Effects of Decomposition of Submerged Aquatic Plants on CO2 and CH4 Release in River Sediment–Water Environment

Abstract

Organic matter was increased due to the input of plant litter, resulting in changes in the physicochemical properties and enhancement of greenhouse gas (GHG) emissions in water bodies. There are few reports on effects of decomposition of aquatic plants on GHGs emissions. This study investigated the effects of the degradation of two aquatic plants, Potamogeton crispus and Typha orientalis Presl, upon release of CO2 and CH4 at the sediment–water interface. During early decomposition, the release of CO2 and CH4 at the sediment–water interface was increased by the degradation of the two aquatic plants, and release flux of CO2 and CH4 were increased rapidly at first and then decreased. Due to the differences in properties of C, lignin, cellulose and other components of the plants, the Potamogeton crispus group obtained higher abundance of genes relevant to CO2 and CH4 metabolism, which leads to the increase of CO2 and CH4 emissions compared with that of the Typha orientalis Presl. In addition, dissolved oxygen and pH were decreased due to the decomposition of organic matter in the plant residues at the sediment–water interface, resulting in growth of anaerobic microorganisms. The increase of the relative abundance of anaerobic microorganisms promoted the decomposition of organic matter in the sediment and the enhancement of cell respiration, promoting the release of CH4 and CO2 during the decomposition of aquatic plants.