The Anzali wetland (37.28N – 49.25E) with less than 100 km2 surface area is located in the southwestern shores of the Caspian Sea in the Guilan province. The benthic macro-invertebrates were studied as a part of a main project titled study of aquatic communities variation in the Anzali wetland. The sampling was performed at the 10 stations with using a Van-Veen grab during 2014-2015. The results showed, 14 macro-invertebrates taxa were identified as Chironomidae (Insecta, Diptera) and Tubificidae (Annelida, Oligochaeta), they were dominated in the wetland. The maximum and minimum densities of macro-invertebrates were observed with 609±1119 and 93.32±27.92 n/m2 respectively at the stations 5 and 1. The silt-clay constitute more than 85 percentage of the wetland sediments with maximum of 93.2±27.92 percentage at the 2 station and minimum 72.21±27.92 at the 5 station. Kruskal Wallis non parametric test(sig. ≤0.05), revealed significant differences for all studied factors at stations while of %tom and grain size had no significant variation. The CCA analysis revealed no accordance of total organic matter (TOM ) and silt- clay percentage vectors with Tubificidae and total benthic frequencies, while Chironomidae frequency is in accordance. Intensifying eutrification process in the Anzali wetland has affected its biota as the benthic fauna are almost limited in to most tolerant taxa which reflect the day after day increasing pollution the Anzali wetland.

Iranian Fisheries Science Research Institute

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