engleski

Taxonomic composition of phytoplankton in the Zmanja Estuary (Adriatic Sea)

Background and Purpose: The Zrmanja is a karstic river that discharges into the eastern Adriatic Sea (Croatian coast) forming a shallow, highly stratified estuary. The area is without significant anthropogenic influence. In this paper we present taxonomic composition of phytoplankton in the upper and middle reach of the Zrmanja Estuary in the period 1998-2000. Material and Methods: The research was carried out in the middle and upper reach of the Zrmanja Estuary in the period 1998 - 2000. The water was sampled using 5 liter Niskin bottles. Subsamples were taken for analyzing phytoplankton and nutrients. Salinity and temperature were measured with CTD probe. Results: Recognizable phytoplankton was composed of 76 diatoms (45 centrics, 31 pennates), 54 dinoflagellates, 9 prymnesiophytes, 3 chrysophyceae, 1 chlorophyceae and one euglenophyte. Dominant species in the estuary were Gymnodinium simplex, Prorocentrum micans, Dinobryon spp, Chaetoceros socialis, Cyclotella sp., Leptocylindrus danicus, Pseudonitzschia spp. and Thalassionema nitzschioides. Shannon Wiever diversity (H’ ) index values mostly ranged from 0.5 to 2. Pielou’ s eveness, as well as the Shannon Wiever index provided maximum values in the summer-autumn period (June – October), while lower and more diverse values were found in winter and spring. Conclusion: The well oxygenated water column, as well as low concentration of nutrients imply the oligotrophy of the estuary. Considering the biological parameters, the abundances of microphytoplankton and the Shannon diversity indexes, the Zrmanja Estuary was categorized as moderately eutrophic. The presence and abundance of species that prefer eutrophicated environments indicated the Zrmanja Estuary as a naturally, moderately eutrophic environment

Taxonomic composition; phytoplankton; estuary; Zrmanja; Adriatic Sea

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