Effect of marine animal excretions on differential growth of phytoplankton species   总被引：2，自引：0，他引：2  

Arzul  Genevieve; Seguel  Miriam; Clement  Alejandro 《ICES Journal of Marine Science》2001,58(2):386-390

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Processes in microbial transport in the natural subsurface     

Timothy R. Ginn  Brian D. Wood  Kirk E. Nelson  Timothy D. Scheibe  Ellyn M. Murphy  T.Prabhakar Clement   《Advances in water resources》2002,25(8-12)

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Distribution and relative density of cetaceans in the Hauraki Gulf,New Zealand     

SL Dwyer  DM Clement  MDM Pawley  KA Stockin 《新西兰海洋与淡水研究杂志》2016,50(3):457-480

Understanding species distributions, and how they change in space and time, is vital when prioritising conservation or management initiatives. We assessed the distribution and density patterns of common dolphins (Delphinus sp.), bottlenose dolphins (Tursiops truncatus) and Bryde’s whales (Balaenoptera edeni) in the Hauraki Gulf, New Zealand. Dedicated boat-based surveys were conducted in the inner Hauraki Gulf (IHG) and off Great Barrier Island (GBI) during 2010–2012. Generalised linear models were used to investigate temporal changes in relative densities and kernel density estimation was implemented to examine spatial trends. Common dolphins were widely distributed during all seasons, with higher densities observed during winter and spring in the IHG but during autumn off GBI. There was inter-annual variation in Bryde’s whale distribution, with high densities recorded off GBI in 2011. Bottlenose dolphins were infrequently sighted in the IHG but regularly encountered off GBI, with the highest densities during spring and summer.  相似文献   

Morphodynamic mechanisms for the formation of asymmetric barchans: improvement of the Bagnold and Tsoar models     

Ping Lv  Zhibao Dong  Clement Narteau  Olivier Rozier 《Environmental Earth Sciences》2016,75(3):259

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Carbon dioxide,water vapor and sensible heat fluxes over a tallgrass prairie     

Shashi B. Verma  Joon Kim  Robert J. Clement 《Boundary-Layer Meteorology》1989,46(1-2):53-67

Fluxes of CO₂, water vapor and sensible heat were measured in a grassland ecosystem near Manhattan, Kansas, employing the eddy correlation technique. The vegetation at this site is dominated by big bluestem (Andropogon gerardii), switchgrass (Panicum virgatum), and indiangrass (Sorghastrum nutans). Diurnal patterns of the energy budget components and CO₂ fluxes are evaluated on a few selected days. Influence of high atmospheric evaporative demand and low availability of soil water are examined on (a) energy partitioning, and (b) the magnitudes and patterns of atmospheric carbon dioxide exchange.Published as Paper No. 8470, Journal Series, Nebraska Agricultural Research Division.  相似文献   

Short polarity intervals within the Matuyama: transitional field records from hydraulic piston cored sediments from the North Atlantic     

Brad M. Clement  Dennis V. Kent 《Earth and Planetary Science Letters》1987,81(2-3)

Detailed sampling of two short magnetozones within the Matuyama Chronozone recorded at DSDP Site 609 (49.86°N, 335.77°E) confirms that one, the Cobb Mountain Subchronozone (1.12 Ma), is a very short, full normal polarity interval and that the other, the older interval, is a record of a geomagnetic excursion which occurred at approximately 1.55 Ma. The Cobb Mountain Subchron lasted approximately 25,000 years, one third the duration of the Jaramillo Subchron. The normal polarity interval is bounded by two transition zones which document an antisymmetry in the sequence of directions in the reverse to normal and normal to reverse polarity transitions. We interpret the antisymmetry as reflecting a dependence upon the sense of the reversal, without significant changes in the relative contributions of non-dipole terms. The polarity interval recorded at 1.55 Ma lasted only 8,800 years with what may be regarded as full polarity directions observed across only 3 cm of stratigraphic section. This feature is interpreted as an excursion of the geomagnetic field and appears to be correlative with the Gilsa Subchron. Similarities between the transition bounding these two magnetozones suggest that these features occur as the result of the same process or triggering mechanisms in the earth's outer core.  相似文献   

The modern geoid and ancient plate boundaries     

Clement G. Chase  Donald R. Sprowl 《Earth and Planetary Science Letters》1983,62(3):314-320

