Transient biouptake flux and accumulation by microorganisms: The case of two types of sites with Langmuir adsorption     

Josep Galceran  Josep Monn  Jaume Puy  Herman P. van Leeuwen 《Marine Chemistry》2006,99(1-4):162

The uptake of a chemical species by an aquatic microorganism is modelled considering two kinds of sites where Langmuirian adsorption is followed by first order internalisation kinetics. Simpler models, such as only one internalisation route (while most of the adsorption takes place on non-internalising sites) or a linear isotherm for adsorption on one or both sites, become limiting cases of this double-Langmuirian model. The model considers the sites located on the spherical (or semi-spherical) surface of the organism, and takes diffusion from the medium into explicit account. The numerical solution for the internalisation flux shows a maximum. We provide an estimate for the time needed to reach a certain proximity to steady state. The transient solution confirms that the analytical expressions for the steady-state flux are usually valid and that the accumulated amounts reflect the impact of the short-time uptake. The Instantaneous Steady-State Approximation (ISSA), where an intercept of the linear regression of accumulated amount as a function of time is interpreted as an adsorbed amount, can be critically assessed with the transient numerical code for two cases: (i) when the total burden of metal on the cell is the input data and (ii) when an extraction procedure provides further information on the adsorbed and internalised amount.  相似文献   

Functional Molecular Biodiversity: Assessing the Immune Status of Two Sponge Populations (Suberites domuncula) on the Molecular Level     

Heinz C. Schröder  Vladislav A. Grebenjuk  Michael Binder  Alexander Skorokhod  Renato Batel  Hamdy Hassanein  & Werner E. G. Müller 《Marine Ecology》2004,25(2):93-108

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The expression of CYP1A,vitellogenin and zona radiata proteins in Atlantic salmon (Salmo salar) after oral dosing with two commercial PBDE flame retardant mixtures: absence of short-term responses     

Boon JP  van Zanden JJ  Lewis WE  Zegers BN  Goksøyr A  Arukwe A 《Marine environmental research》2002,54(3-5):719-724

The short-term effects of the commercial PBDE flame retardant mixtures Penta-BDE and cta-BDE on the expression of cytochrome P450 1A (CYP1A), vitellogenin (Vtg) and zona radiata proteins (Zrp) were investigated in juvenile salmon (Salmo salar). For this purpose, groups of fish were dosed twice (oral intake at days I and 4) with 10 and 50 mg/kg body weight of both commercial mixtures. The fishes were sacrificed at day 7 (n = 5 for each group) and 14 (n = 6 for each group), and blood, liver, fillet, and brain were collected. Blanks and positive controls were also part of the experiment. The expressions of Vtg, Zrp, and CYPIA were measured with several techniques (EROD, ELISA, Western, Northern and Slot Blot). The values in the groups of fish treated with Penta-BDE or Octa-BDE did not significantly differ from the reference group for any of the parameters tested. In contrast, the positive control groups treated with estradiol-17beta for Vtg and Zrp expression, and beta-naphthoflavone for CYP1A expression did show a significant response, indicating the potential sensitivity of the fishes for the parameters measured. Since the results of the chemical analyses showed concentrations of a number of PBDE congeners in liver, fillet, and brain that were about three orders of magnitude above those of fish from the North Sea, it is concluded that the short-term toxicity of both commercial PBDE mixtures for these endpoints was low.  相似文献   

The morphodynamic modelling of tidal sand waves on the shoreface     

P.K. Tonnon  L.C. van Rijn  D.J.R. Walstra 《Coastal Engineering》2007

An artificial sand wave on the Dutch shoreface of the North Sea has been studied in conditions with relatively strong tidal currents in the range of 0.5 to 1 m/s and sediments in the medium sand size range of 0.2 to 0.5 mm. The sand wave is perpendicular to the tidal current and has a maximum height and length of the order of 5 m and 1 km, respectively. The sand wave is dynamically active and shows migration rates of the order of a few metres per year. A numerical morphodynamic model (DELFT3D model) has been used to simulate the morphological behaviour of the sand wave in the North Sea. This model approach is based on the numerical solution of the three-dimensional shallow water equations in combination with a surface wave propagation model (wind waves) and the advection–diffusion equation for the sediment particles with online bed updating after each time step. The model results show that the sand wave grows in the case of dominant bed-load transport (weak tidal currents; relatively coarse sediment; small roughness height; low waves) and that the sand wave decays in the case of dominant suspended transport (strong currents, relatively fine sediment, large roughness height; storm waves).  相似文献   

Spatial variation in abundance and catch composition of Cancer pagurus in Norwegian waters: biological reasoning and implications for assessment     

Woll  Astrid K.; van der Meeren  Gro I.; Fossen  Inge 《ICES Journal of Marine Science》2006,63(3):421-433

