Oceanographic conditions associated with high abundances of the radiolarian Cycladophora davisiana     

Joseph J. Morley  James D. Hays 《Earth and Planetary Science Letters》1983

The cosmopolitan radiolarian Cycladophora davisiana usually comprises less than 5% of the radiolarian fauna in Holocene sediments. In recent sediments from the Sea of Okhotsk, however, this species frequently represents more than 20% of the radiolarian assemblage. At times during the late Pleistocene, abundances of this species in excess of 40% are recorded in marine sediments from high-latitude oceans (> 40°) of both hemispheres. The Sea of Okhotsk apparently represents a modern analogue of climatic and oceanographic conditions that existed throughout large portions of high-latitude oceans at times during the late Pleistocene.The near-surface water structure of the Sea of Okhotsk is characterized by a low-salinity surface layer with a strong temperature minimum near its base. The low surface salinities are responsible for maintaining near-freezing subsurface temperatures as well as establishing relatively stable temperatures and salinities at depths below the temperature minimum. This water structure is produced, at least in part, by intense freezing of sea ice in winter with subsequent summer melting. The physical characteristics of the upper water column affect the abundance and activity of shallow-dwelling flora and fauna, while providing a stable subsurface environment for deeper-dwelling fauna.  相似文献   

A transfer function for estimating paleoceanographic conditions based on deep-sea surface sediment distribution of radiolarian assemblages in the South Atlantic     

Joseph J. Morley 《Quaternary Research》1979,12(3):381-395

A quantitative analysis of radiolarian species in 57 deep-sea surface sediment samples from the South Atlantic Ocean produced four geographically distinct assemblages (tropical, polar, gyre margin, and subtropical). The distributions of these assemblages or factors coincide with present-day patterns of sea-surface temperatures or water masses.These four assemblages were used to construct a transfer function relating radiolarian distribution in the surface sediments to present-day winter and summer temperatures using standard regression techniques. As a test of the quality of this transfer function, temperatures were estimated on surface sediment samples from the eastern South Pacific. The temperatures produced by the transfer function compared favorably with the observed (present-day) winter and summer sea-surface temperatures at these sites.  相似文献   

Cleaning of lake sediment samples for diatom oxygen isotope analysis   总被引：1，自引：0，他引：1  

David W. Morley  Melanie J. Leng  Anson W. Mackay  Hilary J. Sloane  Patrick Rioual  Richard W. Battarbee 《Journal of Paleolimnology》2004,31(3):391-401

Detrital grain contamination in a diatom sample can considerably influence the δ¹⁸O_diatom signal. In order to obtain a meaningful signal, pure samples must be used. This can be achieved via a series of cleaning stages including organic and carbonate material removal, sieving, differential settling and heavy liquid separation. The method described here works best for sediments with >20% diatom content. Based on testing various clean-up methods, we propose a sequence of four clean-up stages to produce pure diatom samples from a range of lake sediments types starting with a few grams of sediment. The diatom content and the oxygen isotope composition of the samples at each stage were measured in order to assess the effect of differential amounts of contamination. Results show that a four stage clean-up is necessary to produce clean diatom samples and that contamination by silt and clay causes lower δ¹⁸O values.  相似文献   

A palaeolimnological meta-database for assessing the ecological status of lakes   总被引：1，自引：0，他引：1  

Richard W. Battarbee  David Morley  Helen Bennion  Gavin L. Simpson  Michael Hughes  Viktorija Bauere 《Journal of Paleolimnology》2011,45(4):405-414

We describe a palaeolimnological meta-database (“LakeCores”) that includes information for lakes in Europe that have been cored for studies of recent environmental change. Only cores with intact mud-water interfaces and good chronologies for the last ~100–200 years are currently included. The information provided in the database includes the general characteristics of the lakes cored, the methods used for dating and analysis and the bibliographic source of the information selected. At present the database contains information on 1847 studies from 975 sites. Here we use the database to identify cores for which diatom-based pH and total phosphorus (TP) reconstructions have been derived and, from an inspection of the relevant papers, we compile summary data for the timing and extent of acidification and eutrophication of lakes across Europe. We show that there were few cases of acidification and eutrophication in Europe prior to about 1850, and therefore that conditions prior to 1850 can be used for reference with respect to current attempts to restore surface waters to “good ecological status”. We also show the extent to which pH and TP levels have changed across the continent both for all lakes, and, in the case of TP, for lakes of different types covering a range of alkalinities, altitudes, water depths and surface areas.  相似文献   

A preliminary methods comparison for measurement of dissolved organic nitrogen in seawater   总被引：2，自引：0，他引：2  

