Hydrographical characteristics and zooplankton distribution in the Mallorca channel (Western Mediterranean): spring 2001   总被引：4，自引：0，他引：4  

Fernandez de Puelles  M. Luz; Valencia  Joaquin; Jansa  Javier; Morillas  Ana 《ICES Journal of Marine Science》2004,61(4):654-666

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Reproductive biology and embryonic development of Centroscymnus coelolepis in Portuguese mainland waters     

Verissimo  Ana; Gordo  Leonel; Figueiredo  Ivone 《ICES Journal of Marine Science》2003,60(6):1335-1341

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Demersal fishes in a tropical bay in southeastern Brazil: Partitioning the spatial, temporal and environmental components of ecological variation     

Mrcia Cristina Costa de Azevedo  Francisco Gerson Araújo  Antnio Gomes da Cruz-Filho  Andr Luiz Machado Pessanha  Mrcio de Araújo Silva  Ana Paula Penha Guedes 《Estuarine, Coastal and Shelf Science》2007,75(4):468-480

This study analyzed the factors structuring demersal fish community in a tropical bay in southeastern Brazil. The results were used to quantify the partitioning of ecological variation among the environmental, spatial and temporal components molding the fish community. Three bay zones (inner, middle and outer) were defined according to depth and salinity gradient. Monthly samplings were conducted by bottom trawl tows during daylight hours, between October 1998 and September 1999. In each zone, three replicate samples were taken. Ninety-three fish species from 73 genera and 37 families were recorded in the 108 samples. Two demersal fish assemblages were evidenced, one in the inner and the other in the outer zone. These assemblages were characterized by changes in species composition and relative abundance. Depth, followed by transparency and salinity, influenced spatial pattern of fish assemblages. The largest part of the explained variation occurred as a result of the spatial structure of environmental variables, which means that both species and environmental variables presented similar spatial structure. The spatial effect, not the seasonal, explained the highest part of species variations. The amount of unexplained variation was relatively high (76%), even assuming that part of it is due to nondeterministic fluctuation, which could be due to local effects of unmeasured (biotic and abiotic) controlling variables. Knowing the relative importance of these factors can be of decisive importance when applying casual hypotheses in the framework of some precise ecological theory and should facilitate management, planning, and usage of bay resources.  相似文献   

High-resolution Surveys for Geohazards and Shallow Gas: NW Adriatic (Italy) and Iskenderun Bay (Turkey)     

Daniel L. Orange  Ana García-García  Dan McConnell  Tom Lorenson  Gary Fortier  Fabio Trincardi  Emrah Can 《Marine Geophysical Researches》2005,26(2-4):247-266

The need for quantifying and understanding the distribution of shallow gas is both of academic interest and of relevance to offshore facilities. The combination of seafloor mapping, subbottom profiling, and multi-channel seismic data can provide information on regions of possible shallow gas, where the gas impacts the acoustic properties of the host material and the seafloor. In this paper, we present two case studies – one academic and one industry – that evaluate the distribution of shallow gas in two field areas in the Mediterranean. In the first case study, geophysical data from Iskenderun Bay, southeastern Turkey, indicate the presence and distribution of shallow gas. Pockmarks on the seafloor are associated with acoustic wipeout in the shallow subbottom data. Although deeper seismic data do not show bright spots or other indicators of possible gas, instantaneous frequency analysis clearly shows laterally restricted anomalies indicating gas-rich zones. The interpretation of possible shallow gas resulted in moving a proposed drilling location to a nearby area characterized by fewer (but still present) shallow gas signatures. In the second case study, cores acquired in the Po Delta, Adriatic Sea, provide quantitative ground-truthing of shallow gas – as suggested by geophysical data – and provide minimum estimates of the percentage of gas in the subsurface. Cores targeted on anomalous subbottom data yielded up to 41,000 ppm methane; cores with anomalous gas content are associated with thick recent flood deposits which may effectively isolate reactive terrigenous organic matter from biologic and physical re-working.  相似文献   

Sardine slipping during purse-seining off northern Portugal   总被引：2，自引：0，他引：2  

Stratoudakis  Yorgos; Marcalo  Ana 《ICES Journal of Marine Science》2002,59(6):1256-1262

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Life Cycle, Demography and Secondary Production of the Polychaete Hediste ­diversicolor in a Non-Polluted Estuary in the Bay of Biscay     

Loreto García-Arberas  & Ana Rallo 《Marine Ecology》2002,23(3):237-251

Abstract. Population dynamics and secondary somatic production data of a population of the polychaete Hediste diversicolor (O. F. Müller) are reported. Monthly samples were taken in a small muddy-sand flat in the Gernika estuary (Basque Country, North Iberian Peninsula) from May 1991 to May 1992. In addition to H. diversicolor abundance, temporal variation of the infauna and sediment conditions were analysed. Size measurements were employed to estimate H. diversicolor biomass and several cohorts were differentiated based on the size distribution. Secondary production was estimated based on cohort summation of growth increments following individual cohorts through time. Results are compared with those of other H. diversicolor populations located along the whole latitudinal gradient of distribution of the species.  相似文献   

New Constraints on Ages of Glasses Proposed as Reference Materials for Fission-Track Dating     

Marinella A. Laurenzi  Maria Laura Balestrieri  Giulio Bigazzi  Julio C. Hadler Neto  Pedro J. Iunes  Pio Norelli  Massimo Oddone  Ana Maria Osorio Araya  José G. Viramonte 《Geostandards and Geoanalytical Research》2007,31(2):105-124

