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1.
Surface sediments of the lagoons of Lomé, Togo, were analyzed for mercury, methylmercury, and trace elements. Concentrations
were greater than typical for natural lagoon sediments, and with greater variability within the Eastern lagoon compared to
the Western one. The Eastern lagoon is larger and has been dredged in the past, while the Western lagoon, which also receives
major waste inputs, has not been dredged and shows less tidal flushing. Accordingly, one naturally believes that the Eastern
lagoon is cleaner and probably safe to use due to its natural resources, including fishes to eat. Unexpectedly, we describe
here that mercury methylation was greater in the Eastern lagoon, indicating increased bioavailability of mercury, as probably
facilitated by past dredging that decreased solid-phase retention of inorganic mercury. Urbanization has historically been
more developed in the southern part of the lagoons, which is still reflected in contamination levels of sediment despite dredging,
probably because sources of contamination are still more important there today. Such urban contamination emphasizes the need
to regulate waste discharges and possible airborne contamination in growing cities of developing countries, and implements
environmental and public health monitoring, especially in relation to misbelieves systematically associated with the cleansing
effect of dredging activity. 相似文献
2.
Fe0-mediated reductive destruction of hazardous organic compounds such as chlorinated organic compounds (COCs) and nitroaromatic compounds (NACs) in the aqueous phase is one of the latest innovative technologies. In this paper, rapid reductive degradation of COCs and NACs by synthesized nanoscale Fe0 in anaerobic batch systems was presented. The nanoscale Fe0, characterized by high specific surface area and high reactivity, rapidly transformed trichloroethylene (TCE), chloroform (CF), nitrobenzene (NB), nitrotoluene (NT), dinitrobenzene (DNB) and dinitrotoluene (DNT) under ambient conditions, which results in complete disappearance of the parent compounds from the aqueous phase within a few minutes. GC analysis reported that the main products of the dechlorination of TCE and CF were ethane and methane as well as that most of the nitro groups in NACs were reductively transformed to amine groups. These results suggest that the rapid reductive destruction by nanoscale Fe0 is potentially a viable in situ or aboveground treatment of groundwater contaminated with hazardous organic compounds including COCs and NACs. 相似文献
3.
Tae Won Kim Kotaro Sakamoto Yasuhisa Henmi Jae C. Choe 《Behavioral ecology and sociobiology》2008,62(7):1139-1147
For males, courting and foraging are often behavioral alternatives, which take time and consume energy. When males have a
possibility of mating with receptive females, there may be a behavioral trade-off between courtship and feeding; the outcome
of which may be affected by male physiological condition and food availability. Although many mathematical models and empirical
studies suggest that the expression of male courtship signals are condition-dependent, decisions about courtship and mating
strategies in relation to food availability have not attracted much attention. In this study, we tested whether daily changes
in food availability affect males’ decisions about whether to court. We conducted experiments with the fiddler crab Uca lactea by providing males with additional food every other day. In food-supplemented enclosures, males did not increase courtship
activity on the days when food was supplemented. However, they built more courtship structures (semidomes) and waved more
on the days when they were not given additional food. Male size had a strong influence on the number of days the males courted.
We also tested whether the frequency of surface mating, as an alternative reproductive tactic, decreased when food was supplemented.
Contrary to our expectation, the number of males that exhibited the surface-mating tactic increased when food was supplemented
whereas the number of mate-searching females did not change. Our findings in this field study suggest that reproductive decisions
by male fiddler crabs are affected by fluctuating food availability and present body condition, and the alternative mating
tactic of this species may be more frequently used by males under good condition. 相似文献
4.
