着生藻类和浮游藻类在三峡库区河流健康评价中的适宜性比较研究

藻类对水体环境变化敏感,其种类和数量与环境因素有密切联系并因环境的变化而发生变化,因此藻类常作为河流健康评价的指示生物。水体中的藻类根据生活习性不同分为着生藻类和浮游藻类,在河流健康评价中,以往的工作中有的采用浮游藻类用于河流健康评价,有的采用着生藻类用于评价,但浮游藻类和着生藻类究竟何者用于河流健康评价更适宜,抑或是二者在用于评价的适宜性上没有明显差别,迄今为止未开展过深入研究。选择三峡库区内的两条河流嘉陵江和乌江作为研究对象,于2015年9月,在两条河流上共布设11个研究断面,对嘉陵江、乌江的水环境理化因子、着生藻类和浮游藻类群落进行调查研究,应用着生藻类生物完整性指数(Periphytic algal index of biological integrity,Pe-IBI)和浮游藻类生物完整性指数(Phytoplankton index of biological integrity,Ph-IBI),并结合水体综合污染指数(Comprehensive pollution index,CPI),对嘉陵江、乌江的健康状况进行评价。研究结果表明,采用着生藻类生物完整性评价(Pe-IBI)能筛选出7个核心生物参数(藻类总分类单元数、蓝藻总分类单元数、绿藻总分类单元数、菱形藻比例、优势分类单元比例、香农多样性指数、均匀度)用于河流健康评价,着生藻类生物完整性指数(Pe-IBI)与水体综合污染指数(CPI)具有极显著的负相关关系,并且与水体中总氮、铅含量也有极显著的负相关关系,表明水环境质量越低则着生藻类的生物完整性越差;当采用浮游藻类生物完整性(Ph-IBI)用于河流健康评价时却只能筛选出1个核心生物参数(藻类密度),而且浮游藻类生物完整性指数(Ph-IBI)与水体综合污染指数(CPI)及12个水体环境指标并无明显的相关性。本研究表明,在河流水体中,与浮游藻类相比,着生藻类更能反映水体环境的状况,对河流水体环境的反映更为准确。因此,在以流动水体为特征的河流的健康评价中,采用着生藻类比采用浮游藻类更为适宜。     

金沙江上段浮游藻类和着生藻类群落格局及其与环境因子的关系比较研究

比较河流浮游藻类和着生藻类群落的时空格局及其与环境因子关系的差异,有助于了解两类藻的区别与联系。然而,目前这方面的研究还不多。基于2019年秋季和2020年夏季金沙江上段干流17个样点藻类及水体理化指标的调查数据,分析了不同季节浮游藻类和着生藻类群落结构及其主要环境驱动因子,比较了两类藻的多样性格局及其与环境关系的异同。结果发现,调查河段的浮游藻类和着生藻类均以硅藻为主,其中浮游藻类以极小曲壳藻(Achnanthes minutissima)、钝脆杆藻(Fragilaria capucina)、适中舟形藻(Navicula accomoda)为主要优势种,着生藻类以极小曲壳藻(Achnanthes minutissima)、扁圆卵形藻(Cocconeis placentula)、橄榄绿色异极藻(Gomphonema olivaceum)为主要优势种。浮游藻类和着生藻类秋季平均密度分别为:2.41×10~5个/L、9.43×10~3个/cm~2,均明显高于夏季的平均密度(4.84×10~4个/L、4.84×10~3个/cm~2)。两类藻的群落格局表现出明显的季节变化,但只有着生藻分类单元...     

