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1.
Copepod assemblages from two cascade reservoirs were analyzed during two consecutive years. The upstream reservoir (Chavantes) is a storage system with a high water retention time (WRT of 400 days), and the downstream one (Salto Grande) is a run-of-river system with only 1.5 days WRT. Copepod composition, richness, abundance, and diversity were correlated with the limnological variables and the hydrological and morphometric features. Standard methods were employed for zooplankton sampling and analysis (vertical 50-μm net hauls and counting under a stereomicroscope). Two hypotheses were postulated and confirmed through the data obtained: (1) compartmentalization is more pronounced in the storage reservoir and determines the differences in the copepod assemblage structure; and (2) the assemblages are more homogeneous in the run-of-river reservoir, where the abundance decreases because of the predominance of washout effects. For both reservoirs, the upstream zone is more distinctive. In addition, in the smaller reservoir the influence of the input from tributaries is stronger (turbid waters). Richness did not differ significantly among seasons, but abundance was higher in the run-of-river reservoir during summer.  相似文献   

2.
In cascade reservoirs, different zonation effects can be observed along the longitudinal axis, depending on the retention time of each reservoir. In this study, we evaluated the relationships among fish and spatial and environmental variables across longitudinal zones within reservoirs with different retention times. Fieldwork was carried out during two periods in three different zones that represent the longitudinal axis (lotic, transitional, and lentic) of three reservoirs. Each reservoir has different retention times (low, intermediate, and high) and all are located in a cascade system of the Paranapanema River, Brazil. In the high retention time reservoir, richness, biomass, and diversity decreased along the longitudinal axis, in contrast to the numerical abundance and dominance. Conversely, in the low retention time reservoir, these community attributes varied in an opposite way. Both spatial (depth, retention time, longitude, and latitude) and environmental (dissolved oxygen, water temperature, Secchi disk, total nitrogen) variables were important controlling factors for fish communities in reservoirs, which confirms the hypothesis that reservoir retention times create a zonation effect with different proportions along the main axis, resulting in a spatial heterogeneity with specific environmental features, and it determines the fish assemblage structure and composition in each reservoirs.  相似文献   

3.
对贵州山区新建水库的浮游植物群落结构特征进行研究,有利于了解同类水库的浮游植物群落演替趋势,还可以评估水华发生的潜在风险,为管理部门提供参考。贵州省六盘水市的观音岩水库和万营水库,分别为2018年和2017年建成蓄水的新建水库,文章以实地调查为基础对两座水库的浮游植物群落结构特征及其与环境因子关系进行了研究。2018年11月至2019年10月间的季度调查显示,两座水库分别检出32种和28种浮游植物,优势种均以硅藻和绿藻为主,藻类平均密度分别为3.46×106和4.79×106 cells/L。RDA分析结果显示,观音岩水库和万营水库浮游植物群落的主要驱动因子相同,均为水温(WT)、总磷(TP)和水体透明度(SD)。总体来说,新建水库在运行初期出现藻类暴发的风险较低,在后续管理中,应着重关注浮游植物密度受温度、外源营养及季节变化的影响。  相似文献   

4.
The purpose of this study was to verify the longitudinal distribution of phytoplankton biomass in two subtropical Brazilian reservoirs in the State of Paraná and investigate intervening factors on changes in phytoplankton biomass according to functional groups. In the Capivari and Segredo reservoirs, samples were obtained every 3 months during 2002, along a longitudinal axis (fluvial, transition, and lacustrine zones) at different depths. One hundred and eighteen taxa were identified, with Chlorophyceae as the most specious group. During the study period, both reservoirs had mostly low biomass values (less than 1 mm3 l−1). The short retention time of these reservoirs constituted the principal limiting factor to phytoplankton development. Biomass values above 1 mm3 l−1 were observed in the Capivari fluvial zone in March and in the Segredo lacustrine zone in December, with dominance by Microcystis aeruginosa Kütz (LM) and Anabaena circinalis Rab. (H1), respectively. Vertical and horizontal gradients of analyzed abiotic variables and phytoplankton biomass were observed. Considering the phytoplankton biomass values, both reservoirs were oligotrophic for the duration of the study. The Canonical Correspondence Analysis (CCA) evidenced temporal and spatial gradients of phytoplankton biomass; nevertheless, it did not follow the classic model proposed for deep reservoirs, since higher biomass was registered in the lacustrine zone during some months and in fluvial zones during other months. Distinct functional groups of phytoplankton characterized both studied reservoirs. Capivari Reservoir was best characterized by LM and Y groups, indicative of its greater water column stability and higher phosphorus concentration, whereas Segredo Reservoir was principally characterized by the MP functional group, indicative of its greater mixing zone extension and higher nitrate concentration. The obtained results also evidenced the influence of morphometric conditions and watershed purposes as important structuring factors of phytoplankton biomass in these reservoirs. Handling editor: L. Naselli-Flores  相似文献   

