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461.
462.
Comparative accumulation of (109)Cd and (75)Se from water and food by an estuarine fish (Tetractenos glaber) 总被引:1,自引:0,他引:1
Few data are available on the comparative accumulation of metal(loid)s from water and food in estuarine/marine fish. Smooth toadfish (Tetractenos glaber), commonly found in estuaries in south-eastern Australia, were separately exposed to radio-labelled seawater (14kBqL(-1) of (109)Cd and 24kBqL(-1) of (75)Se) and food (ghost shrimps; Trypaea australiensis: 875Bqg(-1)(109)Cd and 1130Bqg(-1)(75)Se) for 25 days (uptake phase), followed by exposure to radionuclide-free water or food for 30 days (loss phase). Toadfish accumulated (109)Cd predominantly from water (85%) and (75)Se predominantly from food (62%), although the latter was lower than expected. For both the water and food exposures, (109)Cd was predominantly located in the gut lining (60-75%) at the end of the uptake phase, suggesting that the gut may be the primary pathway of (109)Cd uptake. This may be attributed to toadfish drinking large volumes of water to maintain osmoregulation. By the end of the loss phase, (109)Cd had predominantly shifted to the excretory organs - the liver (81%) in toadfish exposed to radio-labelled food, and in the liver, gills and kidney (82%) of toadfish exposed to radio-labelled water. In contrast, (75)Se was predominantly located in the excretory organs (gills, kidneys and liver; 66-76%) at the end of the uptake phase, irrespective of the exposure pathway, with minimal change in percentage distribution (76-83%) after the loss phase. This study emphasises the importance of differentiating accumulation pathways to better understand metal(loid) transfer dynamics and subsequent toxicity, in aquatic biota. 相似文献
463.
Michael J. Scott James A. Dirks Katherine A. Cort 《Mitigation and Adaptation Strategies for Global Change》2008,13(4):307-339
US residential and commercial buildings were responsible for about 41 exajoules (EJ) of primary energy use per year in 2002,
accounting for approximately 9% of the world fossil-fuel related anthropogenic carbon (C) emissions of 6.7 Gt that contribute
to climate change. US Government-sponsored building energy efficiency research and implementation programs are focused on
reducing energy consumption in US residential and commercial buildings and reducing these carbon (C) emissions. Although not
specifically intended for adaptation to a warmer climate and less effective than under today’s cooler climate, these programs
also could help reduce energy demand in a future warmer world. Warming scenarios projected by the United Nations Intergovernmental
Panel on Climate Change (IPCC) in 2001 imply net overall decreases in both site energy and primary energy consumption in US
residential and commercial buildings, largely because of the reduced need for heating. However, there would be as much as
a 25% increase in building space cooling demand and a significant part of the increase could be offset by energy-efficiency
improvements in buildings. Overall, in the US, buildings-related energy efficiency programs would reduce site energy consumption
in buildings in the US by more than 2 EJ in 2020 and primary energy by more than 3.5 EJ, more than enough to offset the projected
growth in cooling energy consumption due to climate change and growth in the US building stock. The savings would have an
estimated annual net value at 2005 energy prices of between $45.0 and $47.3 billion to consumers.
相似文献
Michael J. ScottEmail: |
464.
Green sea turtles (Chelonia mydas) are renowned for their long-distance migrations but have less fame for short-distance migrations or non-migratory behavior. We present satellite telemetric evidence from Cocos (Keeling) Islands, Indian Ocean for the first predominantly non-migratory green sea turtle (C. mydas) population. The mean migration distance from the nesting beach to the foraging grounds was 35.5 km with a maximum mean transit time of 3.4 days. The behavior of this population has major implications for our general understanding of green turtle behavior and their life cycle and for conservation. Firstly, these results indicate a level of juvenile or adult non-breeding homing behavior from the open ocean to foraging grounds adjacent to their natal nesting beach. Secondly, a non-migratory breeding phase reduces the consumption of reproductive energy utilized, potentially resulting in higher fecundity for this population. Thirdly, the close proximity of the nesting and foraging habitats allows for uniformity in management and conservation strategies rarely possible for wide-ranging green turtle populations. 相似文献
465.
The impact of the lipid fraction of natural geosorbents on the sorption of a polycyclic aromatic hydrocarbon was assessed using several experiments. In the first set of experiments phenanthrene was sorbed on a coastal sediment as well as on its humin and humic acid fractions before and after lipid extraction. Before lipid extraction, sorption shows dominantly partitioning characteristics. However, the extraction of lipids from sediment and humin drastically increases, by up to one order of magnitude, their sorption affinity for phenanthrene at low sorbate concentrations, resulting in increased isotherm nonlinearity. This effect is less pronounced for humic acids. One mechanism proposed for the increasing sorption is that lipids, despite their very low relative abundance in the sediments, can compete with phenanthrene for specific high affinity sorption sites (e.g., matrix pores and adsorption sites). This competition is not surprising considering the similar hydrophobic nature of lipids and phenanthrene. Lipids, or any non-polar molecules, could also act like plasticizers by swelling rigid domains and disrupting high affinity sites. In both cases, the removal of lipids (and extraction solvents) makes those sites available for phenanthrene. These provide alternative explanations to the previously proposed “solvent conditioning effect” believed to occur when geosorbents are treated with non-polar solvents modifying the matrix structure, an effect yet to be proven at molecular scale. To further investigate the impact of lipids on sorption, other independent experiments were performed. In a second experiment, re-addition of lipids to the extracted sediment restored the sorption isotherm linearity observed in the native material supporting the absence of irreversible extraction artifacts. However, high addition of lipids (i.e., after saturation of high affinity sites) seems to also enlarge the low affinity partitioning domain. These results are consistent with dual-mode, hole-filling, sorption models involving diffusion. In the final set of experiments, solid-state 19F-NMR using F-labeled lipids sorbed onto the sediments confirmed that lipids may be in different domains (mobile or rigid) that interact or not with phenanthrene. The possible effects of lipid removal on sorption have been overlooked and should be considered when geosorbents are pretreated. 相似文献
466.