Algal structure of the littoral epilithon in lentic water bodies at Hope Bay, Antarctic Peninsula

We studied the composition and density of the algae of the littoral epilithon and the taxa turnover in nine lentic water bodies at Hope Bay, Antarctic Peninsula, during summer 2002. At each site we measured the main physical and chemical variables, and took epilithic samples for the algal analysis. Two composed samples (one for qualitative and one for quantitative analysis) were taken randomly about 1 m away from the shore-line of each sampling site. The morphology of the algal mats could be included in the ‘moat and pond type’ in which Cyanobacteria are well represented. A total of 69 algal taxa were recorded in the whole study area. Chlorophyceae showed the highest taxa richness (33%), followed by Cyanobacteria (29%), Bacillariophyceae (26%), Chrysophyceae (10%), and Tribophyceae (2%). As a result of the redundancy analysis performed, we found that the number, composition, and density of taxa in the water bodies at Hope Bay were strongly influenced by nitrate and suspended solids concentrations and by the distance from the sea. The geographical trend in taxa turnover within Hope Bay was explained by elements from the combination of the metapopulation dynamics and the continuum theories, which are related to dispersal limitation and environmental heterogeneity, respectively.     

In situ interactions between the effects of season,current velocity and pollution on a river biofilm

1. The development of periphytic algae and bacteria is controlled by a combination of interacting biotic processes and abiotic factors. Distinguishing between the selection pressure resulting from pollution and that of natural environmental factors is therefore one of the most critical aspects of assessing the impact of pollutants on the diversity and function of benthic microbial communities in natural ecosystems. 2. We studied how current velocity and season affect the ability of river biofilms to cope with complex chemical pollution. We compared the diversity, structure and production of periphytic algae and bacteria from four sampling zones with differing chemical water quality levels and different flow velocities over the course of two seasons (summer and winter). 3. The three factors tested all influenced biofilm development, but this depended on the biological variable being measured. Bacterial and algal densities were highly dependent on season and chemical water quality. Algal density was lower in summer than in winter, but bacterial density and production increased from upstream (reference) to downstream (polluted), and this increase was more marked in winter. The impact of chemical water quality was also dependent on the season. 4. An interaction between current velocity and pollution was also detected. During the summer, there was no difference in bacterial density or production between the upstream and downstream segments in the fast current zones, whereas both variables were higher downstream in the slow current zones. Such interactions between environmental factors and the impact of water quality on biofilms must be taken into account in assessments of the effects of chemicals on biofilm community structure and functioning in rivers.     

Impact of Urban Pollution from the Hanoi Area on Benthic Diatom Communities Collected from the Red, Nhue and Tolich Rivers (Vietnam)

The effects of urban pollution from Hanoi city on the benthic diatom communities of the Nhue–Tolich river system were studied during the 2003 dry season. Benthic diatoms were allowed to grow on glass slides suspended in the water flow for 4 weeks. To reveal the relationship between water quality and diatom communities, Canonical correspondence analysis (CCA) was used on data concerning relative abundances of diatom species and environmental variables. Two diatom indices, IPS and DAIpo, were applied to evaluate water quality in the three rivers. A total of 291 diatom taxa were found in the Red, Nhue and Tolich Rivers. These were mainly cosmopolitan taxa, with some tropical, subtropical and endemic taxa. The most abundant taxa at the Red site were Aulacoseira granulata, Achnanthidium minutissimum, Encyonema minutum, Navicula recens and other halophilous taxa such as Nitzschia kurzii, Seminavis strigosa, Entomoneis paludosa, Bacillaria paradoxa. Diatom assemblages at the Tolich site consisted mainly of Nitzschia umbonata, Nitzschia palea and Eolimna minima. Diatom density ranged from 660 to 30,000 cells/cm². Environmental variables and diatom assemblage composition at all sites were significantly correlated. Two diatom indices gave similar results and indicate the Tolich River with the lowest values as a highly polluted site.     

Variance partitioning of deconstructed periphyton communities: does the use of biological traits matter?

