This paper presents the results of investigation on photosynthetic pigments, chlorophyll a in the river Danube (Serbia) during 2002-2005. Field investigations were carried out with seasonal dynamics on the river strech between 1112 and 851 km. Exceptionally in September, during low water period, investigations were carried out on the river strech between km 1260 - 851, including the main tributaries: Tisza, Sava, Velika Morava and Pek. The concentrations of chlorophyll a and phaeophytin a were determined using the standard ISO 10260/92 methodology, variant B. Pigment extraction was done in hot ethanol immediately after sampling, on board of a research ship. The results revealed seasonal concentration dynamics of the mentioned indicators of primary productivity and physiological status of the algae community where fall of chlorophyll a from the upstream towards downstream profiles was evidenced.

The puddles Slatina and Pecena Slatina are the old meanders of the river Tamis. These ecosystems are periodicity fill with moderate salt and high alkaline water. The paper gives a review of qualitative and quantitative analysis of the algal compositions. Cyanoprokaryota and Euglenophyta are more common. All investigated parameters like compositions of lagal communities, their abundace, biomass and chlorphyll-a showed a high level of nature eutriphication in these ecosystems.

A great floristic variety has been noted according to qualitative analysis of phytoplankton. The presence of 187 taxa from 7 divisions of algae has been noted. The results of quantitative analysis show the dominance of centric diatoms. The high values of biomass that point out on the trophicity increase are noted on the strech from Nestin to Zemun (Serbia) with the maximum at Centa (Serbia) with 15,885 mg/cubic dm. Downstream Zemun, it has been noted gradual decrease of biomass up to Pancevo (Serbia), and afterwards downstream the considerable reduction all the way up to Brnjica (Serbia), where the value of algal biomass was 1,697 mg/cubic dm.

Phytoplankton composition of the Hydrosystem Danube-Tisza-Danube (HS DTD) and isolated peaks of chlorophyll a in summer months of 2003 and 2004 revealed moderate ecological potential in Banat and Backa region (Serbia). Investigated HS DTD water pointed out to a slighty better ecological potential in 2004.

Investigation of the nutrients and chlorophyll a concentrations, as indicators of trophic level, in the period from September 2003 to August 2004 in three sampling locations in the inner part of Boka Kotorska Bay varied widely. Nitrate concentration ranged from 0.0 to 2.42 mg/l at the surface and from 0.02 to 3.88 mg/l at the bottom, nitrate concentration from 0.02 to 0.21 mg/l at the surface and from 0.01 to 0.6 mg/l at the bottom, phosphate concentration from 0.03 to 0.18 mg/l at the surface and from 0.01 to 0.22 mg/l at the bottom, silicate concentration from 0.0 to 1.42 mg/l at the surface and 0.45 mg/l at the bottom respectively. Value of phytoplankton biomass, as represented by chlorophyll a, ranged from 1.02 to 8.68 mg/cubic meter and from 0.49 to 5.23 mg/cubic meter at the bottom. According to the UNEP criteria during the investigated period it can be concluded that the area in question is mesotrophic with the exception of December when it is eutrophic.