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Namen magistrskega dela je bil proučiti združbe alg in makrofitov, ki uspevajo v petih zadrževalnikih verige hidroelektrarn na spodnji Savi. Ugotavljali smo, kakšen vpliv imajo spremembe okoljskih dejavnikov na združbe alg in makrofitov. Terensko delo smo opravili med marcem in avgustom 2021. Pred vsako od petih hidroelektrarn smo izbrali vzorčno mesto, kjer smo izmerili fizikalne in kemijske parametre vode. V zimskem in poletnem času smo nabrali vzorce fitoplanktona in vzorce perifitona, poleti smo popisali tudi makrofite. V obeh vzorčenjih smo v vzorcih vode določili koncentracije nitratov in ortofosfatov. Vrstna sestava združb alg v fitoplanktonu in fitobentosu se je med sezonami spreminjala. Ugotovili smo, da na taksonomsko sestavo združb fitoplanktonskih in fitobentoških alg izmed vseh okoljskih dejavnikov najbolj odločilno vpliva temperatura. Združbe so si tudi med seboj bolj podobne glede na letni čas kot pa med posameznimi vzorčnimi mesti. Na vseh vzorčnih mestih skupaj smo zabeležili 51 taksonov alg in 81 vrst kremenastih alg. Tako v fitoplanktonu kot fitobentosu sta bili v poletnem času dominantni vrsti Diatoma ehrenbergii in Cyclotella meneghiniana, v zimskem času pa so bili najpogostejši rodovi Achnanthidium, Cocconeis, Diatoma, Navicula in Nitzschia. Glede na Shannon-Wienerjev diverzitetni indeks smo ugotovili, da je bila vrstna pestrost kremenastih alg enaka v zimskem in poletnem času. Skupno smo na 5 odsekih popisali 15 vrst makrofitov, katerih vrstna sestava se je po toku navzdol spreminjala. Na vseh odsekih je uspeval klasasti rmanec (Myriophyllum spicatum). Algal and macrophyte communities were studied in five river reservoirs of the hydroelectric power plant chain on the Lower Sava River. The aim of the thesis was to find out how environmental factors influenced algal and macrophyte communities. Fieldwork was done between March and August 2021. Sampling sites were selected in the reservoirs of the five hydropower plants, where physical and chemical parameters of water were measured. Phytoplankton and periphyton samples were taken in winter and summer, macrophytes were identified only in summer. Nitrate and orthophosphate concentrations were measured in the laboratory. The species composition of algal communities in phytoplankton and phytobenthos varied between seasons. We found out that temperature of the water was the environmental factor that influenced the taxonomic composition of phytoplanktonic and phytobenthic algal and diatom communities the most. The communities were also more similar between the seasons than between the sampling sites. In total, 51 algal taxa and 81 species of diatoms algae at all sites were recorded. In phytoplanktonic and phytobenthic communities Diatoma ehrenbergii and Cyclotella meneghiniana were the dominant species in summer and the genera Achnanthidium, Cocconeis, Diatoma, Navicula and Nitzschia were the most abundant in winter. According to the Shannon-Wiener diversity index, we found out that the species diversity of diatoms was the same in winter and summer. A total of 15 species of macrophytes were identified in five locations, species composition varied downstream. The species Myriophyllum spicatum was present in all locations. |
