EUGLENOPHYTA OF THE DANUBE RIVER IN SERBIA

Most genera and many species of euglenophytes exist worldwide. They usually occur during the summer months in slow-flowing and stagnant waters, rich with organic substances. Euglenophytes of the Danube River in Serbia were studied at 16 localities during 2002-2003. A total of 61 taxa were found, 21 belonging to the genus Euglena Ehr., eight to Lepocinclis Perty, 15 to Phacus Duj., six to Strombomonas Defl., and 11 to Trachelomonas Ehr. The highest number of taxa (35) was recorded at Bačka Palanka during September 2002, but at the Tekije locality no euglenophytes were detected at all.


INTRODUCTION
The Danube River enters the territory of Serbia from Hungary at its 1433th km and leaves it at its 845 th km, after the mouth of the Timok River.In Serbia, the Danube flows mostly through plains.When the Djerdap Hydroelectric Power Plant was constructed in 1972, the Djerdap Reservoir was formed.The presence of Euglenophyta was first found in the Serbian section of the Danube by P r o t i ć in 1939.M i l o v a n o v i ć and Ž i v k o v i ć (1950,1965) and O b u š k o v i ć ( 1977,1984,1994)
of Serbia.Samples for �ualitative analyses of Euglenophyta for �ualitative analyses of Euglenophyta were taken with a No. 22 plankton net and fixed with 4% formaldehyde solution.Identification of algae was performed using a Reichart Distar TM microscope e�uipped with a Canon Power Shot S40 digital camera.Species of the division Euglenophyta were identified according to P o p o v a (1966), S t a r m a c h (1983), N e m e t h (1997a, 1997b), and W o l o w s k i (1998).The samples were deposited for storage in facilities of the Institute of Botany and Jevremovac Botanical Garden, Faculty of Biology, University of Belgrade, Belgrade.The list of all taxa is arranged on the basis of the classification system according to L e e d a l e ( 1967).

RESULTS
The results of measuring physical and chemical varables at the sampling sites are summarized in Table 1.Water temperature varied from 1 to 26 o C (Table 1).The water had pH values varying from neutral (pH = 7.2) to slightly alkaline (pH = 8.6).The Danube's water is mostly semi-hard, well aerated (10.2 O 2 mg/l), and without organic pollution (BOD 5 = 2.9 mgO 2 /l).The concentrations of nutritients and of nitrogen and phosphorus compounds are within the limits of classes I and II according to the TNMN five-level classification of water �uality recommended by ICPDR (A n o n ., 2 0 0 1 ), except for ocasional increased concentrations of nitrites (max 0.136 mg/l) and total nitrogen (max 4.6 mg/l).The average concentration of analyzed metals according to the same classification belongs to the II/III water �uality class.

DISCUSSION
The highest diversity of this division was recorded at the Bačka Palanka locality (as many as 35 taxa), but not a single taxon was recorded at the Tekije locality.In this investigation, 40 new taxa were found in the Danube,18 al., 2000).The following species were found in the greates numbers: Euglena viridis, Phacus pyrum, Trachelomonas volvocina, and T. pleuronectes.Taxa belonging to this division primarily inhabit stagnant water, such as that of ponds, swamps, lakes, canals, and ditches.Greater water turbulence in the river ecosystem and the presence of an increased �uantity contributed the most to knowledge of Euglenophyta in the Danube, while other authors noted the individual presence of a small number of taxa (M a l e t i n et al., 1994; S i m i ć et al., 1997; N e m e t h et al., 2002; M i l j a n o v i ć et al., 2003).More detailed studies of Euglenophyta in the Danube River in Serbia have not been done so far.
of which are new to the algal flora of Serbia (S u b a k o v -S i m i ć , 2006).The highest number of taxa per single sample was noted at the Bačka Palanka locality on September 11, 2002, when the presence of 21 taxa of the Euglenophyta division was recorded.The most fre�uently found taxa were E. viridis (at eight localities) and T. volvocina (at six localities).So far, 74 taxa of this division have been recorded in the Danube on the territory of Serbia (S u b a k o v -S i m i ć , 2006).As many as 36 taxa noted in earlier studies (P r o t i ć , 1939; M i l o v a n o v i ć a n d Ž i v k o v i ć , 1 9 5 0 , 1 9 6 5 ; O b u š k o v i ć , 1 9 7 7 , 1 9 8 4 , 1 9 9 4 ; M a l e t i n et al., 1 9 9 4 ; S i m i ć et al., 1 9 9 7 ; N e m e t h et al., 2 0 0 2 ; M i l j a n o v i ć et al., 2 0 0 3 ; Đ u r k o v i ć a n d Č a đ o 2004, Č a đ o et al., 2005) were not recorded in this investigation, indicating great variability and instability of Euglenophyta communities in the Danube.Taxa belonging to this division are �uantitatively very rare in the Danube phytoplankton community.Their highest abundance was recorded during summer, which is also confirmed by other references (Mo n t e s a n t o et