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M. A. Khan 《洁净——土壤、空气、水》1994,22(1):28-31
Libya occupies a large part of the Sahara Desert, and is a predominantly arid country with extremely scarce freshwaters. Despite aridity, a distinct higher rainfall zone exists along its mediterranean coastal belt. A lotic environment (perennial stream) in Ain-Scersciara, Tarhunãh in northwest Libya was studied for the species composition of diatom communities and their ecological characteristics. The waters are generally alkaline (pH = 7.5) and of hard-water (conductivity = 2008 μS/cm) type. The epiphytic diatom growth on benthic filamentous algae was high (32 taxa) with Amphora veneta as a very common taxon. Gomphonema parvulum var. micropus was an important taxon found in scrapings from the leaves of macrophytes and stony substratum. Nitzschia and Navicula showed high species richness (9 taxa in each) followed by Gomphonema (6 taxa). The ecological attributes of the majority of taxa show an oligohalobe status and alkaliphilous indicator. 相似文献
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The reduction and equalization of the salt concentrations in the River Werra have resulted in a gradual recovery of the aquatic flora. Spatial high-resolution macrophyte mappings document the spread of the aquatic vascular plants in the middle and lower River Werra. Simultaneously, the plankton blooms have declined. Changes in the composition of the algal communities including diatoms also indicated lower salinity. In addition to the salinity, high nutrient concentrations, waste water discharges and structural degradation are important stressors in the River Werra as shown by e.g. low species richness of vascular plants and the common occurrence of pollution tolerant diatoms. From the existing data it is clear that an encompassing improvement of the ecological conditions in the River Werra can only be achieved by further restoration measures considering all stressors. 相似文献
3.
《Limnologica》2019
To test if phytobenthic algae provide additional important information to macrophytes and phytoplankton for lake monitoring, we sampled two large lakes in Norway. In each lake, we analyzed water chemistry and phytoplankton above the deepest site, recorded macrophytes and non-diatom phytobenthic algae at 20 sites around the shoreline and estimated site-specific nutrient input from land cover. Since no ready-to-use phytobenthos index exists for lakes in Norway, we tested the PIT index developed for rivers, commonly perceived signs of disturbance such as high algal cover, and taxon richness as well as similarity patterns. Both lakes were nutrient poor, but had potential local nutrient inputs (villages, agriculture). In neither of the lakes did phytobenthos indicate a worse overall ecological status than macrophytes and phytoplankton. Our data therefore, did not suggest that it would be useful to add phytobenthos into surveillance monitoring of lakes in Norway. There was a loose correlation between macrophyte and phytobenthic site-specific taxon richness and similarities. This means that macrophytes and phytobenthos do indeed give partly redundant information. High algal cover was found at sites with both high and low phosphorus input. Using algal cover as indicator of site-specific nutrient input is therefore overly simplistic. Urban and cultivated areas were associated with a more eutrophic PIT. This indicates that the PIT, despite being developed for lotic waters, may be used to detect site specific nutrient input in lakes. 相似文献
4.
Luc Denys 《Journal of Paleolimnology》2006,35(4):763-787
Relationships between littoral surface-sediment diatom assemblages and ambient limnological conditions were examined in 186
lentic fresh waters throughout lower Belgium (Flanders). Most of these waters were small, unstratified, alkaline and rich
in nutrients. Using weighted-averaging techniques, robust and accurate transfer functions were developed for median pH-values
ranging from 3.4 to 9.3 and dissolved inorganic carbon concentrations from <1.6 to 63 mg l−1 (jackknifed r
2≈ 0.87, RMSEP <10% of the observed range), while a less precise model was obtained for sodium (2–571 mg l−1; jackknifed r
2 0.69, RMSEP 9.9% of the range). Restricting the data set to circumneutral and alkaline sites (pH≥6.5) revealed the importance
of additional variables, including calcium, silica, chemical oxygen demand and potential gross oxygen production (a proxy
for metabolic activity and phytoplankton abundance). Calibration models for these variables were strong enough to be useful
(jackknifed r
2 0.57–0.59, RMSEP 13.1–16.4% of the observed range), although estimations should not always be considered entirely independent.
