Carbon Isotope Geochemistry of the Orinoco Basin     

F. C. Tan  J. M. Edmond 《Estuarine, Coastal and Shelf Science》1993,36(6)

Stable carbon isotope ratios have been used to study the sources of particulate organic carbon (POC) and total dissolved inorganic carbon in the Orinoco Basin. The isotopic composition of total dissolved inorganic carbon shows a range of from -8·1 to -23·0 ppt, an indication of dominance of biological processes. The isotopic composition of POC exhibits a range of from -24·1 to -34·6 ppt with little seasonal variation. The isotopic evidence indicates that the POC is predominantly of terrestrial origin rather than a result of in situ planktonic production. The similarity of isotopic composition of POC and coastal sediments suggests that riverine organic detritus has been transported 30-50 km offshore in a direction parallel to the Orinoco river channel.  相似文献   

Atlantic salmon ranching: past problems and future management     

Isaksson  A.; Oskarsson  S.; Einarsson  S. M.; Jonasson  J. 《ICES Journal of Marine Science》1997,54(6):1188-1199

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A residual analysis method for quantitative comparison of spatial data from the Iceland-Faeroes Front     

S. Aranuvachapun  S.J. Maskell 《Ocean Engineering》1997,24(8):721-741

A spatial statistical method has been developed from the well-known Kriging technique in geostatistics, as a way of providing quantitative comparison between a pair of spatial data sets, and a measure for such a comparison. This residual analysis method is applied to oceanographic data in order to compare Iceland-Faeroes Front (IFF) model predictions against appropriate field observations, with an aim to assess the IFF model performance and its prediction accuracy. The method is also used to evaluate the model-generated dynamical variability within the model predictions, as well as the natural variability within the frontal observations. From the results, it has been found that the IFF model is highly robust, and gives better predictions at depth 150–350 m than elsewhere. Within such a depth (i.e. 250–350 m), there is also evidence to suggest that the main frontal region is most active above the IF Ridge. The natural variability obtained from the observations appears to be comparable to the model-generated dynamical variability after 20 days of integration, indicating a certain degree of accuracy in the model predictions. The method reported in this paper could also be extended for further use in model data assimilation. Thus, the work not only demonstrates how spatial statistics can be applied to oceanographic data, but also opens up new statistical tools for data handling in ocean modelling.  相似文献   

Environmental overview of Eckernförde Bay,northern Germany     

T. H. Orsi  F. Werner  D. Milkert  A. L. Anderson  W. R. Bryant 《Geo-Marine Letters》1996,16(3):140-147

This environmental overview of Eckernförde Bay (northern Germany) summarizes the results of previous studies relevant to the Office of Naval Research's Coastal Benthic Boundary Layer (CBBL) Baltic field exercise conducted during 1993–1994. Significant environmental characteristics include the following: (1) surface sediment distribution is related to water depth, dictated primarily by hydrodynamic reworking of older glacial deposits; (2) the origin and characteristics of small-scale sedimentary structures depend on storm-generated waves and currents; (3) the proximity of the sea surface and sediment —water interface results in a pelagic—benthic coupling that drives biogeochemical processes and produces organicrich, acoustically turbid sediments; and (4) the bay floor is complicated topographically by pockmarks and manmade sedimentary structures.  相似文献   

Improved precision of acoustic surveys of benthopelagic fish by means of a deep-towed transducer     

Kloser  Rudy J. 《ICES Journal of Marine Science》1996,53(2):407-413

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Estrogenic responses to xenobiotics in channel catfish (Ictalwus punctatus)     

