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1.
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
2.
Rainer Putz 《Aquatic Sciences - Research Across Boundaries》1997,59(1):74-93
Chlorophyll a-concentrations, AFWD (ash-free-dry-weight) and photosynthesis rates were estimated for periphyton assemblages in Amazonian black-and white-water habitats over 14 months. Cellulose-acetate strips were incubated in situ and showed few major differences in periphyton quality as compared to natural substrata. The only exceptions were submersed Igapó forest leaves, which exhibited higher proportions of green algae and cyanobacteria though not producing differences in total periphyton biomass. Enclosure experiments showed a considerable nutrient release by inundated non-senescent Igapó forest leaves. Periphyton biomass and productivity were found to be highest in black-and white water mixing zones, where biomass peaked at 41.6 mg Chla/m2 and 19.8 g/m2 AFDW. Production was estimated to be 380 gC/m2·a. Maximum biomass of periphyton in floating meadows was 46 mg Chla/m2 and 10.6 g/m2 AFDW, with an annual production of 170 gC/m2·a. Solimões main channel periphyton values were low: maximum Chla was 7.1 mg/m2, AFDW 0.8 g/m2 and annual production was estimated to be 30 gC/m2. Blackwater periphyton values were lower compared to whitewater and mixed water values but an enlarged trophogenic zone has to be taken into account. Highest Chla content reached 30.9 mg/m2, AFDW 1.43 g/m2. Estimated annual production was 110 gC/m2. Observed mean periphyton productivity of Amazonian blackwater habitats approximately corresponded to mesotrophic attached algae productivity in temperate zones, whereas productivity of whitewater periphyton approached those of temperate eutrophic lakes. The role of periphyton in the Amazon food web is discussed. 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.
《Limnologica》2021
Ciliated protozoans are important constituents of periphytic communities in aquatic habitats, including river-floodplain ecosystems. As the knowledge about the diversity and ecological importance of periphytic ciliates in floodplain habitats is still limited, the main objectives of this study were to analyse the temporal variations in the community structure and functional role and reveal the main environmental factors controlling community dynamics. The study was conducted in one of the Danube's largest conserved floodplains – Kopački Rit in Croatia. In situ research included two experimental series in a lake, the first from spring till winter and the second from summer till winter. Samples were collected biweekly using glass slides as artificial substrates for periphyton development. During the study, two hydrological (low-water and high-water) periods interchanged. High-water periods were characterized by greater water transparency and nutrient concentrations, while electrical conductivity, chlorophyll a concentration, total suspended solids and particulate organic matter in water were higher during low-water periods. Furthermore, hydrological changes greatly affected the periphytic ciliate communities and the highest abundances were registered during low water levels. We identified a total of 133 ciliate taxa, among which the peritrichs, sessile filter feeders, were the dominant representatives in the periphyton, with the highest densities registered in the absence of floods. During extremely high water levels, the composition of the ciliate community in periphyton changed, with mobile ciliates, predators and filter feeders, becoming dominant. This study indicates that the main food source for periphytic ciliates in a floodplain lake are bacteria and algae, confirming the important role of these microorganisms in the lake food web, by making the carbon fixed in bacteria and algae available for the organisms of higher trophic levels. Additionally, periphytic ciliates have a considerable effect on planktonic organisms in the lake, thus connecting benthic and pelagic food webs, especially during low-water periods. 相似文献
5.
Characterization of the light attenuation by periphyton in lakes of different trophic state 总被引：1，自引：0，他引：1
In order to measure the attenuation of light by periphyton a method has been developed which assures that natural periphyton architecture and therefore its optical characteristics remain preserved. This method has been applied to analyze the transmittance of periphyton of four lakes of different tropic states situated in the Osterseen Lake District (Upper Bavaria, Germany). The seasonal variation of the periphyton's transmittance has been studied using standard microscope glass slides exposed 1 m beneath the water surface within macrophyte beds. The study ran from February to November 1997 in two eutrophic lakes (Lake Waschsee, Lake Sengsee) and from May to November 1997 in the meso-oligotrophic Lake Eishaussee and in the oligotrophic Lake Herrensee.Generally the exposure-period, the seasonality, and the tropic state of the habitat affected the transmittance spectra of the periphyton. In all lakes the attenuation by periphyton increased with longer colonization times but at a different time scale. The periphyton of the nutrient-rich and the nutrient-poor lakes differed clearly in composition and architecture. The eutrophic lakes were characterized by a relatively thick but loosely attached, unstable periphyton community, which was translucent to a certain degree even at the end of the growth period. The transmittance of this periphyton fluctuated considerably and high percentages of filamentous green algae in this periphyton contributed to attenuation maxima within the range 400-500 nm and 650-700 nm due to photosynthetic pigments. By contrast, the periphyton of the meso-oligotrophic and of the oligotrophic lake was quite compact and nearly impervious to light. 相似文献
6.
《Limnologica》2015
To analyse the existence of interactive competition between phytoplankton and periphyton, we studied their photosynthesis–irradiance (P–E) response during one year in a humic lagoon. Lake production was dominated by phytoplankton, which followed seasonal changes in temperature. Periphyton primary production and algae biomass increased in winter, when phytoplankton biomass and production were lower. In this study we show that even in conditions of phytoplankton dominance, the habitat coupling between phytoplankton and periphyton can still be noticed. 相似文献
7.
