Competition between three submerged macrophytes, Elodea canadensis, Elodea nuttallii and Lagarosiphon major.
Species displacements within aquatic plant communities can be driven by external environmental changes or by competitive processes between species. In some lentic British waters Elodea nuttallii has displaced Elodea canadensis and is itself now being displaced by Lagarosiphon major. During photosynthesis, aquatic plant clumps create "envelopes" of raised pH and O2 levels and low CO2 levels. These may extend beyond the plant clump, suppressing photosynthetic performance and increasing photorespiratory stress on neighbouring species. It is suggested that a competitive advantage will be achieved by those species which have the best stress generation/toleration mechanisms.