Rybnik Reservoir Research Articles

Estimation of the level of anthropogenic impact based on the determination of radionuclides and heavy metals in sediments taken from Rybnik reservoir, Poland

The aim of the study was to estimate the degree of anthropogenic risk by evaluating the level of the contamination of sediments collected from the Rybnik reservoir. The results of the determination of radionuclides (137Cs, 40K, 228Th, 228Ra, 226Ra, 210Pb, 238U) and heavy metals (Zn, Cd, Pb, Cu, Cr, Ni) were presented. The Rybnik reservoir is located in a highly urbanised area, the Lower Silesian Voivodeship in Poland. Radionuclides (137Cs, 40K, 228Th, 228Ra, 226Ra, 210Pb, 238U) were measured using gamma spectrometry. The heavy metal (Zn, Cd, Pb, Cu, Ni and Cr) content was determined using an inductively coupled plasma optical emission spectrophotometer (ICP-OES). The classification of sediment pollution was made on the basis of geochemical and ecotoxicological indices. Radioactivity was varied with the highest for 40K (more than 200 Bq·kg−1). The concentrations for the remaining radionuclides were mostly below 20 Bq·kg−1. At the inlet zone (no. 9) an increase in radioactivity of each radioisotope was observed. The values of heavy metals from the lowest to the highest total amount in the sediments were as follows: Cd < Cr < Pb < Ni < Cu < Zn. The sediments of the reservoir are largely contaminated with Cu, but the sediments generally are contaminated to an average degree. Most pollutants accumulate in the inlet zone and near the dam wall. The content of artificial radionuclides, as well as the geochemical and ecological indicators used, can serve as an indicator of the level of anthropopressure in the vicinity of the Rybnik reservoir.

Metal contamination in sediments of dam reservoirs: A multi-facetted generic risk assessment

The quality of bottom sediments is a key factor for many functions of dam reservoirs, which include water supply, flood control and recreation. The aim of the study was to combine different pollution indices in a critical generic risk assessment of metal contamination of bottom sediments. Both geochemical and ecological indices reflected that sediment contamination was dominated by Zn, Pb and Cd. The ecological risk indices suggested a high riks for all three metals, whereas human health risks were high for Pb and Cd. An occasional local contamination of sediments with Cr and Ni was revealed, although at levels not expected to cause concerns about potential ecological or health risk. Sediments from the Rybnik reservoir for Cu only revealed a high potential ecological risk. EF turned to be as being the most useful, whereas TRI (∑TRI) was the most important ecological index. All multi-element indices suggested similar trends, indicating that Zn, Pb and Cd taken altogether had the greatest impact on the level of sediment contamination and posed the greatest potential ecological and health risks to organisms. The use of sequential BCR extraction and ecotoxicity analyses allowed for a multi-facetted generic risk assessment of metals in sediments of dam reservoirs.

Concentration of dioxin and screening level ecotoxicity of pore water from bottom sediments in relation to organic carbon contents

The information about concentrations of dioxin in pore water, ecotoxicity and DOC and TOC content can be key factor for the prediction of the fate of dioxins in the aquatic environment as well as an ecological risk assessment. The aims of the study were to assess the concentration of PCDDs/PCDFs and ecotoxicity of pore water and to compare above results in relation to the dissolved organic carbon (DOC) and total organic carbon (TOC) content. The concentration of dioxins was assessed using an enzyme-linked immunoassay test, while the ecotoxicity of pore water was determined using a crustacean Daphnia magna and bacteria Aliivibrio fischeri. The studies were conducted on two different dammed reservoirs Rożnów (catchment basin of an agricultural character) and Rybnik (catchment basin of an industrial character) located in southern Poland. The concentration of dioxins in pore water was between 8.56 to 90.92 ng EQ/L, with a significantly higher concentration in the pore water from the Rożnów Reservoir than the Rybnik Reservoir. The DOC content in pore water was from 30.29 to 63.02 mg/L (Rożnów Reservoir) and from 35.46 to 60.53 mg/L (Rybnik Reservoir). Higher toxic responses were recorded for A. fischeri than for D. magna. Moreover a significantly higher toxicity for both tested organisms was indicated in pore water from the Rożnów Reservoir. Besides of TOC and DOC, the fine fractions of the sediments were particularly important in the concentration of dioxin in pore water. The other pore water parameters, such as pH and EC can influence the toxicity of water for organisms. The result indicate complex relationships between the PCDD/F, ecotoxicity and DOC, TOC concentration in pore water and confirms that these parameters are important in terms of water environmental contamination.

