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61.
62.
Fisher CR MacDonald IR Sassen R Young CM Macko SA Hourdez S Carney RS Joye S McMullin E 《Die Naturwissenschaften》2000,87(4):184-187
During a research cruise in July 1997 in the Gulf of Mexico we discovered a gas hydrate approximately 1 m thick and over
2 m in diameter which had recently breached the sea floor at a depth of 540 m. The hydrate surface visible from the submarine
was considerably greater than that of any other reported hydrate. Two distinct color bands of hydrate were present in the
same mound, and the entire exposed surface of the hydrate was infested (2500 individuals/m2) with 2 to 4 cm-long worms, since described as a new species, Hesiocaeca
methanicola, in the polychaete family Hesionidae (Desbruyères and Toulmond 1998). H.
methanicola tissue stable isotope values are consistent with a chemoautotrophic food source. No evidence of chemoautotrophic symbionts
was detected, but geochemical data support the presence of abundant free living bacteria on the hydrate. The activities of
the polychaetes, grazing on the hydrate bacteria and supplying oxygen to their habitats, appears to contribute to the dissolution
of hydrates in surface sediments.
Received: 16 August 1999 / Accepted in revised form: 19 January 2000 相似文献
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An economic model of the US aluminium industry is constructed and estimated with annual data over the period 1960–1978. The authors' analysis shows that both the short- and long-term price elasticities of demand are relatively low, and that demand is highly dependent on aluminium end-use activity. A forecasting exercise is also undertaken, and the errors of forecast calculated. 相似文献
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Naturally-occurring lipophilic inducers of larval settlement and metamorphosis wer isolated and identified for Phragmatopoma californica, a gregarious tube worm from southern California. Organic solvent extraction of the sand/organic cement matrix of tubes diminished the inducing capacity of the tube matrix. The inducing capacity was restricted to a single, highly active, HPLC-purified fraction of the organic solvent extract. Chemical analysis of this fraction revealed a mixture of free fatty acids (FFAs), dominated by eicosapentaenoic acid (20:5, 20%), palmitic acid (16:0, 14%) and palmitoleic acid (16:1, 12%). In assays of the nine FFAs that each contributed 3% or more to the active fraction, only 16:1, 18:2, 20:4 and 20:5 induced larval settlement and metamorphosis, while the others were ineffective. The larval response was contact-dependent, highly specific, and concentration-dependent, with a significant response to 16:1 and 20:4 at as low as 10 g FFA spread onto 1 g of sand (surface area 36 cm2). Active FFAs were extracted at approximately 14 g g-1 sand from the tube matrix, although the levels encountered by larvae in nature are believed to be higher. 相似文献
68.
D. Golomb E. Barry G. Fisher P. Varanusupakul M. Koleda T. Rooney 《Atmospheric environment (Oxford, England : 1994)》2001,35(36)
Wet and dry deposition of polycyclic aromatic hydrocarbons (PAHs) was measured at Nahant, Massachusetts, a peninsula jutting into Massachusetts Bay and Wolf Neck, a peninsula jutting into Casco Bay, Maine. Wet deposition (rain and snow) was collected in a funnel which drains into a shielded, temperature controlled receiving bottle. Dry deposition of gaseous and particulate PAHs was collected onto an exposed water surface. PAHs were analyzed by solid phase extraction and gas chromatography-mass spectrometry. Sixteen PAH species were analyzed, ranging from acenaphthylene to coronene. The mean wet deposition rate of the sum of the 16 species is 720 ng m−2 cm−1 precipitation at Nahant, and 831 ng m−2 cm−1 precipitation at Wolf Neck. Wet deposition is attributed to regional PAH emitting sources. Storm patterns appear to bring somewhat higher wet deposition of PAHs to Wolf Neck than to Nahant. The mean dry deposition rate is 95 ng m−2 h−1 at Nahant and 9.3 ng m−2 h−1 at Wolf Neck. The large difference is attributed to the fact that Nahant is close to the urban-industrial metropolitan Boston area and Logan International Airport, whereas Wolf Neck has no major PAH-emitting sources nearby. Individual measurements have an error bracket of ±30%. The Chemical Mass Balance model was used to apportion the dry deposition to source categories. At Nahant, nine samples gave valid statistical attributes with a mean apportionment: jet exhaust 35%, gasoline fueled vehicles 32%, diesel fueled vehicles 17%, wood combustion 13%, others 3%. At Wolf Neck, six samples yielded a mean apportionment: jet exhaust 30%, gasoline vehicles 28%, diesel vehicles 18%, wood combustion 16%, others 8%. There is a considerable variation between the samples. The apportionment is greatly dependent on the quality and selection of the model inputs, i.e. source signatures, which for PAHs are questionable. 相似文献
69.
Anton Eitzinger Peter Läderach Beatriz Rodriguez Myles Fisher Stephen Beebe Kai Sonder Axel Schmidt 《Mitigation and Adaptation Strategies for Global Change》2017,22(5):743-760
Drybeans (Phaseolus vulgaris L.) are an important subsistence crop in Central America. Future climate change may threaten drybean production and jeopardize smallholder farmers’ food security. We estimated yield changes in drybeans due to changing climate in these countries using downscaled data from global circulation models (GCMs) in El Salvador, Guatemala, Honduras, and Nicaragua. We generated daily weather data, which we used in the Decision Support System for Agrotechnology Transfer (DSSAT) drybean submodel. We compared different cultivars, soils, and fertilizer options in three planting seasons. We analyzed the simulated yields to spatially classify high-impact spots of climate change across the four countries. The results show a corridor of reduced yields from Lake Nicaragua to central Honduras (10–38 % decrease). Yields increased in the Guatemalan highlands, towards the Atlantic coast, and in southern Nicaragua (10–41 % increase). Some farmers will be able to adapt to climate change, but others will have to change crops, which will require external support. Research institutions will need to devise technologies that allow farmers to adapt and provide policy makers with feasible strategies to implement them. 相似文献
70.
Mapping socio-economic scenarios of land cover change: a GIS method to enable ecosystem service modelling 总被引:3,自引:0,他引:3
Swetnam RD Fisher B Mbilinyi BP Munishi PK Willcock S Ricketts T Mwakalila S Balmford A Burgess ND Marshall AR Lewis SL 《Journal of environmental management》2011,92(3):563-574
We present a GIS method to interpret qualitatively expressed socio-economic scenarios in quantitative map-based terms. (i) We built scenarios using local stakeholders and experts to define how major land cover classes may change under different sets of drivers; (ii) we formalized these as spatially explicit rules, for example agriculture can only occur on certain soil types; (iii) we created a future land cover map which can then be used to model ecosystem services. We illustrate this for carbon storage in the Eastern Arc Mountains of Tanzania using two scenarios: the first based on sustainable development, the second based on 'business as usual' with continued forest-woodland degradation and poor protection of existing forest reserves. Between 2000 and 2025 4% of carbon stocks were lost under the first scenario compared to a loss of 41% of carbon stocks under the second scenario. Quantifying the impacts of differing future scenarios using the method we document here will be important if payments for ecosystem services are to be used to change policy in order to maintain critical ecosystem services. 相似文献