Where does the carbon go? Carbon dynamics in a temperate salt marsh

Understanding carbon cycling in coastal ecosystems is of paramount importance in assessing the global carbon budget. This presentation will focus on recent findings about carbon sources, sinks, and fluxes across sediments, water, plants, and the atmosphere in a temperate salt marsh. Previous research indicated that this ecosystem acted as a net carbon sink, but recent information on vertical and lateral carbon fluxes has led to a reevaluation of this assumption. With nearly a decade of information at the study site, it is now known that methane production is a significant process that could make the ecosystem a net carbon source. With this updated information, it is estimated that the salt marsh is a net carbon source to the atmosphere, with annual emissions of 13-201 gC-CO₂ m² yr^-1 and 8.5-15.2 g C-CH₄ m² yr^-1. Furthermore, evidence suggests that methane within soils is produced by methylotrophic and hydrogenotrophic methanogenesis, and this methane is not oxidized into carbon dioxide but is instead released into the nearby creek, resulting in a hotspot of methane emissions. This seminar will discuss the challenges and opportunities related to measuring and interpreting the diverse processes that control carbon dynamics in salt marshes at different temporal and spatial scales.