The vertical distribution and population dynamics of the chaetognath Parasagitta elegans Verrill were determined in the water column and hyperbenthic zone of Conception Bay, Newfoundland from April 1997 to June
1998. The water column depth at the study site (47°32.2′N; 53°07.9′W) was 235 m. The temperature below the thermocline was
<0 °C the year round. Chaetognath samples from the water column were collected with a Tucker Trawl. Those from the hyperbenthic
zone, were collected with an epibenthic sledge. Depending upon whether the hyperbenthic zone was assumed to extend either
1 m or 10 m above bottom, the grand mean, areal abundance of chaetognaths in the hyperbenthic zone ranged from 6% to 40% of
the total abundance in the water column (including the hyperbenthic zone), and the grand mean, areal biomass ranged from 25%
to 77%. Large, mature individuals were collected only in the hyperbenthic zone, whereas small, immature individuals were collected
primarily in the water column. According to body length and ovary maturity data, three cohorts were identified in the hyperbenthic
zone during the study period. Within each cohort, the length frequency of reproductively mature individuals was bimodal, with
groups of mean length 33 mm and 41 mm reproducing from May to October. The recruitment period of juvenile chaetognaths extended
from July to February, coinciding with the recruitment period of copepods. The estimated individual growth rate of P. elegans was 1.0 mg C year−1. The approximate generation time of the two groups of individuals with mean length at maturity of 33 mm and 41 mm was 450
and 780 days, respectively. This study demonstrates that a failure to sample the large, mature P. elegans living in the hyperbenthic zone leads to serious underestimates of the total abundance and biomass of chaetognaths and an
inaccurate picture of seasonal population dynamics.
Received: 8 September 1999 / Accepted: 15 September 2000 相似文献
5.
Many orb-weaving spiders decorate their webs with conspicuous ultraviolet (UV)-reflective stabilimenta. The prey-attraction hypothesis suggests that stabilimenta are visually attractive to prey and thus may increase the spiders’ foraging success. However, previous studies on the function of stabilimenta have produced conflicting results in Argiope species. Using a combination of field and laboratory studies, we examined whether the linear stabilimentum of Argiope bruennichi contributes to prey interception. We recorded prey interceptions in 53 webs with stabilimenta and 37 equally-sized webs without stabilimenta, classifying captured prey according to their taxonomical group and size. On average, 6.2?±?4.7 prey items were intercepted in webs with stabilimenta, while 3.2?±?2.9 items were intercepted in webs without stabilimenta. The effects of stabilimenta on foraging success appear to be due to increased interception of UV-sensitive insect pollinators, including 20 families of Diptera, Hymenoptera, Coleoptera, and Lepidoptera. The mean number of UV-sensitive prey was 4.4?±?3.6 in webs with stabilimenta compared with 1.8?±?2.1 in webs without stabilimenta. Webs with and without stabilimenta did not differ in the mean number of UV-nonsensitive prey captured. The linear stabilimentum showed strong positive effects on the interception of large prey: webs with stabilimenta captured more than twice as many large prey (≥5?mm) than webs without stabilimenta, whereas there was only a slight difference in the interception rates for small prey (<5?mm). Comparisons among different Argiope species suggest that the stabilimentum may have different adaptive functions in different species or ecological contexts. 相似文献
6.
Jae C. Choe 《Behavioral ecology and sociobiology》1994,34(4):233-237
Body size is clearly an important factor influencing the outcome of agonistic contests, but is often weakly correlated with dominance ranks in Zorotypus gurneyi Choe (Insecta: Zoraptera). The study of the development and dynamics of dominance relations using artificially constructed colonies show that age, or tenure within the colony, is the prime determinant of dominance among males. Dominance hierarchies become relatively stable within 2 or 3 days and males that emerge later normally begin at the bottom of the hierarchy regardless of size. Males interact much more frequently when they are simultaneously introduced to each other than when they are allowed to emerge at different times. In the latter case, males that emerge late appear to recognize relative dominance of older males and avoid direct contests. Considering the high correlation between dominance rank and mating success, there is a strong selective advantage to males that emerge earlier and such pressure of sexual selection may be responsible for the difference in life history strategies between Z. gurneyi and its sympatric congener, Z. barberi Gurney, in central Panama. 相似文献
7.
