engleski

PHYTOPLANKTON OF LAKE VISOVAC

During ecological research in National park Krka, vertical and seasonal distribution of net phytoplankton together with some physical and chemical parameters, on K1 profile of Lake Visovac was researched. Samples were taken once a month in period from April 1995 to March 1996. Water samples were taken from depths of 1, 2, 5, 10, 15 and 20 meters and filtrated. From number of counted cells on millimeter grid cell, relative abundance (number of cells per liter) of species was calculated. Highest number of phytoplankton was observed in depths from 5 to 10 meters, except in colder period of year. Seasonal distribution of phytoplankton density showed two peaks: during June and September/October. Most abundant species during spring and midsummer were: Asterionella formosa Hass., Cyclotella melosiroides (Kirch.) Lemm. and Fragilaria crotonensis Kitt. Most abundant species was Asterionella formosa with peak in late spring period (1.5-1.7x106 cells/l). Species Cyclotella melosiroides and Fragilaria crotonensis had their peaks during early spring (1.9-7.7x103 cells/l). Species Ceratium hirundinella (O.F. Müller) Dujardin was dominant in phytoplankton community from midsummer until early fall. During late fall and beginning of winter highest phytoplankton density was noted for species Fragilaria crotonensis. In winter, considerable number of benthic Bacillariophyceae was also observed.

phytoplankton; vertical and seasonal distribution; Visovac lake

nije evidentirano