Bioaccumulation of some heavy metals in some organs of Coptodon zilli fish in Old Aswan Reservoirs and Aswan River Nile

: This study was carried out in Aswan's old Reservoirs between the old Aswan Dam at the north and the High Dam at the south and the River Nile at the area of entrance of Aswan town. Eighty (80) live ( Coptodon zilli ) fish species were caught and randomly collected. Water samples were collected at a depth of 30 cm. There were not any abnormal clinical signs between examined fish. The concentration of cadmium (Cd) and lead (Pb) in the liver and kidney exceeded the maximum permissible limit (MPL) at all seasons with significant differences during different seasons. On the other hand, the results of Cd and lead (Pb) in the muscles were within the maximum permissible limit (MPL) during the different seasons except in autumn without significant differences between results. The concentrations of Cd and Pb in the River Nile and Old Reservoir exceeded permissible limits in winter and in summer. While in Autumn were within the permissible limits and less than permissible limits in Spring. All Bioaccumulation factor (BAF) values within the examined organs liver, kidney and muscles are of low concentration according to the WMPT.


1-Introduction
Heavy metal pollution that occurs naturally has limited concentrations, but the intense and diverse human activities have caused an increase in the concentration of incident accumulations (Yona et al. 2018, Yona et al. 2021. These backlogs create numerous and growing community health concerns (Ananthan, et al. 2006, Gupta et al. 2009, Arikibe and Prasad 2020) Toxic concentrations have been detected at common levels in aquatic environmental systems, which poses a grave threat to the public health of both humans and aquatic animals (Yona et al., 2021).
The main sources of dangerous on the aquatic environment including fishes is contamination by inorganic chemicals, that affecting state of health of fish (ECDG, 2002). Heavy metals such as cadmium consider the sources of pond pollution in the ponds, lakes and river systems resulting from industries, sewage and agricultural drains which mainly affected fish (Basha and Rani, 2003).
Fishes considered one of the most common bio indicators for environmental pollutants (Al-Busaidi et al., 2011), Entrance of heavy metals into fish occur through food, water, and sediments (Castro-González and Méndez-Armenta, 2008). There many factors play an important role in accumulation of heavy metals in fish as season, habitat and physiological conditions of fish (Kargin, 1996). Literatures by FAO/WHO (1989) indicate that geographical location play role in bioaccumulation of metal into fish.
Tilapia (Family Cichlid) is a freshwater fish and is considered the most commercially important, and the family Cichlid includes the most widespread fish species in Lake Nasser, Egypt (GAFRD, 2018).
The structural form of heavy metals is the main determinant of their toxicity. Their presence in the environment of fish, along with their solubility in water, increases the likelihood of fish absorbing them and the risk of their association with proteins and enzymes (Wayne and Ho, 1999). The waste resulting from the industry is the main source of lead metal, as the phosphate fertilizers that are used in the cultivation of various crops are the main source of cadmium (Mason, 2002). The River Nile in Aswan receives a lot of amounts of wastes as runoff due to presences of tourist's boats and industry wastes products while old Aswan Reservoirs appear as row area except presences of boats to Filla templates. The importance of this study comes from the real awareness of the health risks posed by heavy metals. This study aimed to determine the level of spoilage and accumulation (cadmium and lead) as samples of heavy metals in some fish organs. (kidney, liver, and muscles of Coptodon zilli fish in Old Aswan Reservoir and Aswan Nile at the north of Aswan town during the different four seasons. make a comparison of their concentration between two different localities throughout the four seasons.

Ethical approval
This study was carried out in the Aswan city and obtained the approval of the Animal Ethics Committee of the Faculty of Fish and Fisheries Technology on the protocol for conducting the research.

The Study Area
Aswan old Reservoirs which is the locality of Nile between the old Aswan Dam at north and the High Dam at south and Aswan River Nile at the area of entrance of Aswan town.

Fish and water samples.
Eighty (80) live (Coptodon zilli ) fish species were caught and randomly collected ) by trammel nets and bottom gill nets throughout the fourth seasons from November 2018 to August 2019 Tilapia fish (Coptodon zilli ) the samples collected were from commercial catches in two regions (Old Aswan Reservoir and Aswan River Nile). Water samples in the two experimental areas were collected at a depth of 30 cm below the surface simultaneously using a PVC vertical water sampler. The water samples were then transferred to the Fish Health and Diseases Laboratory in the Faculty . Samples weighing about 1 g were taken from muscles, kidneys and liver (wet weight) and the samples were washed with distilled water and packed in bags after weighing and then stored until chemical analysis of heavy metals at -18°C.

Clinical and postmortem examinations
All experimental fish were clinically examined following the euthanasia protocol by percussion stunning the brain to destroy it (AVMA (American Veterinary Medical Association), 2013). Internal and external pests were identified in aggregate (Issa, 2016, Nougat 2010).

Fish samples
Heavy metals cadmium and lead (Cd and Pb) concentrations in samples of Coptodon zilli fish organs (liver, kidney and muscles) were determined using Pye Unicum Atomic Absorption Spectrophotometer and Cd and Pb hollow cathode lamps and air-acetylene flame. Calibration was performed by analyzing five standard solutions and two reagent blank samples (Olaifa et al., 2004).

Water samples
Total metal nitric acid digestion method as well as atomic absorption spectrophotometer were used to estimate heavy metal concentrations of water (cadmium and lead) samples (PerkinElmer, A 800 analyzer) according to APHA (American Public Health Association) (2005).

