PHYTOPLANKTON OF THE TISA RIVER

Sampling for qualitative analysis was carried out in February, March, April, june, july, September, and november of 2000, which enabled us to follow the seasonal dynamics of phytoplankton. The standard method was used for sample collection a plankton net was drawn through the water. Samples for quantitative analysis were collected in one-liter plastic bottles every week from February 16, 2000 to january 31, 2001. Altogether, 55 quantitative samples were collected during this period.

The Tisa River is one of the largest Central european flatland rivers and the biggest danube tributary (u h e r k o v i c h , 1971). it is one of the most important rivers of the Balkan region and europe.
Phytoplankton investigation was carried out after the cyanide spill on the Tisa River in january of 2000.
The aim of this study was to determine biodiversity of the phytoplankton community in the Tisa River after this accident.Algae are one of the most important primary producers in almost every water ecosystem.At the same time, these organisms are very sensitive to changes in their environment.
MATHeRiAl And MeTHOdS investigation samples were collected from February of 2000 to january of 2001 near Bečej, weekly and monthly.
Sampling for qualitative analysis was carried out in February, March, April, june, july, September, and november of 2000, which enabled us to follow the seasonal dynamics of phytoplankton.The standard method was used for sample collection a plankton net was drawn through the water.
Samples for quantitative analysis were collected in one-liter plastic bottles every week from February 16, 2000 to january 31, 2001.Altogether, 55 quantitative samples were collected during this period.
Phytoplankton taxa were determined in samples for qualitative analyses.Physical and chemical characteristics -air and water temperature, water pH, water clarity, and oxygen concentration in the water, were measured during collection of the qualitative samples.

ReSulTS And diSSCuSiOn
during the investigation period, we recorded eight algal divisions.The list of divisions and their participation in the phytoplankton community of the Tisa River are  1.
Table 2 gives the list of determinated phytoplankton taxa with their monthly distribution in the Tisa River.
Altogether we recorded 374 taxa (Tables 1 and 2), which indicates high biodiversity of the phytoplankton community in this ecosystem, regardless of the cyanide spill and heavy metal pollution at the beginning of the investigation period.data indicating a rich and heterogeneous phytoplankton community in the Tisa River were also recorded previously The results indicate that Chlorophyta was the qualitatively dominant division, while Bacillariophyta was subdominant during the investigation period.
The highest biodiversity of green algae was during the summer and autumn period, whereas Bacillariophyta was the dominant group during the colder period of the year.A similar situation was observed earlier (K a l a f a t i ć et al. (u h e r k o v i c h , 1971; G u e l m i n o , 1973; S u b a k o v , 2000; B r a n k o v i ć and B u d a k o v , 2001).
1982; Đ u k i ć et al. 1994; d u l i ć and M r k i ć , 1998; S u b a k o v , 2000).This is consistent with ecological characteristics of these algae (T r a i n o r , 1978; B l a ž e n č i ć , 2000) and ecological conditions in the given ecosystem during the period of investigation (R ž a n i č a n i n , 2004).A significant number of taxa were found within Cyanophyta, while representatives of Euglenophyta were less numerous.Most taxa of the Cyanophyta and Euglenophyta found in the Tisa River were characteristic of slow, flatland rivers and stagnant water, and they were also registered during earlier investigations (P r o t i ć , 1939; u h e r k o v i c h , 1971; G u e l m i n o , 1973; K a l a f a t i ć et al. 1982; P u j i n et al. 1999; S ub a k o v , 2000).Rhodophyta, Pyrrophyta, Xanthophyta, and Chrysophyta were represented by a small number of taxa.Their participation in the phytoplankton community of the Tisa River was extremely small.earlier studies likewise revealed a small number of taxa from these divisions (P r o t i ć , 1939; S z a b a d o s , 1966; u h e r k o v i c h , 1971; G u e l m i n o , 1973; K a l a f a t i ć et al. 1982; d u l i ć and M r k i ć , 1998; P u j i n et al. 1999; S ub a k o v , 2000; B r a n k o v i ć and B u d a k o v , 2001).

Table 2 .
Continued given in Table