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551.
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
552.
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
Pt](1 − X)H2 + XCO2|NaHCO3, CO2 in synthetic seawater|AgC1; Ag
Pt, H2(g, 1 atm)|Na2CO3, NaHCO3 in synthethic seawater|AgC1; Ag
lnK*1 = 2.83655 − 2307.1266/T − 1.5529413 lnT + (−0.20760841 − 4.0484/T)S0.5 + 0.08468345S − 0.00654208S1
InK*2 = −9.226508 − 3351.6106/T− 0.2005743 lnT + (−0.106901773 − 23.9722/T)S0.5 + 0.1130822S − 0.00846934S1.5
553.
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
554.
Donald J. Walter Douglas N. Lambert David C. Young Kevin P. Stephens 《Geo-Marine Letters》1997,17(4):260-267
Real-time trackline plots of surficial sediment acoustic impedance delineate several sedimentary facies off Garden Key in
the Dry Tortugas. The sea floor within a 6×6 km surveyed area consists of carbonate muds (silts), sands and shell, rock, and
live corals. The 4-kHz acoustic data supports this finding by providing a pictographic representation of the distribution
and structure of several sediment facies types. Plotting the gridded acoustic data with commercial mapping software (Surfer)
provides a three-dimensional (3D) perspective of the bottom topography with a color contour map of surficial sediment impedance
(upper 0.4 m) draped over the 3D surface. 相似文献
555.
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558.
Maps of the boundary topography for anaerobic waters in the Black Sea are plotted for the summers of the 1920s and 1980s. The mean depths of the H2S boundary for this period are determined. It is shown that the variation in the distribution and average location of the hydrogen sulphide zone has remained constant for the last 60 years.Translated by Mikhail M. Trufanov. 相似文献
559.
560.
Juvenile coho salmon, Onchorynchus kisutch, were exposed to 95mTc in both saltwater and freshwater to study the biokinetic behavior of this element in an anadromous fish. In freshwater, equilibrium whole-body concentration factors (CF5) ranged from 28 to 32 in two separate experiments, in sharp contrast to an equilibriumCF of < 5 in saltwater. While the uptake kinetics were unimodal in saltwater, in freshwater, biomodal uptake kinetics were observed.Technetium-95m retention was biphasic in freshwater depuration experiments, an initial rapid loss of 21% to 26% of the steady-state activity with an elimination half-life of 3 to 5 days was followed by a slower loss rate, with a whole-body elimination half-life ranging from 23 to 33 days. In saltwater, retention was monophasic with an elimination half-life of 5–16 days. Dramatic decreases in 95mTc body burdens when freshwater-labeled fish are transferred to Tc-labeled saltwater indicate that the changes in physiology accompanying saltwater acclimation lead to the loss of 95mTc. 相似文献