| Abstract: |
cultivations (Hayes, 1982).Egypt which is mainly an agricultural country has relied heavily on pesticides to control pests harmful mainly to cotton, maize, rice, wheat, beans and other Pesticides have been routinely used in the north Delta area of Nile River since 1968. Therefore, high levels of pesticides contamination have been observed in both irrigation and drainage water. Consequently, several major fish kills have occurred in recent years which have been traced to pesticides use. As well as, pollution of the aquatic environment with heavy metals has become a more serious concern during the recent years. The loading of metals resulting from industrial and agricultural discharges into our environment creates water pollution problems due to their toxic effect on aquatic biota. In addition, pesticides and heavy metals can be incorporated into food chains and concentrated by fish to a level that affects their physiological status and then fish production (El - Naggar et al., 1998; Haggag et al., 1999; Salah El - Deen et al., 1999; Zaghloul, 2000 and Zaghloul et al., 2000).Qarun Lake is a one large lake in Egypt; it is a model of a closed lake environment that is contaminated with agricultural wastes. The drainage water discharges into Qarun Lake, containing large amounts of pollutants. The risk of contamination of Qarun Lake is significant because Qarun Lake is often used for production fishes in it self and daring fish farming in this region (El-Fayoum, Egypt) and it had a profound effect on its funna and flora.So that, in this study, the author would studied water quality, pesticide residues and heavy metal levels in water collected from Qarun Lake. In addition, the bioaccumulation of pesticides and heavy metals in tilapia fish, Tilapia zilli, as a major fish species in Qarun Lake and their effects on physiological and biochemical status of fish were studied. The water and fish samples were collected from three locations (west, medium and east) of Qarun Lake at two seasons during October 2003 (after summer season) and April 2004 (after winter season). Moreover, the easily and no expensive methods to remediation using UV-rays and various pH were reported in the same study.From the results presented in this study, it could be concluded as follows:1. Water Quality Analysis:1.1. pH:The pH values of water Qarun Lake were ranged from 7.54 to 8.17 after the both seasons at different locations. The pH values of water that obtained in different locations after two seasons were in suitable range for fish growth.1.2. Conductivity of water:Conductivity of water of Qarun Lake was higher after summer than after winter in three locations. The conductivity was increased in lake water because the salinity of water was highly.1.3. Total hardness:Gradual decrease in the total hardness represented was observed after the two seasons at west, medium and east locations of Qarun Lake, respectively. Generally, the obtained levels of total hardness in lake were increased about limited range of fresh water. This increase is out of character for fish growth.1.4. Total alkalinity:Total alkalinity was 450, 462.5 and 425 mg / L as CaCO3 after summer at west, medium and east locations of Qarun Lake. After winter, it was 437.5, 450 and 462.5 mg / L in same locations respectively.1.5. Salinity:From the results in this study illustrated that, salinity in west, medium and east of Qarun Lake was 38.0, 37.0 and 33.0 after summer while, it was 38.0, 36.0 and 35 g / L (ppt) after winter, respectively. The optimum salinity for the growth and reproduction of most fresh water fish species is in range of 0.01 to 1 g / L (ppt).2. Residues Analysis:2.1. Monitoring pesticide residues:2.1.1. Pesticide residues in water:The obtained results can be concluded that, the two most pollutant pesticides were β-BHC and γ-BHC being most conspicuous at the east location after winter. Generally the contents with organochlorine pesticides were more spread in the different locations of the lake than organophosphorus pesticides as well as, organochlorine pesticides were more frequent than organophosphorus.Generally, the frequency of positive samples (F.P.S, %) of both surveyed pesticides were higher after summer than after winter .The west and medium locations of the lake have a very high level of the frequency of positive samples so that, these locations attained the most contaminated after summer by pesticide residues after water samples.2.1.2. Pesticide residues in fish muscles:The results obtained from fish muscles analysis (Tilapia zilli) show that, the highest pollution concentration was recorded for organophosphorus traizophos and disyston in the different locations of Qarun Lake. In addition, the data showed that, heptachlor pesticide was the most appear in different locations since their frequency of pesticide residues was 100%. Generally, organochlorine pesticide residues fluctuated in different locations and after two seasons.Generally, the frequency of positive samples (F.P.S %) was higher after summer than after winter. Moreover the frequency of positive samples of both organophosphorus and organochlorine pesticides were higher after summer than after winter.2.2. Monitoring of heavy metals:2.2.1. Heavy metals in water:Heavy metal levels in water were influenced by two factors (i.e. season and sampling location) as shown from the represented data. Also, the averages of heavy metals such as Cd, Cu, Fe, Pb and Zn in lake water after summer were relatively high concentrations against after winter.In addition, the presented data