The use of species traits offers a promising approach to the understanding of the main processes underlying metacommunity patterns. We analyzed samples of periphytic algae in 30 environments of the Upper Paraná River floodplain in southeastern Brazil, to test the hypotheses that variation in species composition of algal groups with low dispersal abilities would be mainly explained by spatial variables; on the other hand, algal groups with higher dispersal abilities would be better explained by environmental variables. The variation in community structure was mainly correlated with environmental variables. This result is in line with a growing body of evidence indicating a predominant role of species-sorting processes. The more-refined prediction that the spatial variables would gradually become more important across a gradient of adherence or size was, however, not supported by our analyses. Also, the large unexplained variation suggested that these periphytic communities were assembled by idiosyncratic events, or that other variables that are often neglected in studies of aquatic metacommunities needed to be included.     

Phytoplankton Composition and Abundance in Restored Maltański Reservoir under the Influence of Physico-Chemical Variables and Zooplankton Grazing Pressure

In this paper we present the effects of environmental factors and zooplankton food pressure on phytoplankton in the restored man-made Maltański Reservoir (MR). Two methods of restoration: biomanipulation and phosphorus inactivation have been applied in the reservoir. Nine taxonomical groups of phytoplankton represented in total by 183 taxa were stated there. The richest groups in respect of taxa number were green algae, cyanobacteria and diatoms. The diatoms, cryptophytes, chrysophytes, cyanobacteria, green algae and euglenophytes dominated in terms of abundance and/or biomass. There were significant changes among environmental parameters resulting from restoration measures which influenced the phytoplankton populations in the reservoir. These measures led to a decrease of phosphorus concentration due to its chemical inactivation and enhanced zooplankton grazing as a result of planktivorous fish stocking. The aim of the study is to analyse the reaction of phytoplankton to the restoration measures and, most importantly, to determine the extent to which the qualitative and quantitative composition of phytoplankton depends on variables changing under the influence of restoration in comparison with other environmental variables. We stated that application of restoration methods did cause significant changes in phytoplankton community structure. The abundance of most phytoplankton taxa was negatively correlated with large zooplankton filter feeders, and positively with zooplankton predators and concentrations of ammonium nitrogen and partly of phosphates. However, restoration was insufficient in the case of decreasing phytoplankton abundance. The effects of restoration treatments were of less importance for the abundance of phytoplankton than parameters that were independent of the restoration. This was due to the continuous inflow of large loads of nutrients from the area of the river catchment.     

Progressive changes in the structure and dynamics of the phytoplankton community along a pollution gradient in a lowland river — a multivariate approach

The phytoplankton of the River Lujan (Buenos Aires, Argentina) was studied for a period of 18 months, together with physical and chemical variables, in relation to a pollution gradient. 167 taxa were recorded within a seasonal succession characterized by dominance of diatoms with a brief summer green algae facies. A combination of several biotic indices and multivariate analysis was employed to assess the impact of pollution on the phytoplankton community. The biotic indices used were species diversity and richness, algal quotients (green algae/diatom ratio, Centrales/Pennales ratio) and the SD succession rate index. Multivariate procedures included cluster analysis and ordination by PCA of both species and samples, stepwise discriminant analysis and multiple discriminant analysis of variance (MANOVA). Results indicate that community dynamism is attenuated at the more polluted sites, concomitant with an increased predominance of a broad-tolerance algal assemblage, co-dominated by Cyclotella meneghiniana and Nitzschia stagnorum. The changes in the community structure and dynamics described herein involved alterations in the distribution and relative proportions of the algae, rather than modifications in the basic species composition. These changes may not be readily detectable by methods which over-simplify the ecological information, such as systems of indicator species and biotic indices, designed to assess the degree of pollution. The suitability of multivariate analysis and biotic indices in river phytoplankton studies is further discussed.     

