The fact is that in the world today water and land represents limited life resources which are more and more degrade and disturbed, mostly by anthropogenic influence. Especially water (seas, rivers, lakes) is exposed to various types of pollution. The fact is that in the world today water and land represented limited life resources which are more. That why in present time we conduct numerous scientific researches to examine, advance and protect our environment, especially water as a limited and delicate natural resource. In this work results from April to September 2011 are presented, which comprised analyses of samples from 8 stations in Boka Kotorska Bay. The main aim was to estimate trophic level, of determining the concentration of the physico-chemical parameters, chlorophyll a and TRIX index in Boka Kotorska Bay.

The weekly measurement of physico-chemical and biological parameters was done during the spring of 2008 in order to assess the level of eutrophication in the Kotor Bay. Chlorophyll a was used as trophic level indicator and its values varied from minimal 1.00 mg/cubic meter in June on the depth of 10 m to maximal 3.71 mg/cubic meter on the sea surface in May. According to Nixon criteria during investigation period it can be concluded that the area in question is oligotrophic. On the other hand, according to UNEP criteria which are somewhat stricter when the concentration of chlorophyll a is in question, Kotor Bay was mesoeutrophic area.

Influence of eutrophication to the phytoplankton community were studied in the inner part of Boka Kotorska Bay (Kotor Bay and Risan Bay) from September 2003 to August 2004. Kotor Bay and Risan Bay is very interesting area because the influence of natural and anthropogenic eutrophication are mixed very often. Microphytoplankton density is high (greater than 10**6 cells/cubic dm) what is characteristic eutrophic area, to the highest eutrophic area (greater than 10**7 cells/cubic dm). These values we stated in the surface, because in this layer were the best conditions. In same time we stated very high values: SiO2, oxygen saturation and chlorophyll a. The conclusion is: Boka Kotorska Bay and especially Kotor Bay (as a part of Boka Kotorska) has to be protected of dangerous consequences such as blooming. It is needed to regulate wastewater, their purification and permanent control physico-chemical and biological parameters, and especially phytoplankton component.

Research of phytoplankton is conducted in different seasons during 2004 and 2005. River Bojana and Ada Bojana are analyzed on several locations. The objective of research is based on algae as reliable indicator of water quality and ecological condition of water. We would like to show the need for protection of these water ecosystems from permanent contamination, basically sewage waste. Saprobiotic index is determined by Gulyas Pal method. Pantle Buck method is used to calculate saprobiotic level. Chlorophyll A is analyzed by spectrophotometer. Presence of Cyanophytae was established.

The salt pond Velika Slatina is the old meander of the river Tamis (Serbia). The ecosystem is periodically fill with moderate salt water. Phytoplankton production was 10 times bigger in 2003 than 2006. Ecological conditions were unfavourable for development of phytoplankton community. Diatoms show as the most abundant component in 2003, but euglenoids were in 2006, when bloom of Gloeotrichia natans f. bucharica Kissel was recorded. Results of biomass analysis also show dominant role of diatoms in 2003 and euglenoids in 2006.

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.