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31.
Zooplankton in saline lakes of the Southern Interior Plateau of British Columbia were collected on three occasions: mid-May
and early August, 1990, and in late July, 1991. Salinities ranged from 2.6 to 45.8 g L−1. Of the 17 lakes examined, 13 were hyposaline (∼-20g L−1), four, mesosaline (20–50 g L−1) and none, hypersaline (>50 g L−1). pH ranged from 8.7 (Three Mile) to 10.7 (Goodenough), with values <9.6 in 10, and <9.0 in only three lakes. Lakes with
high pHs had high bicarbonate-carbonate alkalinities.
Thirty one species of zooplankton occurred: Protista (1), Rotifera (13), Anostraca (2), Cladocera (7), Ostracoda (1) and Copepoda
(7). Sixteen species were restricted to hyposaline waters, with seven found only in salinities of ≤5 gL−1. Two species (Diaptomus connexus, Artemia franciscana) were restricted to mesosaline waters of salinity >35 g L−1. Eurysaline species includedBrachionus plicatilis, Hexarthra fennica, Limnocythere staplini, Artemia franciscana andDiaptomus connexus. Most species were abundant in 1+ lakes, but six species always had low populations.B. plicatilis, Hexarthra polyodonta, A. franciscana, Limnocythere staplini, Daphnia similis andD. connexus had densest populations in one or more of the three most saline lakes, viz. Long, Goodenough and Three Mile. Cladocerans
other thanD. similis (Alona sp., Ceriodaphnia quadrangula, Daphnia pulex) were usually abundant in lakes of low salinity (<5 g L−1).Diatomus sicilis, present in all except the three most saline lakes, also occurred in abundance in ten of these lakes.Moina hutchinsoni andH. polyodonta were present in both hyposaline and mesosaline lakes, but, more importantly, tended to occur only at higher pH values (>pH
9.4) but not in all such lakes. These can be regarded as alkaline-saline species.
Sorensen’s Coefficient of Community Similarity was used to compare communities in Alberta-Saskatchewan and British Columbia.
It was low (0.37). A comparison restricted to just Cladocera gave a slightly higher value, 0.44, but a comparison of Copepoda
gave a value of 71 per cent similarity between the regions. Multiple regression analyses using pH, TDS and K regressed on
species richness for all samples accounted for only 41 per cent of the variance. However, when the analysis was seasonally
restricted (May), and thus to a limited chemical range, 47 to 77.5 per cent of the variance was accounted for by these three
variables. 相似文献
32.
33.
Ultraviolet complex refractive index of Martian dust: Laboratory measurements of terrestrial analogs
The optical complex index of refraction of four candidate Martian surface materials has been determined between 0.185 and 0.4 μm using a modified Kubelka-Munk scattering theory. The candidate materials were limonite, andesite, montmorillonite, and basalt. The effect of scattering has been removed from the results. Also presented are diffuse reflection and transmission data on these samples. 相似文献
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37.
Normal and accelerated sinking of phytoplankton in the sea 总被引:1,自引:0,他引:1
The sinking and deposition of phytoplankton remains lead to sediment varving, the formation of sedimentary oozes, and the transport of partially decomposed and viable, autotrophic cells to great depths. Some specific examples are discussed, and the associated settling rates, depositional characteristics and individual species responses are examined in relationship to experimentally determined sinking rates of both living and dead, intact phytoplankton. The data include field and experimental observations on the sinking behavior for the same species. The in vitro rates are too low, and a mechanism or mechanisms causing accelerated rates of phytoplankton sinking in situ seems necessary to account adequately for some of the observed transport of phytoplankton remains to great depths and to the sea floor. 相似文献
38.
Meander bends in alluvial rivers morphologically evolve towards meander cut‐off with narrowing intra‐meander necks, and this should steepen hydraulic gradients and intensify intra‐meander hyporheic flux. This research used dye tracking and head loss measurements in a 1 : 500 planimetrically scaled laboratory river table to quantify the spatial and temporal intensification of intra‐meander flux rates at two evolution ages. The younger meander bend, M1, had a sinuosity of 2.3, a river neck width of 0.39 cm, and 0.6% river slope, and the older meander bend, M3, had a sinuosity of 5.2, a river neck width of 0.12 cm, and 0.5% river slope. Flux into and out of the meander bend was estimated along the normalized curvilinear distance s*, with the meander neck at s* = 0.1 and s* = 0.9, the meander centroid at s* = 0.37 and s* = 0.63, and the apex at s* = 0.5. Between the meander centroid and neck, we documented a 60% spatial intensification for M1 and a 90% spatial intensification for M3. Between M1 and M3, we documented a 135% temporal intensification at the neck and a 100% intensification at the centroid. Our empirical spatial and temporal intensification rates involving the M1 and the M3 scenario were one to three times lower than theoretical rates derived from a river evolution model with equivalent M1 and M3 planimetry. Overestimation by the theoretical model was attributed to exaggerated head loss caused by the model neglecting groundwater contributions to river stage. Hyporheic exchange provides critical ecosystem services, and its spatial and temporal variation with meander evolution should be considered in river management. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
39.
Dawit A. Zeweldi Mekonnen Gebremichael Junming Wang Theodore Sammis Jan Kleissl David Miller 《Boundary-Layer Meteorology》2010,135(1):151-159
Scintillometers are becoming increasingly popular for the validation of satellite remote sensing sensible heat-flux estimates due to the comparable spatial resolutions. However, it is important to gain confidence in the accuracy of the sensible heat-flux measurements obtained by the scintillometer. Large aperture scintillometer (LAS) and eddy-covariance (EC) measurements were collected over a homogeneous, dry and semi-arid region near Las Cruces, New Mexico, USA, where the homogeneity allowed direct comparison of the two instruments despite their differences in footprint sizes. The differences between the sensible heat-flux measured by both LAS and EC systems fall within the differences between two EC systems. We conclude that the large aperture scintillometer is a reliable system for measuring sensible heat flux in a dry semiarid region. 相似文献
40.
Ioannis Panagiotopoulos Vasilios Kapsimalis Ioannis Hatzianestis Theodore D. Kanellopoulos Chara Kyriakidou 《Environmental Earth Sciences》2010,61(5):983-993
Surficial and sub-surficial sediments obtained from the lower course of the Kifissos River, which drains the Athens Basin,
have been analyzed for heavy metals and aliphatic and polycyclic hydrocarbons. Oddly, the calculated enrichment factors for
the identified heavy metals, with the baseline taken from a pristine area in the adjacent Saronikos Gulf, are very low excluding
only those related to Cu and Zn. In contrast, the enrichment factors for the measured hydrocarbons are particularly high.
However, physicochemical water conditions and annual flushing episodes of the Kifissos River may have reduced significantly
the sediment chemical fingerprint found out by the present study. Moreover, an evaluation of the fluvial sediment quality
based on the enriched Cu and Zn amounts and concentration of PAH fraction with a consideration of the biological thresholds
proposed by the National Oceanic and Atmospheric Administration (USA) reveals little probability for serious biological impairments.
Additionally, sediment toxicity due to the sediment PAH load may be considered as minimum. 相似文献