Investigation of the trophic state of Anzali international wetland, using TSI

Determining of the wetland trophic condition is the first step at the qualitative assessment. High levels of nitrogen and phosphorus that come with pollutants are one of the major problems affecting on water resources quality. These materials, mainly the results of human activities, are entered to water through the wastewater of agriculture and industry. Eutrophication is one of the effects of increasing nutrients in the aquatic ecosystems that it is most serious environmental threat. Trophic state index (TSI) is a useful tool to ease the expression of water quality and determination of the trophy position, which is presented by Carlsson. Due to importance of Anzali wetland in the region ecosystem, in the present study different models of Carlson index were used to investigate the status of the wetlands Trophy in 2014. For this purpose, 10 stations (brag of Bandar Anzali, Sorkhankal, PirBazar, Siadarvishan, Nokhaleh, Hendkhaleh, East wetlands, output of East wetlands, Abkenar and Mahruzeh) were selected to measure parameters. The data analysis was performed using SPSS 18 software. Normalization and homogeneity of data variances were investigated using Kolmogorov –Smirnov and Leven tests. In order to evaluate differences between sampling stations and stages, one-way ANOVA analysis and Duncan test were performed.
Any change in phosphorus concentration of fresh water ecosystems can alter its trophic status (Carvalho and Kirika, 2003). Kleeberg and Dude (1977) also have pointed to the direct role of phosphorus in the eutrophication process. According to 54 percent portion of forest and grassland of the watershed wetlands, the most important external source of Anzali wetland enrichment is forest floor litter and humus that inter into the wetland by raining flows (Darvishsefat et al. 1999). In addition, domestic sewage and adjacent residential areas, food and animal wastewater that inter into rivers without purification have an important role in intensifying of eutrophication process in the Anzali wetland. Moreover, vastness of the wetland areas, diversity of human activities in the basin and consequently entrance of organic and inorganic maters in to the wetland are the main causes of intensifying eutrophication (Sakizadeh, 2003). In this case, the important sources of nutrients material are including: agricultural fertilizer and domestic sewage. Eutrophication condition extends in wetland due to high consumption of dissolved oxygen by animals in the water, at night. So, the amount of dissolved oxygen reduces significantly in the hours of darkness.
Kimball (1974) studied the first wetland condition in regard to plant growth in Anzali. Mirzajani et al. (2010) showed trophic status of wetland in the years 1992 to 2002. Based on Darvishsefat et al. (1999) research for the years 1991 to1995 in terms of chlorophyll a, Anzali Wetland appears at the end of mesotroph and transferring to trophic status and according to total phosphate is in trophic and goes toward hypertrophy(Darvishsefatet al. 1999). Nezami (1995) assessed Anzali wetland in trophic status, in case of bacterio-plankton.
Solis and Lenard (2009) research on the trophy of three lakes (Piaseczno, Rogóźno and Krasnein Poland) showed changes in Carlson value due to increased amounts of nitrogen and phosphate. A similar study (Ejankowski and Lenard, 2014) on the lake Czarne and Głębokie observed increasing amount of TSI. The results of variance analysis in Anzali indicated a significant difference (P