Herbicides implicated as the cause of severe mangrove dieback in the Mackay region, NE Australia: consequences for marine plant habitats of the GBR World Heritage Area     

Duke NC  Bell AM  Pederson DK  Roelfsema CM  Bengtson Nash S 《Marine pollution bulletin》2005,51(1-4):308-324

Herbicides, particularly diuron, were correlated with severe and widespread dieback of the dominant mangrove, Avicennia marina (Forsk.) Vierh. var. eucalyptifolia (Val.) N.C. Duke (Avicenniaceae), its reduced canopy condition, and declines in seedling health within three neighbouring estuaries in the Mackay region of NE Australia. This unusual species-specific dieback, first observed in the early 1990s, had gotten notably worse by 2002 to affect >30 km(2) of mangroves in at least five adjacent estuaries in the region. Over the past century, agricultural production has responded well to the demands of increasing population with improvements in farm efficiency assisted by significant increases in the use of agricultural chemicals. However, with regular and episodic river flow events, these chemicals have sometimes found their way into estuarine and nearshore water and sediments where their effects on marine habitats have been largely unquantified. Investigations over the last three years in the Mackay region provide compelling evidence of diuron, and possibly other agricultural herbicides, as the most likely cause of the severe and widespread mangrove dieback. The likely consequences of such dieback included declines in coastal water quality with increased turbidity, nutrients and sediment deposition, as well as further dispersal of the toxic chemicals. The implications of such findings are immense since they describe not only the serious deterioration of protected and beneficial mangrove habitat but also the potential for significant direct and indirect effects on other highly-valued estuarine and marine habitats in the region, including seagrass beds and coral reefs of the Great Barrier Reef lagoon. This article reviews all key findings and observations to date and describes the essential correlative and causative evidence.  相似文献   

新疆叶城晚新生代山前盆地演化与高原北缘的隆升—Ⅰ地层学与岩石学证据   总被引：21，自引：2，他引：19  

郑洪波  KatherineButcher 《沉积学报》2002,20(2):274-281

叶城晚新生代山前盆地的岩性主要由中新世的细粒泥岩和砂岩（乌恰群）,上新世的砂岩夹薄层砾岩（阿图什组）及上新世－更新世的粗粒砾岩（西域组）构成。中新世的沉积以细颗粒泥砂岩为主,表明物源区较远,古流域坡度较小,搬运距离较长。古流向分析显示物源区位于南和偏南方,此时昆仑山的地势起伏尚不大。到上新世的阿图什组沉积时,开始出现砾石沉积,反映西昆仑山已经开始有规模地隆升。西域砾岩的沉积标志着作为物源区的西昆仑山民有相当的高度,随着山系的隆升,基底岩石被暴露和剥蚀。  相似文献   

Implications for unified schemes from the quasar fraction and emission-line luminosities in radio-selected samples     

Jennifer A. Grimes  Steve Rawlings  Chris J. Willott 《Monthly notices of the Royal Astronomical Society》2004,349(2):503-517

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On the redshift cut-off for steep-spectrum radio sources   总被引：1，自引：0，他引：1  

Matt J. Jarvis  Steve Rawlings  Chris J. Willott  Katherine M. Blundell  Steve Eales  Mark Lacy 《Monthly notices of the Royal Astronomical Society》2001,327(3):907-917

We use three samples (3CRR, 6CE and 6C*) selected at low radio frequency to constrain the cosmic evolution in the radio luminosity function (RLF) for the 'most luminous' steep-spectrum radio sources. Though intrinsically rare, such sources give the largest possible baseline in redshift for the complete flux-density-limited samples currently available. Using parametric models to describe the RLF, incorporating distributions in radio spectral shape and linear size, as well as the usual luminosity and redshift, we find that the data are consistent with a constant comoving space density between     and     . We find that this model is favoured over a model with similar evolutionary behaviour to that of optically selected quasars (i.e., a roughly Gaussian distribution in redshift) with probability ratios of     and     for spatially flat cosmologies with     and     respectively. Within the uncertainties, this evolutionary behaviour may be reconciled with the shallow decline preferred for the comoving space density of flat-spectrum sources by Dunlop & Peacock and Jarvis & Rawlings, in line with the expectations of unified schemes.  相似文献   

