Effect of Aluminum Concentration in Water on Its Toxicity and Bioaccumulation in Zooplankton (Chaoborus and Chironomus) and Carp (Cyprinus carpio L.) Roe.

An attempt to evaluate aluminum toxicity to living organisms was undertaken in the study. A laboratory experiment was conducted to determine aluminum bioaccumulation and toxicity in Chironomus and Chaoborus larvae and in Cyprinus carpio L. roe depending on aluminum concentration in water reflecting natural chemical composition. Water was examined for temperature, pH, electrical conductivity, dissolved oxygen, color, nitrate nitrogen, nitrite nitrogen, sulfates by spectrophotometric method; total hardness and chlorides by titration method; and calcium, magnesium, sodium by flame atomic absorption spectrometry, total aluminum by electrothermal atomic absorption spectrometry. Determination of aluminum levels in water, roe, and zooplankton was carried out after mineralization using electrothermal atomic absorption spectrometry. Aluminum bioaccumulation factor in roe was determined with respect to concentration in water. Moreover, acute toxicity (LC50) was calculated. In the roe experiment, aluminum concentration in water at the end of the experiment was 0.0635-0.1283 mgAl∙dm-3. The lowest values were noted for the control sample and the highest for water with 0.03 mgAl∙dm-3 aluminum content. The final aluminum level in roe was, like in water, the highest in roe treated with 0.03 mgAl∙dm-3 (18.95 mgAl∙kg-1), and the lowest in roe treated with 3.00 mgAl∙dm-3 (6.96 mgAl∙kg-1). Aluminum bioaccumulation in roe was the strongest in the control. Survival rate ranged from 2.00 to 97.00%, which shows higher sensitivity of roe to aluminum concentration. LC50 value for Chaoborus was 0.6464 mgAl⋅dm-3, and for Chironomus 0.2076 mgAl⋅dm-3 indicating that Chironomus is more sensitive to aluminum toxic effects. Concentration of 3.0 mgAl∙dm-3 caused the highest mortality. Aluminum in both species at each concentration reached the highest levels after one day (24 h), 254.58 mg⋅kg-1 for Chaoborus and 3107 mg⋅kg-1 for Chironomus. After another day, aluminum levels decreased. This demonstrated the differential accumulation of aluminum depending on the species, which predisposes Chironomus as a better indicator organism. This type of research is important from the point of view of aquaculture, which is a targeted activity with a high degree of economic importance, but is also important for aquatic organisms living in natural conditions. Fish reproduction takes place in both types of waters, so all these reservoirs regardless of their source of destination should be inspected.

Emergent (branched bur-reed-Sparganium erectum L.) and submergent (river water-crowfoot-Ranunculus fluitans Wimm., 1841) aquatic plants as metal biosorbents under varying water pH conditions in laboratory conditions.

A laboratory experiment was performed to find out the potential bioaccumulation of metals (Al, Cu, Cd, Ni, Pb, Fe, Mn) in aquatic plants acting as natural biosorbents in the environment depending on the variation of water pH. Two plants were selected for the study: branched bur-reed-Sparganium erectum L., as a representative of emergent plants; and river water-crowfoot-Ranunculus fluitans Wimm., 1841, as a representative of submergent plants. The bioaccumulation of metals in plants relative to water (BCFW) was determined, and the metal pollution index (MPI) was calculated. The metal content in water and plants before the experiment was arranged in the following series of increasing values: Cd = Ni < Cu < Pb < Mn < Al < Fe (water) and Cd < Cu < Ni < Pb < Al < Fe < Mn (in both plants). The lowest concentration of cadmium was found in water both at the end and beginning of the experiment. In turn, aluminum level increased, and its concentration was the highest in both acidic and alkaline water. This suggests that aluminum is definitely more available to the organisms living in it under such conditions, and in higher concentrations may be a limiting factor for them. Bioaccumulation of metals (BCFW) in neutral and alkaline environments was higher in branched bur-reed, and in acidic conditions in river water-crowfoot. This may provide a basis for using specific plant species to selectively accumulate metals depending on the range of water pH. This is also supported by the MPI values, which indicate that they have a very high and often the highest impact on metal pollution levels. The observed variability of metals bioaccumulation against the condition of hydromacrophytes makes it possible to consider these plants as biosorbents used in constructed biological treatment plants, which, depending on the species placed there, can selectively absorb particular trace elements. The plants used in the experiment are common hydromacrophytes of Europe, so they can be used in the construction of artificial wetlands across the continent. The apparent diversity of metal accumulation in relation to hydromacrophytes indicates that this type of site can be inhabited by specific species, which can significantly improve the purification of natural or anthropogenic water reservoirs, i.e., those that are intended to perform a filtering function.