2. Bioaccumulation factor
According to Ezzat et al. (2012) The bioaccumulation factor (BAF) of a specific pollutant was calculated by calculating the ratio between its concentration in a fish organ and its concentration as a water soluble substance. BAF = Pollutant concentration in fish musculature (mg/kg) Pollutant concentration in water (mg/l) The obtained values were compared with those of the Waste Minimization Prioritization Tool (WMPT), Where : score of 1 = low concern (BAF <250), score of 2 = medium concern (BAF from 250 to 1,000), and score of 3 = high concern (BAF exceeding 1,000) (McGeer et al., 2004).

Statistical analysis
With regard to the two different experimental sites, to assess the significant difference in the concentration of the different metals studied, one-way ANOVA was used, and a probability level of 0.05 or less was considered significant (Bailey, 1981). Standard errors were also estimated.

3-1 Results of clinical signs examination:
Results of clinical signs examination reviles that there are not any abnormal clinical signs between examined fish.

3-1-1 Seasonal variations of heavy metals precipitation:
Heavy metals accumulate in water bodies (rivers and lakes) from natural sources such as atmospheric sedimentation, erosion factors, hydrodynamic processes, leaching, and rock carving, as well as from intensive human activities, which are more dangerous and more deadly to the environment than natural polluted sources (Paul, 2017). Through the skin and gills or through feeding, heavy metals are transmitted to aquatic animals (Pulatsü and Topçu 2015) causing a state of nervous poisoning, decreased reproduction, severe imbalances in bio-blood chemistry and changes in tissues. Exposure of fish to heavy metal pollution is also considered a cause of immune system dysfunction and high blood sugar, also depletion in enzymatic activities (Kumari et al., 2017, Ali andKhan, 2019). In the current study there were significant differences in the concentration of lead and cadmium (Pb, and Cd) in the organs examined (liver, kidneys and muscles) of Coptodon zilli fish which were collected from Aswan River Nile and Old Aswan Reservoirs, We found that the concentration of cadmium (Cd) in liver and kidney exceeded the maximum permissible limit (MPL) according to international standards as shown in table (1) at all seasons, and the results of analysis of variance showed significant differences in metal during different seasons, autumn > summer > winter > Spring, except results in fish muscles which within maximum permissible limit (MPL) which agree with results of the muscles of T. nilotica from the High Dam Lake in Egypt . Kucuksegin et al. (2006) determined that the accumulation of heavy metals in the tissues of aquatic organisms is an indirect measure of the presence and availability of heavy metals in the water surface. According to this observation, it can be asserted that muscle tissue cannot be considered an organ characterized by the accumulation of cadmium. Also the concentration of cadmium in Aswan Old Reservoir which shown in table (2) in liver and kidney exceed the maximum permissible limit (MPL) at all seasons, with significant differences between results in liver at summer > autumn > spring > winter and in kidney results at summer > autumn, winter > spring. On the other hand the results of Cd in the muscles within the maximum permissible limit (MPL) during the different seasons except in autumn which is (0.06±0.08) according to E.O.S.Q.C. (2005) without significant differences between results.
Also we found that the concentration of lead (Pb) of Coptodon zilli in in Aswan River Nile which shown in table (3) in liver and kidney exceed the maximum permissible limit (MPL) at all seasons, with significant differences between results in liver at autumn > summer > winter > spring with significant differences and in kidney only exceed maximum permissible limit (MPL) according to FAO/WHO (1999) and EOS (1993) with variation during different seasons autumn > summer > spring > winter without significant differences between results and within maximum permissible limit according to EOS (1993), On the other hand the results of muscles samples within the maximum permissible limit (MPL) during the different seasons, without significant differences between results.  The concentration of lead (Pb) of Coptodon zilli in Aswan Old Reservoir. Which shown in table (4) in liver exceed the maximum permissible limit (MPL) according to international standards as at all seasons, with significant differences between results in liver at autumn > summer > spring> winter and in kidney mean results exceed permissible limit in FAO/WHO(1999) during all seasons except in winter while it consider within permissible limit according to EOS (1993) only exceed permissible limit according to E.O.S.Q.C. ( 2005) and WHO (1989) in summer , While the concentration within permissible limits in other seasons and in the results of muscles samples, without significant differences between results.

3-1-3 Heavy metals concentrations in water:-
Heavy metals are pollutants that are difficult to get rid of, as they remain in the environment for a long time, and they are not degradable, in addition to their impact extending to the next chain levels in the ecosystem (Maurya et al., 2016). Heavy metals are transferred from water to aquatic animals, benthic algae and plankton, and accumulate at varying levels in the internal organs. This accumulation depends on the osmosis of the organisms and animals. It can also be transmitted to humans and cause many diseases and the accumulation of toxins (Usmani et al., 2017). The concentrations of heavy metals in water are presented in Table ( The average concentration of Pb in the water samples of tow localities exceeded the permissible limits all seasons prescribed by EOS (1993), with variation of differences between different seasons.

3-2 Results of Bioaccumulation factor
Bioaccumulation factor (BAF) of fish organs showed that: All Bioaccumulation factor (BAF) values within the examined organs liver, kidney and muscles are of low concentration according to the WMPT.

Conclusions
The prevalence of two elements cadmium and lead was variable between the body organs liver, kidney and muscles during different 4 seasons liver is the target organs of accumulation of metals followed by kidney exceeding the permissible limit and muscles were less within two sampling sites (Aswan River Nile and Aswan Old Reservoir).
Bioaccumulation factor in different examined organs in a score of 1 (low concern) (BAF values <250), according (WMPT) scoring system.