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131.
T. D. Seeley Susanne Kühnholz Anja Weidenmüller 《Behavioral ecology and sociobiology》1996,39(6):419-427
If a forager bee returns to her hive laden with high-quality nectar but then experiences difficulty finding a receiver bee
to unload her, she will begin to produce a conspicuous communication signal called the tremble dance. The context in which
this signal is produced suggests that it serves to stimulate more bees to function as nectar receivers, but so far there is
no direct evidence of this effect. We now report an experiment which shows that more bees do begin to function as nectar receivers
when foragers produce tremble dances. When we stimulated the production of tremble dances in a colony and counted the number
of bees engaged in nectar reception before and after the period of intense tremble dancing, we found a dramatic increase.
In two trials, the number of nectar receivers rose from 17% of the colony’s population before tremble dancing to 30–50% of
the population after the dancing. We also investigated which bees become the additional nectar receivers, by looking at the
age composition of the receiver bees before and after the period of intense tremble dancing. We found that none of the bees
recruited to the task of nectar reception were old bees, most were middle-aged bees, and some were even young bees. It remains
unclear whether these auxiliary nectar receivers were previously inactive (as a reserve supply of labor) or were previously
active on other tasks. Overall, this study demonstrates that a honey bee colony is able to rapidly and strongly alter its
allocation of labor to adapt to environmental changes, and it further documents one of the communication mechanisms underlying
this ability.
Received: 31 May 1996/Accepted after revision: 9 August 1996 相似文献
132.
Mesograzers are thought to play a critical role in seagrass beds by preventing overgrowth of ephemeral algae. On the Swedish
west coast, eelgrass Zostera marina has decreased in recent decades as a result of eutrophication and increased growth of macroalgal mats (mainly filamentous
Ulva spp. and Ectocarpales), with no indication of grazer control of the algae. The aim of this study was to investigate the ability
of the amphipod Gammarus locusta to control algal blooms during nutrient-enriched and ambient conditions, using a combination of laboratory, field and model
studies. Laboratory experiments demonstrated that juvenile and adult G. locusta could consume both Ulva spp. and Ectocarpales, but that consumption of Ulva spp. was significantly higher. Cannibalism was common in individual treatments involving multiple size-classes of G. locusta, but only large, male gammarids consumed smaller juveniles in the presence of Ulva spp. as an alternative food source. However, no negative effects of cannibalism were found on total grazing impact. A model
using size-specific grazing rates and growth rates of G. locusta and of Ulva spp. suggests that approximately 62 young juvenile, or 27 adult G. locusta are needed per gram DW of Ulva spp. to control the algal growth during ambient nutrient conditions, and approximately 2.6 times as many gammarids during
enhanced nutrient conditions. On the Swedish west coast, densities and mean sizes of G. locusta in eelgrass beds are below these critical values, suggesting that the gammarids will not be able to control the growth of
the filamentous macroalgae. However, in the field cage experiment, immigration of juveniles and reproduction of encaged adult
G. locusta resulted in unexpectedly high densities of G. locusta (>4,000 individual m−2), and very low biomass of Ulva spp. in both ambient and nutrient-enriched treatments. Although the high numbers of juveniles in all cages precluded any
significant treatment effects, this suggests that in the absent of predators, the population of G. locusta can grow significantly and control the biomass of Ulva spp. Furthermore, low grazing of Ectocarpales in the laboratory and high biomass of these filamentous brown algae in the
field indicate a preference for the more palatable green algae Ulva spp. This study indicates that the high grazing capacity of G. locusta, in combination with high reproduction and growth rates, would allow the amphipod to play a key role in Z. marina ecosystems by controlling destructive blooms of filamentous green algae. However, high predation pressure appears to prevent
large populations of G. locusta in eelgrass beds on the Swedish west coast today. 相似文献
133.