5.
The effect of water transfers between two reservoirs on the phytoplankton community of the receiving reservoir was investigated over a 9-year period. Canonical correspondence analysis was used to demonstrate the significance of water transfers as an anthropogenic disturbance to the phytoplankton community and its diversity. A mass balance associated with a Granger causality test was applied to discriminate between the cell transport effect from the upstream reservoir and internal processes within the receiving reservoir, and to quantify the net phytoplankton growth in the receiving reservoir. Low and high disturbance regimes were identified and diversity was maximised during low disturbance conditions. The decrease of diversity during high disturbance conditions was explained by decreasing retention time, increasing silica loads and by the transport of specific phytoplankton genera, i.e. diatoms, from the upstream reservoir. Disturbance regimes significantly affected the relationship between phytoplankton production and diversity. Low disturbance regimes were described by phytoplankton dynamics likely influenced by complementarity effects, while high disturbance regimes were characterised by a phytoplankton community dominated by highly productive species and increased productivity, thus indicating an advantage of selection behaviour over complementarity effects. The phytoplankton diversity, expressed as evenness, was identified as a key variable explaining the relationship disturbance-diversity-phytoplankton production.  相似文献   

6.
Changes to the structure of the phytoplankton community and to the physical and chemical variables of the water were investigated in oxbow lakes with different levels of connection to a tropical river and subject to annual hydrological pulse variations. The selected lentic environments are located at the mouth region of the main tributary in a reservoir built for water storage and electric power generation. The temporal variation of phytoplankton in the studied lentic environments can be attributed mainly to the hydrological level of the river. A similar variation pattern of the ecological attributes was observed in the structure of the phytoplankton community in the connected lakes and Paranapanema River, evidencing the high degree of association that the lacustrine systems maintain with the river. The highest values of richness and diversity for connected environments were observed at the end of the emptying period and in the drought. However, considering the isolated lake, the highest values of these attributes were recorded during the flooding period.  相似文献   

7.
Variations in the structure and dynamics of a phytoplankton community were determined during two periods in 2001, along five cascading reservoirs of the Iguaçu River, Paraná State (Brazil). The vertical dynamics of the phytoplankton was related to underwater light availability and the water column-mixing regime. Correlations between physical and chemical variables and phytoplankton abundance were evaluated by Canonical Correspondence Analysis (CCA). No significant cascading effect throughout the serial reservoirs was obtained. Thus, the main factor affecting the structure of the phytoplankton assemblages of each reservoir was the hydrodynamic pattern. The instability of the water column during the winter favored the development of R-strategist species such as Aulacoseira granulata, Urosolenia longiseta and U. eriensis in most reservoirs. In the period of the highest hydraulic stability and temperature, the greatest contribution to biomass came from Cyanophyceae S-strategists such as Aphanocapsa sp.1, Anabaena planctonica and A. crassa. The phytoplanktonic associations recorded were important indicators of the environmental conditions of these reservoirs.  相似文献   