The effect of nanosilver-based preparation on microbiological quality of poultry litter.

The study aimed to examine an effect of the preparation based on nanosilver suspension on mineral carrier on poultry litter microbiological profile. The study was conducted on Ross 308 broiler chickens. Three groups were formed, 84 birds in each. Preparation used in the study was composed of aqueous nanosilver suspension sprayed on mineral sorbent. Birds were maintained on straw-sawdust litter; the groups were differentiated due to preparation application (C - control without preparation, I - preparation applied once at the beginning, II - preparation added each week). Pooled litter samples were collected from the top layer of the litter (six samplings) in order to determine mesophilic bacteria count. Additionally, on the last day of the experiment litter samples were collected from three points (by drinker, feeder, pen corner) to analyze the total number of microorganisms, Salmonella spp., Escherichia coli, Enterococci, and molds. In the case of mesophilic bacteria count, the highest decrease was noted for group II. Total number of microorganisms determined in various points of the pen did not give clear relationship; in some cases even an increase was found. Salmonella spp. decreased as a result of preparation addition; the highest decrease was noted for samples collected by feeders. The results for Escherichia coli are not unequivocal. However, a decrease was found in the case of drinkers and feeders compared to control, especially in group II. An addition of preparation caused a decrease in Enterococci, especially for samples collected by feeders in group II. Similar tendency was found for molds. The study demonstrated that the preparation exhibits bactericidal properties. However, its effect varies depending on microorganism kind and sample collection point.

Total Mercury and Fatty Acids in Selected Fish Species on the Polish Market: A Risk to Human Health.

The muscles of lake trout (Salvelinus namaycush Walbaum, 1792), crucian carp (Carassius carassius Linnaeus, 1758), flounder (Platichthys flesus Linnaeus, 1758), gilthead seabream (Sparus aurata Linnaeus, 1758), mackerel (Scomber scombrus Linnaeus, 1758) and tench (Tinca tinca Linnaeus, 1758) were examined. The total mercury (THg) was processed using the Milestone DMA-80 and the fatty acids were analyzed using the 7890A Agilent Technologies chromatograph. The THg content in analyzed fish ranged from 0.024 (lake trout) to 0.092 mg/kg wet weight (gilthead seabream). The muscles of fish examined had lower amounts of SFAs, and n-3 and n-6 PUFAs than MUFAs. The ratio of n-3/n-6 was higher in muscles of mackerel than other fish (p < 0.05). Due to the fact that both the THQ and HI are below 1, the tested fish are safe for the consumer from a nutritional point of view. Similarly, fatty acid indices indicate the safe consumption of selected fish species, and the daily consumption of the recommended dose of EPA + DHA (250 mg/day) and the concentration of mercury in fish calculations showed a hazard quotient for the benefit−risk ratio HQEFA below 1, suggesting that the intake of EPA + DHA poses no evident risk to human health. The ratio was calculated for a person weighing 60 kg. Therefore, it is important to monitor the fish, not only bought in the store, but also caught in various aquatic environments.

