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11.
Changes in epilithic algal communities colonizing introduced substrata were determined in a stream polluted with oil refinery
effluent at Digboi (Assam, India). The number of algal taxa was reduced but the growth of blue-green algae, particularly two
species ofOscillatoria, was encouraged. Epilithic biomass (as chlorophylla) also declined at polluted stations. The algal community of the upstream station was markedly different from the community
occurring just after the confluence of effluent; however, the differences were gradually reduced downstream, indicating improvement
in water quality. Of the various criteria tested for possible relationships with the level of pollutants, species richness,
Shannon diversity and biomass showed significant relationships. The study demonstrates the usefulness of algal criteria for
monitoring oil pollution in running waters. 相似文献
12.
Effect of high external NaCl concentrations on ion transport within the shoot of Lupinus albus. I. Ions in xylem sap 总被引:1,自引:1,他引:0
RANA MUNNS 《Plant, cell & environment》1988,11(4):283-289
Abstract. Xylem sap was collected from individual leaves of intact transpiring lupin plants exposed to increasing concentrations of NaCl by applying pneumatic pressure to the roots. Concentrations of Na+ and Cl− in the xylem sap increased linearly with increases in the external NaCl concentration, averaging about 10% of the external concentration. Concentrations of K+ and NO3 − , the other major inorganic ions in the sap, were constant at about 2.5 and 1.5 mol m−3 , respectively. There was no preferential direction of Na + or Cl− to either young or old leaves: leaves of all ages received xylem sap having similar concentrations of Na+ and Cl− , and transpiration rates (per unit leaf area) were also similar for all leaves. Plants exposed to 120–160 mol m−3 NaCl rapidly developed injury of oldest leaves; when this occurred, the Na+ concentration in the leaflet midrib sap had increased to about 40 mol m−3 and the total solute concentration to 130 osmol m−3 . This suggests that uptake of salts from the transpiration stream had fallen behind the rate of delivery to the leaf and that salts were building up in the apoplast. 相似文献
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15.
Consumption of leaf detritus by a stream shredder: Influence of tree species and nutrient status 总被引:8,自引:3,他引:5
Four species of riparian vegetation (alder, birch, willow and poplar) were fertilized with nitrogen, phosphorus, nitrogen
+ phosphorus, or no fertilizer (control). The resulting leaf detritus (leached but not microbially colonized) was offered
to a stream shredder, Hydatophylax variabilis (Trichoptera: Limnephilidae). In one experiment, shredder consumption of leaf detritus from different nutrient treatments
(within tree species) was compared, and in a second experiment, consumption of different tree species (within nutrient treatments)
was compared. Larvae preferred leaf detritus from nitrogen + phosphorus treatments (except in poplar where nitrogen treatment
was preferred). Alder was preferred over other tree species for all treatments. Chemical and physical analyses of leaf litter
showed differences between tree species and nutrient treatments in nutrient content, tannins and leaf toughness. Leaf consumption
by larvae was positively associated with nitrogen content and negatively associated with condensed tannin content. Species
composition and nutrient status of riparian vegetation may strongly influence detrital food webs in streams. 相似文献
16.
Field enrichments with nitrate in two spring-fed drainage lines within the riparian zone of a small woodland stream near Toronto, Ontario showed an absence of nitrate depletion. Laboratory experiments with riparian substrates overlain with nitrate enriched solutions revealed a loss of only 5–8% of the nitrate during 48 h incubation at 12°C. However, 22–24% of the initial nitrate was depleted between 24 and 48 h when a second set of substrate cores was incubated at 20°C. Short-term (3 h) incubations of fresh substrates amended with acetylene were used to estimate in situ denitrification potentials which varied from 0.05–3.19 g N g–1 d–1 for organic and sandy sediments. Denitrification potentials were highly correlated with initial nitrate content of substrate samples implying that low nitrate levels in ground water and riparian substrates may be an important factor in controlling denitrification rates. The efficiency of nitrate removal in spring-fed drainage lines is also limited by short water residence times of < 1 h within the riparian zone. These data suggest that routes of ground water movement and substrate characteristics are important in determining nitrate depletion within stream riparian areas. 相似文献
17.
John G. Raei 《Hydrobiologia》1985,126(3):275-285
For two years a community of larval chironomid midges was studied in a sandy-run portion of a fourth order natural stream in SE Ohio, U.S.A. in order to determine if the species partitioned the spatial resources. The habitat structure was simplified from ten habitat variables to three significant principal components. The three eigenvectors were easily interpreted as sediment size, sediment heterogeneity, and organic deposition. Species abundances were loaded on these axes and niche metrics examined. Strong differences in habitat preference were demonstrated for midge species on each component. Also, there were no differences in distributions for the intraspecific instars for each species tested at a given time, but for each of the instars tested, their distributions were found to change from time to time. Apparently, individuals of a species, regardless of instar, simultaneously choose the same habitat, however, the preferred habitat may shift temporally due to change in resource availability, or niche expansion or compression due to competition. 相似文献
18.
Kevin Bales 《Human ecology: an interdisciplinary journal》1985,13(3):371-387
Research on visual blight has been predominantly qualitative and has pointed out salient attributes of blight: that it is durable, visually demeaning, and somehow aesthetically depressing. Data from a national sample (n=3005) are used in this study to measure the effect of demographic variation on the perception of visual blight. The perception of blight shows marked and regular variation with socioeconomic status, marital status, and religiosity.Harris data for this study was purchased with funds from the Shell Foundation. The author wishes to acknowledge Robert Q. Hanham, whose assistance proved invaluable. 相似文献
19.
Simple mathematical models are formulated to describe density independent and density dependent dispersal. These models clarify
hypotheses of density dependence and may be manipulated easily to suit particular applications. The models demonstrate that
the initial composition of a species aggregate must be controlled before valid conclusions can be drawn about the density
dependency of the aggregate's dispersal. Stochastic models of emigration are derived to assess the power of particular experimental
designs and statistical techniques to discriminate a known form of density dependent emigration.
Contribution No. 369, Great Lakes Research Division, University of Michigan
Contribution No. 369, Great Lakes Research Division, University of Michigan 相似文献
20.
Robert J. Kosinski 《Hydrobiologia》1984,119(2):139-148
Several methods for the estimation of the reaeration coefficient were compared by determining the ability of the methods to recover the correct K value from a computer-simulated stream oxygen record affected by a variety of non-ideal conditions. Noisy data and long observation intervals were not a serious problem for most methods. Saturating photosynthesis, fluctuating light intensity, afternoon depression and temperature variation caused failures by some methods but were well handled by others. Serious impairment of all methods occurred with low productivity or high K. In general, the best-performing methods were the modified hysteresis, nighttime regression, daytime regression, Odum and Hornberger-Kelly daytime methods. 相似文献