it could be noticed that, medium location contained higher concentrations of total heavy metals than those estimated for west location or east location.2.2.2. Heavy metals in fish muscles:The average levels of muscle heavy metals fluctuated according to location as found in our data. As well as, the most conspicuous fish muscle contaminated with heavy metals can be observed in the west location. This accumulation of heavy metals may be effect on meat quality.3. Biochemical and Physiological parameters:3.1. The influence of liver function and muscles analysis of fish:Generally, our results of the present study revealed that, AST and ALT in liver were increased while, ALP was decreased. In additional, T.P in liver was fluctuated. For the muscles of fish, AST, ALP and T.P were increased but ALT was fluctuated.3.2. Influence of antioxidant system in gills and liver fish:According to the presented data indicate the influence antioxidants system in gills and liver of fish Qarun Lake, GSH was elevated in gills while, in liver was depletion. Therefore, changes in GSSG levels in gills and liver of fish were increased in all locations after the experimental seasons. On the other hand, the GSH / GSSG ratio was decreased after two seasons, in gills and liver, generally.In addition, the activity of glutathione reductase (GR) in gills was decreased at all locations, also the same trend was observed in liver after winter. While, the activity of GR in liver increased after summer season at same locations. Generally, GST activity was elevated in gills and liver of fish collected from all locations of Qarun Lake after summer and after winter.3.3. The influence of acetylcholinesterase (AChE) activity in brain and liver of fish:Results in the present study showed that, inhibition of AChE in brain and liver of fish collected from three locations (west, medium and east) of Qarun Lake after two seasons (summer and winter) was observed.3.4. Influence of ATPase activity in gills and brain fish:Our results revealed that, the activity of Na+, K+ - ATPase in the gills and brain of fish, Tilapia zilli were inhibited significantly at all locations of Qarun Lake after experimental seasons.3.5. Influence of lipid peroxidation as malondialdehyde (MDA) in gills and liver fish:Our results reported that, MDA was raise in gills and liver of fish, Tilapia zilli collected from all locations in Qarun Lake after two seasons.3.6. Characteristics of fatty acids composition in muscles of fish:The percentage of palmatic acid (16:0) and stearic acid (18:0) in fish muscles were highest saturated fatty acids in all locations of Qarun Lake after two seasons as reported in the present data. In addition, after summer the same fatty acids were higher than in winter at all locations. The monounsaturated fatty acids palmitoleic acid (16:1) and oleic acid (18:1) were highest fatty acids, which represented in fish muscles in all locations after two seasons. In addition, after winter the same fatty acids were higher than after summer at all locations.As well as, the percentage of polyunsaturated fatty acids linolenic acid (18:3 n-3) and DHA (22:6 n-3) were higher than linoleic acid (18:2 n-6) in fish muscles at all locations of Qarun Lake. In addition, after summer the same fatty acids were higher than after winter at all locations.3.7. Characteristics of sodium dodocyl sulphate Polyacrylamide gel electrophoresis (SDS- PAGE) of fish muscle proteins:Data presented in this study summarized the influence of the eletrophoretic patterns of muscle proteins of fish, Tilapia zilli, collected from different locations Qarun Lake after two seasons. The data revealed that, the protein subunits at molecular masses 104, 97, 41, 37, 20 and 15 K.D. appeared in the control sample and disappeared in samples which collected from all locations (west, medium and east) after two seasons (summer and winter). In addition, the samples in same locations after two seasons found some new bands at molecular masses 38 and 21 K.D. As well as, the percentage of muscle protein subunits at molecular masses 27 and 14 K.D. was increased in all samples, which collected from different locations of Qarun Lake after two seasons (summer and winter). On the other hand, the total numbers of protein bands in different locations of Qarun Lake were decreased compared with control sample.From the results, it can be concluded that the eletrophoretic patterns of, Tilapia zilli, muscle proteins depending on the locations and seasons of samples.3.8. Effect of pollutants on histological structure of internal organs of fish:The histopathological studies at examination fish samples Tilapia zilli collected from three locations (west, medium and east) of Qarun Lake were observed in gills, liver and brain at two seasons.The most remarkable cellular change in gills of the fish collected from Qarun Lake were hemorrhages in the branchial tissue and marked telangiectasis were noticed at medium location after summer and after winter, respectively. In addition, lamellae oedema, mononuclear cells infiltration, lamellar fusion, and hyperplasia and mucus cells activation at east location after winter.Also, the main histological lesions that observed in the liver of the fish collected from the west location were characterized by hepatic degeneration and golden-brown pigments deposition in the hepatocytes after summer while, the vacuolar degeneration of the hepatocytes and hemorrhage were showed after winter. As well as, in the medium location after winter, the hepatic lesions (degeneration and pancreatic necrosis) were