The Effect of Copper and Copper Oxide Nanoparticles on Rainbow Trout (Oncorhynchus mykiss W.) Spermatozoa Motility after Incubation with Contaminants.

The study aimed to analyse the effect of copper nanoparticles of similar particle size of Cu and CuO and copper ions (CuSO4) on the motility parameters of rainbow trout spermatozoa after long-term exposure and compare its harmful effect. Nanoproducts of Cu and CuO (Cu NPs, CuO NPs) of primary particle size around 50 nm and ionic solution of CuSO4 were used for the study. Suspension of concentrations 0, 1, 5, 10, 25, and 50 mg Cu·L-1 of Cu NPs, CuO NPs, and CuSO4 was dissolved in an artificial seminal plasma. Milt was mixed with the prepared solution and stored in a fridge, at 6 °C, for 96 h. At the defined incubation time, spermatozoa were activated for movement, and six motility parameters were evaluated using an automated system (CASA). Increasing concentrations of Cu NPs, CuO NPs, and CuSO4 in an incubation medium in parallel decreased the percentage of motile sperm (MOT). The effect of Cu NPs and ionic copper on MOT was more deleterious than that of CuO NPs. Copper products slightly increased the velocity (VCL) compared to the control, particularly up to 24 h of storage. Linearity (LIN) was improved by three tested products, particularly CuO NPs. Generally, the motility duration was prolonged when the sperm was incubated with copper products compared to the control. Nanoproducts made from different compounds of the same elements of similar particle size have a different effect on cells. Cu NPs were more harmful than CuO NPs. The effect of Cu NPs was similar to an ionic form of CuSO4. When incubated, the copper nanoproducts and ionic form exert a slightly positive effect on spermatozoa velocity, linearity, and motility duration, particularly up to 24 h of storage.

Possibility of Metal Accumulation in Reed Canary Grass (Phalaris arundinacea L.) in the Aquatic Environment of South-Western Polish Rivers.

A four-year research study was conducted on aquatic plants (reed canary grass) growing in the beds of three rivers and their tributaries in Lower Silesia, Poland. Metal contents (Cu, Cd, Ni, Pb, Zn, Fe, Mn) were determined in plant samples, metal accumulation in water (BCFw) and sediment (BCFB), Metal Pollution Index (MPI) and Enrichment Factor (EF) were calculated. The highest contents of copper, lead, nickel and cadmium were found in reed canary grass sampled from the Nysa Szalona River. The highest values were recorded for zinc in the Bystrzyca River, and for iron and manganese in the Strzegomka River. The series of metals were as follows: Nysa Szalona and Strzegomka: Cd < Ni < Pb < Cu < Zn < Mn < Fe, Bystrzyca: Cd < Ni < Cu < Pb < Zn < Mn < Fe. Throughout the study period, the lowest values of metals in plants were recorded in 2015 and 2018, and the highest in 2017. The general picture of MPI in aquatic plants is arranged in the series Bystrzyca < Strzegomka < Nysa Szalona. These values classify the studied material at a high level of pollution in all rivers. In the comparison of the two extreme sites, i.e., source−mouth, higher values were found at the mouth of the reservoir, which suggests that metals move with the water current and accumulate more with the direction of the river flow, which is most likely a consequence of the influence of the catchment area as the source of metals. The series of EF enrichment factor values were as follows: Bystrzyca­Ni < Cd < Fe < Cu < Zn < Mn < Pb, Nysa Szalona­Ni < Fe < Zn < Cd < Mn < Cu < Pb, Strzegomka­Ni < Cd < Fe < Zn < Cu < Pb < Mn. For all the samples studied, the values found in spring were much higher than in autumn, which indicates the great importance for research in that area. The levels of copper and iron were within the range of moderate values, lead and manganese reached very high and exceptionally high values, and the remaining metals were within the values described as significant. Bioaccumulation of metals determined relative to bottom sediments was highest in 2017 and lowest in 2018, while bioaccumulation relative to water was highest in 2018 and lowest in 2016. The four-year study found that the metal content in reed canary grass was mostly within the range of mean values presented in the literature from moderately polluted areas. Also, no significant deviation was found from levels that have been recorded for the same rivers for more than two decades.

