The sediment biochemical properties, including pH, NO3--N, ammonia nitrogen (NH4+-N), Fe (Ⅱ), SOC, and acetate (CH3COO-), were measured by standard methods (Table S2). The enzyme activity of DHO, D-glucosidase (D-Glu), BAA-protein hydrolase (BAA-Pro), and methane-producing coenzyme F420 (F420) were determined by specific enzyme kits purchased from Shanghai Hengyuan Biotechnology Co., Ltd (Shanghai, China).
