Application of the concentration hypothesis to English sole in nursery estuaries and potential contribution to coastal fisheries     

Christopher?N.?RooperEmail author  Donald?R.?Gunderson  David?A.?Armstrong 《Estuaries and Coasts》2004,27(1):102-111

Resources in nursery areas can be important determinants of recruitment for juvenile fishes. Most young-of-the-year English sole (Pleuronectes vetulus) appear to rely on estuaries on the U.S. Pacific Northwest coast as nursery areas. Trawl surveys were conducted in four nursery estuaries, and the results show consistent densities were found across all estuaries in August. In June densities were higher and more variable. Application of the average August density to estuaries along the entire Oregon and Washington coasts resulted in an estimated total estuarine abundance of 45.8 million age 0+ English sole. Estimated coast-wide recruitment of age 4+ female English sole based on age 0+ abundance ranged from 3.7 to 4.9 million individuals from 1998–2000, with an average value of 4.3 million. A simple population model was constructed to determine if production from the combined Oregon and Washington estuaries was consistent with the estimates of the adult stock, and the observed catch from 1956–1997. The observed commercial catch has declined over this time period, and the trend could be fit using an availability-gear efficiency of 21% and an exploitation rate of 0.094. The results suggest that the English sole population on the Oregon-Washington shelf could potentially be supported solely by estuarine production, and this production appears to be stabilized by the size of available nursery areas.  相似文献   

Dating ancient wood by high-sensitivity liquid scintillation counting and accelerator mass spectrometry—Pushing the boundaries     

Alan G. Hogg  L. Keith Fifield  Chris S.M. Turney  Jonathan G. Palmer  Rex Galbraith  Mike G.K. Baillie 《Quaternary Geochronology》2006,1(4):241-248

It is critical that a comprehensive terrestrial radiocarbon (¹⁴C) calibration curve is developed beyond 26 ka for high-precision calibration and correlation of climatic, environmental and archaeological records. Abundant sub-fossil New Zealand kauri (Agathis australis) wood, preserved in Oxygen Isotope Stage-2 and 3 peat swamps, provides an important resource for ¹⁴C calibration; nowhere else in the world does such an extensive collection of ancient wood exist. Although finite ¹⁴C ages beyond 50 ka are becoming routinely reported, few attempts have been made to demonstrate their accuracy or precision. Finite ages beyond 50 ka require optimization of all elements involved in sample preparation and ¹⁴C analysis. Here we discuss the methodology employed for optimizing the ¹⁴C dating of near-background wood samples by both benzene synthesis for liquid scintillation counting (LSC) or graphite synthesis for accelerator mass spectrometry (AMS). We report the mean background blank activities for both methods and present a statistical model for assigning blank standard errors when blank activity variation is over and above counting statistics. We also present duplicate analyses (using LSC and AMS) of nine successive samples of wood obtained from a sub-fossil kauri log near-background in age to investigate the significance of the measured blank levels and variability.  相似文献   

Biodiversity of the wetlands of the Kakadu Region, northern Australia     

C. Max Finlayson  John Lowry  Maria Grazia Bellio  Suthidha Nou  Robert Pidgeon  Dave Walden  Chris Humphrey  Gary Fox 《Aquatic Sciences - Research Across Boundaries》2006,68(3):374-399

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Gaussian plume modeling of contaminant transport     

Chris Kennedy  Hans Ericsson  P. L. R. Wong 《Stochastic Environmental Research and Risk Assessment (SERRA)》2006,20(1-2):119-125

A technique for modeling contaminant transport based on Markov process theory is developed. Transport is quantified by summing the first two moments of independent random displacements and applying the central limit theorem (CLT) to obtain solute distributions of a Gaussian nature. For non-uniform flow fields the CLT is applied in a streamfunction/equi-travel time space and transforms are used to give concentrations in Cartesian coordinates. Simulations in uniform, radially converging and circular flow fields show the method to be two to three orders of magnitude faster than modeling with the advection-dispersion equation, using a control volume technique.  相似文献   

Episodic shear zone associated fluid flow in the Curnamona Province, South Australia     

Chris Clark  Andreas Schmidt Mumm  Martin Hand  Kevin Faure 《Journal of Geochemical Exploration》2006,89(1-3):69

Two distinct generations of fluid flow associated with shear zone activity have been identified in Willyama Supergroup rocks of the southern Curnamona Province in northeastern South Australia. Fluids in the first event are inferred to have been sourced from the devolatilisation of Willyama Supergroup metasedimentary rocks during prograde metamorphism associated with the (1.61–1.58 Ga) Mesoproterozoic Olarian Orogeny. The second episode of fluid flow occurred during the (c. 500 Ma) Cambrian Delamerian Orogeny and resulted in localised rehydration of the Willyama Supergroup. Fluids were isotopically light and most likely sourced from prograde Delamerian metamorphism and dehydration of fault rocks and entrained meteoric waters that originally were involved in (c. 700 Ma) Neoproterozoic Adelaidean rifting. A key outcome of this study is the identification of this previously unrecognised fluid flow system that was active during the Delamerian Orogeny.  相似文献   

Inference of past climate from borehole temperature data using Bayesian Reversible Jump Markov chain Monte Carlo     

Peter O. Hopcroft  Kerry Gallagher  Chris C. Pain 《Geophysical Journal International》2007,171(3):1430-1439