Changes in the algal composition and water quality of the Sundays River,Karoo, South Africa,from source to estuary

A first survey was done on algae present in the Sundays River from its source to its confluence with the sea. Species found in the upstream sections of the river included indicators of good water quality, but the quality deteriorated downstream with peaks in algal abundance being ascribed to peaks in nutrient concentrations. Cyanobacteria and euglenoids were present in the upper and middle reaches of the river, but were absent downstream. Dinoflagellates became more important downstream, especially in the estuary. Dominant species, reaching high concentrations along the river, included Nitzschia frustulum, Nitzschia capitellata, Carteria klebsii, Chlorella vulgaris and Anabaena species. The presence of the diatom Eolimna comperei is a first record of its occurrence in South Africa. The Sundays River can be described as a brackish, hard water system with high nutrient concentrations in certain sections. The most important contributors to high nutrient concentrations were point sources in the vicinity of towns along the river banks, as well as diffuse sources contributing to high nitrogen concentrations in the fertile Sundays River valley. Increasing salinities were due to pollution, evaporation and agricultural activities in the valley.     

Attached diatom communities from the lower Truckee River,summer and fall, 1986

The algal flora of the Truckee River below Reno, Washoe County, Nevada was examined during the summer and fall months of 1986. This reach of the lower Truckee River exhibited a substantial gradient in dissolved inorganic nitrogen associated with sources which included treated wastewater from the Reno metropolitan area. The algal communities were similar to those of other river systems of the Great Basin. Cyanophyta and Chlorophyta formed encrusting mats on the substrate, with the nitrogen fixer Calothrix atricha relatively abundant upstream from the nitrogen source. Diatoms were abundant within and upon this mat. A total of 139 diatom taxa and 11 taxa other than diatoms was identified from this flora. Several of the diatom taxa, including Achnanthes minutissima, Diatoma vulgare, Nitzschia dissipata, and Nitzschia palea, demonstrated distinct downriver patterns in relative abundance.     

Community composition and sensitivity of periphyton to atrazine in flowing waters: the role of environmental factors

The relationship between environmental variables, community composition and the sensitivity of periphyton on artificial substrata to the herbicide atrazine (EC₅₀ values obtained by concentration-effect curves of photosynthesis to atrazine) was studied for 20 stream and river sites on a latitudinal across Europe (Sweden, The Netherlands, Spain). Sensitivity to atrazine was higher in Swedish than in the Spanish or Dutch sites. Direct gradient analyses were used to relate diatom taxa and algal groups with environmental variables. A first redundancy analysis (RDA) based on diatom taxa showed a pollution gradient (atrazine and nutrient concentration) associated to diatom taxa that are indicators of different degrees of pollution. A second RDA based on algal groups showed that diatom-dominated communities corresponded both to sites at higher altitudes and less industrialized areas and to sites with higher atrazine concentration; Cyanobacteria were the most common in industrial areas, whereas Chlorophyceae dominated in sites with high water temperature and alkalinity. Linear regression analyses were applied to find the relationship between the ordination axes obtained and the EC₅₀ values. First axes of both RDA showed significant or marginally significant relationship with atrazine sensitivity. Regression analyses for the Spanish sites indicated that the sensitivity to atrazine was related with light conditions (EC₅₀ was positively correlated with light) and the percentage of different algal groups (EC₅₀ was positively correlated with the percentage of diatoms and negatively correlated with the percentage of green algae). The results indicating that differences in sensitivity are related to environmental variables such as light, nutrients or atrazine concentration, permitted us to identify biological indicators of sensitivity to atrazine in lotic systems: Bacillariophyceae-dominated periphyton communities were more tolerant than Chlorophyceae and Chrysophyceae-dominated communities. In addition, diatom taxa found to be tolerant to atrazine in this study have been considered in the literature to be tolerant to organic pollution. This revised version was published online in June 2006 with corrections to the Cover Date.     

