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991.
An investigation on the abundance and distribution of trace metals (Fe, Cu, Zn, Mn, Cr, Cd and Pb) in water, and nine species of fish samples from Calabar river was carried out in 1992. The concentrations of iron (6000–7240gl–1), zinc (4910–7230gl–1), and cadmium (3–7gl–1) showed moderate pollution while those of copper (420–630gl–1), manganese (23–48gl–1), chromium (<10–20gl–1) and lead (<1–10gl–1) in water were well below WHO permissible levels. Significant seasonal changes (0.001p0.25) were obtained for iron, copper, zinc, manganese and cadmium in water. Furthermore, iron, zinc and cadmium showed statistically significant spatial changes (0.005p0.10). Of the nine fish species studied, no statistically significant relationship between body weight and the concentrations of the metals was observed. The concentrations of the metals per mean total body weight apparently decreases in the order Fe>Zn>Cu>Mn>Pb>Cd=Cr and were within the limits that were safe for consumption. 相似文献
992.
Augusthy PO Mani AS 《Journal of environmental biology / Academy of Environmental Biology, India》2001,22(2):137-139
Physico-chemical analysis of the rubber factory effluents revealed high amounts of total suspended and dissolved solids. Sulphate, phosphate, total nitrogen were also present in significant amounts. At higher concentration (above 50%) of effluent, the seed germination percentage was retarded. Diluted effluent (upto 50%) favoured seedling growth. Length of root system, shoot system and number of lateral roots were increased by low concentrations of effluent. 相似文献
993.
Maud C. O. Ferrari Myles R. Brown Michael S. Pollock Douglas P. Chivers 《Chemoecology》2007,17(3):157-161
Summary. Many aquatic prey are known to use chemical alarm cues to assess their risk of predation. In fishes, such alarm cues can be
released either through damage of the epidermis during a predatory attack (capture-released) or through release from the predator
feces (diet-released). In our study, we compared the importance of capture- versus diet-released alarm cues in risk assessment
by fathead minnows (Pimephales promelas) that were na?ve to fish predators. We utilized two different fish predators: a specialized piscivore, the northern pike
(Esox lucius) and a generalist predator, the brook trout (Salvelinus fontinalis). Handling time of pike consuming minnows was much shorter than for trout consuming minnows, likely resulting in less epidermal
damage to the minnows during attacks by pike. In accordance with this, minnows showed a less intense antipredator response
to capture-released cues from pike than capture-released cues from trout. This represents a paradox in risk assessment for
the minnows as they respond to the specialized piscivore, the more dangerous predator, with a less intense antipredator response.
In contrast, the minnows showed a stronger antipredator response to the specialized piscivore than to the generalist when
given diet cues. This work highlights the need for researchers to carefully consider the nature of the information available
to prey in risk assessment. 相似文献
994.
Human-imprinted ruffed grouse (Bonasa umbellus) chicks were used to evaluate grouse brood food and cover conditions on reclaimed surface mines in northern West Virginia. Reclaimed surface-mined areas did not provide the quality of habitat for ruffed grouse chicks that unmined land provided. On the surface-mined areas, grasslegume reclamation provided the poorest cover and next to the lowest feeding rates. Of the surface-mined areas a 25-year-old reclaimed mine planted to autumn olive had canopy provided a more favorable micro-climate for insects and herbaceous vegetation was established around the edge. Planting rows of shrubs in addition to the current practice of planting grasses and legumes on surface-mined areas is suggested to create ruffed grouse brood habitat. 相似文献
995.
