Physicochemical properties and greenhouse gas emissions of water body during the decomposition of Potamogeton crispus with different values of initial debris biomass.

A sediment-water mesocosm experiment was set up to identify the effects of different debris biomass P. crispus decomposition on water body physicochemical properties and greenhouse gas emissions in Dongping Lake, a typical shallow macrophytic lake in the north of China. The results indicated that the decomposition of high biomass (BL-2) of P. crispus could significantly affect the physicochemical properties of water bodies, especially within the first 47 days. During the experiment, DO and water pH in BL-2 were significantly lower, while NH-N, NO-N, DOC, and DRP in surface water and OM in sediment were significantly higher than those in the low biomass treatment (BL-1) and zero control (CK). Moreover, the DOC in BL-1 were significantly higher than CK. The decomposition of P. crispus significantly affected the emission fluxes of CH and CO, but had no significant impact on NO emission. CH and CO fluxes were generally more significantly correlated with the properties of surface water in BL-2 than in BL-1. High debris biomass decomposition significantly promoted the emission of CH enhancing the source effect of water body, while the decomposition of both low and high biomass notably promoted the emission of CO converting the water bodies from sink to source of CO. There were significant differences in global warming potential among the three groups in which CH contributed most. Considering the negative impact on water environment and elevated carbon emission during the decomposition of P. crispus, it was suggested to strengthen the management of P. crispus in Dongping Lake.