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61.
The trophic dynamics of Bagré reservoir which has been recently impounded in Burkina Faso was based on the data collected during 1997–1998 period using the Ecopath model and software. Total fish biomass is 22.63 t km−2 and mainly represents trophic levels (TLs) 2 and 3. The trophic food chain is relatively long and the overall transfer efficiency is quite low. Grazing foodweb based on primary producers is prominent in the reservoir ecosystem and detritus plays a less significant role. Seasonal and long-term variations in water quality have significant influences on the lower TLs clearly showing a bottom-up functioning of the ecosystem. Environmental degradations, such as siltation occurring in the lake, suggest possible risks in limiting ecosystem productivity. 相似文献
62.
Jacques M. Pasteels Claudine Theuring Donald M. Windsor Thomas Hartmann 《Chemoecology》2003,13(1):55-62
Summary. Sequestration and processing of pyrrolizidine alkaloids
(PAs) by leaf beetles of the genus Platyphora were investigated. Tracer
experiments with labeled alkaloids were performed with P. eucosma
feeding on Koanophyllon panamense (Asteraceae, tribe Eupatorieae). P.
eucosma catalyzes the same reactions previously demonstrated for P.
boucardi specialized to Prestonia portobellensis (Apocynaceae): (i)
epimerization of rinderine to intermedine; (ii) esterification of
retronecine yielding insect-specific PAs; (iii) efficient transport of
the PAs as free bases into the defensive secretions. P. bella feeding on
Tournefortia cuspidata (Boraginaceae) shows the same sequestration
behavior and ability to synthesize the specific retronecine esters. P.
ligata, a species phylogenetically closely related to the PA adapted
species and clustering in the same clade, but feeding on a host plant
devoid of PAs, feeds easily on PA treated host-plant leaves, but does
not sequester or metabolize PAs. P. kollari a species clustering outside
the PA clade refused to feed on its food-plant leaves painted with PAs.
The results are discussed in relation to host-plant selection of the PA
adapted species and the role of PAs in chemical defense.
Received 20 September 2002; accepted 18 November 2002. 相似文献
63.
A century-long increase in nitrate (NO3-) in the water column of Lake Superior is a classic example of recent nitrogen accumulation in ecosystems, but its cause and relationship to historical NO3- deposition is unknown. We used stable isotope ratios of oxygen and nitrogen in nitrate (delta18O-NO3 and delta15N-NO3) to examine its sources in this large lake, which represents 10% of the world's surficial liquid freshwater. The most parsimonious hypothesis to explain the rise in NO3- is that the lake is accruing NO3- deposited directly on the lake surface because it is too unproductive to completely assimilate all of it. Data for delta18O-NO3 in external sources and the water column, however, are inconsistent with this hypothesis. Instead, the isotopic evidence indicates strongly that the accumulating NO3- is almost entirely derived from nitrification occurring within the lake. While increases in atmospheric deposition of NO3- may have played a role in its buildup in the lake, other factors such as increases in NH4+ and dissolved organic nitrogen inputs from precipitation or rivers, increases in nitrogen fluxes from the sediments, and decreases in burial rates must also be considered as potential drivers of rising NO3-. The sustained accumulation of nitrogen in Lake Superior is thus more complex and incompletely understood than previously assumed. 相似文献
64.
Jacques Loeb 《Die Naturwissenschaften》1923,11(26):525-525
65.
Takayuki Miura Sébastien Lhomme Jean-Claude Le Saux Philippe Le Mehaute Yvonnick Guillois Elizabeth Couturier Jacques Izopet Florence Abranavel Françoise S. Le Guyader 《Food and environmental virology》2016,8(3):194-199
A hepatitis E outbreak, which occurred on a small isolated island, provided an opportunity to evaluate the association between the number of hepatitis E cases in the community and the concentration of virus detected in sewage. Samples were collected from the different sewage treatment plants from the island and analyzed for the presence of hepatitis E (HEV) virus using real-time RT-PCR. We demonstrated that if 1–4 % of inhabitants connected to a WWTP were infected with HEV, raw sewage contained HEV at detectable levels. The finding that such a small number of infected people can contaminate municipal sewage works raises the potential of the further distribution of the virus. Indeed, investigating the routes of transmission of HEV, including the potential for sewage effluent to contain infectious HEV, may help us to better understand the epidemiology of this pathogen, which is considered to be an emerging concern in Europe. 相似文献
66.
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68.
Kamran Moradkhani Laurence Cuisset Pierre Boisseau Olivier Pichon Marine Lebrun Houda Hamdi-Rozé Marie-Laure Maurin Nicolas Gruchy Marie-Christine Manca-Pellissier Perrine Malzac Frédéric Bilan Marie-Pierre Audrezet Pascale Saugier-Veber Anne-Laure Fauret-Amsellem Chantal Missirian Paul Kuentz Gregory Egea Agnès Guichet Isabelle Creveaux Caroline Janel Ines Harzallah Renaud Touraine Carole Goumy Nicole Joyé Jacques Puechberty Emmanuelle Haquet Sandra Chantot-Bastaraud Sébastien Schmitt Philippe Gosset Bénédicte Duban-Bedu Bruno Delobel Philippe Vago François Vialard Denise Molina Gomes Jean-Pierre Siffroi Jean-Paul Bonnefont Jean-Michel Dupont Philippe Jonveaux Martine Doco-Fenzy Damien Sanlaville Cédric Le Caignec 《黑龙江环境通报》2019,39(11):986-992
69.
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