8.
Trait-based approaches have become increasingly important and valuable in understanding phytoplankton community assembly and composition. These approaches allow for comparisons between water bodies with different species composition. We hypothesize that similar changes in environmental conditions lead to similar responses with regard to functional traits of phytoplankton communities, regardless of trophic state or species composition. We studied the phytoplankton (species composition, community trait mean and diversity) of five reservoirs in Brazil along a trophic gradient from ultra-oligotrophic to meso-eutrophic. Samples at two seasons (summer/rainy and winter/dry) with a horizontal and vertical resolution were taken. Using multivariate analysis, the five reservoirs separated, despite some overlap, according to their environmental variables (mainly total phosphorus, conductivity, pH, chlorophyll a). However, between the seasonal periods, the reservoirs shifted in a similar direction in the multi-dimensional space. The seasonal response of the overall phytoplankton community trait mean differed between the ultra-oligotrophic and the other reservoirs, with three reservoirs exhibiting a very similar community trait mean despite considerable differences in species composition. Within-season differences between different water layers were low. The functional diversity was also unrelated to the trophic state of the reservoirs. Thus, seasonal environmental changes had strong influence on the functional characteristics of the phytoplankton community in reservoirs with distinct trophic condition and species composition. These results demonstrate that an ataxonomic trait-based approach is a relevant tool for comparative studies in phytoplankton ecology.  相似文献   

9.
A study was carried out over a period of six years to determine the effects of eutrophication upon standing crop and composition of the phytoplankton in four recently constructed flood control reservoirs in Nebraska. Water samples collected weekly during June, July, and August from 1968–73 were analyzed for chlorophyll a, phytoplankton composition, and phytoplankton abundance. Total volume of phytoplankton was calculated from appropriate dimensions and formulae. Inorganic turbidity in one reservoir was an important factor regulating the size and composition of the phytoplankton standing crop. In that reservoir diatoms were the most important component of the phytoplankton community during those years in which inorganic turbidity was greatest. When inorganic turbidity declined, blue-green algae became dominant.In the clear-water reservoirs chlorophyll a, phytoplankton number, and phytoplankton volume were significantly correlated with reservoir age, with the oldest containing chlorophyll a concentrations up to 247 mg/m3 and mean phytoplankton volumes up to 329 mm3/l, values sufficient to place it in the hypereutrophic category. The reservoirs had 2–6 times more chlorophyll a present at the end of the study than at the beginning, with the increase being greatest in the newest reservoir. Phytoplankton volume was significantly correlated with chlorophyll a in all the reservoirs.Blue-green algae quickly became established as community dominants in the reservoirs, making up over 80 percent of the phytoplankton volume in the newest reservoir by the second year of its existence. In the other clear-water reservoirs, blue-greens usually constituted over 95 percent of the total phytoplankton volume in summer. three genera, Microcystis, Aphanizomenon, and Anabaena, were responsible for virtually the entire standing crop of blue-greens in all the reservoirs.  相似文献   

10.
Densities of bacterioplankton and phytoplankton were studied in relation to water retention time, temperature, nutrient concentrations, and other variables in a eutrophic montane reservoir (Bluestone Lake, West Virginia, U.S.A.). Weak temperature stratification occurred occasionally during the summer, but the reservoir did not become anaerobic. Water retention times were short (3.9 to 9.7 days between June and December), and differences in flushing rate within that range were important in regulating phytoplankton populations. Green algae and planktonic diatoms were dominant in summer during periods when water residence times were shorter. The occurrence of blue-green algal blooms in fall was related to increased water residence times. Retention time was highly correlated with the percent composition of phytoplankton represented by Anabaena spp. and Microcystis sp. (r=0.898, p<0.001). Advective effects limited phytoplankton biomass when retention time was shortest, but were not as important when retention times were longer. Peaks in bacterial densities often coincided with decreases in viable algal cell densities, so bacterioplankton were less directly related to retention time.  相似文献   