Matriphagous young of a subsocial spider Amaurobius ferox exhibit collective predation during their post-maternal social period. In this paper, we examine functional mechanisms of collective predation by sibling groups. Predation efficiency increased with increasing number of individuals within each group. Solitary or paired individuals were generally unable to capture a 20 mg cricket. In larger groups, more individuals participated and captured the prey more quickly. Some siblings did not take part in paralyzing prey, but later consumed it. The proportion of these profiteers within a group increased with the group size. Presented with prey of different sizes (1, 5, or 40 mg), siblings were most aggressive towards each other when predating on 5 mg prey. Prey of this size could be captured by a single individual and yet were sufficiently large for more than one individual to eat. Siblings were much less aggressive towards one another during the capture of 40 mg prey, which require the assistance of other individuals to capture. By providing the same mass of prey in different numbers of individuals (a single cricket of 40 or 40 mg of first-instar crickets), we tested the influence of cooperation on the post-maternal social period. We found no difference in the development of young during the social period nor the timing of dispersal and the body mass of dispersing individuals. We conclude that the young of this subsocial animal increased predation efficiency by cooperative hunting after the mother's death. 相似文献
8.
Effect of reactive media composition and co-contaminants on sulfur-based autotrophic denitrification 总被引:3,自引:0,他引:3
Moon HS Chang SW Nam K Choe J Kim JY 《Environmental pollution (Barking, Essex : 1987)》2006,144(3):802-807
As a part of a study developing a biological reactive barrier system to treat nitrate-contaminated groundwater, the effects of reactive media composition and co-contaminants on sulfur-oxidizing autotrophic denitrification were investigated. The size of sulfur granules affected the denitrification rates; kinetic constants of 2.883, 2.949, and 0.677 mg-N(1/2)/L(1/2)/day were obtained when the granule sizes were below 2 mm, between 2 and 5 mm, and over 5 mm, respectively. When the volume ratios of sulfur to limestone were 1:1, 2:1, 3:1, and 4:1, kinetic constants of 5.490, 3.903, 4.072, and 2.984 mg-N(1/2)/L(1/2)/day were obtained, respectively. The presence of TCE up to 20 mg/L didn't significantly affect nitrate removal efficiency. At the TCE concentration of 80 mg/L, however, nitrate removal was markedly inhibited. Also, Zn and Cu inhibited the denitrification activity at more than 0.5 mg/L of concentration whereas Cr (VI) did not significantly affect the nitrate removal efficiency at all levels tested. 相似文献
9.
Geonha Kim Woohyeok Jeong Seunghee Choe 《Journal of environmental science and health. Part. B》2013,48(3):287-295
This research investigated the role of the pH buffer capacity of sediment on the dechlorination of atrazine using zero valent iron (ZVI). The buffer capacity of the sediment was quantified by batch experiments and estimated to be 5.0 cmol OH? · pH?1. The sediments were spiked with atrazine at 7.25-36.23 mg kg?1 (6.21 × 10?7–3.09 × 10?6 mol atrazine · g?1 sediment) for the batch experiments. The buffer capacity of the sediment maintained the sediment suspension at neutral pH, thereby enabling continuous dechlorination until the buffer capacity of the sediment was depleted. The pseudo-first order dechlorination constants were estimated to be in the range of 1.19 × 10?2?7.04 × 10?2 d?1 for the atrazine-spiked sediments. 相似文献
10.
This research investigated the role of the pH buffer capacity of sediment on the dechlorination of atrazine using zero valent iron (ZVI). The buffer capacity of the sediment was quantified by batch experiments and estimated to be 5.0 cmol OH(-) . pH(-1). The sediments were spiked with atrazine at 7.25-36.23 mg kg(-1) (6.21 x 10(-7)-3.09 x 10(-6) mol atrazine . g(-1) sediment) for the batch experiments. The buffer capacity of the sediment maintained the sediment suspension at neutral pH, thereby enabling continuous dechlorination until the buffer capacity of the sediment was depleted. The pseudo-first order dechlorination constants were estimated to be in the range of 1.19 x 10(-2)-7.04 x 10(-2) d(-1) for the atrazine-spiked sediments. 相似文献