EFFECTS OF FLOATING HYDROCHARIS DUBIA ON CO-CULTURED SUBMERGED MYRIOPHYLLUM SPICATUM AND CERATOPHYLLUM DEMERSUM IN DIFFERENT SEDIMENTS

Cultivating combination of different life forms is an efficient way to restore aquatic vegetation. A common combination is the floating and submerged plants. In this study, we cultivated two submerged plants with different types of nutrient uptake (rootless Ceratophyllum demersum, absorbing nutrients only from water column; and rooted Myriophyllum spicatum, taking up nutrients from both water and sediment) in three kinds of sediment with different levels of nutrients. The floating Hydrocharis dubia was added to explore the effects of floating plants on submerged plants in different sediments. The results showed that H. dubia grew more vigorously in silt and the mixed sediment of sand and silt that contained higher level of nutrients than sand sediment. However, the total mass and ramet number of C. demersum and M. spicatum were not affected significantly by sediment. The floating H. dubia did not suppress the growth of the two submerged plants. To compete with H. dubia for light and nutrients in water, rootless C. demersum tended to increase leaf mass ratio, branch number and stem length. As a result, C. demersum accumulated higher total mass in presence of H. dubia. Rooted M. spicatum adapted to shading of H. dubia by regulating plant morphology without suppressing growth of M. spicatum. These results revealed an efficient way to increase the species diversity of aquatic community by cultivating submerged plants with a small amount of floating plants.