New analyses have been performed in order to enhance the data-set on the independent ages of four glasses that have been proposed as reference materials for fission-track dating. The results are as follows. Moldavite - repeated ⁴⁰Ar/³⁹Ar age determinations on samples from deposits from Bohemia and Moravia yielded an average of 14.34 ± 0.08 Ma. This datum agrees with other recent determinations and is significantly younger than the ⁴⁰Ar/³⁹Ar age of 15.21 ± 0.15 Ma determined in the early 1980s. Macusanite (Peru) -four K-Ar ages ranging from 5.44 ± 0.06 to 5.72 ± 0.12 Ma have been published previously. New ⁴⁰Ar/³⁹Ar ages gave an average of 5.12 ± 0.04 Ma. Plateau fission-track ages determined using the IRMM-540 certified glass and U and Th thin films for neutron fluence measurements agree better with these new ⁴⁰Ar/³⁹Ar ages than the previously published ages. Roccastrada glass (Italy) - a new ⁴⁰Ar/³⁹Ar age, 2.45 ± 0.04 Ma, is consistent with previous determinations. The Quiron obsidian (Argentina) is a recently discovered glass that has been proposed as an additional reference material for its high spontaneous track density (around 100 000 cm^-2). Defects that might produce "spurious" tracks are virtually absent. An independent ⁴⁰Ar/³⁹Ar age of 8.77 ± 0.09 Ma was determined and is recommended for this glass. We believe that these materials, which will be distributed upon request to fission-track groups, will be very useful for testing system calibrations and experimental procedures.  相似文献   

Sulfur and carbon isotope geochemistry of coal and derived coal-combustion by-products: An example from an Eastern Kentucky mine and power plant     

Erika R. Elswick  James C. Hower  Ana M. Carmo  Tao Sun  Sarah M. Mardon 《Applied Geochemistry》2007

The isotopic compositions of S (δ³⁴S) and C (δ¹³C) were determined for the coal utilized by a power plant and for the fly ash produced as a by-product of the coal combustion in a 220-MW utility boiler. The coal samples analyzed represent different lithologies within a single mine, the coal supplied to the power plant, the pulverized feed coal, and the coal rejected by the pulverizer. The ash was collected at various stages of the ash-collection system in the plant. There is a notable enrichment in ³⁴S from the base to the top of the coal seam in the mine, with much of the variation due to an upwards enrichment in the δ³⁴S values of the pyrite. Variations in δ³⁴S and in the amount of pyritic S in the coal delivered to the plant show that there was a change of source of coal supplied to the plant, between week one and week two of monitoring, supporting a previous study based on metal and sulfide geochemistry for the same plant. The fly ash has a more enriched δ³⁴S than the pulverized coal and, in general, the δ³⁴S is more enriched in fly ashes collected at cooler points in the ash-collection system. This pattern of δ³⁴S suggests an increased isotopic fractionation due to temperature, with the fly ash becoming progressively depleted in ³⁴S and the flue gas S-containing components becoming progressively enriched in ³⁴S with increasing temperatures. Substantially less variation is seen in the C isotopes compared to S isotopes. There is little vertical variation in δ¹³C in the coal bed, with δ¹³C becoming slightly heavier towards the top of the coal seam. An 83–93% loss of solid phase C occurs during coal combustion in the transition from coal to ash owing to loss of CO₂. Despite the significant difference in total C content only a small enrichment of 0.44–0.67‰ in ¹³C in the ash relative to the coal is observed, demonstrating that redistribution of C isotopes in the boiler and convective passes prior to the arrival of the fly ash in the ash-collections system is minor.  相似文献   

Accessibility to basic services in one of the most sparsely populated areas in Europe: the province of Teruel (Spain)     

Ana Isabel Escalona-Orcao  Carmen Díez-Cornago 《Area》2007,39(3):295-309

This paper analyses local differences in access to basic health services in the province of Teruel (Spain), one of the most sparsely populated areas in Europe. The demographic decline and the concentration of the remaining population in the main settlements has meant that there is a high degree of spatial fit of supply and demand and average aggregate accessibility is good. However, access costs are high for the scarce and aged population resident in the most remote villages and hamlets scattered over an extensive and tacitly ignored territory. In such circumstances the demands of the inhabitants for more attention from the public authorities, expressed through the 'Teruel Exists' movement, can be readily understood.  相似文献   

Isotopic evidence on the diagenetic evolution of coastal sabkha reservoirs from the Solimões Basin, northern Brazil     

Andreia Dias Elias  Luiz Fernando De Ros  Ana Maria Mizusaki  Koji Kawashita 《Gondwana Research》2007,11(4):553-567

The isotopic composition of diagenetic carbonates, sulfates, illites and associated diagenetic constituents of the Carboniferous Juruá sandstones, Solimões Basin, largest hydrocarbon reservoirs of northern Brazil, was analyzed in conjunction with petrographic characterization and chemical composition. Eolian Juruá sandstones, deposited in a coastal sabkha of a wide cratonic sag, are the best reservoirs, but diagenetic processes introduced strong and complex heterogeneities, which affect hydrocarbon production. Dolomite and anhydrite cementation, together with compaction, exerts the main control on the quality of the reservoirs. Early dolomite cements precipitated under strong evaporation, while late dolomites are related to thermal decarboxylation. Late anhydrite cements are related to the interbedded evaporites and possibly to the oxidation of dissolved sulfide. Authigenic illite K–Ar ages are related to the voluminous Triassic basic magmatism (around 200 Ma), and to the Jurassic–Cretaceous tectonism (around 150 Ma), which may have also affected the late anhydrite and dolomite–ankerite cementation. This isotopic study revealed the major conditions of the diagenetic processes that strongly affected the Juruá reservoirs, which are essential for the development of models that will optimize the production, as well as decrease the risks in the exploration for new Juruá reservoirs.  相似文献