Understanding the role of freshwater wetlands in the global carbon cycle has become more important as evidence of climate change grows. In this paper, we examine the burial and decomposition of particulate organic matter (POM) in a temperate, siliciclastic, seasonal wetland. High POM abundances are found in silt layers, while sand units preserve very little POM. The POM distribution with depth is compared to the biogeochemistry of sediment porewater with depth. POM acts as a driver for reduction reactions within the wetland soil. Porewater biogeochemistry and POM decomposition are controlled by seasonal changes in the level of the water table which cause seasonal shifts in the oxic/anoxic boundary. At the oxic/anoxic boundary, reoxidation of FeS minerals in the soil cause rapid POM decomposition at the average minimum water table level in the late summer and early fall. Variation in the minimum depth of the water table from year to year may account for fluctuating POM numbers in the upper silt layers. The results from this study can be used to predict seasonal water level fluctuations in ancient wetland and to explain recurrence horizons in peat.