An empirical model to predict methane production in inland water sediment from particular organic matter supply and reactivity

Abstract

Abstract The highest CH 4 production rates can be found in anoxic inland water surface sediments however no model quantifies CH 4 production following fresh particular organic matter (POM) deposition on anoxic sediments. This limits our capability of modeling CH 4 emissions from inland waters to the atmosphere. To generate such a model, we quantified how the POM supply rate and POM reactivity control CH 4 production in anoxic surface sediment, by amending sediment at different frequencies with different quantities of aquatic and terrestrial POM. From the modeled CH 4 production, we derived parameters related to the kinetics and the extent of CH 4 production. We show that the extent of CH 4 production can be well predicted by the quality (i.e., C/N ratio) and the quantity of POM supplied to an anoxic sediment. In particular, within the range of sedimentation rates that can be found in aquatic systems, we show that CH 4 production increases linearly with the quantity of phytoplankton‐derived and terrestrially derived POM. A high frequency of POM addition, which is a common situation in natural systems, resulted in higher peaks in CH 4 production rates. This suggests that relationships derived from earlier incubation experiments that added POM only once, may result in underestimation of sediment CH 4 production. Our results quantitatively couple CH 4 production in anoxic surface sediment to POM sedimentation flux, and are therefore useful for the further development of mechanistic models of inland water CH 4 emission.