A time-dependent radiation condition for transient wave-structure interactions     

J.F. Lee  J.W. Leonard 《Ocean Engineering》1987,14(6)

An extrapolated version of a time-dependent nonreflecting boundary condition is developed for use at artificial boundaries to truncate infinite/semi-infinite domains for transient water wave problems. Test examples include single- and multiple-frequency flap wavemaker problems and free vibrations of a floating circular cylinder. The finite element results compare favorably to analytical solutions. It is shown that with the proposed boundary condition the numerical simulations have little reflections from the artificial boundaries.  相似文献   

Death in the sea: Enigmatic phytoplankton losses     

John J Walsh 《Progress in Oceanography》1983,12(1):1-86

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Interstitial water chemistry of villefranche bay sediments: Trace metal diagenesis   总被引：1，自引：0，他引：1  

J.-F Gaillard  C Jeandel  G Michard  E Nicolas  D Renard 《Marine Chemistry》1986,18(2-4)

Pore water aliquots were taken with an in situ close interval sampler: the “Peeper”.We report here the pore water concentration profiles of TCO₂, SO₄, TH₂S, Ca and the trace metals Mn, Cu, Pb, Cd and Cr from sediments of a relatively polluted area, the Villefranche Bay, on the French Riviera (close to Nice).We investigated the major ion concentrations in order to establish geochemical mass balances of organic matter oxidation. ΔTCO₂/ΔSO₄ was <−2.0, reflecting the precipitation of calcite as confirmed by the calcium profile. Reduction of sulfate led to increasing sulfide concentrations with depth.Trace metal interstitial water concentrations decreased from 63 to 5 nM, 18 to 4 nM and 6.6 to less than 2 nM for Cu, Pb and Cr, respectively. Cd showed a different pattern with top and deep values of 0.7 nM and a minimum of 0.27 nM.Thermodynamic calculations were performed which suggest the potential formation of mineral phases such as sulfides.  相似文献   

Cytochrome P450 differences in normal and imposex-affected female whelk Buccinum undatum from the open North Sea     

Santos MM  ten Hallers-Tjabbes CC  Vieira N  Boon JP  Porte C 《Marine environmental research》2002,54(3-5):661-665

Normal and imposex-affected female Buccinum undatum were sampled from the open North Sea at three locations, one with low, and two with high shipping densities. Cytochrome P450 components and P450 aromatase activity were determined in the microsomal fractions isolated from pooled digestive gland/gonads. Cytochrome P450 aromatase activity was significantly higher (P < 0.05) in normal females collected in the low shipping density area (1,325 +/- 295 fmol/h/mg protein) than levels from imposex animals from a high shipping density area (620 +/- 287 fmol/h/mg protein). A negative correlation was found between aromatase activity and organotin body burden (r = -0.99). Levels of CYP450, cytochrome b5 and NADPH cytochrome c reductase activity did not show differences among groups. This is the first field evidence of depressed aromatase activity in imposex affected females, although additional research under laboratory controlled conditions is required to fully understand the mechanisms underlying the development of imposex in this species.  相似文献   

The dissociation constants of carbonic acid in seawater at salinities 5 to 45 and temperatures 0 to 45°C     

Rabindra N Roy  Lakshimi N Roy  Kathleen M Vogel  C Porter-Moore  Tara Pearson  Catherine E Good  Frank J Millero  Douglas M Campbell 《Marine Chemistry》1993,44(2-4)

The pK₁^* and pK₂^* for the dissociation of carbonic acid in seawater have been determined from 0 to 45°C and S = 5 to 45. The values of pK₁^* have been determined from emf measurements for the cell: where X is the mole fraction of CO₂ in the gas. The values of pK₂^* have been determined from emf measurements on the cell: The results have been fitted to the equations: where T is the temperature in K, S is the salinity, and the standard deviations of the fits are σ = 0.0048 in lnK₁^* and σ = 0.0070 in lnK₂^*.Our new results are in good agreement at S = 35 (±0.002 in pK₁^*and ±0.005 in pK₂^*) from 0 to 45°C with the earlier results of Goyet and Poisson (1989). Since our measurements are more precise than the earlier measurements due to the use of the Pt, H₂|AgCl, Ag electrode system, we feel that our equations should be used to calculate the components of the carbonate system in seawater.  相似文献   

