engleski

Floods as a disturbance factor for cyanobacterial bloom in a temperate floodplain lake

In spite of the whole knowledge about cyanobacterial blooming in freshwater ecosystems, there are lots of unresolved questions concerning its appearance, especially in complex, dynamic ecosystems as Kopački Rit, one of the largest riverine wetlands in Europe. The main objective of the present study was to analyze the influence of flooding dynamics of the River Danube in the period from 2003 till 2007 on the development of Cyanobacteria in the fringing floodplain lake (Lake Sakadaš). During the investigated period, a total of 16 Cyanobacteria species were determined, among which 9 taxa achieved a biomass higher than 5% of total phytoplankton biomass. Cyanobacterial bloom was recorded in 2003, 2004 and 2007, only in the conditions of hydrological isolation of the lake from the income of riverine water. Different filamentous species from functional groups H1, S1 i SN were replaced during the Cyanobacteria bloom. Their contributions in total phytoplankton biomass reached up to more than 80% during the summer period. The highest biomass of Cyanobacteria species (245 mg/L) was recorded in August in extremely dry year 2003. In the conditions of extreme flooding (late spring and summer of 2005 and 2006), cyanobacterial blooming was absent and very low phytoplankton biomass was established (mean value less than 12 mg/L). All given results indicate that flooding could be qualified as a disturbance factor for the development of Cyanobacteria bloom in the investigated floodplain lake.

Danubian floodplain; Cyanobacterial bloom; Equilibrium phase; Disturbance; Invasive species.

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