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991.
Integrated fishery assessments are intended to take an integrated and wholistic view of fisheries management, to provide comprehensive systems-based evaluations of the sustainability of individual fisheries and their products. Using guidance derived from decision theory and management science, we develop 18 criteria to evaluate the likely effectiveness of nine integrated fishery assessment systems. The assessment systems do not consistently consider four key criteria: the socio-economic impacts of fisheries, the provision of food security, the local relevance of the assessment to the fishery under assessment, and the independent peer review of assessment outcomes. Other important areas of weakness include the lack of appropriate consultation processes relating to both the design of the assessment system and the outcomes of fishery assessments, and limitations in the quality of data and information used in assessments. Improvements will be needed in these areas across all the systems we evaluated if fishers, consumers, managers and other stakeholders are to be provided with consistently reliable assessment outcomes, and an assurance of the sustainability of capture fisheries. 相似文献
992.
A Bianchi J Garcin O Tholosan 《Deep Sea Research Part I: Oceanographic Research Papers》1999,46(12):2129
A high-pressure serial sampler (HPSS) has been developed to obtain microbial activity data unbiased by decompression during retrieval with the same frequency as used for the measurement of other hydrological parameters. We fitted a commercially available multisampling device with eight pressure-retaining vessels. This device allows the collection of eight 500 ml samples of undecompressed water during the same hydrocast to a depth of 3500 m. The HPSS includes a CTD; therefore the eight sampling depths can be selected using the conventional hydrological parameters. During the retrieval and the incubation period pressure conditions of each sampler are permanently recorded on the surface computer. Incubation is in a temperature-controlled water bath to keep the samples in the natural temperature conditions. During the incubation period, several sub-samples may be successively collected without pressure loss within the culture vessel, allowing time-course experiments. During a stratified period, comparison of microbial production rates simultaneously measured on the decompressed and undecompressed seawater samples collected between 850 and 2000 m depth showed that the deep-sea bacteria were affected by decompression during retrieval. 相似文献
993.
High-resolution seismic studies of gas hydrates west of Svalbard 总被引:2,自引:0,他引:2
A strong bottom-simulating reflection (BSR) with high-amplitude variations is detectable in high- resolution reflection seismic
profiles west of Svalbard. Above the BSR, anomalously high velocities up to 1840 m/s, calculated from high-frequency ocean-bottom
hydrophone (HF-OBH) data, indicate the existence of gas-hydrated sediments. Below the BSR, a low-velocity layer, interpreted
as gas-bearing sediments, shows thickness variations from 12 to 25 m. In addition, two other low-velocity layers clearly containing
free gas are detected within the classic hydrate stability zone (HSZ) where, a theoretical viewpoint, free gas cannot exist.
Received: 6 August 1997 / Revision received: 26 January 1998 相似文献
994.
Assessment of a Sr isotope vital effect (87Sr/86Sr) in marine taxa from Lee Stocking Island, Bahamas
Data from Lee Stocking Island, Bahamas, confirms the hypothesis that there are no vital effects with the uptake of Sr isotopes
(87Sr/86Sr) at the present mass spectrometer resolution [±2×10-5 (2σ)]. Our data set contains analyses of 40 samples derived from 37 different calcareous taxa inhabiting a wide range of
carbonate subenvironments (i.e., reefal, intertidal, supratidal, mangrove). The mean value of our analyses was 0.709179 with
a standard deviation of 2.4×10-5 (2σ) which was very close to the long-term uncertainty of the strontium isotope methodology [±2.0×10-5 (2σ)] and to the widely reported 87Sr/86Sr value of seawater, which clusters around 0.709175.
Received: 14 October 1997 / Revision received: 20 March 1998 相似文献
995.
J. C. Balanyá J. Galindo-Zaldívar A. Jabaloy G. Leitchenkov A. Maldonado J. Rodríguez-Fernández O. Vinnikovskaya 《Geo-Marine Letters》1999,18(3):215-224
The structure of the South Powell Ridge (SPR), separating the Late Cenozoic ocean-floored Powell Basin and the Mesozoic Weddell
Sea domain, is revealed by multichannel seismic data. The SPR appears as a basement high, bounded northward by transtensional
faults and by normal and major reverse faults to the south. These margin features seem to be linked to the Powell Basin southern
strike-slip margin and to the Jane Arc paleotrench, respectively. We suggest the ridge evolved from the Antarctic Peninsula
passive margin to become the deformational front of the Scotia/Antarctica Plate boundary, later being welded to the Antarctic
Plate.
Received: 18 August 1997 / Revision received: 4 May 1998 相似文献
996.
997.
998.
The Effect of Macrofauna on Porewater Profiles and Nutrient Fluxes in the Intertidal Zone of the Humber Estuary 总被引:3,自引:0,他引:3
R. J. G. Mortimer J. T. Davey M. D. Krom P. G. Watson P. E. Frickers R. J. Clifton 《Estuarine, Coastal and Shelf Science》1999,48(6):683
Macrofauna, nutrient fluxes, porewater chemistry and sediment characteristics were measured at six intertidal mudflat sites in the Humber Estuary, U.K., during the different seasons. Nereis diversicolor , Macoma balthica and Corophium volutator were found to be the dominant macrofauna. Salinity was the baseline control on macrofauna distribution but this was overprinted by periodic impoverishment due to sediment mobilization. High resolution gel probe porewater samplers provided direct evidence for the impact of burrows on porewater chemistry. The macrofauna modified nutrient fluxes during periods of mud flat stability. Nereis caused a decrease in silicate and phosphate effluxes but enhanced ammonia release and nitrate uptake. Macoma enhanced ammonia and nitrite release. The impact of Corophium was not possible to discern. The Humber is a large, highly dynamic macrotidal estuary in which sediment resuspension has a large impact on porewater profiles, nutrient fluxes and macrofaunal communities. Simple patterns and inter-relationships which are seen in small sheltered estuaries are not observed in the Humber. 相似文献
999.
Ocean Science Journal - The abundance of bacteria inhabiting the sediment-water interface and their taxonomic composition were determined with the fluorescence in situ hybridization (FISH) method... 相似文献
1000.