Effects of grass carp introduction on macrophyte communities in a shallow lake

In 2002, 2005 and 2007 vegetation and physicochemical properties of pelagial water were investigated in a shallow mid-forest lake. In 2002, the highest phytocoenotic diversity was recorded; charophytes and vascular submerged macrophytes formed their own extensive communities. After stocking with grass carp (Ctenopharyngodon idella Val.) in 2002, reduction of water transparency, as well as changes in qualitative and quantitative composition of macrophyte communities were observed. Submerged vegetation declined during subsequent growing seasons. Charophyte meadows vanished first. The introduction of grass carp appeared to be a potential trigger for the rapid changes observed in the vegetation.