Aluminum Bioaccumulation in Reed Canary Grass (Phalaris arundinacea L.) from Rivers in Southwestern Poland.

This study aimed to determine aluminum levels in reed canary grass Phalaris arundinacea L.) in rivers in southwestern Poland­Bystrzyca, Strzegomka, and Nysa Szalona, together with their tributaries. The samples were collected in spring and autumn 2015−2018. The highest amounts of aluminum were recorded in the Nysa Szalona, and the lowest in the Bystrzyca. During the four-year cycle of studies, the highest values were recorded in the last year, and the lowest in the first year. The highest amounts of aluminum were found in all three rivers in the lowland tributaries. In the main rivers, higher amounts of aluminum were found at the mouth of the Nysa Szalona and Strzegomka reservoirs, while the opposite situation was found for the Bystrzyca. Higher aluminum contents were recorded in autumn than in spring, and the values of BCFW (aluminum bioaccumulation factor in relation to water) and BCFB (aluminum bioaccumulation factor in relation to bottom sediments) coefficients were also higher. The MPI (metal pollution index) was arranged in a series: Bystrzyca < Strzegomka < Nysa Szalona, while the degree of pollution was high for Bystrzyca and very high for the other two rivers. The variability in Al levels may be attributed to pollution level in the catchments, but also to successive modernization works carried out in the beds of the main rivers and their tributaries. All these works were carried out in a variable way and often covered only a fragment of the riverbed; therefore, the consequences of activity may have been visible in the catchment but not necessarily in the same vegetation cycles.

Safer plant-based nanoparticles for combating antibiotic resistance in bacteria: A comprehensive review on its potential applications, recent advances, and future perspective.

BACKGROUND: Antibiotic resistance is one of the current threats to human health, forcing the use of drugs that are more noxious, costlier, and with low efficiency. There are several causes behind antibiotic resistance, including over-prescription of antibiotics in both humans and livestock. In this scenario, researchers are shifting to new alternatives to fight back this concerning situation. SCOPE AND APPROACH: Nanoparticles have emerged as new tools that can be used to combat deadly bacterial infections directly or indirectly to overcome antibiotic resistance. Although nanoparticles are being used in the pharmaceutical industry, there is a constant concern about their toxicity toward human health because of the involvement of well-known toxic chemicals (i.e., sodium/potassium borohydride) making their use very risky for eukaryotic cells. KEY FINDINGS AND CONCLUSIONS: Multiple nanoparticle-based approaches to counter bacterial infections, providing crucial insight into the design of elements that play critical roles in the creation of antimicrobial nanotherapeutic drugs, are currently underway. In this context, plant-based nanoparticles will be less toxic than many other forms, which constitute promising candidates to avoid widespread damage to the microbiome associated with current practices. This article aims to review the actual knowledge on plant-based nanoparticle products for antibiotic resistance and the possible replacement of antibiotics to treat multidrug-resistant bacterial infections.

Aluminum in Bottom Sediments of the Lower Silesian Rivers Supplying Dam Reservoirs vs. Selected Chemical Parameters.