11.
Phytoplankton is widely recognized as being regulated mainly by resources (nutrients and light) and predation by higher trophic levels. In reservoirs, these controls also can be modulated by hydrology, for example through the influence of flow pulses generated by the operation of the dam. In this study, we tested the influence of light, nutrients, and zooplankton grazing pressure, and also hydrology (as water residence time) on the phytoplankton biomass in eight tropical hydroelectric reservoirs, which differ in size, morphometry, location, trophic state, and water residence time. Our hypothesis was that, as these reservoirs are used for hydroelectric purposes, the control that would otherwise be exerted on phytoplankton biomass primarily by resource availability and grazing will also be modulated by hydrology. Low phytoplankton biomass (range of system medians = 12–299 μg C l−1) occurred in most systems, except for one highly eutrophic reservoir (median = 1331 μg C l−1). Our data showed that phosphorus was more often likely to be the limiting nutrient in these systems, as assessed through nutrient limitation indexes (nitrogen and phosphorus), based on concentrations and ratios. For most reservoirs, excluding the eutrophic system with high cyanobacteria biomass, seasonal water residence time was the variable that best explained phytoplankton variation among the several environmental variables analyzed in this study (P < 0.0001; adjusted r 2 = 0.38). Hydrology was an important and additional factor modulating phytoplankton in these tropical reservoirs, directly removing phytoplankton populations and their potential zooplankton grazers by washout, and also affecting nutrient availability.  相似文献   

12.
In reservoirs or lakes, mixing depth affects growth and loss rates of phytoplankton populations. Based on 1-year data from the Zeya reservoir, China, we scaled the mixing depth throughout a whole year by utilizing cluster analysis, and then investigated its influence on phytoplankton dynamics and other physical and chemical parameters. Over the whole year, all physical and chemical parameters except TN and temperature had significant correlations with mixing depth, indicating that mixing depth is one of the important driving factors influencing water environment. According to mixing depth, a year can be divided into three different periods, including the thermally stratified period, isothermally mixed period, and transition period between them. When considering the former two different periods separately, mixing depth had no correlation with the phytoplankton biovolume. However, over the whole year a significant correlation was observed, which indicated that the influence of mixing depth on phytoplankton growth in the Zeya reservoir still followed Diehl’s theory. Furthermore, according to the steady-state assumption, a unimodal curve (mixing depth—phytoplankton biovolume) with a significant peak appearing at a mixing depth of 2 m was observed, closely agreeing with Diehl’ prediction.  相似文献   

13.
A previous pioneering study of freshwater bodies in Sri Lanka revealed the presence of toxic cyanobacteria in three out of four water bodies tested. It was therefore important to perform a more detailed investigation into the presence of cyanobacteria and their toxins throughout Sri Lanka. The country has a long history of well-planned water management with the agricultural economy and drinking water supply still dependent on thousands of man-made tanks. Seventeen reservoirs from different user categories and different climatic zones were selected to study variations in phytoplankton communities with relation to major nutrients, with particular emphasis on cyanobacteria. The study was carried out during a two-year period and heavy growths or blooms of cyanobacteria observed during the study period were tested for microcystins. The results clearly categorised the 17 reservoirs into four groups parallel to the classification based on the user categories of water bodies. Biomass of total phytoplankton, the abundance of cyanobacteria, the dominance of Microcystis spp. and concentration of nitrate (N) and total phosphorous (P) were the lowest in drinking water bodies and the highest in aesthetic water bodies. Irrigation water bodies showed the second lowest values for phytoplankton biomass, and concentration of N and P, while hydropower reservoirs showed the second highest values for the same parameters. The fraction of cyanobacteria in irrigation waters was higher than that in hydropower reservoirs, but surprisingly the dominance of Microcystis spp. was reversed. Possible reasons for these variations are discussed. More than half of the bloom material tested contained microcystins up to 81microgl(-1). Our findings indicate the potential for high-risk situations due to toxigenic cyanobacterial blooms in susceptible freshwaters of Sri Lanka.  相似文献   

14.
Autumn picoplankton (Synechococcus, picoeukaryotes and heterotrophic bacteria) and environmental factors have been investigated in a series of reservoirs along the Wujiang River in Guizhou Province, SW China. The average abundances of Synechococcus, picoeukaryotes and heterotrophic bacteria was 104, 102 and 106 cells ml−1, respectively. In autumn meso-eutrophic reservoirs, thermal stratification was clear and abundances of different picoplankton groups in release water was low; whereas these phenomena were not obvious in autumn hypereutrophic reservoir. Picoplankton numbers decreased with increasing water depth and showed a positive correlation with water temperature, which reflected the importance of light and temperature on the picoplankton growth. Contribution of Synechococcus to total phytoplankton production and contribution of picoeukaryotes to total phytoplankton production asynchronous changed with varying trophic states. Synechococcus preferred meso-eutrophic reservoirs over hypereutrophic reservoir and picoeukaryotes showed no preference for the investigated reservoirs in autumn. Handling editor: L. Naselli-Flores  相似文献   