Estimates of past climate derived from borehole temperatures are assuming a greater importance in context of the millennial temperature variation debate. However, recovery of these signals is usually performed with regularization which can potentially lead to underestimation of past variation when noise is present. In this work Bayesian inference is applied to this problem with no explicit regularization. To achieve this Reversible Jump Markov chain Monte Carlo is employed, and this allows models of varying complexity (i.e. variable dimensions) to be sampled so that it is possible to infer the level of ground surface temperature (GST) history resolution appropriate to the data. Using synthetic examples, we show that the inference of the GST signal back to more than 500 yr is robust given boreholes of 500 m depth and moderate noise levels and discuss the associated uncertainties. We compare the prior information we have used with the inferred posterior distribution to show which parts of the GST reconstructions are independent of this prior information. We demonstrate the application of the method to real data using five boreholes from southern England. These are modelled both individually and jointly, and appear to indicate a spatial trend of warming over 500 yr across the south of the country.  相似文献   

Realizing the Literate Traveller     

William E Cartwright  Bob Williams  Chris Pettit 《Transactions in GIS》2007,11(1):9-27

A current research project is addressing the problem of finding appropriate geographical information by developing a (geo)information realization resource based upon the concepts of the Literate Traveller. It has as its main goal to provide tools for geographical knowledge building and exploration, by providing conventional spatial information plus geographical interpretation and appreciation artifacts. These artifacts are delivered in an interactive multimedia environment. This research examines the formulation of an initial prototype component to assist in providing geographical knowledge. The prototype is based on a study site in Townsville, Australia, and is being used as a vehicle to explore enhanced spatial information provision through the use of rich media. The research examines new ways to prospect for, discover and disseminate spatial knowledge within an intelligence‐briefing context. The paper reports on the concepts behind the design of the application developed for the test site, and presents initial findings from the early evaluation of the prototype.  相似文献   

On 50th Anniversary of the Global Carbon Dioxide Record     

Georgii A Alexandrov  Martin Heimann  Chris D Jones  Pieter Tans 《Carbon balance and management》2007,2(1):11-2

The 50-year global CO₂ record led the way in establishing a scientific fact: modern civilization is changing important properties of the global atmosphere, oceans and biosphere. The evidence on which this scientific fact is based will be refined further, but the next challenge for scientists is broader. In addition to its traditional role in providing discovery, diagnosis, and prediction of the changes that are taking place on our planet, science has now also a role in helping society mitigate emissions by objectively quantifying them, and in helping adaptation by providing environmental forecasts on regional scales. Science is also expected to provide new options for society to tackle the transition to a new energy system, and to provide thorough environmental evaluation of all such options. This is what the meeting recognized as planetary responsibilities for scientists in the next 50 years.  相似文献   

Assessing the vulnerability of food crop systems in Africa to climate change     

Andrew Challinor  Tim Wheeler  Chris Garforth  Peter Craufurd  Amir Kassam 《Climatic change》2007,83(3):381-399

Africa is thought to be the region most vulnerable to the impacts of climate variability and change. Agriculture plays a dominant role in supporting rural livelihoods and economic growth over most of Africa. Three aspects of the vulnerability of food crop systems to climate change in Africa are discussed: the assessment of the sensitivity of crops to variability in climate, the adaptive capacity of farmers, and the role of institutions in adapting to climate change. The magnitude of projected impacts of climate change on food crops in Africa varies widely among different studies. These differences arise from the variety of climate and crop models used, and the different techniques used to match the scale of climate model output to that needed by crop models. Most studies show a negative impact of climate change on crop productivity in Africa. Farmers have proved highly adaptable in the past to short- and long-term variations in climate and in their environment. Key to the ability of farmers to adapt to climate variability and change will be access to relevant knowledge and information. It is important that governments put in place institutional and macro-economic conditions that support and facilitate adaptation and resilience to climate change at local, national and transnational level.  相似文献   

A transboundary study of urban sprawl in the Pacific Coast region of North America: The benefits of multiple measurement methods     

Chris Davis  Tim Schaub   《International Journal of Applied Earth Observation and Geoinformation》2005,7(4):268-283

Sprawling urban development has emerged as a primary concern of policy makers, land preservationists and both urban and rural communities in developing regions across the globe. For the first time in history, more global residents lived in urban areas than not and the trend to urbanization is in full force at the start of the 21st century. An understanding of the nature and character of urban sprawl is complicated by a failure to satisfactorily define it and by the limitations of measurement techniques designed to characterize complex landscape forms. Like other landscape patterns, the quantification of urban sprawl is highly spatially and temporally scale-dependent. This paper summarizes a recent project to measure urban sprawl in the transboundary region of the Pacific Coast of North America. The metropolitan centers of Portland, OR, Seattle, WA and Vancouver, BC, span two nations, three state/provincial governments and dozens of cities. As a region, this was a global leader in population growth in the 1990s. The study relied on three separate methods – an impervious surface metric, a neighborhood density metric and a building permit metric – for quantifying urban growth. The results provide insight on the strengths and shortcomings of different methods with respect to the challenges posed by data availability and format. Taken together they demonstrate the richer understanding that combined methods may offer in characterizing phenomena as difficult to communicate and agree upon as urban sprawl.  相似文献