The beneficial effect of barley straw extract addition on the growth of two aquatic invasive alien species (Elodea nuttallii and Cabomba caroliniana) under laboratory conditions

Barley straw has been used around the world for decades as a simple, cost-effective and harmless phytoplankton growth inhibition method. Although the effect of this method on algal blooms is quite well depicted, it has not yet been tested what effect it has on submerged vascular plants and if it could be used to control the spread of alien macrophytes. In this study two highly invasive plant species: Cabomba caroliniana and Elodea nuttallii were exposed to different concentration of the barley straw extract (BSE) in laboratory conditions for a duration of four weeks. In the course of the investigations, responses of 8 traits associated with growth, biomass and chlorophyll concentration of specimens to three dosages (Low, Medium, High) of BSE corresponding to concentrations: 0.03, 0.30 and 1.50 ml l(-1) were analysed. The result showed that although dry mass and total length of the plants did not differ significantly between the test groups, increase in tillering and internodes number was observed for certain concentrations of the extract. This shows that if BSE has any effect on submerged macrophytes it is a positive one and thus the method is not suitable for invasive submerged aquatic plant control. Furthermore, it is recommended that before using barley straw for algae bloom control one should make sure that there are no alien aquatic submerged plants in the area that could benefit from such a treatment.