Invasive Water Hyacinth (Eichhornia crassipes) Increases Methane Emissions from a Subtropical Lake in the Yangtze River in China

Lakes represent an important source of atmospheric methane (CH4); however, there are few studies on which lake-dwelling invasive aquatic plants generate CH4. Therefore, in this study, CH4 emissions were measured using a floating chamber and gas chromatography in a subtropical lake in China. We considered four community zones of invasive plants (Eichhornia crassipes), emergent vegetation (Zizania latifolia), floating-plant (Trapa natans) and open-water zones. The results indicate that the flux of CH4 emissions varied between -5.38 and 102.68 mg m(-2) h(-1). The higher emission values were attributed to lake eutrophication. Moreover, the flux of CH4 emissions in the invasive plant zone was 140-220% higher than that in the open-water and the floating-plant zones. However, there was no significant difference in CH4 emissions between the invasive plant and the emergent vegetation zones. This may be due to a higher production of plants, as well as the rapid reproductive rate of the invasive plants. Finally, CH4 emissions were positively associated with the air and water temperature; however, the emissions were also negatively associated with water depth. Our results suggest that invasive plants enhance freshwater CH4 emissions, thus contributing to global warming.