Large-scale contaminated sites with multiple contaminants in the groundwater present a challenge to risk assessment and remediation. Attenuation reactions take place in the subsurface and act to contain contaminants, but must be thoroughly investigated on a site-specific basis. Field data from monitoring wells at a contaminated industrial site in Bitterfeld, Germany, are presented and analyzed for evidence of the prevalent biodegradation reactions. The groundwater in the Tertiary aquifer is contaminated with large quantities of chlorinated aliphatic compounds, in addition to chlorobenzenes and BTEX. In this strictly anaerobic environment, geochemical indications for several microbial processes were found, including methanogenesis, sulfate and iron reduction as well as reductive dechlorination of the chlorinated hydrocarbons. Direct evidence for the latter degradation reaction was observed along the flowpath due to the appearance of intermediates and an increase in the degree of dechlorination. 相似文献
134.
The authors evaluate the possibilities of modifying the chemical characteristics of refuse-derived fuels (RDF) that are processed from residual household waste by mechanical operations to achieve and assure quality targets for relevant chemical concentrations, especially for heavy metals and chlorine. Quality assurance in the production of RDF demands that, together with an enrichment of the calorific value, highly toxic waste components are selectively separated and concentrated in a small stream to produce high yields of a relatively low polluted fuel. Based on the method of material flow analysis, a process evaluation is developed that considers the aspect of minimizing hazardous chemicals along with classical process data such as yield and product quality. Data on specific concentration of hazardous chemicals in waste components and their distribution in residual household waste as well as the results from large-scale test runs using different separation techniques demonstrate that mechanical operations alone are insufficient for separating hazardous chemicals. In the test runs, chemical compounds such as chlorine, cadmium and lead were often concentrated in the product. Even using optimized techniques, the ability to reduce hazards in the product is limited due to the distribution of the element concentration in the various components of the waste stream. 相似文献
135.
136.
To study future, sustainable production systems, a step-wise method was used to create three future scenarios for pig production based on different sustainability goals. The first scenario focused on animal welfare and the natural behavior of the animals. The second targeted low impacts on the environment and the efficient use of natural resources. The third scenario aimed at product quality and safety. Each scenario fulfilled different aspects of sustainability, but there were goal conflicts because no scenario fulfilled all sustainability goals. The scenarios were then parameterized. The environmental impact was calculated using the life-cycle assessment (LCA) methodology, and the economic cost was calculated from the same data set. The cost per kilo of pork was highest for the animal welfare scenario and similar for the other two scenarios. The environmental scenario had the lowest environmental impact, and the product-quality scenario the highest. The results are discussed based on different future priorities. 相似文献
137.
Adaptation to climate change in the Northeast United States: opportunities, processes, constraints 总被引:1,自引:1,他引:0
Susanne C. Moser Roger E. Kasperson Gary Yohe Julian Agyeman 《Mitigation and Adaptation Strategies for Global Change》2008,13(5-6):643-659
Scientific evidence accumulating over the past decade documents that climate change impacts are already being experienced in the US Northeast. Policy-makers and resource managers must now prepare for the impacts from climate change and support implementing such plans on the ground. In this paper we argue that climate change challenges the region to maintain its economic viability, but also holds some opportunities that may enhance economic development, human well-being, and social justice. To face these challenges and seize these opportunities effectively we must better understand adaptation capacities, opportunities and constraints, the social processes of adaptation, approaches for engaging critical players and the broader public in informed debate, decision-making, and conscious interventions in the adaptation process. This paper offers a preliminary qualitative assessment, in which we emphasize the need for (1) assessing the feasibility and side effects of technological adaptation options, (2) increasing available resources and improving equitable access to them, (3) increasing institutional flexibility, fit, cooperation and decision-making authority, (4) using and enhancing human and social capital, (5) improving access to insurance and other risk-spreading mechanisms, and (6) linking scientific information more effectively to decision-makers while engaging the public. Throughout, we explore these issues through illustrative sectoral examples. We conclude with a number of principles that may guide the preparation of future adaptation plans for the Northeast. 相似文献
138.
