Assessment of Gahar Lake Trophic Status using TLI Index

Gahar Lake is an unique high-mountain lake, "Paternoster" form with glacial origin. There isn’t any research on the ecology of the lake, so in order to assess trophic status of small and great Gahar lake for the first time using TLI, the present study was conducted during a period of 1 year (except 3 months of ice period) from May 1389 to May 1390. Trophical parameters, Secchi depth (SD, transparency), chlorophyll a concentration and nutrients including Total Nitrates (TN) and Total Phosphorus (TP) was sampled monthly and zooplankton assemblage was measured. For statistical analysis of data in this study, we used the SPSS and Excel softwares. Based on the study of small Gahar lake, mean concentration of chlorophyll was 2.96µg.l-1, TN 801µg.l-1 and TP 25.3µg.l-1. In great Gahar lake, mean concentration of chlorophyll was 1.6µg.l-1, TN 976.5µg.l-1, TP 24.2µg.l-1 and mean value of secchi depth was 6.8m. According to TLI, the great Gahar Lake belongs to status of Mesotrophic level and the small Gahar Lake to Eutrophic level of the trophic scale.