The concern about the long-term effects of heavy metals as the environmental pollutants has been increased greatly. It is assumed that biological monitoring can be a satisfactory way to measure the level of heavy metals and their bioavailability. Because of difficulties of detecting biological effects in the habitats, it is more logical to measure the amount of pollutants in the organisms. It is stated that fish eating birds due to being located in high-trophy levels in ecosystems and being highly sensitive to toxic substances, are considered appropriate bio indicators for heavy metal pollutions. Therefore, to fulfill the requirements of the Survey phase of the ecotoxicological classification, a study was conducted to determine the level of Cd, Zn, Fe, Cu & Cr in the liver, kidney and pectoral muscle of great cormorant (Phalacrocorax carbo) in Anzali wetland in 2004.Statistical tests results indicate that concentration of Cd in adults' livers were significantly higher than the immature(?= 0/05), which can be related to their long term exposure to low concentrated Cd. Zn (?= 0/05) and Fe (?= 0/01) amounts in the females' muscle and Cr amounts in the males' kidneys were significantly higher(?= 0/01). Also, the mean concentration of Cd, Cr in all three organs was lower in comparison with global proposed levels for waterfowls. However, high level of Cr and Cd in some samples implies that those birds may be exposed to them in their habitat. Fe, Zn and Cu contents in some organs were higher than the suggested figures. Generally, different human activities around the wetland and also sewage discharge can be considered as the main source of pollution and they may be affective factors in increasing the metal contents. Therefore, finding the main sources of pollutants adjacent to the wetland is very important. The results of this study can be used in consistent monitoring of heavy metals in P.carbo in Anzali wetland.
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