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221.
222.
Ecological network analyses and their use for establishing reference domain in functional assessment of an estuary 总被引:1,自引:0,他引:1
Robert R. Christian Mark M. Brinson James K. Dame Galen Johnson Charles H. Peterson Daniel Baird 《Ecological modelling》2009,220(22):3113
We developed a framework to use ecological network analysis for functional assessment of large aquatic ecosystems in the context of ecosystem-based management. We established a reference domain for the Neuse River Estuary, North Carolina, USA, from changes over time. Four reference network models of the trophic structure of the estuary during early and late summers of 1997 and 1998 were constructed and analyzed. The estuary has experienced various symptoms of eutrophication during the past 20 years, including summer-time hypoxia and fish kills. The networks were used to quantify indices of nominal trophic dynamics and their variation. The ratio of biomass of nekton to that of macrobenthos, derived from network construction, was used to index severity of eutrophication and to promote accessibility of ecological network analysis to environmental management. The ratio increased from early to late summer, and network metrics demonstrated a variety of responses in association with that change. Some variables from network analysis, especially related to consumers, reflected some but not all of this change. Others reflected the most severe increase in the ratio in late summer 1997 when hypoxia was most extensive. We evaluated uncertainty and the modulating effects of hierarchy by comparing variation of input biomasses with integrative response variables. Relative variation in input variables was generally greater than that of the integrative response variables as predicted by hierarchy theory. Ecological network analysis has previously served as support for ecosystem-based management of large aquatic systems with some success. However, its use can be enhanced by making it more accessible to environmental managers and policy makers. Ways to do this include promoting simple metrics from network construction and explicitly associating network analysis to concepts familiar to the management community, such as functional assessment and reference. 相似文献
223.
Tolerated transfer of food among adults is rare among primates, except in humans. Here, we present data on a consistent pattern
of tolerated intersexual transfer of food (held in hand, foot, or mouth by the owner) among adult orangutans, in two different
natural populations (Pongo abelii and Pongo pygmaeus wurmbii), based on ca. 9,000 h of focal observation per site. Although rare, intersexual food transfers were disproportionately from
males to sexually active females and involved food that was equally available to both sexes. There was no evidence for direct
trading of food for social favors (mating, grooming, or agonistic support) or for sharing under pressure of harassment. However,
females frequently protested with loud screams when males, especially unflanged ones, attempted to take food they possessed,
and also when males responded aggressively to their taking attempt. Since associations ended sooner when the female emitted
noisy calls, a male who did not allow a female to take food from him risked losing the association. These findings support
the hypothesis that by taking food, a sexually active female may test the male's tendency toward violence. Thus, intersexual
food taking in orangutans is based on female leverage, resulting in a species-wide female entitlement to male “generosity”.
The inhibition of food defense required for this kind of transaction may also form the basis for sharing patterns among species
in which nutritional benefits have become important, such as chimpanzees and perhaps human foragers. 相似文献
224.
Guillaume Rieucau William L. Vickery G. Jean Doucet 《Behavioral ecology and sociobiology》2009,63(6):891-897
The giving-up density of food (GUD), the amount of food remaining in a patch when a forager ceases foraging there, can be
used to compare the costs of foraging in different food patches. But, to draw inferences from GUDs, specific effects of foraging
costs (predation risk, metabolic and missed opportunities costs) on GUDs have to be identified. As high predation risk, high
metabolic costs and abundant food all should produce high GUDs, this does not allow us to infer directly the quality of a
habitat. In order to separate the effect of each foraging cost, we developed an optimal foraging model based on food supplementation.
We illustrate the use of our model in a study where we assessed the impact of a power line right-of-way in a white-tailed
deer (Odocoileus virginianus) winter yard by determining whether the negative effects of cover loss outweigh the positive effects of browse regeneration. 相似文献
225.