Downstream variations of phytoplankton in the St.Lawrence River (Québec, Canada)

Longitudinal variations of phytoplankton biomass and composition were assessed in a 250 km-long section of the St.Lawrence River, which alternately runs through narrow (< 2 km) river cross sections and wide (up to 10 km) fluvial lakes. In the main river stem, concentrations of suspended matter and total phosphorus increased with distance downstream, whereas light penetration decreased. Seasonal changes in plankton composition and biomass were more important than those resulting from differences in water mass (tributary) of origin. Sampling at three cross river sections and in two fluvial lakes showed a progressive downstream decrease in phytoplankton biomass and changes in size structure and taxonomic composition. River plankton was primarily composed of small (< 10 µm equivalent spherical diameter), truly planktonic cells belonging to Cryptophyceae and diatoms, with Chlorophyceae in summer. Plankton sampled in summer among rooted macrophytes in fluvial lakes exhibited a higher biomass of resuspended periphytic algae than in the main river stem, which contributed slightly to downstream phytoplankton biomass.Successive river cross sections always shared about 50% of their taxa, indicating a rapid downstream transport of algae within the main water mass. However, the proportion of species common to all cross sections was highest during the spring freshet, and lowest during summer low discharge, likely resulting from the development of a distinct flora in fluvial lakes during summer. Conversely, about 30% of the identified taxa were exclusive to a cross section and were replaced by others occurring downstream. Overall, phytoplankton composition along the St.Lawrence River is primarily controlled by advective forces, which result in a homogeneous flora in the main river stem, with a local contribution of resuspended periphyton from fluvial lakes.     

Réponses et stratégies d'adaptation des communautés algales épilithiques à différents régimes hydrologiques

Responses of epilithic algal communities were studied in a regulated river presenting two different hydrological regimes. Upstream of the Escale reservoir, the hydrological regime is characterized by a flow compensation with discharge continuous release responsible for the most significant disturbances occurring in the regulated River Durance. Downstream of this reservoir, the river presents a stable and low compensation flow. The analysis of the epilithic algal communities submitted to contrasting flow regimes has shown responses at different levels: a) at the level of the whole community, a global response by changes in species richness and abundance, as well as in community structure; b) at the level of the particular taxonomic groups, such as, for instance, a more important development of filamentous green algae, observed in the downstream reach; c) at the species level: the acquisition, by some diatoms, of an architectural type adapted to the flow regime.     

Early dry-season community structure and habitat use of young fish in tributaries of the River Sinnamary (French Guiana, South America) before and after hydrodam operation

We examined fish community structure and habitat use at the start of the dry seasons: (1) in 10 tributaries of the River Sinnamary (French Guiana) before and after the start of dam operation, and (2) in 10 upstream tributaries and at 10 littoral sites in the newly-created reservoir after the start of operation to assess the impact on fish juveniles of a hydroelectric dam built on the river's lower section. After the first year of dam operation, juvenile fish communities downstream of the dam showed an important decrease of the relative abundance of Characiformes, and Perciformes dominated. Principal components analysis revealed a distinct upstream-to-downstream progression in the juvenile fish communities with post-reservoir downstream and reservoir sites representing transitions between the upstream and pre-reservoir downstream sites. Canonical correspondence analysis and electivity indices of fish-habitat associations revealed three relatively distinct groups of sites, corresponding to the downstream, reservoir and upstream taxa. The proportion of juveniles presenting higher-than expected frequencies (Fisher's exact test) towards local environmental variables was higher for taxa more often caught in upstream sites. Inversely, juvenile taxa more frequently observed in downstream and reservoir sites appeared less selective towards local environmental characteristics. In the downstream reaches of the river, hydrodam operation is expected to drive the fish community towards a new biologically accommodated state where tolerant species will dominate and sensitive species will be lacking. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effects of nitrogen,phosphorus and carbon enrichment on planktonic and periphytic algae in a softwater,oligotrophic lake in Florida,USA