A One-Equation Turbulence Model for Geophysical Applications: Comparison with Data and the k−ε Model
A one-equation turbulence model is presented, in which the turbulent kinetic energy k is calculated with a transport equation whereas the turbulent length scale l is calculated with an algebraic expression. The value of l depends on the local stratification and reduces to the classical |z| scaling for unstratified flows near a wall, where |z| is the distance to the wall. The length scale decreases during stable stratification, and increases for unstable stratification compared to the neutral case. In the limit of strong stable stratification, the so-called buoyancy length scale proportional to k
1/2
N
–1 is obtained, where N is the buoyancy frequency. The length scale formulation introduces a single model parameter which is calibrated against experimental data. The model is verified extensively against laboratory measurements and oceanic data, and comparisons are made with the two-equation k- model. It is shown that the performance of the proposed k model is almost identical to that of the k- model. In addition, the stability functions of Launder are revisited and adjusted to obtain better agreement with recent data. 相似文献
996.
Caglar G Caglar S Ergin O Yarim M 《Journal of environmental biology / Academy of Environmental Biology, India》2005,26(3):479-485
The objectives of this study were to examine the effect of TDZ and BAP on shoot proliferation and to develop a satisfactory rooting procedure for in vitro propagation of caper (Capparis spinosa L). TDZ was found to be more effective than BAP in shoot production. The highest shoot number per explant (45.7) was achieved on the media that contained 4.54 microM TDZ in the absence of IAA. TDZ at 4.54 microM alone or in combination with 0.57 microM IAA did not inhibit shoot elongation, although they produced the most shoots. Dipping the caper shoots in the solution of IBA at 24.6 microM for 10 minutes before planting on MS media, improved the rooting percentage up to 80.5% under a 16 hr photoperiod. 相似文献
997.
Sean O’Donnell 《Behavioral ecology and sociobiology》1996,38(2):83-88
Genetic variability within insect societies may provide a mechanism for increasing behavioral diversity among workers, thereby
augmenting colony efficiency or flexibility. In order to assess the possibility that division of labor has a genetic component
in the eusocial wasp Polybia aequatorialis, I asked whether the genotypes of workers within colonies correlated with behavioral specialization. Workers specialized
by foraging for one of the four materials (wood pulp, insect prey, nectar, or water) gathered by their colonies. I collected
foragers on 2 days from each of three colonies and identified the material the foragers were carrying when collected. I produced
random amplified polymorphic DNA (RAPD) markers from the genomic DNA of these foragers and estimated genotypic similarity
of foragers based on sharing of variable RAPD marker bands. Contingency tests on 20 variable loci per colony showed statistically
significant (P <0.05) biases in RAPD marker frequencies among forager types in the three colonies. Patterns of association of RAPD marker
bands with specializations were constant in two colonies, but changed between collection days in one colony. RAPD marker biases
suggest that division of labor among workers includes a genetic component in P. aequatorialis. Colony-level selection on variation in division of labor is a possible factor favoring the evolutionary maintenance of high
genotypic variability (low relatedness) in epiponine wasp colonies and in other eusocial insects.
Received: 18 July 1995/Accepted after revision: 1 October 1995 相似文献
998.
Eugene P Seskin Robert J Anderson Robert O Reid 《Journal of Environmental Economics and Management》1983,10(2):112-124
In evaluating current environmental protection policy, economists often note that current regulations are more costly than necessary to meet environmental quality standards. While the a priori case is strong that current regulatory approaches are resulting in higher-than-necessary costs to attain environmental standards, there is relatively little empirical evidence to support this claim. The purpose of this paper is to supply some of the missing evidence by presenting the results of one study that assesses some of the potential savings associated with implementing economic, rather than command-and-control, regulatory approaches to abate one type of air pollution in one region of the country. Specifically, the paper examines the costs of meeting a prospective short-term standard for nitrogen dioxide under a range of alternative emissions control strategies for stationary sources of nitrogen oxide emissions in the Chicago Air Quality Control Region. The alternative strategies that are considered range from those that might result under current regulatory policy to those that economic policy approaches (such as emissions charges or marketable permits) are designed to implement. The analysis shows that the most efficient program of emissions controls may be more than an order of magnitude less costly than current regulatory strategies, and that economic approaches have additional advantages over more conventional regulatory approaches. 相似文献
999.
1000.