467.
Valuation of Ecological Resources and Functions 总被引:8,自引:0,他引:8
Michael J. Scott Gordon R. Bilyard Steven O. Link Carlos A. Ulibarri Howard E. Westerdahl Paolo F. Ricci Harold E. Seely 《Environmental management》1998,22(1):49-68
/ Ecological resources are natural resources that provide certain necessary but overlooked system maintenance functions within ecosystems. Environmental economics is in search of an appropriate analysis framework to determine economic values of such resources. This paper presents a framework that estimates and compiles the components of value for a natural ecosystem. The framework begins with the ecological processes involved, which provide functions within the ecosystem and services valued by humans. We discuss the additive or competive nature of these values, and estimate these values through conventional and unconventional techniques. We apply the framework to ecological resources in a shrub-steppe dryland habitat being displaced by development. We first determine which functions and services are mutually exclusive (e.g., farming vs soil stabilization) and which are complementary or products of joint production (e.g., soil stabilization and maintenance of species). We then apply benefit transfer principles with contingent valuation methodology (CVM), travel cost methodology (TCM), and hedonic damage pricing (HDP). Finally, we derive upper-limit values for more difficult-to-value functions through the use of human analogs, which we argue are the most appropriate method of valuation under some circumstances. The highest values of natural shrub-steppe habitat appear to be derived from soil stabilization.KEY WORDS: Natural resource economics; Ecological economics; Ecological resources; Shrub-steppe; Environmental valuation; Cost; Benefit; Value 相似文献
468.
Baraka Kuguru Gidon Winters Sven Beer Scott R. Santos Nanette E. Chadwick 《Marine Biology》2007,151(4):1287-1298
Corallimorpharians may dominate some habitats on coral reefs and compete with stony corals for access to light, yet little
is known concerning their photosynthetic traits. At Eilat in the northern Red Sea, we observed that the abundance of individuals
of the corallimorpharian Rhodactis rhodostoma decreased significantly with depth on the reef slope. Field and laboratory experiments revealed that they employ several
mechanisms of photoadaptation to high irradiance on the shallow reef flat. Their endosymbiotic microalgae (zooxanthellae)
varied significantly in both abundance and chlorophyll content with level of irradiance. Use of a diving pulse amplitude modulated
fluorometer revealed that the zooxanthellae of R. rhodostoma effectively disperse excess light energy by expressing significantly higher values of non-photochemical quenching and maximum
excitation pressure on photosystem II when experimentally exposed to high light (HL) versus low light (LL). Host corallimorpharian
tissues mediated this response by shielding the algal symbionts from high irradiance. The endoderm of host tentacles thickened
significantly and microalgal cells were located further from the mesoglea in HL than in LL. The clades of zooxanthellae hosted
by the corallimorpharians also varied with depth. In shallow water, all sampled individuals hosted clade C zooxanthellae,
while in deep water the majority hosted clade D. The photosynthetic output of individuals of R. rhodostoma was less affected by HL than was that of a stony coral examined. When exposed to both high temperature (HT) and HL, individuals
of R. rhodostoma reduced their maximum quantum yield, but not when exposed to HL at low temperature (LT). In contrast, colonies of the scleractinian
coral Favia favus reduced their photosynthetic output when exposed to HL in both temperature regimes. After 2 weeks of HT stress, R. rhodostoma polyps appeared to bleach completely but re-established their zooxanthella populations upon return to ambient temperature.
We conclude that mechanisms of photoadaptation to high irradiance employed by both the endosymbiotic zooxanthellae and host
corallimorpharians may explain in part the abundance of R. rhodostoma on some shallow reef flats. The ability to survive for weeks at HT while bleached also may allow corallimorpharians to repopulate
shallow reef areas where scleractinians have been killed by thermal stress.
B. Kuguru and G. Winters contributed equally to this work. 相似文献
469.
470.
Limitations of Captive Breeding in Endangered Species Recovery 总被引:17,自引:0,他引:17
Noel F.R. Snyder Scott R. Derrickson Steven R. Beissinger James W. Wiley Thomas B. Smith William D. Toone Brian Miller 《Conservation biology》1996,10(2):338-348
The use of captive breeding in species recovery has grown enormously in recent years, but without a concurrent growth in appreciation of its limitations. Problems with (1) establishing self-sufficient captive populations, (2) poor success in reintroductions, (3) high costs, (4) domestication, (5) preemption of other recovery techniques, (6) disease outbreaks, and (7) maintaining administrative continuity have all been significant. The technique has often been invoked prematurely and should not normally be employed before a careful field evaluation of costs and benefits of all conservation alternatives has been accomplished and a determination made that captive breeding is essential for species survival. Merely demonstrating that a species' population is declining or has fallen below what may be a minimum viable size does not constitute enough analysis to justify captive breeding as a recovery measure. Captive breeding should be viewed as a last resort in species recovery and not a prophylactic or long-term solution because of the inexorable genetic and phenotypic changes that occur in captive environments. Captive breeding can play a crucial role in recovery of some species for which effective alternatives are unavailable in the short term. However, it should not displace habitat and ecosystem protection nor should it be invoked in the absence of comprehensive efforts to maintain or restore populations in wild habitats. Zoological institutions with captive breeding programs should operate under carefully defined conditions of disease prevention and genetic/behavioral management. More important, these institutions should help preserve biodiversity through their capacities for public education, professional training, research, and support of in situ conservation efforts. 相似文献