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41.
Jeffrey Wielgus Leah R. Gerber Enric Sala Jeff Bennett 《Journal of environmental management》2009,90(11):3401-3409
Stated-preference surveys for the economic valuation of environmental resources typically assume no uncertainty in the hypothetical valuation scenarios. However, the outcomes of environmental policies are uncertain. We explored the effects of including information on probabilities of attribute improvement and provision in choice experiments. Our results suggest that stating explicitly a high probability for the occurrence of the valuation scenario can improve the goodness of fit of choice models and the consistency of choices. As the general public becomes more aware of the uncertainty of environmental outcomes under global change, omitting information on scenario risk may contribute to hypothetical bias and impair the validity of stated-preference valuations. 相似文献
42.
Incorporating Uncertainty into Demographic Modeling: Application to Shark Populations and Their Conservation 总被引:5,自引:0,他引:5
Enric Cortés 《Conservation biology》2002,16(4):1048-1062
43.
Here we evaluate the effects of two quantitatively very important components of the water soluble fractions of fuel oils (naphthalene
and 1,2-dimethylnaphthalene, hereafter NAPH and C2-NAPH, respectively) on the survival, feeding and egg production rates,
and viability of eggs of the coastal copepod Paracartia (Acartia) grani. Acute toxicity responses resulted in lethal concentrations (LC50) of 2,535 and 161 μg l−1 for NAPH and C2-NAPH, respectively, with no evidence of narcotic effects. Hydrocarbon-specific differences in the toxicity
response indicate that sublethal effects (EC50) on feeding by C2-NAPH were likely driven by induced mortality, whereas NAPH
has direct negative effects on feeding. Sublethal effects on egg production rates followed a similar detrimental pattern to
the one exhibited by feeding rates, suggesting that the lower egg production rates were mediated by the decrease in feeding
rates. At the exposure time tested (24 h), the 50% reduction effective concentrations (EC50) determined for sublethal effects
were relatively high in comparison with hydrocarbons’ concentrations found under natural circumstances. Long exposure (4 days)
of P. grani adults to the tested hydrocarbons at concentrations well below the recorded EC50, however, had no significant effects on
feeding, egg production and hatching rates. The viability of the eggs was either not affected or only slightly influenced
when healthy eggs were incubated under very high concentrations (up to 6,400 and 700 μg l−1 NAPH and C2-NAPH, respectively). The significance of the effects of oil spills on marine zooplankton communities is discussed
in light of the results presented in this study. 相似文献
44.
Dacha Atienza Albert Calbet Enric Saiz Miquel Alcaraz Isabel Trepat 《Marine Biology》2006,150(2):221-235
In this work we studied the trophic ecology and feeding impact of the cladoceran Penilia avirostris and the cyclopoid copepod Oithona nana, the two dominant zooplankters in the summer communities of the coastal NW Mediterranean, on the naturally occurring microbial communities. In order to ascertain carbon surplus for growth and reproduction and the contribution to carbon and nitrogen recycling of these two species, we also determined their basal metabolism and excretion rates. The experiments conducted during summers 2002, 2003, and 2004 indicate that P. avirostris grazed mostly upon small flagellates, dinoflagellates, and diatoms, whereas O. nana had a narrower prey range, selecting motile organisms such as ciliates and occasionally dinoflagellates. The grazing impact of both species accounted, on average, for <10% of the standing stock of the microbial groups considered. In spite of the oligotrophic conditions, the feeding activity of P. avirostris is in general sufficient to compensate basal metabolism and allows a surplus for growth and reproduction. This was not the case for O. nana, its daily rations being often lower than the carbon basal demands. Regarding excretion rates, both species presented different N:P excretion ratios, the ones of O. nana falling within values typical for copepods, whereas the absence of detectable phosphorus excretion by P. avirostris implied an unbalance recycling with respect to typical Redfield ratio composition of marine seston. 相似文献