The study was carried out on sediments collected from three rivers: Nysa Szalona, Strzegomka and Bystrzyca flowing in southwestern Poland. The content of Al in sediments and in bottom water was determined in relation to chemical conditions. The study was carried out in a four-year cycle, during spring and autumn. The aim of the study was to determine the level and accumulation of aluminum in sediments of rivers supplying dam reservoirs storing water for consumption. The sediments studied were mineral in nature, with neutral pH and moderate sulfate content. The level of Al and heavy metals in the sediments was the highest in the Nysa Szalona River and the lowest in the Strzegomka River, which was also evident in the concentration factor (CF). In terms of season, higher Al contents were recorded in sediments in autumn than in spring, which was also reflected in the concentration factor (CF). Along the course of the river, a gradual decrease in Al levels was observed in successive tributaries in the Nysa Szalona and Strzegomka Rivers, while there was no apparent regularity for the Bystrzyca. Against this background, a comparison of extreme sites below the springs and at the reservoir outlet shows that values were higher in the Nysa Szalona below the springs, and lower in the Strzegomka and Bystrzyca below the reservoir outlet. The general picture of Al and heavy metal loading of the studied sediments shows the lowest loading for the Strzegomka, only the enrichment factor (EF) was the lowest for the Nysa Szalona: metal pollution index (MPI)-S < B < NS, contamination factor (Cf)-S < B < NS, degree of contamination (DC)-S < NS < B, EF-NS < B < S, geoaccumulation index (Igeo)-S < B < NS, CF-S < NS < B. There was no effect of catchment size and river length on Al levels in sediments.

Survival of Embryos and Fry of Sea Trout (Salmo trutta m. trutta) Growing from Eggs Exposed to Different Concentrations of Selenium during Egg Swelling.

Adequate selenium (Se) availability enhances the health and growth of organisms, but overdose of it can be harmful and pathogenic. The study's objective was to analyse the impact of short-term exposure of sea trout fertilised eggs to inorganic selenium (SeO2) at concentrations from 0 to 32 mg Se L-1 to find the optimal and toxic dose of Se on early fish development. Se accumulated in the body, embryos' survival rate, and growth in the first four months of life was examined. Swelling of fertilised eggs in water supplemented with Se at a concentration from 0.5 to 8 mg Se L-1 was associated with a slightly positive impact on the hatching rate. At higher Se concentration, a harmful effect on the survival of the embryo was observed. The survival of fry was similar in all groups, while the fry length and weight correlated positively with Se concentration in its body. Immersion of fertilised eggs in water enriched with Se during egg swelling can constitute a method to supplement the element to non-feeding stages of fish. In selenium-poor areas, this innovative method can be implemented in aquaculture to improve breeding outcomes. Se concentration should be adjusted to the chemical compound, fish species, and Se's content in the yolk.

Using Rutilus rutilus (L.) and Perca fluviatilis (L.) as Bioindicators of the Environmental Condition and Human Health: Lake Lanskie, Poland.

The aim of this study was to determine the mercury content and fatty acids profile in roach (Rutilus rutilus L.) and European perch (Perca fluviatilis L.) from Lake Lanskie (Poland). Mercury content was higher in the muscles than other organs in both species (p < 0.05). Mercury accumulates along the food chain of the lake's ecosystem. The value of the bioconcentration factor (BCF) indicated that Hg had accumulated in the highest amounts in muscles and in the other organs as follows: muscles > liver > gills > gonads. The metal pollution index (MPI) and target hazard quotient (THQ) were below 1, which means that these fish are safe for consumers. The values of HIS, GSI and FCF indicators show that both species of fish can be good indicators of water quality and food contamination. There were few differences between fatty acid content in the muscles of perch and roach. Contents of fatty acids having an undesirable dietary effect in humans (OFA-hypercholesterolemic fatty acids) were lower compared to hypocholesterolemic fatty acids (DFA, i.e., the desirable ones). In addition, the lipid quality indices AI and TI in the muscles of fish were at 0.40 and 0.22 (perch) and at 0.35 and 0.22 (roach), respectively. On this basis, it can be concluded that the flesh of the fish studied is beneficial from the health point of view.

Effects of the Ionic and Nanoparticle Forms of Cu and Ag on These Metals' Bioaccumulation in the Eggs and Fry of Rainbow Trout (Oncorhynchus mykiss W.).