Jonathan H. Sharp  Kathrine R. Rinker  Karen B. Savidge  Jeffrey Abell  Jean Yves Benaim  Deborah Bronk  David J. Burdige  Gustave Cauwet  Wenhao Chen  Marylo D. Doval  Dennis Hansell  Charles Hopkinson  Gerhard Kattner  Nancy Kaumeyer  Karen J. McGlathery  Jeffrey Merriam  Nick Morley  Klaus Nagel  Hiroshi Ogawa  Carol Pollard  Mireille Pujo-Pay  Patrick Raimbault  Raymond Sambrotto  Sybil Seitzinger  Georgina Spyres  Frank Tirendi  Ted W. Walsh  C. S. Wong 《Marine Chemistry》2002,78(4)

Routine determination of dissolved organic nitrogen (DON) is performed in numerous laboratories around the world using one of three families of methods: UV oxidation (UV), persulfate oxidation (PO), or high temperature combustion (HTC). Essentially all routine methods measure total dissolved nitrogen (TDN) and calculate DON by subtracting the dissolved inorganic nitrogen (DIN). While there is currently no strong suggestion that any of these methods is inadequate, there are continuing suspicions of slight inaccuracy by UV methods.This is a report of a broad community methods comparison where 29 sets (7 UV, 13 PO, and 9 HTC) of TDN analyses were performed on five samples with varying TDN and DIN concentrations. Analyses were done in a “blind” procedure with results sent to the first author. With editing out one set of extreme outliers (representing 5 out of 145 ampoules analyzed), the community comparability for analyzing the TDN samples was in the 8–28% range (coefficient of variation representing one standard deviation for the five individual samples by 28 analyses). When DIN concentrations were subtracted uniformly (single DIN value for each sample), the comparability was obviously worse (19–46% cv). This comparison represents a larger and more diverse set of analyses, but the overall comparability is only marginally better than that of the Seattle workshop of a decade ago. Grouping methods, little difference was seen other than inconclusive evidence that the UV methods gave TDN values for several of the samples higher than HTC methods. Since there was much scatter for each of the groups of methods and for all analyses when grouped, it is thought that more uniformity in procedures is probably needed. An important unplanned observation is that variability in DIN analyses (used in determining the final analyte in most UV and PO methods) is essentially as large as the variability in the TDN analyses.This exercise should not be viewed as a qualification exercise for the analysts, but should instead be considered a broad preliminary test of the comparison of the families of methods being used in various laboratories around the world. Based on many independent analyses here, none of the routinely used methods appears to be grossly inaccurate, thus, most routine TDN analyses being reported in the literature are apparently accurate. However, it is not reassuring that the ability of the international community to determine DON in deep oceanic waters continues to be poor. It is suggested that as an outgrowth of this paper, analysts using UV and PO methods experiment and look more carefully at the completeness of DIN conversion to the final analyte and also at the accuracy of their analysis of the final analyte. HTC methods appear to be relatively easy and convenient and have potential for routine adoption. Several of the authors of this paper are currently working together on an interlaboratory comparison on HTC methodology.  相似文献   

Metal fluxes through the Strait of Gibraltar: the influence of the Tinto and Odiel rivers (SW Spain)     

Franoise Elbaz-Poulichet  Nicholas H. Morley  Jean-Marie Beckers  Philippe Nomerange 《Marine Chemistry》2001,73(3-4)

A large set of new data concerning dissolved metal concentrations has been acquired in the Gulf of Cadiz and in the Strait of Gibraltar from 1996 to 1999. These data, associated with models (hydrodynamic, tracer advection–dispersion and mixing), have been used to assess the influence of rivers draining the South Iberian Pyrite Belt on the Gulf of Cadiz and on the Atlantic inflow in the Strait of Gibraltar.Metal concentrations in surface waters from the Gulf of Cadiz are maximal near the mouth of the Tinto/Odiel rivers with values exceeding 50 nmol/kg (Mn), 5 nmol/kg (Ni), 30 nmol/kg (Cu), 100 nmol/kg (Zn), 0.9 nmol/kg (Cd) and 45 nmol/kg (As). From the Tinto/Odiel river, a plume of contamination follows the coast in the direction of the Strait of Gibraltar. The computation of a tracer advection–dispersion model confirms that the coastal currents carry the metals discharged from the Tinto and Odiel to the Strait of Gibraltar.From temperature–salinity and metal–salinity plots, four water masses can be recognised in the Gulf of Cadiz and in the Strait of Gibraltar: North Atlantic Surface Water (NASW), North Atlantic Central Water (NACW) and metal-enriched Spanish Shelf Waters from the Gulf of Cadiz (SSW). The Mediterranean Outflow Water (MOW) is also clearly seen at depths greater than 300 m.The chemical characteristics of these various water masses have been used in a mixing model to evaluate their relative contribution to the Atlantic inflow through the Strait of Gibraltar. These contributions are seasonally variable. In June 1997, the contribution was: 80±20%, 5±5% and 15±10% for NASW, NACW and SSW, respectively. In September, the SSW contribution was apparently negligible.Finally, these relative contributions allow the evaluation of the metal fluxes in the Strait of Gibraltar. The presence of SSW in the Strait increases the metal flux to the Mediterranean Sea by a factor of 2.3 (Cu), 2.4 (Cd), 3 (Zn) and 7 (Mn). It does not modify significantly As and Ni fluxes.  相似文献   

