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141.
Growth kinetics and competition between Methanosarcina and Methanosaeta in mesophilic anaerobic digestion. 总被引:4,自引:0,他引:4
Methanosarcina species with a high maximum specific growth rate (mumax) and high half-saturation coefficient (KS) and Methanosaeta species with a low mumax and low KS are the only known aceticlastic methanogens. Because of Methanosaeta's low KS, the low acetate concentrations in conventional, mesophilic anaerobic digestion yield Methanosaeta dominance. However, Methanosarcina absorbs increases in acetate more efficiently and thus promotes more stable digestion. This paper tests the hypothesis that decreasing digester feeding frequencies can increase Methanosarcina predominance. Two acetate-fed reactors were established at a 17-day solids retention time. One reactor was fed hourly, and one was fed once daily. Microscopic and molecular methods were used to verify that the hourly fed reactor enriched for Methanosaeta, while the daily fed reactor enriched for Methanosarcina. Growth and substrate-use kinetics were measured for each reactor. A digester overload condition was simulated, and the Methanosarcina-enriched reactor was found to perform better than the Methanosaeta-enriched reactor. These findings indicate that Methanosarcina dominance can be achieved with infrequent feedings, leading to more stable digestion. 相似文献
142.
K. Bruce Jones Daniel T. Heggem Timothy G. Wade Anne C. Neale Donald W. Ebert Maliha S. Nash Megan H. Mehaffey Karl A. Hermann Anthony R. Selle Scott Augustine Iris A. Goodman Joel Pedersen David Bolgrien J. Max Viger Dean Chiang Cindy J. Lin Yehong Zhong Joan Baker Rick D. Van Remortel 《Environmental monitoring and assessment》2000,64(1):227-245
The Environmental Monitoring and Assessment Program (EMAP) is proposing an ambitious agenda to assess the status of streams and estuaries in a 12-State area of the western United States by the end of 2003. Additionally, EMAP is proposing to access landscape conditions as they relate to stream and estuary conditions across the west. The goal of this landscape project is to develop a landscape model that can be used to identify the relative risks of streams and estuaries to potential declines due to watershed-scale, landscape conditions across the west. To do so, requires an understanding of quantitative relationships between landscape composition and pattern metrics and parameters of stream and estuary conditions. This paper describes a strategic approach for evaluating the degree to which landscape composition and pattern influence stream and estuary condition, and the development and implementation of a spatially-distributed, landscape analysis approach. 相似文献
143.
Anne W. Goldizen 《Behavioral ecology and sociobiology》1989,24(2):79-89
Summary This paper presents detailed data on the social relationships among the adults, and between the adults and young, of a cooperatively polyandrous saddle-back tamarin (Saguinus fusciollis; Callitrichidae) group studied for one year. Some data are also presented from groups studied in other years. Adult males in the study groups gave more grooming than they received, while the opposite was true for females (e.g. Fig. 1). The two polyandrous males in the main study group were very rarely aggressive to each other, rarely tried to disrupt each others' copulations, groomed each other, and occasionally shared food, suggesting that their relationship was more affiliative than agonistic. Data on grooming (Fig. 2), spatial relationships, and the initiation of copulations suggest that the males of this group, may have been somewhat more responsible than the female for the maintenance of male-female relationships. Both males and females performed all forms of parental care except lactation. In the main study group each of the males groomed the offspring and remained in close proximity to them more than did the female (Figs.3 and 4). These data are compared with existing data on social relationships in bird species that exhibit cooperative polyandry. 相似文献
144.
Virtually every environmental planner at some time deals with environmental impact assessment (EIA). Public participation is required in most environmental impact assessment programmesaround the world. However, citizen involvement is often reduced to a procedural exercise instead of a substantive process to include the public in environmental decision making. This paper examines public participation in EIA and provides ways to improve its effectiveness. We first examine the rationales for public involvement and its institutionalization through EIA. Next, we analyse the shortcomings and strengths of common approaches to public involvement. Our analysis, supported by two case studies, suggests that going beyond the minimum requirements can benefit the public, the project proponent and the final plan. We conclude with practical steps to improve public participation programmes in environmental planning and decision making. 相似文献
145.
146.
Research examining the effects of unemployment among white collar workers has produced patterns of findings different to those for lower socio-economic groups. The present longitudinal questionnaire study examines the psychological impact of managerial job moves which are downward in status, and considers the effects of periods of unemployment between job changes. The results indicate that among managers the negative impact of downward status moves on psychological adjustment is greater than that of temporary role loss. These effects are associated with decrements in preceived growth and development opportunities at work. The relationship between work and non-work life for our understanding of psychological adjustment is considered. 相似文献
147.
