Introduction to the Proceedings of the ECONORTH Symposium on Ecosystem Dynamics in the Norwegian and Barents Sea     

Torstein Pedersen  Kurt S. Tande  John G. Pope   《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(21-22):1893

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Mesoscale physical processes and zooplankton transport-retention in the northern Norwegian shelf region     

Yiwu Zhu  Kurt S. Tande  Meng Zhou 《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(21-22):1922

Northern Norwegian shelf regions are highly productive, supporting fisheries rich in commercially important species such as cod, herring and capelin. It has been long recognized that the mesoscale jets, meanders and eddies associated with interactions between the North Atlantic Current, Norwegian Coastal Current and regional bottom topographic features such as troughs, banks and shelfbreaks play important roles in transporting and retaining zooplankton. To investigate zooplankton distributions and their correspondence with the physical fields, three large-scale surveys with mesoscale resolutions on physical and biological fields were conducted in northern Norwegian shelf regions between latitudes 68°15′N and 70°15′N in springs of 2000–2002. Survey results provide insights into the relationships between zooplankton distributions and the physical features such as fronts, the Norwegian Coastal Current and eddies related to topographic features. The physical and biological data are integrated and analyzed focusing on water types, estimation of geostrophic currents from direct current measurements, along-shelf transport of zooplankton, and retention of zooplankton by the mesoscale meander–eddy over a typical bank area on the shelf. The estimated mean transport in the upper 100 m on the shelf in the survey region is approximately 6.4×10³ tonnes wet weight day⁻¹ northward. High zooplankton abundances were found over both Malangsgrunnen and Sveinsgrunnen banks. The specific accumulation rate from northward–southward transport in the upper 100 m over Malangsgrunnen was approximately 0.08 day⁻¹, while variable currents with an offshore gradient of zooplankton abundance over Sveinsgrunnen implies an offshore dispersion of coastal-originated zooplankton cohort.  相似文献   

Phytoplankton productivity in relation to light intensity: A simple equation     

D. H. Peterson  M. J. Perry  K. E. Bencala  M. C. Talbot 《Estuarine, Coastal and Shelf Science》1987,24(6)

A simple exponential equation is used to describe photosynthetic rate as a function of light intensity for a variety of unicellular algae and higher plants where photosynthesis is proportional to (1-e^−β1). The parameter β ( ) is derived by a simultaneous curve-fitting method, where I is incident quantum-flux density. The exponential equation is tested against a wide range of data and is found to adequately describe P vs. I curves. The errors associated with photosynthetic parameters are calculated. A simplified statistical model (Poisson) of photon capture provides a biophysical basis for the equation and for its ability to fit a range of light intensities. The exponential equation provides a non-subjective simultaneous curve fitting estimate for photosynthetic efficiency (a) which is less ambiguous than subjective methods: subjective methods assume that a linear region of the P vs. I curve is readily identifiable. Photosynthetic parameters β and a are used widely in aquatic studies to define photosynthesis at low quantum flux. These parameters are particularly important in estuarine environments where high suspended-material concentrations and high diffuse-light extinction coefficients are commonly encountered.  相似文献   

High‐Arctic climate conditions for the last 7000 years inferred from multi‐proxy analysis of the Bliss Lake record,North Greenland     

Jesper Olsen  Kurt H. Kjær  Svend Funder  Nicolaj K. Larsen  Anna Ludikova 《第四纪科学杂志》2012,27(3):318-327

The Arctic is more vulnerable to climate change than are mid latitudes. Therefore, palaeolimnological studies from the High Arctic are important in providing insights into the dynamics of the climate system. Here we present a multi‐proxy study from one of the world's northernmost lakes: Bliss Lake, Peary Land, Greenland. The early Holocene (10 850–10 480 cal. a BP) is characterized by increased erosion and gradually more marine conditions. Full marine conditions developed from 10 480 cal. a BP until the lake was isolated at 7220 cal. a BP. From its marine isolation at 7220 cal. a BP Bliss Lake becomes a lacustrine environment. Evidence from geochemical proxies (δ¹³C and total organic carbon) suggests that warmer conditions prevailed between 7220 and 6500 cal. a BP, corresponding to the Holocene thermal maximum, and from 3300 until 910 cal. a BP. From 850 to 500 cal. a BP colder climate conditions persisted. The transition from warmer to colder climate conditions taking place around 850 cal. a BP may be associated with the transition from the Medieval Warm Period to the Little Ice Age. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Food habits and distribution of wintering canvasbacks,Aythya valisineria,on Chesapeake Bay     

