Concentration of heavy metals in tissues of golden gray mullet (Liza aurata) in different areas of the southern coast of the Caspian Sea

Heavy metal pollution of water is one of the most serious environmental problems in the world and the Caspian Sea, the largest lake in the world, is exposed to high levels of industrial, agricultural and oil pollutants. Fish species are the ultimate consumer in the food pyramid in aquatic ecosystems. Since the fish form a large part of the human diet, heavy metals enter the human body through contaminated fish. This study was conducted to measure the concentration of five heavy metals, including lead, cadmium, mercury, arsenic, and chrome in the edible tissues (muscle) and non-edible tissue (liver and gill) of the gray mullet, Liza aurata and its seasons and living environment in the southern coast of the Caspian Sea. and also to compare their amounts with World Health Organization, Australian National Health and Medical Research Council, Food and Drug Administration standards. A total of 100 adult golden gray mullet were caught from 10 sites (Including Astara, Talesh, Anzali, Rudsar, Tonekabon, Nowshahr, Fereydunkenar, Behshahr, Bandar-e Torkaman and Hojanepes) in various coastal areas near inflows of urban, agricultural and industrial waste water and along the waterfront and fishing areas. After biometry, metals were extracted from the tissue using a mixture of acid digestion and determination was conducted by graphite furnace atomic absorption system. The results showed that the metal accumulation in tissue was different and significant, the concentration of the metals in the three tissues was as follows: liver>gill>muscle. Heavy metals choose their target organ based on its metabolic activity and this explains the reason why more metals accumulate in tissues such as the liver and gills compared to muscle tissue (with low metabolic activity). Liver tissue tends to be high in accumulation of heavy metals. The high concentration of metals in the context of the gills, is the first sign of contamination in the water. Mixing elements with gill mucus, full transposition of the lamella gill elements when preparing tissue for testing impossible to screw???. Metal concentrations in muscle are lower than those in liver because muscle is not the first storage place for these metals; heavy metals are first stored in the liver and then transferred to the muscle. Metal accumulation was as Pb> Cd> Cr> Hg> As. The study of heavy metals between stations, in muscle tissue was significantly different. This may be due to differences in pollutant sources in sampling areas. The accumulation of heavy metals increases from the southwest to the southeast coast. According to the Pearson test, there was the significant negative linear relationship between the Pb, Cd and As accumulation tissues by weight. Except for arsenic, there was no significant correlation between the metals with any total length. Moreover, there was a positive relationship (p<0.01) between the Pb, cd, Hg and As concentrations, with the exception of Cr. comparison of the data obtained for muscle tissue with the global standard level (WHO /NHMRC) showed that the concentration of the heavy metals Pb, Cr, Cd, Hg was higher than the global standard level, except for As. The least metal absorption and accumulation is in the muscle of mullet that is a source of human nutrition, followed by aquatic to the above elements. Since the concentration of the heavy metals tested above was higher than the global standard, this reflects the increasing water pollution of the Caspian Sea