Sarah A. Collins Christene Hubbard Anne M. Houtman 《Behavioral ecology and sociobiology》1994,35(1):21-25
Studies of female mate preference in zebra finches (Taenopygia guttata) have shown that male beak colour and song rate are important. However, the two characters are correlated. Here the effect of beak colour and song rate on female choice are examined independently. In mate choice tests involving two males, beak colour was manipulated artificially using nail varnish. The results showed that females showed a significant preference for males with a high song rate, but not with a red beak. Females did not prefer males with a red beak if song rate was low and females preferred males with orange beaks who expressed a high song rate. Female preference for males with red beaks was not found when beak and song characters were no longer correlated. 相似文献
148.
Anthony B. Anderson Pennie Magee Anne Gély Mário Augusto Gonçalves Jardim 《Conservation biology》1995,9(1):47-61
In the Amazon basin, few studies have focused on environmentally sound land-use alternatives that are linked to markets. This paper analyzes land uses carried out by traditional inhabitants ( ribeirinhos ) on three islands in the Amazon estuary. Management of the native floodplain forest is the most extensive form of land use on these islands. Such management varies in response to local economic and ecological conditions but invariably targets key nontimber forest resources destined for local markets, requires minimal input of labor and capital, and maintains a considerable stock of biotic resources. While restricted to a specific forest type, this form of land use is associated with relatively high population densities and, if supported by appropriate development policies, could provide an environmentally sound land-use alternative for hundreds of thousands of rural inhabitants of Amazonia. 相似文献
149.
Anne Wilson Goldizen 《Behavioral ecology and sociobiology》1987,20(2):99-109
Summary Wild saddle-back tamarins (Saguinus fuscicollis) in southeastern Peru have a variable mating system that can differ both between territories at any one time and within territories over time. Groups are usually monogamous or cooperatively polyandrous, but are occasionally even polygynous. This study addressed the following questions: why does this population contain both monogamous and polyandrous groups simultaneously? What factors determine whether specific groups are monogamous or polyandrous? The data from this study population tentatively support the hypothesis that adults should mate monogramously only if they have nonreproductive helpers (usually older offspring) to help rear infants. Without helpers, the reproductive success of both males and females is hypothesized to be higher, on average, if they mate polyandrously than if they mate monogamously. The proposed benefits of polyandry to males and females differ quantitatively, but in both cases benefits stem from the help that males provide in rearing young. The following results support this hypothesis. (1) Lone pairs were never seen to attempt breeding, and calculations suggest that the costs of lactation and infant-carrying are too great for lone pairs to have a high probability of being able to raise twin offspring (the normal litter size). (2) Polyandrous males and nonreproductive offspring contributed substantially to infant care, particularly infant-carrying (fig. 2). (3) Adult males carried infants approximately twice as often as did lactating females, presumably because of the combined costs of (a) lactation (Fig. 3) and (b) infant-carrying (Fig. 4). The proximate causes of cooperative polyandry inS. fuscicollis appear to be different from those responsible in several bird species, showing that cooperative polyandry is a complex phenomenon. 相似文献
150.
To determine the genetic population structure of blue crabs (Callinectes sapidus Rathbun), electrophoretic allozyme analysis was performed on 750 individuals collected from 16 nearshore locations ranging from New York to Texas, USA. Twenty enzymes and non-enzymatic proteins coded by 31 presumptive loci were examined. Twenty-two loci were either monomorphic or polymorphic at less than theP
95 level; alleles for these polymorphic loci were geographically dispersed. Allele frequencies for three of the remaining polymorphic loci were homogeneous over all populations, as were levels of polymorphism and heterozygosity. Phenograms generated by the UPGMA (unweighted pair-group method using arithmetic averages) and distance Wagner methods exhibited no geographic pattern in the clustering of populations. Estimates ofN
em (effective number of migrants per generation between populations) indicated substantial gene flow, with aalues sufficiently high to infer panmixia between all blue crab populations from New York to Texas. However, despite this high level of gene flow, two striking patterns of geographic differentiation occurred: genetic patchiness and clinal variation. Allele frequencies atEST-2, GP-1, IDHP-2, DPEP-1, DPEP-2, andTPEP exhibited genetic patchiness on local and range-wide geographic scales, and allele frequencies atEST-2 varied temporally. Genetic patchiness in blue crabs is likely to be the result of the pre-settlement formation and subsequent settlement of genetically heterogeneous patches of larvae; allele frequencies of those larval patches may then be further modified through ontogeny by localized selection. In the Atlantic Ocean, a regional latitudinal cline ofEST-2 allele frequencies was superimposed on the range-wide genetic patchiness exhibited by that locus. This pattern against a background of high gene flow is highly likely to be maintained by selection. In estuaries along the Atlantic Ocean coast, a combination of low adult long-distance migration and a high retention rate of locally spawned larvae could serve to segregate populations and allow for the development of the geographic cline inEST-2. The Gulf of Mexico showed no apparent cline, perhaps due to long-distance migration of females in some regions of the Gulf, or to masking by genetic patchiness. These results emphasize the importance of both ecological and evolutionary time scales and structuring mechanisms in determining genetic population structure. 相似文献