engleski

Phytoplankton community in two slow flowing hypereutrophic rivers - ecological traits and potential toxic threat to environment

Toxic cyanobacteria in hypereutrophic water systems can cause serious problems for water use, especially when nutrients are not the only limiting factor for their growth. The research of phytoplankton was conducted from April until September 2012 in two alluvial rivers of Pannonian lowlands, Spačva and Bosut. Spačva River is medium sized tributary to large Bosut River and both rivers are slow-flowing with large proportion of agricultural use in the catchment area. Except of the size, the rivers differ significantly according to sampling site. In Bosut River sampling site was covered with duckweed, while sampling site in Spačva River had no floating macrophytes, allowing direct sunlight to phytoplankton. Highest chlorophyll a concentration was similar in both rivers reaching 364.1 μgL-1in Spačva River and 364.4 μgL-1 in Bosut River. Based on biomass calculations, phytoplankton in Bosut River was represented with shade-adapted cyanoprokaryotes belonging to functional group S1, as well as with functional groups C and D tolerant to low light conditions. In Spačva River succession from functional group E to H1 and S1 with subdominance of SN, was detected. Cyanobacteria Dolichospermum flosaquae, Aphanizomenon flosaquae, Planktothrix agardhii and Cylindrospermopsis raciborskii were species which contributed most to the total phytoplankton biomass. All of the dominant taxa have high toxic risk suggesting potential threat to humans and animals and that monitoring of cyanotoxins should be designed in the near future.

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