Eutrophication Trend of the Caspian Sea Water Based on Absolute Trophic Scaled (TRIXCS) and Unscaled (UNTRIX)

This study was conducted to assess the trophic status based on scaled trophic state index (TRIXCS) and unscaled trophic index (UNTRIX) in the southern of Caspian Sea. The results showed that TRIXCS and UNTRIX values fall in the range from about 4.69 to 5.58 (Meso-eutrophic) and 3.58 to 4.16 (No and high eutrophication risk) at different seasons, respectively. As a conclusion, the trophic index of Caspian Sea (TRIXCS) which evaluated for long-term trend was suitable and potential for classification of trophic status of Caspian Sea. The UNTRIX and TQRTRIX-based trophic classification is in good agreement with TRIXCS for summer and winter respectively, however, there is no agreement regarding annual classification. Therefore, this alternative method will be able to apply for short-term trend with taking into account ecological events and other indices in the southern Caspian Sea.