Effects of nutrient levels and light intensity on aquatic macrophyte (Myriophyllum aquaticum) grown in floating-bed platform

In recent years, Myriophyllum aquaticum grown on floating beds has been widely applied to the treatment of the malodorous black river water with high nutrient concentrations. This is due to the ability of the effective removal of nutrients by this plant. However, environmental factors such as light and nutrients influence plant growth, which may negatively affect the results of ecological restoration. To test the effects of nutrient levels and light intensity on the growth of M. aquaticum, a 21-day outdoor two-factorial experiment (three levels of nutrient loadings and three light intensities) was conducted from September 3 to September 30, 2016. Results showed that the addition of nutrients had no significant effects on the growth of M. aquaticum. Reduced light intensity led to a decrease in Chlorophyll a concentration in the water column and the growth of M. aquaticum. All growth indicators in the full sunlight treatment were significantly higher than in the shading treatments. The lowest growth was found in the 60% shading treatment. The mean plant height and the number of roots responded significantly to the interaction between light intensity and nutrient level. This study reveals that M. aquaticum planted on the floating beds could grow normally in eutrophic waters and can be used as a restoration technique to treat eutrophic water. However, shading (e.g., riparian trees) may be a major limiting environmental factor to M. aquaticum.