Seasonal Changes in Crustacean Mesozooplankton Biomass and its Relationship with Physicochemical Parameters of Water in Hanna Wetland, Isfahan Province

Zooplankton are important wetland organisms that their abundance and distribution are influenced by different physicochemical and biological factors. In this research, the relationship between biomass and abundance of zooplankton with the most important physicochemical water parameters (from summer 2007 to spring 2008) in Hanna Wetland located in eastern part of Isfahan province, were studied. The sampling from three sites in the Hanna Wetland was carried out by vertical haul using a plankton net (140 μm, diameter of 25 cm) in the mid-season for one year. Results showed that the zooplankton biomass and abundance significantly varied in different seasons (P<0.05). The zooplankton biomass in the spring, summer, autumn and winter was estimated to be 26.0, 8.6, 20.9 and 6.2 mg/m3, respectively while the abundance was 99.9, 54.1, 23.9 and 149.6 individuals/L, respectively. Physicochemical water parameters showed significant differences in different seasons (P<0.05). Water temperature, dissolved oxygen, pH, depth of Secchi disk, nitrate and phosphate concentration ranged from 5.3 to 20.7 C◦, 7.5 to 9.7ppm, 8.07 to 8.2, 96.9 to 118.9 cm, 1.2 to 5.3 ppm and 0.03 to 1.2 ppm, respectively. The results obtained by Pearson’correlation showed that the zooplankton biomass in Hanna Wetland had significant correlations with water temperature (P<0.01, r=0.78), pH (P<0.05, r=0.60) and phosphate (P<0.01, r=0.84). In addition, zooplankton abundance correlated significantly with Secchi depth (P<0.05, r=0.64) and nitrate (P<0.05, r=-0.67).