Nanotechnology is a rapidly growing field of science, and an increasing number of nanoproducts, including nanometals, can be found on the market. Various nanometals and the products that are manufactured based on them can help to fight bacteria and fungi, but they can also penetrate organisms and accumulate in them. This study aimed to compare the effects of two metals, silver (Ag) and copper (Cu), with known antibacterial and fungicidal properties in their ionic (AgNO3, CuSO4·5H2O) and nanoparticle (AgNPs, CuNPs) forms on rainbow trout eggs and fry. Concentrations of metals ranging from 0 to 16 mg/L were used during egg swelling for 2 h. The swelling of eggs in Cu solutions resulted in an increase in Cu content in the eggs (just like in the case of Ag); however, the changes in fry were not significant in the case of both Ag and Cu. The concentrations of these metals in eggs was greatly affected by the applied form of Ag and Cu. Because CuNPs penetrated the embryo in fish eggs at lower concentrations compared to AgNPs, it would be worth considering them for antibacterial applications during egg incubation.

The Influence of Available Cu and Au Nanoparticles (NPs) on the Survival of Water Fleas (Daphnia pulex).

Applications of nanotechnologies in different sectors and everyday items are very promising and their popularity continues to grow. The number of products containing nanoparticles makes environmental exposure to nanoparticles inevitable. The current understanding of the relationships between nanoparticles and the environment is inadequate despite the fast growth of nanotechnologies. The aim of the study was to investigate the influence of copper and gold nanoparticles on Daphnia pulex survival. Our study included 48-hour acute toxicity tests and determination of median lethal concentration values (LC50s) for Cu-NPs and Au-NPs. For nano-copper, 24 h LC50 was assumed > 1 mg/L, and 48 h LC50 = 0.5117 mg/L. For nano-gold the LC50 value after 24 h was 0.4027 mg/L, and after 48 h 0.1007 mg/L. The toxicity of nano -gold solutions was thus found to be higher than that of nano-copper. The addition of Cu-NPs at 0.0625 mg/L and 0.125 mg/L caused an increased multiplication of daphnia, while Au-NPs at 1 mg/L was an inhibitor of reproduction.

Effect of copper nanoparticles and ions on spermatozoa motility of sea trout (Salmo trutta m. Trutta L.).

Nanoproducts are being increasingly used in various industrial products, leading to a greater risk of water pollution through their discharge into environment as production byproducts. Increased levels of environmental pollution with nanoproducts pose a threat to all living organisms. Nanopollutants may have toxic effects on gametes and fertilization process in species with external fertilization, thereby reducing effectiveness of reproduction or greatly impairing it. The objective of the present study was to determine the effect of copper nanoparticles (Cu and CuO) and copper ions (CuSO4·5H2O) on the spermatozoa motility of sea trout and compare their harmful effects. Copper nanoparticles (NPs) of primary particle size <100 nm and CuO NPs of particle size <50 nm as well as a solution of CuSO4·5H2O were used for the study. Concentration of the products tested (CuNPs, CuONPs, and CuSO4·5H2O) was expressed as mg Cu L-1 in the media regardless of dissolution and aggregation. A suspension with concentration up to 500 mg L-1 in an aquatic environment was tested. Spermatozoa motility under direct contact with copper at 10 s post activation was evaluated using an automated system (CASA). Copper products in an aqueous environment primarily cause a reduction of spermatozoa velocity (VCL). A significant reduction of velocity in CuSO4·5H2O salt solution occurred at concentration starting from 8 mg L-1, whereas in solutions containing CuNPs and CuONPs this process is observed from 50 mg L-1. Reduction of percentage of motile spermatozoa occurred in CuNPs from a concentration of 125 mg L-1, while in CuONPs and CuSO4·5H2O, the effect began at concentration from 250 mg L-1. In a solution of CuSO4·5H2O at a concentration of 500 mg L-1, strong agglutination of sperm cells occurred and movement ceased (immobilization IC100). Exposure to CuONPs decreased the motility rate to below IC50, while for CuNPs, the motility rate reached 80%. Changes in linearity (LIN) and amplitude of head displacement (ALH) differed according to Cu products. Cu as CuSO4·5H2O and CuONPs impaired the LIN, while CuNPs lowered ALH. Duration of motility increased at low CuSO4·5H2O concentration. The effect of Cu ion on sea trout spermatozoa motility was more harmful than that of copper nanoparticles. The various copper products used affected motility parameters differently. Contamination of aqueous environment with copper primarily caused reduction in male gamete velocity, which may impair reproduction. Various copper products had different effects on LIN, ALH, and motility duration, which can also affect fertilization.

