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51.
One of the mechanisms by which honeybees regulate division of labour among their colony members is age polyethism. Here the younger bees perform in-hive tasks such as heating and the older ones carry out tasks outside the hive such as foraging. Recently it has been shown that the higher developmental temperatures of the brood, which occur in the centre of the brood nest, reduce the age at which individuals start to forage once they are adult. It is unknown whether this effect has an impact on the survival of the colony. The aim of this paper is to study the consequences of the temperature gradient on the colony survival in a model on the basis of empirical data.We created a deterministic simulation of a honeybee colony (Apis mellifera) which we tuned to our empirical data. In the model in-hive bees regulate the temperature of the brood nest by their heating activities. These temperatures determine the age of first foraging in the newly emerging bees and thus the number of in-hive bees present in the colony. The results of the model show that variation in the onset of foraging due to the different developmental temperatures has little impact on the population dynamics and on the absolute number of bees heating the nest unless we increase this effect by several times to unrealistic values, where individuals start foraging up to 10 days earlier or later. Rather than on variation in the onset of foraging due to the temperature gradient it appears that the survival of the colony depends on a minimal number of bees available for heating at the beginning of the simulation. 相似文献
52.
Haoduo Zhao Min Liu Junjie Yang Yuyang Chen Mingliang Fang 《Frontiers of Environmental Science & Engineering》2023,17(1):4
53.
长春市热岛效应的时空演变研究 总被引:2,自引:0,他引:2
以长春市为例,借助1988年9月25日,1995年9月29日和2000年9月18日三个时相的TM/ETM+遥感影像,研究长春市近12年热岛效应的时空演化规律。研究发现:长春市热岛效应明显且多年稳定存在,热岛中心主要分布在宽城区南部、二道区北部伊通河两岸和绿园区西南部;绿园区西南部和宽城区西北部强热岛区面积呈逐年增加态势,二道区北部伊通河两岸热状况有所改善;从1998年到1995年和从1995年到2000年,热岛面积分别增加约9.32 km2和14.93km2,增长速度加快。 相似文献
54.
Pierre A. Maron Christophe Mougel David P. H. Lejon Esmeralda Carvalho Karine Bizet Graldine Marck Nadge Cubito Philippe Lemanceau Lionel Ranjard 《Atmospheric environment (Oxford, England : 1994)》2006,40(40):8074-8080
Temporal airborne bacterial genetic community structure and meteorological factors were analysed above an urban area in the northwest of France from December 2003 to April 2004 with a sampling strategy considering different time intervals (from an hour to a month). Principal component analysis (PCA) of B-ARISA (Bacterial-Automated Ribosomal Intergenic Spacer Analysis) profiles revealed a hierarchy in the temporal variability of bacterial community: daily<weekly<seasonal. Co-inertia analysis between B-ARISA data and meteorological factors demonstrated the correlation between the seasonal variability in the bacterial community and climatic conditions such as temperature and relative humidity, whereas daily and weekly variability seemed likely to be managed by other factors such as anthropogenic activities. 相似文献
55.
Grant E. Brown Alix C. Rive Maud C. O. Ferrari Douglas P. Chivers 《Behavioral ecology and sociobiology》2006,61(1):9-16
Prey animals often have to face a dynamic tradeoff between the costs of antipredator behavior and the benefits of other fitness-related activities such as foraging and reproduction. According to the threat-sensitive predator avoidance hypothesis, prey animals should match the intensity of their antipredator behavior to the degree of immediate threat posed by the predator. Moreover, longer-term temporal variability in predation risk (over days to weeks) can shape the intensity of antipredator behavior. According to the risk allocation hypothesis, changing the background level of risk for several days is often enough to change the response intensity of the prey to a given stimulus. As the background level of risk increases, the response intensity of the prey decreases. In this study, we tested for possible interactions between immediate threat-sensitive responses to varying levels of current perceived risk and temporal variability in background risk experienced over the past 3 days. Juvenile convict cichlids were preexposed to either low or high frequencies of predation risk (using conspecific chemical alarm cues) for 3 days and were then tested for a response to one of five concentrations (100, 50, 25, 12.5%, or a distilled water control). According to the threat-sensitive predator avoidance hypothesis, we found greater intensity responses to greater concentrations of alarm cues. Moreover, in accordance with the risk allocation hypothesis, we found that cichlids previously exposed to the high background level of risk exhibited a lower overall intensity response to each alarm cue concentration than those exposed to the low background level of risk. It is interesting to note that we found that the background level of risk over the past 3 days influenced the threshold level of response to varying concentrations of alarm cues. Indeed, the minimum stimulus concentration that evoked a behavioral response was lower for fish exposed to high background levels of predation than those exposed to low background levels of predation. These results illustrate a remarkable interplay between immediate (current) risk and background risk in shaping the intensity of antipredator responses. 相似文献
56.
Pereira MG Walker LA Best J Shore RF 《Environmental pollution (Barking, Essex : 1987)》2009,157(1):155-163
Gannet (Morus bassanus) eggs from Bass Rock (North Sea) and Ailsa Craig (eastern Atlantic) were monitored for PCB congeners (1990-2004) and total mercury (1974-2004). Congener profiles for both colonies were dominated by PCBs 153, 138, 180, 118 and 170. All declined in concentration at Ailsa Craig but some (153, 170, 180) remained stable or increased slightly at Bass Rock. Egg congener concentrations at Bass Rock were typically 10-fold higher than at Ailsa Craig by 2002, and Principal Component Analysis indicated that colony differences were driven by the dominant congeners. Egg mercury concentrations were significantly lower at Bass Rock than at Ailsa Craig and temporal trends differed, there being a significant decline at Ailsa Craig but a marginal increase at Bass Rock. Our results suggest there may be differences in contamination between the eastern Atlantic and North Sea and/or there are colony differences in prey selection and associated contaminant loads. 相似文献
57.