An assessment of the concentrations of PCDDs/Fs in contaminated bottom sediments and their sources and ecological risk

PurposeThe purpose of the study was to determine the levels of polychlorinated dibenzo-p-dioxin and polychlorinated dibenzofuran (PCDD/F), two types of persistent organic pollutant (POP), in an urban retention reservoir located in an industrial zone within a coal-mining region. It also assesses the potential ecological risk of the PCDDs/Fs present in bottom sediments and the relationship between their content and the fraction of organic matter.Materials and methodsThe sediment samples were collected from Rybnik Reservoir, located in the centre of the Rybnik Coal Region, Silesia, one of Poland’s major industrial centres. Seventeen PCDD/F congeners in the surface of the sediments were analysed using high-resolution gas chromatography and high-resolution mass spectrometry (HRGC/HRMS).Results and discussionThe toxic equivalency (TEQ) of the PCDDs/Fs in the sediments ranged from 1.65 to 32.68 pg TEQ g−1. PCDDs constituted 59–78% of the total PCDDs/Fs, while the PCDFs accounted for 22–41%. The pattern of PCDD/F congeners in the sediments was dominated by OCDD. However, the second-most prevalent constituents were OCDF and ∑HpCDFs in the low TOC sediment (< 10 g TOC kg−1), but HpCDD in the rich TOC samples (> 10 g TOC kg−1). PCDD/F concentrations in the sediment samples were 2- to 38-fold higher than the sediment quality guidelines limit, indicating high ecological risk potential. Although a considerable proportion of PCDDs/Fs in the bottom sediments from the Rybnik Reservoir were derived from combustion processes, they were also obtained via transport, wastewater discharge, high-temperature processes and thermal electricity generation. The PCDD/F concentrations were significantly correlated with all fractions of organic matter; however, the strongest correlation coefficients were found between PCDDs/Fs and humic substances. Besides organic matter, the proportions of silt/clay fractions within sediments played an important role in the transport of PCDDs/Fs in bottom sediments.ConclusionsThe silt/clay fraction of the bottom sediments plays a dominant role in the movement of PCDDs/Fs, while the organic matter fraction affects their sorption. The results indicate that the environmental behaviour of PCDDs/Fs is affected by the quantity and quality of organic matter and the texture of sediments.

The influence of the quantity and quality of sediment organic matter on the potential mobility and toxicity of trace elements in bottom sediment

Knowledge on the fraction of trace elements in the bottom sediments is a key to understand their mobility and ecotoxicological impact. The purpose of this study was to assess the influence of the content of organic matter fractions on the mobility and ecotoxicity of trace elements in sediments from the Rybnik reservoir. The most refractory fraction of organic matter—Cnh (non-hydrolysing carbon)—dominated in the sediments. The content of organic matter fractions are arranged in the following order: Cnh (non-hydrolysing carbon) > Cfa (fulvic acid) > Cha (humic acid) > DOC (dissolved organic carbon). On the other hand, the highest value of correlation coefficients was found for different fractions of trace elements and DOC content in the bottom sediments. A higher content of TOC in the sediments significantly increased the share of elements in the potential mobile fraction and, at the same time, decreased the binding of elements in the mobile fractions. Moreover, in sediments that contain more than 100 g/kg d.m. TOC, no and medium risk of trace element release from sediments was observed. The Cu, Cd and Ni were potentially the most toxic elements for biota in the Rybnik reservoir. However, the correlation between the content of trace elements and the response of bacteria was insignificant. These results suggested that the complexation of trace elements with organic matter makes them less toxic for Vibrio fischeri. The transformation and sources of organic matter play an important role in the behaviour of trace elements in the bottom sediments of the Rybnik reservoir.