Matthew C. Perry  Francis M. Uhler 《Estuaries and Coasts》1988,11(1):57-67

Baltic clams (Macoma balthica) were the predominant food items of 323 canvasbacks (Aythya valisineria) collected throughout Chesapeake Bay during 1970–1979. Natural vegetation constituted 4% of the food volume. Widgeongrass (Ruppia maritima) and redhead grass (Potamogeton perfoliatus) constituted the greatest percent volume and frequency of occurrence among the plant species, whereas wild celery (Vallisneria americana) constituted only a trace of the food volume. These results contrast with historical records of food habits of canvasbacks in Chesapeake Bay. Canvasback population estimates during the 1970’s were examined to detect annual and seasonal changes in distribution. Linear regression analyses of winter canvasback populations in the bay showed a significant decline in the upper-bay and middle-bay populations, but no significant changes in the lower-bay and Potomac River populations. The changes in winter distribution and abundance of the canvasback appear related to changes in natural food availability, which is the result of altered environmental conditions.  相似文献   

Book reviews     

John S. Perry  A. Henderson-Sellers  P. M. Morrisette 《Climatic change》1989,15(3):487-494

The National Center for Atmospheric Research is sponsored by the National Science Foundation.  相似文献   

Transition enthalpies and entropies of high pressure zinc metasilicates and zinc metagermanates     

Kurt Leinenweber  Alexandra Navrotsky  Paul McMillan  Eiji Ito 《Physics and Chemistry of Minerals》1989,16(8):799-808

The enthalpies of transition at T= 298 K between zinc metasilicate assemblages, measured by molten oxide solution calorimetry, are:

相似文献    38. The triple multimineral barrier for hazardous waste encapsulation      Kurt A. Czurda 《Engineering Geology》1993,34(3-4):205-209 According to the present state of science and technology, the ultimate disposal of critical substances such as chemotoxic wastes, metal slurries, radioactive substances, etc., as well as houshold waste, necessitates enclosure within a multi-barrier system. The geology of the disposal site plays an important role. The site itself defines the geological barrier which has to fulfill at least two requirements: namely low permeability and retention, respectively retardation qualities. These can be achieved to a certain degree either by clay minerals, zeolites or an artificial product such as active coal. In order to increase the imperviousness and retardation potentials of e.g. clayey geological barriers, technical barriers have to be added. One of them and the most important is the mineralogic barrier. It consists of clay dominated layers and according to the multimineral barrier concept the different layers have to meet different functions.  相似文献    39. A Field Evaluation of In-Situ Biodegradation of Chlorinated Ethenes: Part 3, Studies of Competitive Inhibition   总被引：1，自引：0，他引：1   Lewis Semprini  Gary D. Hopkins  Paul V. Roberts  Dunja Grbic-Galic  Perry L McCarty 《Ground water》1991,29(2):239-250   相似文献    40. Evaluation and application of dialysis porewater samplers for microbiological studies at sediment-water interfaces   总被引：1，自引：1，他引：1   Helmut Brandl  Kurt W. Hanselmann 《Aquatic Sciences - Research Across Boundaries》1991,53(1):55-73 The equilibrium diffusion technique has become a valuable tool for ecological and biogeochemical studies in aquatic environments. In sediment ecosystems, changes in concentration of microbial metabolites with increasing depth can be determined dependably and reproducibly with this technique. Since the permeation characteristics of the membranes employed are crucial, selecting the proper membrane requires knowledge about its behavior under conditions which prevail in the natural environment. Thirteen polymer sheets were evaluated comparing permeation terms for biogeochemically relevant solutes, biodegradability, and mechanical strength. Cellulose-based dialysis membranes are most satisfactory when employed in low temperature anoxic environments. For this membrane, correction terms were calculated to account for diffusion losses during retrieval and sampling. Optimal incubation times can now be predicted from experimentally determined permeation coefficients for several porewater solutes. Dialysis porewater samplers (DPS) have been successfully applied during more than 100 independent experiments for the collection of interstitial water from surface sediments. DPS were used for water depths as deep as 290 meters.  相似文献    [首页] « 上一页 [1] [2] [3] 4 [5] [6] [7] [8] [9] [10] [11] 下一页 » 末  页»