I _C and R_C band time-series observations of some bright ultracool dwarfs     

Chris Koen 《Monthly notices of the Royal Astronomical Society》2005,360(3):1132-1142

The results of more than 100 h of CCD photometric monitoring of 10 L dwarfs and two T dwarfs are presented. Reasonable evidence is shown for I _C band variability in DENIS 0255−4700, DENIS 1705−0516 and 2M 2104−1037. Substantial brightening of the T dwarf binary ε Indi Bab was observed over the course of 3.6 h; it is unlikely that this could have been caused by surface spots. No unequivocal variability could be detected in the R _C band.  相似文献   

Bias properties of logarithmic and asinh magnitudes at very low flux levels     

Chris Koen 《Monthly notices of the Royal Astronomical Society》2001,325(4):1335-1340

The observation of flux sources near the limit of detection requires a careful evaluation of possible biases in magnitude determination. Both the traditional logarithmic magnitudes and the recently proposed inverse hyperbolic sine (asinh) magnitudes are considered. Formulae are derived for three different biasing mechanisms: the statistical spread of the observed flux values arising from e.g. measurement error; the dependence of these errors on the true flux; and the dependence of the observing probability on the true flux. As an example of the results, it is noted that biases at large signal-to-noise ratios R , at which the two types of magnitude are similar, are of the order of −( p +1)/ R ², where the exponent p parametrizes a power-law dependence of the probability of observation on the true flux.  相似文献   

The 2dF galaxy redshift survey: near-infrared galaxy luminosity functions     

Shaun Cole  Peder Norberg  Carlton M. Baugh  Carlos S. Frenk  Joss Bland-Hawthorn  Terry Bridges  Russell Cannon  Matthew Colless  Chris Collins  Warrick Couch  Nicholas Cross  Gavin Dalton  Roberto De Propris  Simon P. Driver  George Efstathiou  Richard S. Ellis  Karl Glazebrook  Carole Jackson  Ofer Lahav  Ian Lewis  Stuart Lumsden  Steve Maddox  Darren Madgwick  John A. Peacock  Bruce A. Peterson  Will Sutherland  Keith Taylor 《Monthly notices of the Royal Astronomical Society》2001,326(1):255-273

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Epicentre estimator distributions     

Robert McGonigle 《Geophysical Journal International》1981,67(3):771-777

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Kinematics of the Galactic halo from horizontal branch stars in the Hamburg/ESO survey     

Christopher Thom  Chris Flynn  Michael S. Bessell  Jyrki Hänninen  Timothy C. Beers  Norbert Christlieb  Dionne James  Johan Holmberg  Brad K. Gibson 《Monthly notices of the Royal Astronomical Society》2005,360(1):354-359

Large samples of field horizontal branch (FHB) stars make excellent tracers of the Galactic halo; by studying their kinematics, one can infer important physical properties of our Galaxy. Here we present the results of a medium-resolution spectroscopic survey of 530 FHB stars selected from the Hamburg/ESO survey. The stars have a mean distance of ∼7 kpc and thus probe the inner parts of the Milky Way halo. We measure radial velocities from the spectra in order to test the model of Sommer-Larsen et al., who suggested that the velocity ellipsoid of the halo changes from radially dominated orbits to tangentially dominated orbits as one proceeds from the inner to the outer halo. We find that the present data are unable to discriminate between this model and a more simple isothermal ellipsoid; we suggest that additional observations towards the Galactic Centre might help to differentiate them.  相似文献   

The distribution of satellite galaxies: the great pancake     

Noam I. Libeskind  Carlos S. Frenk  Shaun Cole  John C. Helly  Adrian Jenkins  Julio F. Navarro  Chris Power 《Monthly notices of the Royal Astronomical Society》2005,363(1):146-152

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