The objective of this study was to investigate nutrient limitation of algal abundance in Anderson-Cue Lake, a softwater clear oligotrophic lake in north-central Florida. Nutrient diffusing clay pots and cylindrical enclosures were used in the field to test effects of different combinations of nitrogen, phosphorus, silica, and carbon on algal standing crop and composition of periphytic and planktonic algae, respectively. Effects of nutrient enrichment on periphytic algae were examined in two studies conducted 31 May – 8 July and 10 June – 15 July 1991. Nutrient effects on planktonic algae were examined in one study from 13 June – 1 July 1991. Planktonic and periphytic algal biovolume was significantly higher (p<0.05) when nitrogen and carbon were added in combination than with treatments without nitrogen, carbon, or nitrogen and carbon. Treatments with nitrogen and carbon combined resulted in lower algal diversity and dominance by coccoid green algae andScenedesmus. Results indicate that carbon and nitrogen can be limiting factors to algal growth in Anderson-Cue Lake and possibly other lakes of similar water quality.     

An experimental study of the influence of periphytic algae on invertebrate abundance in a Hong Kong stream

1. Small cages (294cm²) containing unglazed clay quarry tiles were used to investigate the influence of periphytic algae on macroinvertebrate abundance in a Hong Kong stream. Algal biomass was manipulated by shading cages with plastic sheets. Individual cages were assigned to one of three treatment groups: unshaded, shaded and deeply shaded. Invertebrate densities and algal biomass within cages were monitored after 23, 37 and 65 days. 2. Multiple-regression analysis revealed that algal biomass, invertebrate morphospecies richness and total abundance declined with greater shading intensity. The responses of individual invertebrate taxa varied: some (especially Trichoptera) were unaffected by shading, whereas grazers (Baetidae, Psephenidae and Elmidae) declined as shading increased. 3. Significant regressions of the densities of individual taxa upon algal and detrital standing stocks in cages had positive slopes, but algal biomass increased during the study while detrital standing stocks declined. Abundance of invertebrates declined or remained rather stable over time. Density increases resulting from a positive association with algae were apparently offset by declines in abundance correlated with reductions in detritus. 4. Declines in algal biomass were associated with greater shading to which animals may respond directly. To uncouple the link between scarcity of algae and reduction of light intensity, the plastic covers on two groups of cages (deeply shaded and unshaded) which had been placed in the stream for 28 days were reversed so that cages which had been shaded became unshaded and vice versa. The cages were recovered on day 33, Only Coleoptera demonstrated a positive association with atgae inside cages; no relationship between population densities and algal biomass or light intensity was apparent for other taxa. However, the design may have been confounded by deposition of sediment in the cages (due to declining stream discharge) which reduced population densities of colonizers. 5. This study documents changes in invertebrate abundance and morphospecies richness in response periphyton and detritus standing stocks within patches. Summation of such responses may account for observed variations in benthic communities among Hong Kong streams which differ in the extent of shading by riparian vegetation.     

Spatial distribution of epiphytic chironomid larvae in a shallow macrophyte-dominated lake: effect of macrophyte species and food resources

Four submerged macrophytes were analysed with their respective assemblages of chironomid and algal taxa. Studies were made bimonthly, from January to November, in a shallow macrophyte-dominated lake. The periphytic algal community was represented by chlorophytes, diatoms and cyanobacteria; diatoms showed the highest relative abundance on the macrophyte species during the study. Algal biomass was affected by the season, and in January the highest values were found on Stratiotes aloides L., Potamogeton lucens L., Myriophyllum spicatum L.; in July on Chara aculeolata Kütz. The lowest algal biomass, on most of the macrophytes studied, was found in September. Larvae of Dicrotendipes sp., Diplocladius cultriger Kieffer, Endochironomus albipennis gr., Endochironomus impar (Walker), Glyptotendipes sp. and Paratanytarsus austriacus Kieffer were dominant within the chironomid community. The spatial distribution of chironomids between macrophytes species was related to periphytic algae biomass and certain environmental variables (temperature, water transparency, biomass of chlorophytes and diatoms). Analysis of chironomid diet and the results of canonical correspondence analysis confirmed this relationship. The strongest chironomid-algae relationships were observed on S. aloides and P. lucens.     