The impact of mesoscale eddies on plankton dynamics in the upper ocean     

C. L. Smith  K. J. Richards  M. J. R. Fasham 《Deep Sea Research Part I: Oceanographic Research Papers》1996,43(11-12)

A coupled QuasiGeostrophic mixed-layer ECOsystem model (QGECO) is used to investigate the impact of the underlying mesoscale eddy field on the spatial and temporal scales of biological production and on overall rates of primary productivity. The model exhibits temporal trends in the biological and physical fields similar to those observed in the North Atlantic; i.e. the mixed layer shallows in spring causing a rapid increase in phytoplankton concentrations and a corresponding decline in nutrient levels. Heterogeneity is produced in the mixed layer through Ekman pumping velocities resulting from the interaction of windstress and surface currents. This variability impacts on biological production in two ways. Firstly, spatial variations in the depth of the mixed layer affect the photosynthetically active radiation (PAR) availability and hence production rates, and secondly, eddy enhanced exchange between the surface water and those at depth bring additional nutrients into the euphotic zone. These processes result in significant spatial and temporal heterogeneity in the ecosystem distributions.Investigation of the spatial heterogeneity of the biological system finds variability to be significantly greater than that of the mixed layer. The relationship between the eddy field and the ecosystem is investigated. The structure and correlation of the biogeochernical fields change with time. The biological fields are found to have a shorter horizontal scale, but whiter spectrum than the underlying eddy field.Overwinter conditions are found to have a profound effect on the variability, size and timing of the following spring bloom event. Variations in the nitrate levels are primarily responsible for the variability in the biological system in the first year. In subsequent years the variation in the overwintering population is found to be dominant.  相似文献   

An inexpensive instrument for measuring benthic current velocity and direction at sea     

J. R. Craig  S. J. Kennelly 《Estuarine, Coastal and Shelf Science》1991,32(6)

An instrument which measures the velocity and direction of benthic water currents at depths of up to 80 m is described. Characteristics of this meter include: (i) readings are not affected by water flow during sinking or retrieval; (ii) it is portable; (iii) it operates unattended; (iv) it is inexpensive; and (v) it requires only simple maintenance. A timing circuit which operates two time periods in succession is used to activate and de-activate a revolution counter and a fluidfilled compass which are mounted on a special frame and vane system. In the field, the instrument accurately measured average current velocities of up to 6 m s⁻¹. Data are presented which illustrate the usefulness of this instrument in describing the velocity and direction of benthic currents along the east coast of Australia and demonstrate a positive correlation between benthic current velocity and catch rates of the commercially-exploited spanner crab Ranina ranina.  相似文献   

Stability analysis of a two-inlet bay system     

J. van de Kreeke 《Coastal Engineering》1990,14(6)

The stability analysis for a double-inlet bay system is applied to an inlet system resembling Big Marco Pass and Capri Pass on the lower west coast of Florida. Since the opening of Capri Pass in 1967, the length of Big Marco Pass has increased from 2000 m in 1967 to 3000 m in 1988 and the cross-sectional area has decreased from 1200 m² in 1967 to 1000 m² in 1988. Since 1967, the cross-sectional area of Capri Pass has steadily increased and in 1988 was 700 m². Tides off the inlets are of the mixed type with a diurnal range of 1 m. The gross littoral transport rate in the vicinity of the inlets is estimated at 150,000 m³ yr⁻¹.For each inlet the maximum tidal velocities are calculated as a function of the gorge cross-sectional areas using a lumped-parameter model to describe the hydrodynamics of the flow. In the model it is assumed that the bay level fluctuates uniformly and the bay surface area remains constant. The velocities are used to calculate the tidal maximum of the bottom shear stress in each inlet as a function of the cross-sectional areas of the two inlets (=closure surface). Values of the equilibrium shear stress are derived from an empirical relationship between cross-sectional area and tidal prism for stable inlets along the west coast of Florida. Closure surfaces and equilibrium stress values are calculated for values of friction factors ranging from F=4×10⁻³ to F=6×10⁻³. Using the closure surfaces and equilibrium stress values, the equilibrium flow curve for each inlet is determined. The equilibrium flow curve represents the locus of the combination of cross-sectional areas for which the actual bottom shear stress in the inlet equals the equilibrium shear stress.Based on the equilibrium flow curves and the known values of the cross-sectional areas of the two inlets in 1988, it is expected that, ultimately, Big Marco Pass will close and Capri Pass will remain as the sole inlet with a cross-sectional area of 1250 m² and a maximum tidal velocity pertaining to a diurnal tide of 0.85 m s⁻¹.  相似文献   

Hydrography and phytoplankton of waters off south-west Ireland     

R. Raine  J. O'Mahony  T. McMahon  C. Roden 《Estuarine, Coastal and Shelf Science》1990,30(6)

Distributions of physical, chemical and biological characteristics were recorded for coastal waters off south-west Ireland during the summers of 1985–1987. A number of thermal fronts were identified from both shipboard measurements and satellite imagery. Upwelling was shown to be an important process in the area and enhanced phytoplankton biomass and productivity were associated with areas of upwelling and the fronts. Phytoplankton species composition, although varying between cruises, was associated with differences in hydrographic features.  相似文献   

Exposure of the scallop Placopecten magellanicus (Gmelin) to sublethal copper and cadmium: Effects on the reproductive effort     

E. Gould  R.J. Thompson  L.J. Buckley 《Marine environmental research》1985,17(2-4)

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