磷在"沉积物-自然生物膜-上覆水"三相体系中的迁移转化 总被引：1，自引：0，他引：1
地表水体中沉积物表面通常会附着一层自然生物膜,对上覆水-沉积物界面化学物质的迁移转化有着重要的影响.以往研究往往会忽略这一生物层面,因而,开展磷在"沉积物-自然生物膜-上覆水"三相界面之间的迁移转化研究具有重要的实际意义.以软性填料表面形成的自然生物膜模拟沉积物表层以及悬浮颗粒物表层的自然生物膜,开展磷在沉积物-自然生物膜-上覆水之间的迁移转化过程研究.结果表明:有无曝气情况下,自然生物膜界面的存在均能够显著降低上覆水中总磷、溶解态总磷、溶解态无机磷的含量,明显抑制沉积物中可交换态磷向上覆水释放.研究证明自然生物膜在水体磷的迁移转化中起着不可忽视的作用,在研究沉积物-上覆水界面之间磷的迁移转化行为时,要充分考虑自然生物膜界面的存在. 相似文献
8.
《Limnologica》2014
Drastic changes in the composition and physiognomy of riparian vegetation, such as the conversion of grassland to forest, are expected to alter interactions among light availability, primary producers and herbivores. Our aim was to examine in laboratory the influence of a ubiquitous grazer on periphyton grown in a grassland unshaded stream (reference) vs. periphyton from a nearby pine afforested stream. Besides, we evaluated how the community responds to the removal of grazing. Given that grassland streams are exposed to higher light intensity and grazers are more abundant compared to afforested streams, we proposed that if biofilm grown in the afforested stream are dominated by grazing-vulnerable algal species, grazing pressure by Helicopsyche sp. should be stronger. In addition, if biofilm from the afforested stream has low quality or is less abundant as food for consumers, the effects of Helicopsyche sp. may be stronger or weaker depending on their feeding decisions. Helicopsyche sp. caused a decrease in richness and diversity in periphyton grown in the grassland stream and its net grazing effect on chlorophyll a (Chl a) was higher. Algal community composition from grassland stream was strongly changed after grazing, with a decrease in the proportion of overstory algae. In contrast, algal community structure of periphyton from the afforested stream was neither affected by grazing nor by grazing exclusion. Helicopsyche sp. produced significant changes in a short time in structural attributes of algal communities, mainly in periphyton from the grassland stream suggesting that herbivory, as a functional factor, is diminished following afforestation. 相似文献
9.
Measurements of groundwater–surface water exchange at three wetland stream sites were related to patterns in benthic productivity as part of the US Geological Survey's Northern Temperate Lakes–Water, Energy and Biogeochemical Budgets (NTL–WEBB) project. The three sites included one high groundwater discharge (HGD) site, one weak groundwater discharge (WGD) site, and one groundwater recharge (GR) site. Large upward vertical gradients at the HGD site were associated with smallest variation in head below the stream and fewest gradient reversals between the stream and the groundwater beneath the stream, and the stream and the adjacent streambank. The WGD site had the highest number of gradient reversals reflecting the average condition being closest to zero vertical gradient. The duration of groundwater discharge events was related to the amount of discharge, where the HGD site had the longest strong-gradient durations for both horizontal and vertical groundwater flow. Strong groundwater discharge also controlled transient temperature and chemical hyporheic conditions by limiting the infiltration of surface water. Groundwater–surface water interactions were related to highly significant patterns in benthic invertebrate abundance, taxonomic richness, and periphyton respiration. The HGD site abundance was 35% greater than in the WGD site and 53% greater than the GR site; richness and periphyton respiration were also significantly greater (p≤0.001, 31 and 44%, respectively) in the HGD site than in the GR site. The WGD site had greater abundance (27%), richness (19%) and periphyton respiration (39%) than the GR site. This work suggests groundwater–surface water interactions can strongly influence benthic productivity, thus emphasizing the importance of quantitative hydrology for management of wetland-stream ecosystems in the northern temperate regions. 相似文献
10.
A controlled reservoir release from Llyn Celyn to the Afon Tryweryn, Wales, U.K., has been used to study suspended load and turbidity variations. Turbidity was monitored continuously at two sites and 235 suspended solids samples were obtained at these and three additional sites during the passage of the release wave. The results are compared with data for a natural tributary flood event. The reservoir release data relate to sediment source depletion and reflects changing sources along the channel. Close to the dam, fine organic matter dominates the seston which scanning electron microscopy revealed to be predominantly allochthonous organic matter, with algal fragments and inorganic diatom frustules, derived from the periphyton of the channel bed. Coulter Counter analysis showed the seston to be relatively coarse with a median particle-size of 20 μm. Within 3 km of the dam, however, minerogenic particles dominate the sediment load of which more than 90 per cent is finer than 10 μm. This represents the flushing of channel-bed accumulations derived from tributary sources. The relationships between suspended sediment concentration and turbidity during the release are characterized by a marked, anticlockwise hysteresis. This contrasts with the clockwise hysteresis for the tributary flood event, but the different relationships cannot be explained by particle-size variations alone; seston composition also appears to be an important control. 相似文献