Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Allelopathic activity and chemical analysis of crude extracts from the macrophyte Egeria densa on selected phytoplankton species.

Abstract

Egeria densa is an invasive macrophyte in Mexico and its allelopathic effects on phytoplankton species are poorly documented. Hence, we evaluated the inhibitory effects of different concentrations of crude extracts (hexane, ethyl acetate and methanol) from E. densa on Scenedesmus acutus, Chlorella vulgaris, Monoraphidium sp. and Nitzschia palea. The hexane extracts yielded less quantity of crude extract, while methanol resulted in higher amount. We detected 9-compounds, of which saponins, tannins, cardiac glycosides and phenols were most abundant. Agar diffusion in disc bioassays showed inhibition halos of different sizes depending on the extract, concentration, solvent type used and the tested phytoplankton species. In C. vulgaris and S. acutus, the inhibition halos of >20 mm diameter were observed in treatments containing ethyl acetate and methanol extracts. The results suggested that E. densa contained substances that could change the composition of phytoplankton communities through their inhibitory and/or allelopathic effects.