Distribution and Community Structure of Crustacean Mesozooplankton of Hanna Wetland, Isfahan Province

Distribution and community structure of crustacean mesozooplankton of Hanna Wetland, Isfahan province were investigated during four seasons. Seasonal mean of water temperature, dissolved oxygen, nitrate and phosphate was 14.79 ºC, 8.01, 1.18 and 0.05 mg/l in spring, 20.65 ºC, 7.46, 2.26 and 1.20 mg/l in summer, 11.33 ºC, 7.94, 1.89 and 0.67 mg/l in fall, and 5.34 ºC, 9.73,5.27 and 0.03 mg/l in winter, respectively. The dominantphytoplanktons were Strastrum, Gonium, Chlorella and Aphanthece with the highest density in all seasons. The green algae, Chlorophyta, had highest abundance followed by blue-green algae, Cyanophycea. The relative abundance (%) of cladocearn ranged from 27.2 in summer to 74.3 in spring while copepods ranged 25.6 in spring to 72.7 in fall. Cladocerans including;Daphnia longispina, Daphnia dubia, Daphnia pulex, Ceriodaphnia sp., Moina sp., Moina macrocopa,Bosmina sp.and copepods including; Apocyclops procerus, Acanthocyclops sp., Microcyclops varicans,Allocyclops sp., Diacyclops bicuspidatusand Macrocyclops albidus. The zooplankton dry biomass was ranged from 0.1 to 28.9 mg/m3.Although cladocerans constituted major mesozooplankton assemblages, copepods (including nauplii and copepodids) were distributed in all sampling stations. D. longispina was a common species in all stations and seasons, except winter and Bosmina had short life cycle, and was rare occurence in winter. Hanna wetland had eutrophic state and removal of mesozooplankton biomass would result in a better pelagic environment for colonization of aquatic planktonic organisms.