VNN,which necessitates looking for alternate sources for effective antiviral drugs.The aim of the present study was to screen antiviral potential of gymnemagenol(C30H50O4)previously extracted from leaves of Gymnema sylvestre.The fish nodavirus,grouper nervous necrosis virus(GNNV)in infected Sahul Indian Grouper Eye(SIGE)cell lines were used to study the antiviral activity of gymnemagenol under in vitro conditions.The susceptibility of the virus to gymnemagenol was confirmed by measuring the viral titre(TCID50 mL?1)in virus-infected SIGE cells every 24 h.Gymnemagenol at 20 μg mL?1 inhibited the prolifera-tion of GNNV to 53% at the end of the 6th d by inhibiting the proliferation of GNNV-infected SIGE cells.The viable SIGE cells were reduced to 47% as determined by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide(MTT)assay.The viral titre(TCID50 mL?1)was also reduced to log 2.8 at the end of the 7th d in gymnemagenol-treated SIGE cells after inoculated with GNNV when compared to untreated control SIGE cell viral titre(log 4.1).Based on our results it can be concluded that gymnemagenol could be used as an antiviral agent against GNNV infection.  相似文献   

THE URBAN GEOGRAPHY OF CHUNGKING (ABSTRACT)     

R.S.CHEN 《地理学报》1943

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一种类型的冲积谷对入射SH波的地震反应     

Sa－S.  FJ 张杰 《地震译文集》1989,(1):10-17

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TENSORIAL RESOLUTION:A DIRECT TRILINEAR DECOMPOSITION   总被引：4，自引：0，他引：4  

EUGENIO SANCHEZ~ BRUCE R.KOWALSKI Laboratory for Chemometrics Department of Chemistry BG-.University of Washington  Seattle WA  U.S.A. Mobil Research  Development Corporation  Paulsboro Research Laboratory  Billinsport Ro  Paulsboro  NJ  U.S.A. 《地理学报(英文版)》1990,(1)

Modern instrumentation in chemistry routinely generates two-dimensional(second-order)arrays of data.Considering that most analyses need to compare several samples,the analyst ends up with a three-dimensional(third-order)array which is difficult to visualize or interpret with the conventional statisticaltools.Some of these data arrays follow the so-called trilinear model,(?)These trilinear arrays of data are known to have unique factor analysis decompositions which correspondto the true physical factors that form the data,i.e.given the array (?),a unique solution can be found inmany cases for each order X,Y and Z.This is in contrast to the well-known second-order bilinear datafactor analysis,where the abstract solutions obtained are not unique and at best cannot be easilycompared with the underlying physical factors owing to a rotational ambiguity.Trilinear decompositions have had the disadvantage,however,that a non-linear optimization withmany parameters is necessary to reach a least-squares solution.This paper will introduce a method forreducing the problem to a rectangular generalized eigenvalue-eigenvector equation where the eigenbectorsare the contravariant form(pseudo-inverse)of the actual factors.It is shown that the method works wellwhen the factors are linearly independent in at least two orders(e.g.X_(jr),and Y_(jr) are full rank matrices).Finally,it is shown how trilinear decompositions relate to multicomponent calibration,curve resolutionand chemical analysis.  相似文献   

新人文地理学     

M.S.劳  J.R.萧特  肖建成 《地理科学进展》1991,10(4):44-48

引言《地理学进展》的创刊号于1969年出版,在刊物创刊21周年之际,有必要对其宗旨和目的再作一次评析。本文将考察进步的概念,让我们先从定义入手。地理科学的进步,常常被定义为地理学家使他们的研究领域变得更具可知性的能力。像所有社会学科一样,这里存在着下定义的问题。更具知识性和可知性是什么意思?另一个更重要的问题是谁来决定这种进步是什么?学术研究来源于商界和政府在安排研究项目方面起至关重要且举足轻重作用的大千世界中,有时用一般的方式,有时则用特殊的方式。  相似文献   

An Exact Solution for Two-Dimensional Frictionless Motion in the Atmosphere     

S.Panchev 《大气科学进展》1990,(2)

A solution of the nonlinear problem for determining the wind velocity in frictionless atmosphere (the gradient wind) under given geopotential (pressure) field is proposed. The approach is analytical and is based on quadratic polynomial approximation of the geopotential field and linear approximation of the wind velocity field with respect to x and y, the coefficients of the expansions being functions of the time t. The derived system of ordinary nonlinear differential equations is analyzed as a dynamical system. Exact analytical solutions are found for some particular cases. Some of their properties bear a resemblance to those or really existing atmospheric vortices (cyclones and anticyclones).  相似文献   

THE PROBLEM OF ADEQUATE SAMPLE SIZE IN PATTERN RECOGNITION STUDIES:THE MULTIVARIATE NORMAL CASE     

J.H.HAN A.J.I.WARD B.K.LAVINE Department of Chemistry  Clarkson University  Potsdum  NY  U.S.A. 《地理学报(英文版)》1990,(1)

Because many pattern recognition techniques are predicated on the assumption of mutivariate normaldata,Monte Carlo simulation studies were performed to determine the number of samples that arenecessary to describe a multivariate normal population adequately.From these studies we have learnedthat hundreds of sainples are required.These results suggest that parametric procedures should only beused to analyze very large data sets.  相似文献