engleski

Changes of microphytoplankton species dominance in Lake Visovačko jezero

The microphytoplankton in Lake Visovačko jezero was studied during one year period, on base of monthly sampling data covering period from April 1995 to March 1996. Changes in species composition and seasonality of the dominant species were investigated in relation to the environmental variables. Diatoms dominated the phytoplankton assemblage of the lenitic barrage area of karstic River Krka. The master species in Lake Visovačko jezero was Asterionella formosa Hass. The dinoflagellates (Ceratium hirundinella (O. F. Müller) Bergh) were generally the second most representative group in terms of abundance, where their annual development has been shifted to the late summer and autumn period. In the Lake Visovačko jezero, under mesotrophic conditions Reynolds groups B and C are present, with exception of late summer and autumn assemblages which were characterized by association of large dinoflagellate species known as Group LM. The effects of the short term dynamics of environmental factors on the algal growth in barrage lenitic area of calcareous river stressed several variables as important factors controlling annual microphytoplankton distribution. The temperature was the most valuable variable affecting the species abundance, changes in dominance and species composition (Primer 5, BIO-ENV). CCA analysis performed on abundance dataset and environmental variables confirm the importance of temperature but also highlighted total phosphorus, conductivity and silica.

microphytoplankton; seasonality; diatoms

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