Estimation of field biotic index and water quality of lake of Doroodzan dam using aquatic insects fauna

Benthic macroinvertebrate species are differentially sensitive to many biotic and abiotic factors in their environment. The field biotic index is based on family level identification of water arthropods، amphipods and isopods. An interest in environmental quality is one of the major reasons for the study of aquatic insects. The idea of using the aquatic insect community to “indicate” the degree of purity or pollution of a body of water is over half a century old. It is based on the concept of indicator organisms and tolerance levels. During 2010-2011 studies were carried out on the field biotic index of lake of Doroodzan dam in Fars province using aquatic insects fauna. A total of 23 families were collected and identified in 12 habitat codes of the lake. Aquatic insects are given a numerical pollution tolerance score ranging from 0 to 10. The value is based on field and laboratory responses of these organisms toward organic pollution. Zero taxa are extremelyintolerant to low dissolved oxygen; taxa with score of 2 through 9 are tolerant to varying degrees; taxa which can survive great amounts of pollution are scored 10. In this survey، biotic index of lake of Doroodzan dam was 3. 92 which places in the rank of very good during this survey.