Impact of submerged macrophytes including charophytes on phyto- and zooplankton communities: allelopathy versus other mechanisms

Submerged macrophytes are crucial for the stabilization of the clear water state in shallow, mesotrophic and eutrophic lakes. Especially, charophytes often play an important role because they are typically rapid colonizers and because charophyte meadows are believed to have a particularly strong positive effect on water transparency compared to other macrophytes. Several mechanisms may contribute to the impact of submerged macrophytes on the planktonic food web. In this paper, the available literature on these mechanisms is briefly reviewed and special attention is paid to the impact of charophytes on the structure and dynamics of phyto- and zooplankton communities. The paper focuses on allelopathy, and possible differences between charophytes and other macrophytes, as well as gaps in our knowledge are discussed. (C) 2002 Elsevier Science B.V. All rights reserved.