The content and composition of organic matter in bottom sediments of the Rybnik reservoir – preliminary studies

Organic matter has important influences on the fate of environmental pollution in water dam reservoirs. The aim of the studies was to assess content of organic matter fractions in Rybnik reservoir bottom sediments, and to determine their influence on the content of heavy metals and PAHs. In three sediment samples, the content of C organic (Corg), C extracted (Cex), C humic acid (Cha), C fulvic acid (Cfa) and C non-hydrolyzed (Cnh), buffer capacity, and content of heavy metals and PAHs was analyzed. We found the highest content of Corg, Cex, Cha, Cfa and Cnh in sample 3 (the outlet, near the dam), while the lowest content was found in sample 2 (middle). The fraction of Cnh was dominant in sediment sample 3 (outlet, near dam) and 1 (inlet), whereas the fraction of Cha dominated in sample 2 (middle). Rybnik bottom sediments are characterized by their high buffer capacities (samples 3, 1) shaped among others by the high content of organic matter. The high organic matter content in samples 3 (outlet) and 1 (inlet) and also high total contents of heavy metals and PAHS in these sediments demonstrate that these pollutants have a strong affinity for organic matter in the sediments. Moreover, the highest mobility of metals, from sample 2 (middle), is connected with the low content of organic matter substances and the low buffer capacities of sediments.

Temporal and spatial variability in concentrations of phosphorus species under thermal pollution conditions of a dam reservoir – the Rybnik Reservoir case study

AbstractThe research objective was to study temporal and spatial relations between specific phosphorus species as well as to examine total phosphorus content in the bottom sediments of an anthropogenic, hypertrophic limnic ecosystem Rybnik Reservoir, functioning under thermal pollution conditions. The chemical extraction procedure for the speciation of bioavailable phosphorus forms was used. It was found that available algae phosphorus was the most dominant phosphorus species in both sediment layers (83%), while the lower share was readily desorbed phosphorus form (0.1%). The phosphorus species concentrations depended on the organic matter concentration. The differences between phosphorus species contents in the upper (5 cm) and lower (15–20 cm) sediment core layers were low. The biologically active sediment layer extended from the sediment surface to at least 20 cm depth of the sediment core. Distributions of the concentrations within the year and at specific sampling points resulted from the variability observed for particular points and transformation intensity. Furthermore in the following study, the reaction rate constant for the increase and decrease in the concentrations of the phosphorus species in sediments was given. It was indicated that the speed of the phosphorus species transformations was affected by the environment temperature. In the heated water discharge zone (water temp. 17–35°C) the concentrations of selected speciation phosphorus forms increased more than in the dam zone (5–25°C). It was also found that the abundance of the bottom sediments with phosphorus species was related to the oblong and transverse asymmetry of reservoir depth.

Concentration, sources and risk assessment of PAHs in bottom sediments

The aims of the study were to investigate the concentration, sources and ecological risk of PAHs (polycyclic aromatic hydrocarbons) in bottom sediments collected from nine reservoirs located in south-eastern Poland. The concentration of ∑PAHs in sediments ranged from 150 to 33,900 μg kg−1. The total PAH concentration in the bottom sediments was arranged in the following order: Rybnik > Rzeszów > Brzóza Królewska > Brzóza Stadnicka > Besko > Chechło > Ożanna > Głuchów > Narożniki. BAP was the major compound in sediments from the Besko, Brzóza Stadnicka and Rzeszów reservoirs; FLT in the sediments from the Rybnik, Narożniki, Ożanna and Brzóza Królewska reservoirs; and FLN from the Głuchów and Chechło reservoirs. The major inputs of PAHs were of pyrolytic origin. However, petrogenic sources of PAHs occurred especially in the Chechło and Głuchów reservoirs. The ecological risk assessment indicated that non-adverse effects on the benthic fauna may occur for sediments from the Głuchów, Narozniki and Ożanna reservoirs, while slightly adverse effects were found for sediments from the Brzóza Królewska, Besko, Brzóza Stadnicka and Chechło reservoirs. The other sediments showed moderate (Rzeszów reservoirs) and strong effect (Rybnik reservoir) on biological communities. Individual PAHs such as NAP, PHE, FLT, PYR, BAA, CHR and BAP in sediments from the Rybnik reservoir and BAP in sediments from the Rzeszów reservoirs indicated a higher possibility of occurrence of an adverse ecological effect. PCA analysis found slight difference between the reservoirs in the profile of variable PAHs. Only the sediments from the Rybnik and Chechło reservoirs differ considerably from this grouping.

