| Abstract [eng] |
The objective set in the Master’s Thesis is to evaluate the quality of water in the Nevėžis River after conducting the analysis of diatoms and to provide recommendations for the improvement of the situation after identifying the main contamination sources and threats to water quality in different river sections. In order to attain the objective the following tasks were set: to select a substantiated river study method; to analyse and determine the species composition of diatoms and their relative density in the laboratory environment; to evaluate the quality of water in different sections of the Nevėžis River and to propose recommendations for the management of water quality in the Nevėžis River. The research was performed in 2013 and the samples were taken in July, August and October. Bricks with holes and rough surfaces were used as artificial substrata; ethanol (70%) was used for sample fixation and centrifuge “Eppendorf Centrifuge 5702” was used for sample precipitation; samples were studied at 600 magnification using “Nikon Eclipse 50i” microscope. The methodology for diatom sample taking was selected based on LST EN 13946 (2004), water quality was determined according to: phytoperiphyton species composition and the frequency of the incidence of every species in samples as well as water quality indices were determined based on relative taxon density by applying the R. Pantle and H. Buck‘s (1955) method. 48 samples were taken in which 36 diatom species were identified, which were belonged to 8 diatom families and 17 genuses. Almost all samples contained Melosira varians Ag. (0.6–14.2%), Stauroneis anceps Ehr. (1.3–10.9%), Amphora ovalis Ehr. (0.6–9.4%) and Rhoicosphenia abbreviata (Kutz.) Grun. (2.1–9.3%) species of diatoms. Tthe most abundantly represented species in the samples taken at release units were Rhoicosphenia curvata (Kutz.) Grun. (19.0–24.6%). Cocconeis placentula Ehr. (11.6–21.1%) and Navicula lanceolata (Ag.) Kutz. (13.8–19.9%). When evaluating the quality of water in the Nevėžis River nearby Panevėžys according to the numerical values of the saprobity index it was established that in the year 2013 in all sections under research water was ascribed to beta-mezosaprobic (β) zone and is to be evaluated as moderately contaminated. It is suggested to fill the trenches dug at the source of the greatest threat of the Nevėžis River contamination, i. e. release unit on Raginėnų st., and to level them out. |
