RESEARCHES CONCERNING THE DETERMINATION OF BIOCENOSIS COMPOSITION FROM LAKE VENETIA - IASI

Valerica Gîlcă, I. Gîlcă, Doina Leonte, Elena Ignat

Abstract
   The purpose of the research was to determine the composition of the biocenoses in Venice lake, Iasi county. Research was conducted in the summer of 2016 for three months, June, July and August respectively. For the determination of phyto and zooplacton, three samples were taken from the surface of the lake, and for studying phyto and zoobenthos, the samples were collected from the substrate level.
   Also, three more samples were collected to determine the necton specific species. For collecting phytoplankton, we used the graduated cup method, which the easiest way for collecting samples. To collect the necton, trawl and tramme were used. For the collection of zooplankton, used a planktonic nettingh consisting into a metallic frame with dimension of 10-15 cm to which it was fixed a conical bag of silk screen and in the top attached and a conical metal cup with tap. The collection of macrobenthos samples was carried out in the seaside area using a metal frame with dimension of 0,8 m² to determine the density and qualitative composition of macrophytes. The collection of the zoobenthos was made with a drag, and the analysis of the samples was done in the laboratory.
   As a result of the researches carried out in the phytobenthos structure, 4 species of cyanophytes, 5 species of bacillaryophites, 3 species of euglenophytes and 5 species of chlorophytes was indentified. Of the four most systematic groups, the most abundant were chlorophytes followed by bacilariofites, and the fewest euglenophytes. In the zooplankton structure four systematic groups were identified, the most abundant being the ciliophores followed by cladocere and rotifers. In the phytobenthos structure, the most numerous species were: Phragmites, Glyceria and Typha. Among the main zoobenthos groups the most numerous were oligochetes, ephemeropter larvae, diptere and chironomide. In the structure of the necton dominated the group of fish.
   The investigated aquatic basin has a rich trophic base, which is an important source of food for hydrobionts.

Key words: biocenosis, plankton, necton, benthos, water