Short communication: Study on bioaccumulation of heavy metals (cadmium, nickel, zinc and lead) in the muscle of wels catfish (Silurus glanis) in the Anzali Wetland

After entering aquatic ecosystems, heavy metals accumulate in the organs and tissues of aquatics including fish and finally enter the food chain. These heavy metals can enter the human body through eating contaminated fish. Absorbance values and accumulation of heavy metals in aquatics especially the fish depend on ecological conditions, physical, chemical and biological factors of water, the element type, and the physiological state of the aquatic (Oryan et al., 2010). Among aquatic ecosystems, wetlands and rivers are considerably important from the point of ecology. Rivers act as carriers of nutrients and non–nutrients and wetlands act as sinks for these substances. Now this effect will be more apparent if the wetland is an intermediary between a river and a static ecosystem. The Anzali Wetland is the type of ecosystem that embraces water from 11 rivers from one side and passes water into the Caspian Sea through a second outlet on the other side. The rivers passing through urban and rural areas and forests carry different types of organic matter, minerals, sediment, and industrial sewage (Taheri, 2013). The Anzali Wetland is one of the valuable wetlands registered in the Ramsar International Convention the contamination of which has become the main challenge for the people and officials during the past two decades (Khosravi, 2011)