Allelopathic activity of Myriophyllum spicatum L. on natural phytoplankton assemblages

Widespread eutrophication of the water bodies and consequential occurrence of toxic algal blooms is one of the most serious environmental problems. Considering that aquatic macrophytesand microalgae compete for nutrients and light, allelopathic inhibition of algal growth is considered to be an effective macrophyte competitive strategy against algae that can bloom and thus significantly decrease an amount of light that reaches macrophytes. Three different concentrations of Myriophyllum spicatum ethanolic extract were tested for their inhibitory allelopathic activity on natural phytoplankton assemblages. After applying the extract, the average biomass of 3 replicates was measured during the experimental time. All the three concentrations of the M. spicatum extracts showed inhibitory effect to a certain extent. The maximal inhibitory effect was achieved with the 5g/50 ml concentration of extract at first sampling time. The inhibitory effect of extracts is evident within all recorded algal phyla. Phylum Cyanobacteria is found to be the most sensitive to applied extracts compared with Chlorophyta and Bacillariophyta