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251.
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
252.
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
253.
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
254.
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
255.
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
256.
The assimilation of PCDD/Fs and PCBs in chickens, pigs and sheep was investigated in studies using conventional animal husbandry practices. Closely matched samples of muscle (meat), liver, kidneys, eggs, milk, feed, soil and grass were collected of which 105 were analysed. The data obtained were consistent with the PCB and PCDD/F TEQ concentrations to be expected in rural background locations. A slight decline in TEQ values in meat with increasing age was evident in pigs, sheep and broiler chickens. Higher TEQ values in meat from outdoor pigs compared to those raised indoors, and an increase in TEQs in eggs as a result of free-range conditions might be attributable to additional contaminant intakes from soil. TEQ values in samples of sheep meat were slightly higher than those for pigs and chickens and market ready lowland sheep showed higher meat TEQs than the highland species. PCDD/F TEQs were considerably higher in the liver than meat. Contaminant transfer from dietary sources was investigated using biotransfer factors (BTFs) which tended to be higher in chickens than in sheep or pigs. BTFs for all animals declined in magnitude with age, but on average, BTFs for pigs and chickens showed a sharper initial decline than for sheep. The relative magnitude of the BTFs usually followed the order: (highest first) PCB 153, PCB 169, PCB 126, 1,2,3,7,8-PeCDD/2,3,4,7,8-PeCDF and 2,3,7,8-TCDD. This may suggest that higher chlorinated congeners accumulate more readily in meat tissues. Congener-specific BTF variations were found to be associated with variables such as dietary composition during rearing, differences between feed and animal species. 相似文献
257.
Soto DX Roig R Gacia E Catalan J 《Environmental pollution (Barking, Essex : 1987)》2011,159(6):1481-1489
Comparative studies of biomonitors of trace metal contamination are relatively scarce. We took advantage of a point source pollution in a reservoir (Flix, Spain) to compare trace metal (Hg, Pb, Cd, Se, As, Zn, Cu, Cr) bioaccumulation patterns among 16 food web components. Our results indicate that most organisms are suitable for Hg biomonitoring, whereas other metals are better monitored by only some of them. Biofilms and zebra mussel were the organisms with larger and more diverse biomonitoring capacity. However, we show that using groups of biomonitors increase the scope and strengths of the conclusions and specific goals can be better addressed. We conclude providing an overview of the strengths and weaknesses of the main organisms considered for biomonitoring trace metals in rivers and reservoirs. 相似文献
258.
Historical trends in human dietary intakes of endosulfan and toxaphene in China, Korea and Japan 总被引:2,自引:0,他引:2
Desalegn B Takasuga T Harada KH Hitomi T Fujii Y Yang HR Wang P Senevirathna ST Koizumi A 《Chemosphere》2011,83(10):1398-1405
Recently, the Stockholm Convention prohibited the use of toxaphene and has been reviewing endosulfan. The historical use of these pesticides may contaminate food and tend to accumulate in the food chain. In this study, to evaluate the spatial and temporal trends of food contamination, the endosulfan and toxaphene levels were measured in pooled 24-h food composite samples from Chinese (n = 10), Korean (n = 10) and Japanese (n = 40) adults in the 1990s and 2007-2009. Endosulfan was detected in 32 of 40 samples from Japan, but its levels (sum of α- and β-isomers) were low in both the 1990s and 2009 (range as geometric mean (geometric standard deviation) [GM (GSD)]: 0.96 (1.6)-1.42 (1.4) ng kg−1 d−1). The dietary intakes of endosulfan in Seoul as GM (GSD) were 38.68 (1.3) ng kg bw−1 d−1 in 1994 and 92.17 (4.4) ng kg bw−1 d−1 in 2007, and significantly higher than those in Japan (p < 0.05). The samples from Beijing showed a 50-fold increase in the endosulfan levels from 1993 (GM: 0.58 ng kg−1 d−1) to 2009 (GM: 24.91 ng kg bw−1 d−1) (p < 0.05). Toxaphene was detected in 33 of 40 samples from Japan. The dietary intake of toxaphene in Japan (sum of Parlars #26, #50 and #62) was 0.32-1.21 ng kg bw−1 d−1 (range as geometric mean) and no temporal trend was observed. The dietary intake of toxaphene in Seoul increased significantly from 0.2 ng kg bw−1 d−1 (GM) in 1994 to 3.6 ng kg bw−1 d−1 (GM) in 2007 (p < 0.05). Only one of 10 pooled samples from Beijing contained a detectable level of toxaphene (0.3 ng kg bw−1 d−1). For the entire population, the risk of adverse health effects from dietary intakes of endosulfan and toxaphene is unlikely. However, the concentrations of endosulfan in several samples exceeded 10% of the acceptable daily intake limit value of 6 μg kg bw−1 d−1 set by the World Health Organization (WHO). It appears important to refine dietary intake estimates targeting food types and source identification to ensure safe food for consumers. 相似文献
259.
Fiona Armstrong Simmance Alison Budden Simmance Jeppe Kolding Kate Schreckenberg Emma Tompkins Guy Poppy Joseph Nagoli 《Ambio》2022,51(3):700
Small-scale inland capture fisheries provide an important source of nutritious food, employment and income to millions of people in developing countries, particularly in rural environments where limited alternatives exist. However, the sector is one of most under-valued fisheries sectors and is increasingly experiencing environmental change. This study adopts a Sustainable Livelihoods Approach and investigates how important a fluctuating inland fishery is to livelihoods, and how local perceptions on challenges corresponds to global evidence. Through an innovative participatory method; photovoice, the lived experiences and perceptions of fishers are depicted. The findings illuminate the valuable role of the sector to food and nutrition security and the complex nexus with vulnerability to climate change. The study responds to the call for more local level assessments of the impacts of climate change on inland fisheries in data-limited environments, and the value of the sector in underpinning the Sustainable Development Goals. Supplementary InformationThe online version contains supplementary material available at 10.1007/s13280-021-01583-1. 相似文献
260.
Exponential Growth, Animal Welfare, Environmental and Food Safety Impact: The Case of China’s Livestock Production 总被引:1,自引:0,他引:1
Peter J. Li 《Journal of Agricultural and Environmental Ethics》2009,22(3):217-240
Developmental states are criticized for rapid “industrialization without enlightenment.” In the last 30 years, China’s breathtaking
growth has been achieved at a high environmental and food safety cost. This article, utilizing a recent survey of China’s
livestock industry, illustrates the initiating role of China’s developmental state in the exponential expansion of the country’s
livestock production. The enthusiastic response of the livestock industry to the many state policy incentives has made China
the world’s biggest animal farming nation. Shortage of meat and dairy supply is history. Yet, the Chinese government is facing
new challenges of no less a threat to political stability. Production intensification has created a welfare crisis impacting
the world’s biggest number of farm animals. The resulting food safety incidents are affecting consumer confidence and health.
Untreated waste contributes to the nation’s environmental degradation. Developmental states may have a proud record of growth
in the initial stage of industrialization. Their prospects for sustained development have long been questioned. China has
come to an important juncture to march towards a sustained development. 相似文献