Anzali International wetland is located in the south coast of the Caspian Sea. Physicochemical analysis and zooplankton survey of the wetland were carried out on monthly basis for the period of one year from January 2012 to December 2013 at 9 different stations of Anzali wetland and its related channel to the Caspian Sea. Water temperature of the wetland followed more or less similar trend as that of air temperature. pH determined alkaline nature of the wetland ranging between 7.05 to 9.47, dissolved oxygen was recorded in the range of 3.36 mg/l to 10.51 mg/l while other parameters recorded were water temperature (10 to 23 C), Nitrate (0.48 to 4.36 mg/l), Total Phosphates (0.15 to 0.67 mg/l), Salinity (220 to 692 mg/l), Electrical Conductivity (235 to 1369 µs/cm), TDS (246 to 1971 mg/l), BOD (2 to 36 mg/l) and COD (4 to 74 mg/l). During study period, total 60 species of zooplankton were identified in four main groups such as Protozoa (22 sp.), Rotifera (29 sp.), Copepoda (5 sp.) and Cladocera (4 sp.). The highest numbers of zooplankton were recorded in summer months and lowest in winter which is the second rainy season of this area. The water body is receiving domestic discharge, agricultural run-off and industrial wastes leading to large amount of nutrient inputs to the ecosystem which indicates the eutrophic statue of the wetland. The aim of present study was to investigate the interrelationship between physicochemical factors and zooplankton population in context of their seasonal abundance.

Anzali International wetland is one of the most important places for various organisms such as fishes. Zooplankton are the first consumers in the ecosystem, and they are perfect food for the larvae of fishes. The present study conducted monthly during January 2012 to December 2013 in 9 different stations with zooplankton population and chemical characteristics analysis such as water temperature ranged from 10˚C -22˚C, pH determined alkaline nature of the wetland ranged from 7.05 to 9.47, dissolved oxygen was recorded in the range of 3.36 mg/l to 10.51 mg/l, nitrate was ranged between 0.48 -4.36 mg/l, total phosphates was between 0.15 -0.67 mg/l, salinity was recorded between 220 -692 mg/l, TDS was determined between 246 -1971 mg/l, BOD and COD was also recorded 2 -36 mg/l and 4 -74 mg/l respectively. Total 61 zooplankton species were found belonging to 4 groups: Protozoa (22 sp.), Rotatoria (29 sp.), Copepoda (5 sp.) and Cladocera (4 sp.). Rotatoria were found dominating other groups of zooplankton. Kruskal Wallis test showed that there was significant difference between density of zooplankton in different stations, months and seasons (P ≤ 0.05) and significant differences were found between densities of different zooplankton phylum (P ≤ 0.05). The water body is continuously receiving domestic discharge leading to large amount of nutrient inputs and high amount of phosphate and nitrate in the water body indicates that water is eutrophic in nature.