The application of the germination index in the assessment of the phytotoxicity of bottom sediments from the Rybnik Reservoir

The aims of the study were to assess the phytoxicity of bottom sediments collected from the Rybnik Reservoir. The water reservoir in Rybnik is located in the Silesian Voivodeship. The reservoir constitutes a part of the technological chain of Elektrownia Rybnik S.A. as a direct receiver of industrial and rainwater sewage, sewage from a water treatment plant, blowdowns from cooling towers, and as an essential source of cooling water. Sediment samples were collected with an Eckman sampler from 33 locations. The toxicity of bottom sediments was determined using the Phytotoxkit direct contact test, carried out for 3 plants: Sorghum saccharatum, Sinapis alba and Lepidium sativum. On the basis of the data received, the germination index (GI) was calculated. We found the mean value of the germination index indicated the dominance of the inhibitory effect of bottom sediments on plant growth. Sorghum saccharatum was the most sensitive to pollutants in sediments, while Lepidium sativum was the least sensitive. The Phytotoxkit is a good tool for assessing the toxicity of bottom sediments.

Spatial distribution of trace elements and ecotoxicity of bottom sediments in Rybnik reservoir, Silesian-Poland.

The aim of study was to integrate chemical analyses and toxicity bioassays in order to assess the environmental risk connected with the presence of trace elements in the sediments. This study examined the ecological significance of trace elements in bottom sediments by applying a set of complementary sediment quality assessment methods sediment quality guidelines (SQGs) (mean probable effect concentration quotient (PECQ)), potential ecological risk index (PERI), contamination degree (Cd) and two bioassays: the bacterial luminescence inhibition test with Vibrio fischeri on sediment elutriates and the direct contact test with the ostracod crustacean Heterocypris incongruens. The samples were collected from 50 stations of Rybnik reservoir. The reservoir is a region with enormous concentration of industry, mainly hard coal mining, electric power industry, and transportation. Despite the high diversity in metal concentration in the sediments, the spatial distribution of trace elements in the sediments was very similar. Moreover, the strong positive correlations between individual pairs of trace elements indicate that they may derive from a similar source and move together. According to mean PECQs, 68 % of the samples were potentially non-toxic and 32 % of the samples were potentially toxic. PERI values suggested that 70 % of the sediment sampling sites exhibited low ecological risk from metal pollution while 24 % of the samples had severe and serious risk. Based on our combined evaluation, we believe that Cd and Cu in the sediment samples frequently caused adverse biological effects. Higher toxic responses were observed in the Microtox test than in the Ostracodtoxkit test. All the sediment samples were found toxic to V. fischeri, and 96 % of the samples had effect percentages >50 %. For H. incongruens, 12 % of the sediments were not toxic and 44 % had effect percentages >50 %. In order to perform a complex assessment of the environmental impact of metal pollution, both chemical and ecotoxicological analysis should be carried out.

Assessment of heavy metals mobility and toxicity in contaminated sediments by sequential extraction and a battery of bioassays.

The aim of this study was to assess heavy metals mobility and toxicity in sediments collected from a dam reservoir in the conditions of intensive human impact by using chemical fractionation and a battery of bioassays. In the studies, the test organisms were exposed to substances dissolved in water (Microtox, Phytotestkit) as well to substances absorbed on the surface of solid particles (Phytotoxkit, Ostracodtoxkit F). The studies showed that sediments from the Rybnik reservoir are toxic, but the tested organisms showed different sensitivity to heavy metals occurring in the bottom sediments. The sediment samples were classified as toxic and very toxic. Moreover, the studies showed a higher toxicity in solid phases and whole sediment than in pore water. The lowest sensitivity was observed in H. incongruens (solid phases) and V. fischeri (pore water, whole sediment). The studies revealed that the toxicity of the sediments is caused mainly by heavy metal forms associated with the solid phase of the sediments. The studies did not confirm the metals occurring in fraction I (exchangeable) to be bioavailable and toxic to living organisms because most correlations between the metal concentration in fraction I and the response of the organisms were negative. The highest mobility from the bottom sediments was found in zinc, average mobility—in copper, cadmium and nickel, and low mobility—in chromium and lead. Organic matter is likely to be the most important factor controlling metal distribution and mobility in the studied sediments.

Chemometric and environmental assessment of arsenic, antimony, and chromium speciation form occurrence in a water reservoir subjected to thermal anthropopressure.