observed. The degeneration and pancreatic necrosis could indicate possible series damage of liver structure.For the histological lesions of brain, the intracellular oedema and congestion of the blood capillaries were showed in the west location after winter.The histopathological lesions could be concluded that, the gills of collected fish samples from medium and east locations of Qarun Lake after both seasons had more severe changes. Also, the changes in the liver of fish collected from west location after two seasons were markedly clear than medium location. In addition at the west location of Qarun Lake after winter, more severe changes were noticed in the brain fish.4. Remediation:As respects the remediation methods for a one pesticide that found in lake at highest concentrations in water and fish samples, our results illustrated that,4.1. Effect of ultraviolet - ray on the tested pesticide (profenofos):The fate and behavior of micropollutants especially, of pesticides is of great concern. The different pathways of degradation in the aquatic environment must include photolysis. The percentage losses of profenofos under UV- wavelength (254 nm) after 1, 3, 6 and 24 hours was determined in this study. Our results illustrated that, profenofos concentration reduced with increased exposure time to UV-light. Generally, it is known that photodecomposition is positively correlated with the exposure period. Degradation time for 50 % (half-life, DT50) of profenofos was 5.53 hours under UV-light (245 nm) at room temperature.4.2. Effect of pH on the tested pesticide (profenofos):Our results in this experiment demonstrated the effect of pH (2.75, 6.8 and 8.75) on profenofos. The hydrolysis study was carried out in darkness at room temperature for 1, 3, 6 and 24 hours. Gradually increase in losses of profenofos in all tested pH with time was observed. The percentage of losses in alkaline pH was higher than both pHs (acidic and neutral) 24 hours. Degradation time for 50 % (half-life, DT50) of profenofos was 6.44 hours in alkaline pH at room temperature.*Conclusion: -From our results and the previous investigations, we could be summarized the main factors accounted for the decline of fisheries in Qarun Lake as follow:1 - Some predatory marine fish species were introduced into the lake leading to destroy the fry of fish.2- With time, the salinity and total hardness of lake started to increase owing to inflow of dissolved salts with the drainage water and high rate of evaporation, particularly during summer due to lowering of water level, resulting to many nests and egg masses are destroyed also affect the growth rate fishes in the lake.3 - The drainage water discharges into Qarun Lake, containing large amounts of pollutants such as pesticides, heavy metals and etc. Consequently, several major fish kills have occurred in recent years which have been traced to pollutants use. As well as, pollution of the Qarun Lake with these pollutants due to their toxic effect on aquatic biota. In addition, pesticides and heavy metals can be incorporated into food chains and concentrated by fish to a level that affects their physiological and biochemical status and then fish production, also these pollutants effect on meat quality.4- Also, these pollutants lead to depletion in foodstuffs (phytoplankton and zooplankton) for all fish which inhabiting Qarun Lake.5- On the other hand, fish of Qarun Lake exposure to a mixture of pesticide residues may cause risks exceeding those induced from exposure to residue of a single pesticide. This mixture of pollutants may be effect on fish reproductive causing retardation of development and decrease in fish production of Qarun Lake.In addition, this study reported that, there are different ecological factors such as UV-ray and media pH, especially alkaline pH, that play an important role in degradation of pollutants and then due to remediation of aquatic environments. Fortunately, the conditions of Qarun Lake (salinity, alkalinity and sun light) may be remedy it self. This automatically remediation not only decrease the concentration of pollutants in the Lake but also it may be resulting more toxic metabolites than the parent compounds. This may be illustrating physiological and biochemical disruption of fish collected from Qarun Lake after winter although the concentrations of pesticides and heavy metals were decreased after this season.* Recommendations:-It is necessary to solve the problem of pollution and decline of fisheries in Qarun Lake, some suggestions may be recommended as following:-1- Doing national project by Ministry of Agriculture aimed to solve the problem of pollution, from our results and previous studies, for development of fisheries and doing permissible limits of pollutants in irrigation and drainage water to compare any pollutant level in water of lakes and fish farms that used irrigation and drainage water for mass rearing of fishes.2- Remediation of agricultural wastewater drainage before discharge into the Lake by building of remediation stations on two main drains.3- Preventing industrial and human discharges into Qarun Lake before remediation.4- Avoiding introduced of predator marine fish species into the lake with the fry of fish and doing survey annually to discard these predators.5- From our observations, we noticed that, the fishermen were illiterate and poor, so their children go out from education. We must be caring with economic and health status of fishermen to development of and nationality.
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