Daisuke Imaeda Yoko Ochi Oyuna Tsydenova Masao Amano Valeriy B. Batoev 《Environmental pollution (Barking, Essex : 1987)》2009,157(3):737-747
This study investigated the accumulation features and temporal trends of PCDD/Fs, dioxin-like PCBs (DL-PCBs) and non-dioxin-like PCBs (NDL-PCBs) in the blubber of Baikal seals collected in 1992 and 2005. DL-PCBs (480-3600 ng/g) and NDL-PCBs (980-35,000 ng/g) were dominant contaminants. Concentrations of PCDDs and PCBs in males were significantly higher than in females. In males, age-dependent accumulation was observed for PCDDs, mono-ortho PCBs and NDL-PCBs. PCDFs and non-ortho PCBs showed no such trends, implying that exposure of seals to these contaminants has been decreasing in recent years. No decreasing temporal trend was observed for PCDDs, mono-ortho PCBs and NDL-PCBs, suggesting that Baikal seals are still exposed to PCDDs and PCBs. TEQs of PCDDs and mono-ortho PCBs in seals collected in 2005 accounted for 62-77% of total TEQs. The TEQ levels in 40% of the specimens exceeded the threshold level for immunosuppression observed in harbor seals (209 pg/g). 相似文献
58.
This study is based on raw data obtained from 1 225 samples of herring (Clupea harengus), sprat (Sprattus sprattus), and cod (Gadus morhua) collected in the 1994–2003 period from the Polish coastal zone of the Baltic Sea. This paper presents the results of investigations of the contents of Cu, Zn, Cd, Pb, Hg, and As in fish. The aim was to identify temporal trends in trace metal contamination and variations in the concentrations of Hg in the flesh of herring, sprat, and cod of different lengths. A positive correlation between fish length and Hg concentration was noted for cod, sprat, and herring. The temporal trend analyses of heavy metal concentrations in the fish in the 1994–2003 period indicated ten significant downward trends out of eighteen tests; these referred to concentrations of Cd, Hg, and Pb in all the species studied, and to As in sprat. Concentrations of Cu and Zn remained stable in all the species studied, as did As in herring and cod. No upward trends were detected in the concentration of trace metals in the fish studied. Smaller scale temporal variations in concentrations of some elements were also observed and were associated with natural events, such as increased river discharge resulting from floods. The most likely factors which contributed to the observed downward trends in heavy metals concentrations in fish could possibly stem from lesser quantities of Cd, Pb, and Hg being introduced to the Baltic Sea with the waters of rivers from Baltic countries, including Poland, and atmospheric depositions in the 1994–2003 period. Diminishing trends of concentrations of these elements in Baltic Sea waters are also evidence of this. These facts might indicate that advantageous changes are occurring in the concentrations of heavy metals in the southern Baltic environment. 相似文献
59.
M. Blinda Y. Sabhi S. El Quessar M. Fekhaoui L. Aï t Brahim 《Chemistry and Ecology》2005,21(4):279-301
This study deals with the transfer of heavy metals (Hg, Cd, Pb, Cr, Ni, Ti, Zn, and Cu) between abiotic and biotic components (Cytheria chione and Cerastoderma edule) in the inshore intertidal zones of Tetouan/Martil over 2 yr of investigation (1992-1994). Analysis of the heavy-metal accumulation kinetics in Cytheria chione and Cerastoderma edule shows that their highest contents occur during the spring-summer period when an important proliferation of the plankton biomass occurs. However, the accumulation of Cd is higher during the period between winter and spring. In general, heavy-metal concentrations are higher at Cytheria chione than at Cerastoderma edule. These results, according to previous studies, suggest the presence of significant correlations and dynamic reciprocal transfer of heavy metals among seawater, sediment, and molluscs. They also suggest that the level of contamination of decreasing heavy metals follows the sequence: sediment, organisms, and water. Among the molluscs investigated, the variability of the thallium (Tl) contents is difficult to detect due to the very weak presence of this metal in the analysed tissues. 相似文献
60.
Effect of pyrene on denitrification activity and abundance and composition of denitrifying community in an agricultural soil 总被引:4,自引:0,他引:4
Guo GX Deng H Qiao M Mu YJ Zhu YG 《Environmental pollution (Barking, Essex : 1987)》2011,159(7):1886-1895
Toxicity of pyrene on the denitrifiers was studied by spiking an agricultural soil with pyrene to a series of concentrations (0-500 mg kg−1) followed by dose-response and dynamic incubation experiments. Results showed a positive correlation between potential denitrification activity and copy numbers of denitrifying functional genes (nirK, nirS and nosZ), and were both negatively correlated with pyrene concentrations. Based on the comparison of EC50 values, denitrifiers harboring nirK, nirS or nosZ gene were more sensitive than denitrification activity, and denitrifiers harboring nirS gene were more sensitive than that harboring nirK or nosZ genes. Seven days after spiking with EC50 concentration of pyrene, denitrifiers diversity decreased and community composition changed in comparison with the control. Phylogenetic analyses of three genes showed that the addition of pyrene increased the proportion of Bradyrhizobiaceae, Rhodospirillales, Burkholderiales and Pseudomonadales. Some species belonging to these groups were reported to be able to degrade PAHs. 相似文献