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161.
This article 1) examines the policy context that created a demand for biogeographic information, 2) describes early national and regional experiences in applying biogeographic classifications, 3) extracts lessons about their usefulness, 4) introduces a broad-scale biogeographic classification for the open ocean and deep seabed called the Global Open Ocean and Deep Seabed (GOODS) biogeographic classification and explains its relevance in this policy context. In so doing it highlights potential uses of biogeographic classifications for the open ocean and deep seabed: these include ecosystem-based management approaches, marine spatial planning and identification of representative networks of MPAs. It also discusses approaches for dealing with problems of uncertainty and connectivity. The article concludes with recommendations for the further development of the GOODS and finer-scale biogeographic classifications. 相似文献
162.
Gordeev V. V. Dara O. M. Alekseeva T. N. Kochenkova A. I. Boev A. G. Lokhov A. S. Belorukov S. K. 《Oceanology》2020,60(3):384-392
Oceanology - The paper presents the first results of a study of seasonal variations in the grain size distribution and mineral compositions of suspended particulate matter (SPM) of the Northern... 相似文献
163.
An important aspect of shellfish restoration projects is to evaluate whether potential sites are likely to be recolonised naturally once disturbances are removed and habitats are restored. Similarly, if active translocation or reseeding of juveniles or adults is undertaken, it is important to understand whether these introduced populations will be self‐maintaining in future, and whether any seed they produce are likely to be retained within the restored area. We used a combined hydrodynamic and particle tracking model to predict larval dispersion patterns for the common cockle Austrovenus stutchburyi under different hydrodynamic scenarios for seven release locations in Whangarei Harbour, New Zealand. Our results implied that sites varied substantially in their potential for self‐seeding and for exporting seed to other locations. For sites with more restricted dispersal, the model predicted that most larvae originating at these sites would settle inside the release region (68–94% for passive particle simulations), whereas relatively few larvae originating from the other release sites settled at these sites. In contrast, model larvae released from sites exhibiting high connectivity dispersed to all sub‐regions in the harbour, and export outside of the model region was high. Forthcoming field validation of these model predictions will result in better integration of hydrodynamic connectivity in whole estuary restoration programs. 相似文献
164.
G.P. Glasby 《Marine Chemistry》1973,1(2):105-125
The rare-earth distribution has been determined in five manganese nodules from a range of marine environments. Manganese nodules from Loch Fyne, Scotland, and the Gulf of Aden are characterized by a low absolute abundance of the rare-earth elements and a low Ce/La ratio compared with deep-sea nodules. This difference is interpreted in terms of the diagenetic remobilization of manganese in the high sedimentation regimes leading to the effective fractionation of manganese from the rare-earth elements and the resultant depletion of the rare earths in nodules from these environments. The mechanism of incorporation of the rare-earth elements into manganese nodules is thought to be either the direct adsorption of these elements from seawater or the scavenging of the elements by colloidal iron oxide prior to their incorporation into the authigenic phase of nodules. There appears to be no evidence for the surface transfer of these elements from inorganic detritus into the authigenic phase of nodules as suggested by previous authors. The distribution of U and Th in the nodules is controlled by factors similar to those controlling the rare-earth abundance in nodules. The higher U/Th ratios in nodules from Loch Fyne and the Gulf of Aden is considered to be due to the preferential reduction of UO2(CO3)34? to some lower-valency uranium species such as U3O8 in nodules from less oxidizing environments. 相似文献
165.
The most important feature of the distribution of the alkalinity and calcium in the Sea of Japan—the increase in the potential
alkalinity with depth under the conditions when the waters are supersaturated in relation to calcium carbonate—is considered.
It is demonstrated that this fact cannot be accounted for by the reaction of the formation-dissolution of calcium carbonate.
A new concept explaining the alkalinity distribution in the sea is proposed. According to it, the biological pump is the basic
process responsible for the alkalinity transport from the euphotic layer into the interior of the sea. Photosynthesis is the
driving force for this process. The role of the active element transporting the alkalinity is not calcium carbonate, as has
been claimed elsewhere, but extracellular polysaccharides (EPSs) produced by phytoplankton. EPSs bind to calcium and other
cations to form transparent exopolymer particles (TEPs). The proposed conception makes it possible to explain the following:
(a) the vertical flux of calcium carbonate that is independent of the super-saturation—undersaturation state of the ambient
water regarding calcium carbonate; (b) the existence of the calcium carbonate flux regardless of the nature of the plankton
skeletons; (c) the nonstoichiometric ratio between the alkalinity and calcium fluxes. 相似文献
166.