Rizk ZS 《Environmental geochemistry and health》2009,31(1):27-45
The concentration of selected inorganic chemicals was determined for 396 samples of bottled water, desalinated water, and
groundwater used for drinking and domestic purposes in the United Arab Emirates (UAE). The objective of this study was to
compare the concentrations of inorganic chemicals in different domestic water types used in the UAE with the World Health
Organization (WHO) limits for drinking water. Results of the present study revealed a wide variation in the concentrations
of major, minor, and trace inorganic chemicals in domestic water of the UAE. For example, the bottled water sold for drinking
is depleted in major ions and the total dissolved solids (TDS) in some brands do not exceed 100 mg/l. On the other hand, some
of the domestic water used may contain as much as 3,000 mg/l TDS, which is above the WHO recommended limit for drinking water
(500–1,500 mg/l TDS). Similarly, while bottled water is almost free of trace ions and minor constituents, some natural groundwater
may have concentrations higher than the WHO recommended limits for drinking water. The cause of this variation is related
to the different water sources and the large number of companies producing and distributing drinking and domestic water. Moreover,
it is clear that the current controls on domestic water quality in some areas, namely conformance of pH and electrical conductivity
measurements with prescribed ranges of values, are currently inadequate. These two parameters are not enough to judge if water
is suitable for drinking or not and some consumers may receive domestic water of uncertain quality. 相似文献
226.
Indices based on network theory are often used to describe food web functioning. These indices take as input food web flows that are estimated based on merging of (scarce) data with linear inverse methods (LIMs). Due to under sampling, most food webs are highly uncertain and can only be quantified within a specific uncertainty range. The linear inverse method (LIM) can estimate food web flows using a variety of techniques, e.g. the parsimonious or minimum norm (MN) solution, which selects one food web, based on a quadratic minimization technique or the Monte Carlo solution where a finitely many random solutions are generated which are then averaged. We use the Monte Carlo approach (MCA) to estimate the values of several indices from four published food webs, the Gulf of Riga for the autumn, summer and spring seasons, and the Takapoto atoll system. We first show that network indices are much better constrained than the uncertain food webs from which they are calculated. Therefore, even in the face of food web uncertainty, they are robust estimators of food web functioning. We then use the MCA-derived network indices to generate cumulative density functions for each index. These serve to compute the probabilities of the MN indices estimates being an extreme solution as compared to the median values. Our findings show that 82% of the MN solutions are smaller than the MCA solutions, and 63% of the network indices are significantly under-estimated. 相似文献
227.
Galen A. Johnson Nathalie Niquil Harald Asmus Cédric Bacher Ragnhild Asmus Daniel Baird 《Ecological modelling》2009
Food webs are usually aggregated into a manageable size for their interpretation and analysis. The aggregation of food web components in trophic or other guilds is often at the choice of the modeler as there is little guidance in the literature as to what biases might be introduced by aggregation decisions. We examined the impacts of the choice of the a priori model on the subsequent estimation of missing flows using the inverse method and on the indices derived from ecological network analysis of both inverse method-derived flows and on the actual values of flows, using the fully determined Sylt-Rømø Bight food web model. We used the inverse method, with the least squares minimization goal function, to estimate ‘missing’ values in the food web flows on 14 aggregation schemes varying in number of compartments and in methods of aggregation. The resultant flows were compared to known values; the performance of the inverse method improved with increasing number of compartments and with aggregation based on both habitat and feeding habits rather than diet similarity. Comparison of network analysis indices of inverse method-derived flows with that of actual flows and the original value for the unaggregated food web showed that the use of both the inverse method and the aggregation scheme affected indices derived from ecological network analysis. The inverse method tended to underestimate the size and complexity of food webs, while an aggregation scheme explained as much variability in some network indices as the difference between inverse-derived and actual flows. However, topological network indices tended to be most robust to both the method of determining flows and to the inverse method. These results suggest that a goal function other than minimization of flows should be used when applying the inverse method to food web models. Comparison of food web models should be done with extreme care when different methodologies are used to estimate unknown flows and to aggregate system components. However, we propose that indices such as relative ascendency and relative redundancy are most valuable for comparing ecosystem models constructed using different methodologies for determining missing flows or for aggregating system components. 相似文献
228.