A. C. Nimrod  W. H. Benson 《Marine environmental research》1996,42(1-4)

Several environmentally relevant contaminants are characterized as xenoestrogens by virtue of their ability to induce responses similar to 17β-estradiol (E2). There is concern that exposure to these xenoestrogens may result in endocrine and, thus, reproductive disruption. The objective of the present research was to determine whether xenobiotics known to elicit estrogenic responses in mammals were estrogenic in channel catfish, and if these compounds were capable of altering normal physiological response to E2. Sexually immature catfish were exposed by intraperitoneal injection to E2, suspected xenoestrogens or combination doses of E2 and xenoestrogen. Appearance of vitellogenin (Vg) in serum was used as the bioindicator of estrogenicity; Vg was measured by ELISA 7 days after injection. The ED₅₀ of E2 for the appearance of Vg in blood, 0.6 mg/kg, was used as the positive control. Synthetic estrogens, ethinylestradiol, mestranol and DES were effective in inducing Vg; the antiestrogen tamoxifen inhibited response to E2 when given in a combination dose. Treatment by both methoxychlor and p-nonylphenol resulted in Vg appearance in serum; the doses required were 300 times that of E2, and the vitellogenic response was less when compared to the E2-induced response. In addition, a combination dose of methoxychlor with E2 decreased the magnitude of the response to E2. Other mammalian xenoestrogens, o,p′-DDT, chlordecone, lindane and β-HCH, were not able to produce a vitellogenic response in this study.  相似文献   

Video observations of marine gravel transport     

Jon J. Williams 《Geo-Marine Letters》1990,10(3):157-164

In an analysis of video observations of gravel transport in the West Slent, UK, collective and individual characteristics of 458 bursts of bedload have been examined and the transport velocity and distance of 1680 individual particles in a consecutive succession of burst events determined. Infrequent, long duration, high stress events account for 60% of total transport in only 24% of the total time with the mean free path and transport velocity for particles being 0.16 m and 0.22 m/s, respectively. Clear links between intense intermittent turbulence and bedload transport revealed in this study, suggest progress in modelling requires a clearer understanding of near bed flow structure.  相似文献   

Modern swathe sounding and sub-bottom profiling technology for research applications: The Atlas Hydrosweep and Parasound Systems     

J. A. Grant  R. Schreiber 《Marine Geophysical Researches》1990,12(1-2):9-19

This chapter describes two separate but complementary research echosounder systems originally developed by Krupp Atlas Elektronik GmbH for the new German oceanographic research vessel Meteor.The Hydrosweep is a Hydrographic wide-swathe sweep survey echosounder for both shallow and deep water applications providing accurate bathymetric surveys and terrain-following navigation capabilities.The Parasound system is a hull-mounted dual channel parametric narrow-beam deep sea survey and sub-bottom profiling echosounder enabling particularly high vertical and horizontal resolution of seabed features.  相似文献   

Three-dimensional visualization of mission planning and control forthe NPS autonomous underwater vehicle   总被引：1，自引：0，他引：1  

Zyda  M.J. McGhee  R.B. Kwak  S. Nordman  D.B. Rogers  R.C. Marco  D. 《Oceanic Engineering, IEEE Journal of》1990,15(3):217-221

The Naval Postgraduate School (NPS) is constructing a small autonomous underwater vehicle (AUV) with an onboard mission control computer. The mission controller software for this vehicle is a knowledge-based artificial intelligence (AI) system requiring thorough analysis and testing before the AUV is operational. The manner in which rapid prototyping of this software has been demonstrated by developing a controller code on a LISP machine and using an Ethernet link with a graphics workstation to simulate the controller's environment is discussed. The development of a testing simulator using a knowledge engineering environment (KEE) expert system shell that examines AUV controller subsystems and vehicle models before integrating them with the full AUV for its test environment missions is discussed. This AUV simulator utilizes an interactive mission planning control console and is fully autonomous once initial parameters are selected  相似文献   

Numerical simulation of unsteady free-surface motions using a boundary integral formulation     

D. Sen  M. J. Hinchey  J. H. Lever 《Ocean Engineering》1988,15(4)

A numerical time simulation method is described to solve fluid flow problems including unsteady free surface motion. The method is based on potential flow theory. At every time step, the problem is solved using a boundary integral formulation of the fluid domain. The linearized free surface conditions are integrated in time and the solution is marched forward. Computational results simulating the free surface motion for the cases of a linear progressive wave, wave propagating into a region of calm water and the wave maker motion are presented. Comparison with theoretical results demonstrate the feasibility of the proposed simulation scheme.  相似文献