Evaluation Trophy Based on Carlsson Index (TSI) Case study: Permanent wetlands in Pol-e-dokhtar County

Determining the amount of trophy in aquatic ecosystems is important because increasing the availability of nutrients is affectings all levels of aquatic ecosystems as well as changes in species abundance, migration, reduce in biodiversity and changes in the structure and composition of communities. Therefore, there should be a proper method for determining the trophy state or production in the ecosystem. The current methods for determining the amount of trophy are based on three physical, chemical and biological parameters. Pole-dokhtar County has 11 wetlands with 8 permanent and 3 seasonal wetlands and is known as the wetland city of Iran. In this research to assess the trophic status of 8 permanent Pole-dokhtar wetlands, monthly sampling were conducted in summer and winter of 2017 and the Carlsson Trophy Index (TSI) was used for calculation of total phosphoric (TP) concentration and total nitrogen (TN). The results showed the Lfanhe wetland 1 was in yotrophic conditions, the Lfanhe wetland 2 was in acute mesotrophy and other wetlands were located in mild mesotrophic nutrition in the summer. In the winter, due to the reduction of air temperature and consequently the decrease of evaporation and the increase in the input of surface and underground waters to wetlands, all of wetlands were in the mild mesotrophic conditions. Based on the average annual Carlson index, the Lfanhe 1 and Lfanhe 2 wetlands were in mesotrophic conditions and 6 wetlands were in mild mesotrophic conditions. Valiasr Natural Park wetlands with annual mean 42.3 characterized by mesotrophic conditions and Tang Fani wetlands with annual mean 34.08 was in the low mosotrothic conditions. In the Pole-Dokhtar wetlands, the annual suspended sediment load and water turbidity have increased due to the large amounts of sediment accumulation in the area, which eventually leads to the development of aquatic plants in the water surface and accelerates utrification of wetlands.