In this study male largemouth bass (LMB) were exposed to the naturally occurring androgens, dihydrotestosterone (DHT) or 11-ketotestosterone (11-KT) in order to identify genes that are differentially regulated by these steroid hormones. Using subtractive hybridization on livers of fish treated with DHT against vehicle control, many novel LMB genes were cloned. These genes were added to our gene library and arrayed. Six genes were up-regulated and five were down-regulated by both androgens. But, each androgen also regulated specific genes. One gene that was identified as a potential androgen marker was spermidine-spermine-N(1)-acetyltransferase that was up-regulated by both androgens. Determining which genes are responsive to natural androgens will help to identify biochemical pathways that are impacted. 相似文献
167.
The macrobenthos is important in benthic remineralization processes; it represents a trophic link and is also often used as a bio-indicator in monitoring programs. Variations of the environmental parameters strongly influence the structure of the macrobenthic communities in the marshes and since macrobenthos is the most important food item for marsh-visiting fish species in the Schelde, the variation in food resources can have a strong effect on the higher trophic level. The present study deals with the variation in macrobenthic communities in different habitats of intertidal marshes along the salinity gradient and the differences between the marsh creeks and the intertidal part of the estuary. The study measured density and species richness together with the biomass, and sampled a large intertidal channel and a smaller creek within five marshes along the salinity gradient of the Schelde estuary every six weeks between May and October in 2000. 相似文献
168.
Magnetotelluric soundings are frequently carried out on a single profile or on profiles remote from each other. Interpretation of the obtained data is difficult in the presence of spatially heterogeneous geoelectric structures. We evaluate its capabilities on the basis of the synthetic data, that correspond to a geoelectric model, which consists of a three-layered section in the background and three rectangular prisms, differently arranged relative to the profile. Using the simple methods of analysis of magnetotelluric data, we succeeded in allocating all three heterogeneities over the area that surrounds the profile of observations. As a result of the fast smoothed-structure 1D and 2D inversion of different components of data, taking into account their specific features, the depths of the occurrence of anomalies and the order of the values of their electrical resistivity were evaluated, and the background section was also reconstructed. On this basis, and, also, with the use of a priori geological-geophysical information, the construction of a 3D model in a more or less broad band around the profile and its correction with the aid of 3D data inversion are possible. 相似文献
169.
Résumé Cette étude présente l'application du modèle déterministe de simulations hydrologiques CEQUEAU pour la reconstitution des débits moyens journaliers et mensuels de quatre stations hydrométriques du bassin versant de l'oued Miliane (Tunisie) ainsi que les niveaux moyens journaliers dans le barrage Bir Mcherga. Le modèle a été calibré avec les données de trois années d'observation (de 1972/73 à 1974/75). Durant cette période, les débits moyens journaliers sont reconstitués avec des coefficients de Nash variant de 0.88 à 0,97 et des écarts relatifs qui varient entre ?2.3% et ?4.7%. Pour les débits de pointe les biais sont plus élevés. L'analyse des séries résiduelles a montré que les résidus sont homogènes et temporellement dépendants mais les résidus des différents stations sont indépendants. Durant la période de validation (de 1975/76 à 1976/77), les coefficients de corrélation et de Nash se sont dégradés pour les deux stations restées en fonctionnement (0.71 et 0.89). Les biais obtenus varient entre ?3.7% et +5.5%. 相似文献
170.
J.W. Deardorff 《地球物理与天体物理流体动力学》2013,107(3-4):377-410
Abstract The nonlinear equations of motion are integrated numerically in time for a region of x‐y‐z space of volume 3h × h × h, where h turns out to be a height slightly above the level where the wind first attains the geostrophic flow direction. Only the ideal case is treated of a horizontal lower boundary, neutral stability, horizontal homogeneity of all dependent mean variables except the mean pressure, and statistically steady state. The resulting flow patterns are turbulent and the eddies transport required amounts of momentum vertically. Topics which are investigated include the relative directions of stress, wind shear and wind; differences in Ekman wind spirals for the neutral numerical case and a stable atmospheric case; profiles of dimensionless turbulence statistics; effect of allowing the mean density to be either constant or to decrease with height; effect of the wind direction or latitude upon the turbulence intensities; and characteristic structure of the eddies in the planetary boundary layer. 相似文献