15.
The growing need to analyse the present state of ecosystems and predict their rate of change has triggered a demand to explore species environment relationships for assessing alterations under anthropogenic influence. The Water Framework Directive (WFD) requires the definition of different types of water bodies which are of relevance when assessing their ecological status. The main aim of this study was to define of the types of Portuguese reservoirs located in the North and Centre of Portugal and to assess their ecological status using phytoplankton as water quality indicators. In this study, sampling was carried out in 34 reservoirs during four seasons (spring, summer, autumn and winter), through a period of 8 years (1996–2004).Two groups of reservoirs could be distinguished, from the multivariate statistical analysis based on environmental variables and on phytoplankton assemblages: G1, lowland reservoirs located in the main rivers (Douro and Tagus), with a very low residence time, characterized by higher water mineral content (hardness and conductivity), higher concentrations of nutrients (namely, nitrates), dominated by Bacillariophyta and Chlorophyta and characterized by the presence of tolerant of poor environmental conditions species, mainly associated with meso and eutrophic states of water bodies; G2, deeper high altitude reservoirs, largely located in tributaries, with high residence time, presenting a specific species composition under reference conditions, with higher species richness. The transition from deeper and colder reservoirs (reference sites) to shallow and warmer reservoirs (impaired sites), was evident in G2, contrarily to G1, and was mostly positively correlated to organic pollution and mineral gradients. The results presented here are fundamental for the development of a routine for monitoring ecological status according to the WFD.  相似文献   

16.
In reservoirs, water level fluctuations strongly influence phytoplankton development. However, studies on the response of phytoplankton in the reservoir-bay to water level fluctuations are very scarce, especially in the highly dynamic reservoir system, for instance, the Three Gorges Reservoir (TGR) on the Yangtze River in China. Therefore, we carried out weekly monitoring in a typical tributary bay—Xiangxi Bay of the TGR from March 2008 to March 2009, to analyze the dynamics of phytoplankton functional groups, as well as their response to the water level fluctuations and other environmental conditions. The phytoplankton functional groups G (short, nutrient-rich water columns with high light and without nutrient deficiency), M (dielly mixed layers of small eutrophic, low latitude with high insolation and without flushing and low total light) and Lo (summer epilimnia in mesotrophic lakes with segregated nutrients and without prolonged or deep mixing) were the most important in biomass, mainly represented by Pandorina morum and Eudorina elegans, Microcystis aeruginosa, Peridiniopsis niei and Ceratium hirundinella, respectively. The dominant functional groups had close relationships with the water level fluctuations, light and nutrient, etc. Principal components analysis and redundancy analysis indicated that phytoplankton functional groups in Xiangxi Bay were restricted by the mixing regime and other abiotic variables under the influences of the mixing regime. In Xiangxi Bay, the water level fluctuation showed significant correlations with many physicochemical variables, including the mixing depth (r = 0.97, p < 0.001) and the relative water column stability (r = −0.80, p < 0.001). The study implied that water level fluctuations had complex influence on environmental changes and selecting for phytoplankton functional groups in a highly dynamic reservoir-bay. The important characteristics of the dominant phytoplankton functional groups in Xiangxi Bay were also discussed.  相似文献   

17.
三峡水库运行期间原生动物群落的时空异质性   总被引:1,自引:0,他引:1  
郑金秀  池仕运  李聃  汪红军  胡菊香 《生态学报》2015,35(11):3569-3579
于2010年10月—2011年6月三峡水库正常运行周期内对库区干流原生动物进行调查,研究其空间分布及水库周期排蓄期间的变化。共检测到原生动物99种,蓄水后纤毛虫有增多的趋势。水库运行的不同阶段优势种不同,大致演变为:砂壳纤毛虫(蓄水期)—非砂壳类纤毛虫(高位运行期间)—有壳肉足虫(低位运行期间)。不同水域优势种也存在差异,从上游到下游特征指示种变化为:有壳肉足虫(变动回水区)—纤毛虫(湖泊区)。结果表明,三峡水库原生动物的分布具有明显的时空异质性(P0.05),影响原生动物时空分布的主要因素有透明度、温度、电导率和叶绿素a。原生动物平均密度为952.19个/L,平均生物量为8.14μg/L。蓄水期上游现存量高于下游,低位运行期间则低于下游。原生动物Marglef和Shannonn-Weiver多样性指数平均值分别为3.78和2.18,1月份最低,6月份最高。蓄水175 m后上游变动回水区原生动物具有较高的丰度。水库冬蓄夏排的运行模式模糊了河流本身的季节变化,使原生动物的种类和现存量更多的受水库水动力学的影响,使水体理化因子和水文特征呈现明显的时空差异,最终形成原生动物种群的时空异质性分布。  相似文献   