In the study, arsenic, antimony, and chromium concentrations and selected physicochemical parameters in water and sediment samples from the thermal anthroporessure subjected Rybnik Reservoir (Poland) were determined. As(III), As(V), Sb(III), and Sb(V) ions were successfully separated on Dionex IonPac AS7 column, and Cr(III) and Cr(VI) on Dionex IonPac AG7 column. The obtained limits of detection were 0.18, 0.22, 0.009, 0.012, 0.11, and 0.17 μg/L, respectively. Water and bottom sediment samples were collected monthly at three-point transect between January and November 2013. The As(III) and Sb(III) speciation forms dominated in the bottom water, and Cr(VI) concentration in the bottom water was twice as high as the value measured for the surface water. The oxidized arsenic, antimony, and chromium forms dominated in the bottom sediments in the heated water discharge zone of the Rybnik Power Plant. The location of sampling point had a significant influence on the observed transformations and contents of the analyzed speciation forms. The chemometric analysis coupled with the dissimilarity analysis and principal component analysis helped to visualize the variability in the concentrations of the element speciation forms within the researched period and analyzing correlations.

Mobility and toxicity of heavy metals in bottom sediments of Rybnik reservoir

Heavy metals are one of the most important factors among many others in biosphere pollution. Mobility and toxicity of metals associated with bottom sediments are generally affected by metal speciation and sediments compositions. The aims of this study were to investigated the distribution of metal speciation in sediment collected from Rybnik dam reservoir and to asses their toxicity for aquatic ecosystem. The speciation analysis of metal was performed using the three-step method of sequential fractionation by means of the modified BCR technique. Toxicity assestement of the bottom sediment samples was preformed using tests: Phytotoxkit TM , Ostarcodotoxkit F TM , Microtox ® . According to the above results, the mobilization potential of heavy metals in sediments in a decreasing order (fraction I+II): Zn > Cd > Ni > Pb > Cu > Cr. According to the Risk Assessment Code (RAC), the sediments having at low risk (Pb, Cu, Cr), medium risk (Cd, Ni) and high risk (Zn). The analysis of all sediment samples collected from the suited reservoir showed that Classes III (acute hazard 50% ≤ PE < 100%) was represented by 80% samples.

Multivariate Statistical Analyses on Arsenic Occurrence in Rybnik Reservoir

Popular statistical techniques, such as Spearman's rank correlation matrix, principal component analysis (PCA) and multiple linear regression analysis were applied to analyze a large set of water quality data of the Rybnik Reservoir generated during semiannual monitoring. Water samples collected at 9 sampling sites located along the main axis of the reservoir were tested for 14 selected parameters: concentrations of co-occurring elements, ions and physicochemical parameters. The aim of this study was to estimate the impact of those parameters on inorganic arsenic occurrence in Rybnik Reservoir water by means of multivariate statistical methods. The spatial distribution of arsenic in Rybnik Power Station reservoir was also included. Inorganic arsenic As(III), As(V) concentrations were determined by hydride generation method (HG-AAS) using SpectrAA 880 spectrophotometer (Varian) coupled with a VGA-77 system for hydride generation and ECT-60 electrothermal furnace. Spearman's rank correlation matrix was used in order to fi nd existing correlations between total inorganic arsenic (As Tot ) and other parameters. The results of this analysis suggest that As was positively correlated with PO 4 3- ; Fe and TDS. PCA confi rmed these observations. Principal component analysis resulted in three PC's explaining 57% of the total variance. Loading values for each component indicate that the processes responsible for As release and distribution in Rybnik Reservoir water were: leaching from bottom sediments together with other elements like Cu, Cd, Cr, Pb, Zn, Ni, Ca (PC1) and co-precipitation with PO 4 3- , Fe and Mn (PC3) regulated by physicochemical properties like T and pH (PC2). Finally, multiple linear regression model has been developed. This model incorporates only 8 (T, pH, PO 4 3- ,Fe, Mn, Cr, Cu, TDS) out of initial 14 variables, as the independent predictors of total As contamination level. This study illustrates the usefulness of multivariate statistical techniques for analysis and interpretation of complex environmental data sets.