Peter C. Frumhoff James J. McCarthy Jerry M. Melillo Susanne C. Moser Donald J. Wuebbles Cameron Wake Erika Spanger-Siegfried 《Mitigation and Adaptation Strategies for Global Change》2008,13(5-6):419-423
The papers in this Special Issue are the primary technical underpinnings for the Northeast Climate Impacts Assessment (NECIA), an integrated regional-scale assessment of projected climate change, impacts and options for mitigation and adaptation across the US Northeast. The consequences of future pathways of greenhouse gas emissions on projected climate and impacts across climate-sensitive sectors is assessed by using downscaled projections from three global climate models under both higher (Alfi) and lower (B1) emissions scenarios. The findings illustrate that near-term reductions in emissions can greatly reduce the extent and severity of regionally important impacts on natural and managed ecosystems and public health in the latter half of this century, and increase the feasibility that those impacts which are now unavoidable can be successfully managed through adaptation. 相似文献
139.
Susanne Heiska Olli-Pekka Tikkanen Matti Rousi Riitta Julkunen-Tiitto 《Chemoecology》2007,17(4):245-253
Summary. Vole feeding amongst herbal willows that have a high concentration of salicylates in their bark and leaves, and may therefore
be cultivated for use as raw material for herbal medicine was tested in the field and in laboratory conditions. Eight clones
of dark-leaved willow (Salix myrsinifolia Salisb.) were cultivated for two years with six different methods combining three fertilisation levels (none, low and high),
black plastic mulch applied for suppressing weed competition and unmulched control. Samples for the laboratory feeding trial
were taken from the unfertilised plants during willow winter dormancy and twigs were fed to 16 voles as a multi-choice experiment.
The bark area removed was calculated from image analysis of the material left by the voles. The diameter and the bark thickness
of the twigs were measured. Concentrations of salicin, salicortin, HCH-salicortin, picein, triandrin, triandrin derivative,
gallocatechin, (+)-catechin, luteolin-7-glucoside, hyperin, total condensed tannins and total nitrogen were measured from
the twigs fed to voles in the laboratory. Browsing by a natural population of voles amongst winter-dormant willows was measured
in the field. In the laboratory, voles browsed on 80% of the twigs and in the field voles browsed on 33% of the twigs. Vole
feeding followed similar patterns in the field and in the laboratory experiment; feeding was clearly higher amongst the plants
grown in unmulched control compared to those in plastic mulch. The same clones, 1, 2 and 6 were preferred in both experiments.
Voles preferred thin twigs to thick ones. Feeding correlated negatively with concentrations of salicylates and tannins. As
vole feeding seems to be highly affected by willow cultivation method and plant genotype, careful selection of cultivated
clones and cultivation methods can enhance the reliability of herbal willow cultivation. 相似文献
140.
Heidelore Fiedler Gerd Rippen Susanne Sievers Peter Friesel Birgit Gras Christoph Lau Thomas Reich Uwe Schacht Roland Schwörer Hansjörg F. Wesp Otto Hutzinger Fritz Vahrenholt 《Environmental Sciences Europe》1997,9(3):131-135
The sources and reservoirs of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/PCDF) in the city of Hamburg, Germany, in the year 1992 were identified and quantified combining analytical data of PCDD/PCDF with statistical data on annual fluxes of materials and products. Fluxes and amounts of PCDD/PCDF were estimated for the environmental compartments water, air, and soil. Dioxin emissions originating from industrial, commercial or private activities were also calculated. Together with the analysis of the specific regional nutrition data, the human exposurevia the various pathways could be determined. It could be shown that the total PCDD/PCDF intake of individuals in Hamburg was about the same as the national average. High annual fluxes of PCDD/PCDF connected with the trade of industrial products and the waste management and disposal: system in Hamburg obviously had no influence on the human intake of PCDD/PCDF. 相似文献