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Trace element fractionation and distribution in turbidites,homogeneous and pelagic deposits; the Zaire Fan,Southeast Atlantic Ocean     

Tjeerd C. E. van Weering  Gerard Th. Klaver 《Geo-Marine Letters》1985,5(3):165-170

In turbidites, homogeneous and pelagic deposits of the Zaire Fan Th, La, Sm, and Rb and to a lesser extent Yb and Ta correlate strongly. La, Sm, Yb, Rb, Ta, and Th increase two-fold in Te3 turbidite intervals relative to Te 1 due to an increase in clay fraction with which these elements occur associated preferentially.Hf and Zr are anomalously high in Tel and Tel intervals which is probably a result of mineral separation. Zr is absent in Te3 intervals and the homogenous and pelagic deposits. Ba, Br. and U are lowest in turbidites and highest in homogenous continental slope deposits which is probably caused by upwelling. Cc anomalies may be related to the crystallinity of smectite.  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   

Diet shifts of Caribbean grunts (Haemulidae) and snappers (Lutjanidae) and the relation with nursery-to-coral reef migrations     

E. Cocheret de la Morinire  B. J. A. Pollux  I. Nagelkerken  G. van der Velde 《Estuarine, Coastal and Shelf Science》2003,57(5-6):1079-1089

The spatial size distribution of grunts and snappers have previously indicated the separation of juveniles in nursery habitats from the adults on the coral reef. This implies life cycle migrations from nursery habitats (such as seagrass beds and mangroves) to the coral reef. If diet shifts are related to such migrations, then the diets of these fish must change before or around the fish size at which such migrations take place. A wide size range of juveniles of two grunt species (Haemulon sciurus and Haemulon flavolineatum) and of two snapper species (Lutjanus apodus and Ocyurus chrysurus) were caught in seagrass beds and mangroves, and their gut contents identified and quantified. Regression analysis between fish size and dietary importance of small crustaceans showed a negative relationship in all four species. Positive relations were found for H. sciurus, L. apodus and O. chrysurus between fish length and the dietary importance of decapods, and for L. apodusand O. chrysurus between fish length and prey fish importance. Critical changes in the fish diets with fish size were examined by application of a Canonical Correspondence Analysis (CCA). The CCA yielded three clusters of size-classes of fishes with similar diets, and application of a Mantel test showed that each of these clusters had significantly different diets, and that each cluster diet was significantly specialised. The size at which a fish species ‘switched’ from one cluster to another was compared with size-at-maturity data and with the typical size at which these species migrate from the nursery habitats to the coral reef. H. sciurus and H. flavolineatum may be prompted to migrate from the nursery habitats to coral reef habitats because of dietary changes, or because of the development of the gonads. For L. apodus and O. chrysurus, a dietary changeover forms a more likely explanation for nursery-to-reef migrations than does sexual maturation because these species reach maturity at sizes much larger than the maximum size of individuals found in nursery habitats. Although other factors may theoretically initiate or promote the migration patterns, the results of this study indicate that ontogenetic dietary changes may crucially influence the nursery-to-coral reef migrations of these reef fish species.  相似文献   

Distribution of trace and major elements in sediment and pore waters of the Lena Delta and Laptev Sea   总被引：1，自引：0，他引：1  

Rob F. Nolting  Maarten van Dalen  Willem Helder 《Marine Chemistry》1996,53(3-4)

Sediment cores collected during the SPASIBA expedition in 1991 were analysed for their trace- and major element concentrations. Leachable (0.1 N HCl) as well as residual concentrations were determined. Fe and Mn were measured in the interstitial waters to characterize redox conditions. Lateral distribution patterns of solid phase Cu, Cd, Ni, Pb and Zn show a small increase in concentration from the Lena Delta in seaward direction. In general concentrations of these metals are very low and similar to natural background values. With some exceptions, solid phase profiles with depth of all investigated elements do not show strong variations. No enrichment of Pb and Zn in surface layers was found. Remobilization processes and transport of particles enriched in Mn are responsible for Mn accumulation in a particular area. Pore-water concentrations of dissolved Mn in the latter sediments are very high (> 700 μM) and suggest strong Mn reduction directly below the sediment-water interface. In contrast to Mn, the depth profiles of Cd show a surface layer with lower concentrations and an increase deeper down the sediment. The C/N ratio in the sediment decreases from 13 in the Lena mouth to 9 in the more marine part of the Laptev Sea. Surface sediments in the Laptev Sea are very uniform and homogeneous and show only small concentration gradients.  相似文献   

On changes in some biological parameters in the North Sea sole (Solea solea L.)     

de Veen  J. F. 《ICES Journal of Marine Science》1976,37(1):60-90

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