Effects of cooling water discharges from a power plant on reservoir water quality

Abstract The use of natural or artificial water reservoirs by thermal power plants for cooling purposes alterswater ecosystems. Water ecosystems are mainly subjected to the abiotic influences of higher temperature and increased mixing. This study presents the thermal and oxygen conditions in a lake used for cooling water as well as the chemical changes occurring in it. There is a spatial differentiation in the temperature of the water surface over time periods (in summer and winter). The vertical water temperature changes were definitely different from those of natural, unaffected lakes. Apart from a higher average water temperature, typical mixing and stratification periods were not observed. This apparently affected the dissolved oxygen conditions. The observed absence of a dissolved oxygen deficit resulted from the lack of a thermocline, which positively affected water quality. As a result, the two anthropogenic factors, i.e., the discharge of warm water and increased mixing, have flattened the negative effects on the lake. A new characteristic equilibrium for this lake was established. Single factors have been compensated for by this equilibrium. A relationship between temperature and biomass concentration was observed. The trophic state index (TSI) values permit classifying Rybnik Reservoir as a eutrophic lake.

Lead Partitioning in the Bottom Sediment of Rybnik Reservoir (Southern Poland)

Total concentration of lead and its individual partitioning, i.e. exchangeable, adsorbed, organically bound, carbonate, sulfide and residual have been assayed in the bottom sediment of Rybnik reservoir applying AAS. The contribution of particular fractions to the total lead concentration was as follows: carbonates (37%) > sulfides (28%) > residual (14%) > adsorbed (10%) > exchangeable (8%) > organic bonds (3%). The multiple regression analysis applied led to the conclusion that the increase in lead content in the bottom sediment resulted from an increase in poorly mobile forms, notably carbonates.

Application of principal component analysis for the estimation of source of heavy metal contamination in surface sediments from the Rybnik Reservoir

The concentrations of metals, loss of ignition and nutrient (N, P) were determined in the bottom sediments of the Rybnik Reservoir (southern Poland). The mean concentrations of the metals in the bottom sediments were: Cd 25.8 μg/g, Cu 451.7 μg/g, Zn 1583.4 μg/g, Ni 71.1 μg/g, Pb 118.6 μg/g, Cr 129.8 μg/g, Fe 38 782 μg/g and Mn 2018.7 μg/g. The bottom sediments are very heavily loaded with zinc, manganese, copper, nickel, phosphorus and lead (percentage enrichment factor), and cadmium, phosphorus and zinc (index of geoaccumulation). The increase of cadmium, lead, nickel and zinc concentrations was connected with the inflow of the contaminated water of the river Ruda and long-range transport. The contamination of the reservoir with copper and manganese resulted mainly from atmospheric precipitation. The variability of the bottom sediment loading with metals during the investigations was affected in the first place by changes in the concentration of iron, but also those elements whose concentrations in the bottom sediment were elevated compared to the concentrations in shale––cadmium, nickel and lead.

Speciation of Cadmium in the Bottom Sediment of Rybnik Reservoir

Forms of cadmium occurrence in the bottom sediment of a heated water reservoir, polluted substantially with this metal was analysed in the paper. Apart from the analysis mentioned above, a total cadmium content in the bottom sediment and a content of cadmium dissolved in the water of the reservoir was also determined. Dependences between particular forms of cadmium occurrence and its total content in the bottom sediment were analysed. An influence of cadmium content in water on the level of particular cadmium forms in the bottom sediment and an influence of other parameters of the reservoir's water on the content of cadmium in the bottom sediment were also examined.

Use of Enrichment, and Contamination Factors Together with Geoaccumulation Indexes to Evaluate the Content of Cd, Cu, and Ni in the Rybnik Water Reservoir in Poland

In this paper, the contamination degree of the Rybnik Reservoir with cadmium, copper and nickel was analyzed. Quality of the water from the reservoir was determined by drawing comparisons between the metal content in the water and both the officially permitted levels (contamination factor) and levels of metals occurring in the water of non-contaminated areas (enrichment factor). Contamination of bottom sediment with chosen metals was analyzed with reference to the metal content in mudstone (geoaccumulation index, enrichment factor, contamination factor). Trends towards changing the metal content in the bottom sediment was analyzed by determining the enrichment factor of the surface layer of the bottom sediments in relation to a deeper layer. Enrichment of the bottom sediments with metals coming from the water was also determined.

Influence of temperature on morphological variation in populations of Keratella cochlearis (Gosse) in Rybnik Reservoir

Influence of temperature on morphological variation in populations of Keratella cochlearis (Gosse) in Rybnik Reservoir