Effects of water nutrients on regeneration capacity of submerged aquatic plant fragments

Aquatic plants play a substantial role in almost all freshwater habitats throughout the world. Even though submerged aquatic plants dominantly spread by the dispersal of vegetative plant fragments, most aquatic plant species show a broad distribution range. Here we studied the differences in the regeneration capacity and the regeneration type of fragments (by root and/or shoot growth) of eight submerged plant species (Ceratophyllum demersum, Egeria najas, Elodea canadensis, Elodea nuttallii, Hydrilla verticillata, Myriophyllum aquaticum, Myriophyllum heterophyllum and Myriophyllum spicatum) under different water nutrients in sediment-free conditions. Overall, M. spicatum showed the highest regeneration (82±2%) in this study, followed by C. demersum (73±2%) and M. aquaticum (47±4%), whereas M. heterophyllum showed the lowest (1±1%). The shoot fragments of E. canadensis, H. verticillata, E. najas and E. nuttallii regenerated by 40±2, 23±2, 16±2 and 7±1%. The nitrate concentration affected the regeneration capacities of E. najas (P=0.05), M. spicatum (P=0.013) and C. demersum (P=0.001), whereas phosphate had no significant effect. Additionally, the different nutrient concentrations had a significant effect on the portion of the regeneration types within E. canadensis, E. nuttallii and H. verticillata. Summarizing, submerged plants differ significantly in their regeneration capacity, and water nutrients have a potential effect on the regeneration of submerged plant fragments. This might influence the further colonization and spread of the species under field conditions.