THE DENSITY AND DISTRIBUTION OF PLANKTONS IN HEVIGH RIVER, GUILAN PROVINCE

A Comprehensive hydrobiological and hydrological investigation was conducted on Hevigh River, west of GuilanProvince from 2001 to 2002. Totally, 4 Phyla of phytoplanktons including 21 genera were observed. The maximum phytoplankton density belonged to the Phylum Chrysophyta with genera, Nitzchia, Diatoma, Cocconeis, Navicula and Cymbella comprising 95.7% of the phytoplankton population throughout the year. Chlorophyta ranked second with genera Scenedesmus, Cruciginia and Ankistrodesmus, comprising 2.20% of the population during the year. Cyanophyta with Oscillatoria and Euglenophyta with Euglena consisted the remaining few percents of the phytoplankton population.
Zooplankton population in Hevigh River was found to be very poor, and mostly belonged to Protozoa and Rotatoria. However, 4 Phyla and 12 genera of zooplanktons were distinguished in the River the highest density of which belonged to Protozoa with genera Arcella, Difflugia, Cyphoderia and Euglypha, comprising 64% of the total population. Rotatoria with genera Keratella, Cephalodella, Lecane and Rotaria, consisted 14% of the zooplankton population during the year. Arthropoda, Nematoda, Tardigrada were very low in numbers.