The Impact of Land Use Transformations on Zooplankton Communities in a Small Mountain River (The Corgo River, Northern Portugal).

Transformation of the river catchment and the river bed cause significant changes in the functioning of river ecosystems. The main effects of anthropogenic transformations are hydrological changes, such as lower current velocity or an increase of nutrient content, and higher temperature. Zooplankton reacts rapidly to the new environmental conditions in rivers, increasing its richness and abundance. We tried to answer two questions: what type of catchment use has a greater influence on the zooplankton communities in a river and how do dam impoundments influence the zooplankton communities downstream? The study was conducted in the Corgo river (drainage of the Douro river, Northern Portugal) at 17 sampling sites in the lotic, free-flowing sections. Crustaceans present in the Corgo can attain relatively high densities in the rural section, which offers them better trophic conditions. The urban catchment use and the presence of dams have a greater impact on the rotifer density and the increase of zooplankton density downstream. The results of this study confirm that zooplankton properties allow for the evaluation of the degree of river-bed transformation.

Spatial changes in zooplankton communities in a strong human-mediated river ecosystem.

River damming causes a decrease in water current velocity which leads to an increase in richness and abundance of organisms atypical for running waters. Zooplankton is a representative example of such organisms. The influx of zooplankton from carp ponds is an additional factor that increases richness and abundance of zooplankton in rivers. We hypothesized that zooplankton dispersing from the carp ponds colonize the impoundments in river and the richness of zooplankton increase in impoundments by development of new species, not observed in the upstream. The zooplankton was collected monthly from April to September of 2013 and 2014. Sampling sites were located in the Barycz river (in the lotic sections and in the dam impoundments), as well as in its tributaries, which are the outlets of carp ponds. The most changes in zooplankton richness and abundance were observed at sites located within the dam impoundments, especially in relation to the lower values of the current velocity. Since the abundance of pelagic rotifers, cladocerans and copepods in the carp pond outlets was similar to that at lower sites in the Barycz, the influence of the carp pond outlets on the abundance in the dam and lotic sections was significant. The river itself in its impounded sections provides advantageous conditions for retention and colonization by a high abundance of zooplankton dispersing from the carp ponds, and for the development of species not occurred in the upstream, which, in turn, increases richness.

Diurnal Changes of Zooplankton Community Reduction Rate at Lake Outlets and Related Environmental Factors.

The reduced zooplankton abundance at the outlet sections of lakes depends on the occurrence of preying fry. Therefore, light conditions can play a major role in the drift of zooplankton along river outlets. The aim of this study was to determine the influence of diurnal light conditions on the decline of zooplankton densities at lake outlets. Photosynthetically active radiation (PAR) levels were measured to determine their effect on the rate of reduced zooplankton abundance. Cladocerans and copepods showed a significantly greater reduction in abundance than rotifers and nauplii. A significant positive relationship was observed between the PAR levels and the reduced abundance of Asplanchna sp., small cladocerans, large cladocerans and Copepoda at the lake outlets. Among the rotifers, small pelagic rotifers drifted the farthest at all hours of the day. Large crustaceans, especially the large cladocerans and copepodites and adult copepods, had the lowest chance of dispersing over a wide area. Our results indicate that light conditions play an important role in the reduction of zooplankton abundance at lake outlets and have an indirect influence on the downstream food web.