A graph-based algorithm to define urban topology from unstructured geospatial data     

J.-P. de Almeida  J.G. Morley  I.J. Dowman 《International journal of geographical information science》2013,27(8):1514-1529

Interpretation and analysis of urban topology are particularly challenging tasks given the complex spatial pattern of the urban elements, and hence their automation is especially needed. In terms of the urban scene meaning, the starting point in this study is unstructured geospatial data, i.e. no prior knowledge of the geospatial entities is assumed. Translating these data into more meaningful homogeneous regions can be achieved by detecting geographic features within the initial random collection of geospatial objects, and then by grouping them according to their spatial arrangement. The techniques applied to achieve this are those of graph theory applied to urban topology analysis within GIS environment. This article focuses primarily on the implementation and algorithmic design of a methodology to define and make urban topology explicit. Conceptually, such procedure analyses and interprets geospatial object arrangements in terms of the extension of the standard notion of the topological relation of adjacency to that of containment: the so-called ‘containment-first search’. LiDAR data were used as an example scenario for development and test purposes.  相似文献   

Mapping Collaboration in Open Source Geospatial Ecosystem     

Jianhua Shao  George Kuk  Suchith Anand  Jeremy G. Morley  Mike J. Jackson  Tyler Mitchell 《Transactions in GIS》2012,16(4):581-597

Over the last decade, there has been a tremendous growth and exploitation of open source geospatial software and technologies. A combination of factors is driving this momentum, including the contributions made by hundreds of developers and the leading role played by the Open Source Geospatial Foundation (OSGeo), aiming primarily to support and promote the collaborative development of open source geospatial technologies and data. This article seeks to map out the social history of collaborative activities within the OSGeo ecosystem. We used the archival logs of developers' contributions, specifically looking for boundary spanning activities where contributions crossed multiple projects. The analysis and visualization of these activities allow us to have a better understanding of the role of boundary spanning in the resourcing of each project, the incubation mechanism advocated by OSGeo, and the significance of the social interrelatedness among projects. The data consisted of the subversion (SVN) commit history made by individual developers in the programming code repository. We applied several network analytical and visualization techniques to explore the data. Our findings indicate that more than one in seven developers spanned multiple projects which potentially had the effects of shaping the projects' directions, and increased knowledge flow and innovation. In addition, the OSGeo's incubation mechanism provided an important encouragement for boundary spanning and increased knowledge sharing. By studying the social history of contributions, further tools can be developed in future to assist tracking of the social history, and make developers mindful of the significance of the interdependence among projects and hence continuously contribute to the health of the OSGeo ecosystem.  相似文献   

Discovering stellar core collapse events using satellite-born RF detectors     

P. D. Morley  David W. Eastin 《Astrophysics and Space Science》2008,314(4):275-279

Previous research has shown that a massive electromagnetic pulse (MEMP) is the precursor to type II stellar core collapse events. While Earth’s ionosphere makes ground-based detection of this RF (radio frequency) electromagnetic pulse improbable, it can be readily observed by satellite-born detectors. The expected radius of detection using presently available COTS (commercial-off-the-shelf) equipment is 2.67 billion light-years. A new class of astronomical objects is predicted to exist.  相似文献   

Parasitism as a source of potential distortion in studies on endocrine disrupting chemicals in molluscs     

Morley NJ 《Marine pollution bulletin》2006,52(11):1330-1332

The effects of endocrine disrupting chemicals (EDC) on molluscs in both marine and freshwater polluted environments are a continuing area of concern resulting in many field and laboratory studies. However, molluscs are commonly infected with trematode parasites which, in order to obtain sufficient nutrients for their own development, naturally disrupt the functioning of the endocrine system of the host. The physiological effects of parasitisation on the reproduction and immune response of molluscs are summarised, using a number of examples, and the implications for EDC studies are discussed.  相似文献