Filamentous algal communities related to pH in streams in The Trossachs, Scotland

• 1 A survey of acidified streams in the Loch Ard area of The Trossachs, Scotland, was carried out between 1986 and 1988, to determine the influence of physical and chemical factors on the distribution of benthic algae. Samples were taken on thirty-five occasions from fifteen sites on ten streams. Forty-nine operational taxa of filamentous algae were distinguished. Relative abundance of taxa in samples was scored on a seven-point scale. Estimates of standing crop were made by pigment extraction and ash-free dry weight (AFDW) determination from biomass developed on artificial substrata.
• 2 No evidence was found for seasonality in standing crop, nor for an increase in standing crop with a decrease in pH. Seasonality in relative abundance was evident for few taxa. Species richness and diversity were highly correlated with pH and correlated chemical variables.
• 3 Canonical correspondence analysis (CCA) carried out using the CANOCO program ordinates species and sites and relates them directly to environmental variables. The most important variable was found to be pH (or an acidification-related variable that is highly correlated with pH), with percentage forest cover and total oxidized nitrogen being of secondary importance. The effect of subdividing the data set, using data based on presence-absence as well as estimated relative abundance, was tested. A comparison of the effects on the distribution of site and species values on the pH vector showed that the results are robust, confirming the value of this semi-quantitative sampling method for use with a difficult algal group. It was possible to infer pH from algal community structure using CANOCO.
• 4 The pH ranking of species derived from CCA revealed that larger cell diameter taxa do not predominate at low pH, implying that reduction of invertebrate grazing was not an important determinant of algal community composition.

     

Phytoplankton structure in two contrasting cascade reservoirs (Paranapanema River,Southeast Brazil)

A series of eleven reservoirs was constructed in the Paranapanema River, southeast Brazil, for hydropower production. The phytoplankton structure and its relations with the environmental variables were studied in two of these reservoirs: a large upstream located storage system (high water retention time) and a small run-of-river system (short water retention time). The samples were collected quarterly for two consecutive years, at four sampling stations in each reservoir. Higher phytoplankton richness was observed in the semi-lotic compartments. Higher values of diversities were observed in the upper region of the run-of-river reservoir, under the influence of the larger storage reservoir discharges, and lower values were observed in deeper layers of this same reservoir. The pronounced variation on seasonal rain precipitation and operational water releases, retention time and quota had major influence in the phytoplankton assemblages. The influence of other environmental variables was also indicated by a canonical correlation analysis. Chlamydophyceae, Dinophyceae, Zygnemaphyceae, Chrysophyceae, Chlorophyceae, Bacillariophyceae and Cyanobacteria were positively correlated with higher transparency and depth; Euglenophyceae with temperature and Cryptophyceae with total phosphorus, dissolved oxygen, conductivity, turbidity, total nitrogen and total suspended solids. The influence of the storage reservoir on the phytoplankton of the downstream run-of-river reservoir was more evident in the dry period. During the rainy period the lateral tributaries effects seems to have a higher influence, especially on the smaller studied reservoir.     

Algal response to a thermal effluent: study of a power station on the provo river,Utah, USA

The effect of a thermal effluent on the attached algae of the Provo River, Utah, USA, was studied from 1975 to 1977. Data for macroscopic and microscopic algae were collected and analyzed. Diatoms, Cladophora glomerata, and Hydrurus foetidus dominated the flora. The thermal effluent significantly affected the algal flora in a section of river 100 to 135 meters long immediately below the discharge point. Cladophora growth was increased and Hydrurus was absent in this area. In addition, diatom production was often higher and diversity lower than in the rest of the river. Community structure was unique from all other adjacent areas. Small temperature increases which occured as effluent and river waters mixed farther downstream were apparently not as important to the algal flora as other environmental factors.