Except for the predominant pH gradient, removal of all taxa with a distribution unrelated to the variable of interest improved
model performance. In general, such taxa were proportionally represented among taxa classified according to their principal
habitat. Application of the present models to diatom assemblages of shallow-water sediments obtained from historical samples
and, most importantly, herbarium-macrophyte specimens, will improve hindsight into regional freshwater conditions and add
to base-line setting of ecological quality standards in a highly impacted region.
Electronic supplementary material Electronic supplementary material is available for this article at
and accessible for authorised users. 相似文献
5.
Luc Denys 《Journal of Paleolimnology》2007,38(1):97-116
Quantitative inference models for water-chemistry variables are derived from epiphytic diatom assemblages in 186 lentic and
mostly shallow freshwaters in lower Belgium (Flanders). When the complete pH range is considered (pH 3.4–9.3), robust transfer
functions are obtained for median pH (jack-knifed r
2 = 0.88, RMSEP = 0.38 pH units or 6.4% of the observed range) and dissolved inorganic carbon concentration (jack-knifed r
2 = 0.86, RMSEP = 0.194 log10 mg DIC l−1 or 10.2% of the observed range) by means of weighted-averaging partial least squares regression (WA-PLS). For these variables,
the calibration models are as reliable as those based on sedimentary diatom assemblages. Inferences of pH may be improved
by combining estimates from epiphytic and sediment assemblages. In circumneutral and alkaline conditions, WA-PLS calibration
of maximum or median total phosphorus is possible (log-transformed; jack-knifed r
2 = 0.64 or 0.66 and RMSEP = 14% or 12.3% of the observed range, respectively). It makes little difference if taxa showing
no response to TP are taken into consideration or not. These models considerably expand the prospects of using historical
herbarium materials to hindcast environmental conditions and also allow more accurate interpretation of current compositional
changes in epiphytic communities. Compared to littoral sediment assemblages, fewer water-column variables can be inferred
reliably from epiphyton. This probably results from differences between the effective gradients in both habitats, together
with lower in situ species diversity and less effective spatial integration (i.e. lower recruitment of phytoplankton) in the
epiphyton. A comparison of the HOF response-model types and WA-optima of diatom taxa for epiphytic and sediment assemblages
shows that the relationship to individual variables, and in particular to those related to trophic status, may differ with
habitat. Thus, the combination of samples from both habitat types in the same calibration model is not recommended.
Electronic Supplementary Material Supplementary material is available and is accessible for authorised users in the online version of this article at 相似文献
6.
Improving Water Quality by submerged and emergent Macrophytes. — A Review of Ecotechnological Application. Measures of ecotechnology using submerged and emergent macrophytes in native stands or planted littoral stands on the one hand, ingenious swimming plant mats on the other, may be assessed to be successful if applied in combination with additional measures, for instance — reorganization (sanition) of all the area collecting water — biomanipulation of pelagic food chains. Plantation of submerged macrophytes as oxygenators in standing and impounded waters to improve water quality should be avoided. To the contrary, the strategy should be taking measures in order to maximize the light penetrated euphotic zone (zeu) and simultaneously minimize the mixed zone (zmix) in order to improve spontaneous settlements of submerged macrophyte stands. 相似文献
7.
Kate?ina ?erná 《Limnologica》2010,40(4):315-321
Spatial patterns on a very small scale (10 cm), and the effect of artificial barriers on the composition of phytobenthic algal assemblages along two transects within different microhabitat types were investigated. Samples were taken in a peat bog along linear transects on a scale of 10 cm, and water chemistry was examined. The distribution of algae along both transects was influenced by both spatial distance and environmental conditions in similar proportions. Differences in species composition in various parts of the transects were observed, but this pattern was primarily related to the abundance of species, rather than to their presence/absence in samples. Similarity in species composition correlated with spatial distance and environmental parameters in both microhabitat types. I concluded that, given a homogenous environment on a small scale, spatial distribution of algae is affected by both the environmental conditions of the microhabitats and their dispersal limitations. Moreover, an artificial barrier constituted an obstruction for water and nutrient flow, as well as algal migration, and had an impact on species composition. 相似文献
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