The non-hydrostatic geoid is dominated by three large anomalies: an area of high gravity potential in the equatorial Pacific; another stretching from Greenland through Africa to the southwest Indian Ocean; and a semi-continuous low region passing from Hudson's Bay through Siberia to India and on to Antarctica. None of these three high-amplitude (greater than 60 m) and long-wavelength anomalies corresponds to present-day plate boundaries. However, if the modern geoid is plotted over the positions of continents and plate boundaries at 125 Ma B.P. (reconstructed relative to hotspots) a strong correlation emerges. The modern geoidal low corresponds in position to the areas of subduction surrounding the Pacific 125 Ma ago. The geoidal high now centered on Africa is entirely contained within ancient Pangaea, and the equatorial Pacific high overlies the location of the spreading centers preserved in the magnetic anomalies of the central Pacific. The most plausible cause of the large geoidal undulations is lower mantle convection only weakly coupled to plate motions. The correspondence between modern geoid and ancient plate boundaries implies either that the coupling was much more intimate in the past, or that there is a lag of at least 100 Ma in response of the lower mantle to upper mantle conditions.  相似文献   

Macroscopic Models for Predicting Changes in Saturated Porous Media Properties Caused by Microbial Growth   总被引：8，自引：0，他引：8  

T. P. Clement  B. S. Hooker  R. S. Skeen 《Ground water》1996,34(5):934-942

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Eddy correlation measurements of methane flux in a northern peatland ecosystem   总被引：1，自引：0，他引：1  

Shashi B. Verma  Frank G. Ullman  David Billesbach  Robert J. Clement  Joon Kim  E. S. Verry 《Boundary-Layer Meteorology》1992,58(3):289-304

A pilot study to measure methane flux using eddy correlation sensors was conducted in a peatland ecosystem in north central Minnesota. A prototype tunable diode laser spectrometer system was employed to measure the fluctuations in methane concentration.The logarithmic cospectrum of methane concentration and vertical wind velocity fluctuations under moderately unstable conditions had a peak nearf = 0.10 (wheref is the nondimensional frequency) and was quite similar to the cospectra of water vapor and sensible heat. Daytime methane flux during the first two weeks of August ranged from 120 to 270 mg m^-2 day^-1. The temporal variation in methane fluxes was consistent with changes in peat temperature and water table elevation. Our results compared well with the range of values obtained in previous studies in Minnesota peatlands.These field observations demonstrate the utility of the micrometeorological eddy correlation technique for measuring surface fluxes of methane. The current state-of-the-art in tunable diode laser spectroscopy makes this approach practical for use in key ecosystems.Published as Paper No. 9556, Journal Series, Nebraska Agricultural Research Division.  相似文献   

Achieving a paradigm shift in environmental and living resources management in the Gulf of Guinea: the large marine ecosystem approach     

Ukwe CN  Ibe CA  Alo BI  Yumkella KK 《Marine pollution bulletin》2003,47(1-6):219-225

The Gulf of Guinea is situated in the narrow protrusion of eastern Equatorial Atlantic between latitudes 2 degrees S and 5 degrees N and longitudes 8 degrees W to 12 degrees E, spanning a coastline length of approximately 130 nautical miles. The dominant feature of this shallow ocean off the coast of countries in Western Africa is the Guinea Current. The distinctive bathymetry, hydrography, productivity and trophodynamics of this shallow ocean qualify it as a large marine ecosystem (LME) and is indeed recognized as the number 28 of the 64 delineated LMEs globally. This area is one of the world's productive marine areas that is rich in fishery resources, oil and gas reserves, precious minerals and an important global reservoir of marine biological diversity. Unfortunately, pollution from residential and industrial sources has affected the waters of the Gulf of Guinea resulting in habitat degradation, loss of biological diversity and productivity, and degenerating human health. In reversing this trend of marine environmental degradation, the countries of the region adopted an integrated and holistic approach using the LME concept to sustainably manage the environmental and living resources of the region. The concept is predicated on the fact that marine environmental pollution and living resources respect no political or geographical boundaries and so require a holistic and regional approach for its management. The Gulf of Guinea countries through the Global Environment facility funded regional/communal project on water pollution control and biodiversity conservation achieved a paradigm shift in living resources and environmental management in the region using the LME concept.  相似文献