Takeki Maeda Juzo Matsuda Hiroshi Nakashima Koichi Yoshida Joji Suzuki 《Journal of Material Cycles and Waste Management》2000,2(2):143-149
Over a period of 21 months, we composted food refuse from a student restaurant in Hokkaido University using a commercially
available composting machine. The machine had two reactors, each with a working volume of 250 l. The refuse was mixed with
sawdust in a ratio of 5 l sawdust to 10 kg refuse, and this mixture was fed into the machine daily. We studied the characteristics
of the refuse, the composting mixture, and the finished compost in an effort to optimize the operating parameters. We also
evaluated the effectiveness of the composting process by determining the decomposition rates of the composting materials.
The optimum moisture content of the composting mixture was between 30% wet basis (wb) and 40% wb in this machine. The composting
machine worked well when the first reactor was filled with composting mixture and 0.5 kg lime was added once per week. The
mass of the materials supplied was reduced by 84% over the study period. The decomposition rate of the volatile matter in
all composting materials was 66%. The mass of the food refuse supplied was 14.8 kg/day on average, and the moisture content
of the refuse was 77% wb on average.
Received: October 4, 1999 / Accepted: April 4, 2000 相似文献
229.
Goscinny S Vandevijvere S Maleki M Van Overmeire I Windal I Hanot V Blaude MN Vleminckx C Van Loco J 《Chemosphere》2011,84(3):279-288
A study was performed to assess exposure of the Belgian population to HBCD diastereoisomers. Measurements of HBCD were performed by UPLC-MS/MS, on 45 composite samples from 5 major food groups: dairy (products), meat (products), eggs, fish (products) and a group of “other” products. The medium bound estimated average daily intake (EDI) of ΣHBCD in the Belgian population was 0.99 ng kg−1 bw d−1. The diastereoisomer contribution to the mean EDI showed a predominance of γ-HBCD at 67%, followed by α-HBCD at 25% and 8% for β-HBCD. These results are consistent with the pattern found in the two food groups contributing the most to the EDI: meat (products) and the group of “other” products. Anyway, it has to be noted that diastereomeric distribution of HBCD can change due to bioisomerisation in biological material. Levels of HBCD diastereoisomers found in Belgian food samples of animal origin were low in comparison with those found in other EU countries and the resulting EDI was substantially below the proposed thresholds. 相似文献
230.
Abalos M Parera J Estévez A Solé M Fabregat MC Piña B Navarro A Abad E 《Chemosphere》2011,82(1):64-71
Aquacultured fish gilthead seabream (Sparusaurata), previously exposed to low levels of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) trough the diet for a 13 months period, were fed on a clean feed for another 22 months. Gilthead seabream is a protandrous hermaphrodite species and this “decontamination” period coincided with the stages of sex differentiation, maturity and reproduction of the fish. PCDD/F levels in the fish tissues (i.e. muscle, liver, perivisceral fat and gonads), expressed in pg WHO-TEQ g−1 fresh weight, showed a general decreasing trend during the “decontamination” period. However, this general trend varied among tissues and was also dependent on sex and lipid contents. Toxicological effects affecting fish behaviour and hepatic marker responses were also evaluated. The results pointed out that exposure to PCDD/Fs did not have an impact on fish development and reproduction, since the proportion of sexes found after the sex reversal process was within the normal range described for this species. In addition, long-term exposure to low PCDD/F levels did not significantly affect the response of most of the biochemical markers considered. On the contrary, some of them (e.g. EROD activity) showed variations in their responses during the sex differentiation process and onwards. Finally, the hepatic AhR mRNA levels increased during dioxin exposure but they returned to values typical for non-exposed fish after the “decontamination” period. 相似文献