18.
The principal environmental factors influencing the seasonal dynamics of phytoplankton were examined from September 1997 to July 1998 in three stations along a 26-km stretch of the lowland course of River Adige (northeast Italy). Nutrient concentrations did not appear to be limiting for the phytoplankton growth. Annual minimum concentrations of reactive and total phosphorus, and dissolved inorganic nitrogen were 22 μg P l−1, 63 μg P l−1 and 0.9 mg N l−1, respectively. The most critical forcing factors were physical variables, mainly water discharge and other variables related to hydrology, i.e. suspended solids and turbidity, which acted negatively and synchronously by diluting phytoplankton cells and decreasing light availability. Higher algal biomass was recorded in early spring, in conditions of lower flow velocity and increasing water temperature. In late spring and summer, higher water discharge caused a decrease in phytoplankton biomass. Conversely, low algal biomass in late autumn and winter, during low discharge, was mainly related to low water temperatures and shorter photoperiod. Physical constraints had a significant and measurable effect not only on the development of total biomass, but also on the temporal dynamics of the phytoplankton community. Abiotic and biotic variables showed a comparable temporal development in the three sampling stations. The small number of instances of spatial differences in phytoplankton abundance during the period of lower flow velocity were related to the increasing importance of biological processes and accumulation of phytoplankton biomass.  相似文献   

19.
In order to understand the environmental variables which promote the proliferation of cyanobacteria and variation in microcystin concentrations in the Nui Coc reservoir, Vietnam, physicochemical parameters, the occurrence, and abundance of phytoplankton, cyanobacteria, and microcystin concentration were monitored monthly through the year 2009–2010. The relationships between these parameters were explored using principal component analysis (PCA) and Pearson correlation analysis. The phytoplankton community was mainly dominated by the cyanobacterium Microcystis with higher cyanobacteria abundance during summer and autumn season. PCA and Pearson correlation results showed that water temperature and phosphate concentration were the most important variables accounting for cyanobacteria, Microcystis, and microcystin occurrence. Analysis of the toxins by high-performance liquid chromatography demonstrated the presence of two microcystin variants: microcystin-LR (MC-RR) and microcystin-ddRR (MC-ddRR) with total concentrations of the toxins in filtered samples from surface water ranging from 0.11 to 1.52 μg MC-LR equiv L?1. The high concentrations of microcystin in the Nui Coc reservoir highlighted the potential risk for human health in the basin. Our study underlined the need for regular monitoring of cyanobacteria and toxins in lakes and reservoirs, which are used for drinking water supplies, not only in Vietnam but also in tropical countries.  相似文献   

20.
于2005年1-6月,对南亚热带调水水库—大镜山水库的水文、营养盐(N、P)和浮游植物进行了调查研究。共检测到浮游植物76种;浮游植物总的细胞数量在4.925×106-63.65×106cellsL-1之间,浮游植物的总生物量在1.632-20.420mgL-1之间。假鱼腥藻(Pseudanabaena sp.)是主要优势藻,但是早春(1-3月)假鱼腥藻和肘状针杆藻(Synedraulna)共同成为优势藻。浮游植物细胞的丰度晚春(4-6月)比早春的要高,但是生物量却比早春的低。在水文过程与其它水库有一定差别的典型调水水库,水温是引起浮游植物种类组成变化的主要原因。浮游植物组成与动态是受入库营养盐和水动力学的变化所影响的。  相似文献   

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