CHARACTERIZING SEASONAL SEDIMENTARY CARBON FLUXES WITHIN A RESTORED COASTAL WETLAND

Coastal wetlands are important environments that support diverse ecosystems, provide flood protection, and can help mitigate the impacts of climate change. While important, coastal wetlands have been undervalued in the past with much of their area lost due to land use changes and urban development. As wetland restoration projects increase, it is critical to understand the value these ecosystems provide, such as their role in sequestering atmospheric carbon to combat future climate change. In this project we investigated seasonal sedimentary carbon fluxes within a restored wetland in the Eden Landing Ecological Reserve in San Francisco Bay. Sediment cores were collected from 3 different habitats within the wetland (mudflat, Spartina – low marsh, and pickleweed – high marsh) over the course of 1 year, with coring locations reoccupied every ~3-4 months. From these cores we determined seasonal mass accumulation rates via short-lived radioisotopes (⁷Be) and percent organic carbon (%OC) using an elemental analyzer, and used these data to determine the net carbon accumulation rates (CAR) for each habitat type seasonally (between coring periods). The results showed that %OC remained constant seasonally within the mudflat, decreased over the winter in the low marsh, and increased over the winter in the high marsh. Seasonal CAR increased throughout all marsh and mudflat areas during the winter, and increased in the low marsh during the spring but decreased in the high marsh and mudflat during spring. We hypothesize that the increased above ground growth of Spartina in the spring acts a sediment trap, focusing sediment and sedimentary carbon in the low marsh and preventing material from reaching the high marsh, while concurrently the mudflats may become a sediment source for other wetland areas. This research highlights the spatial and temporal heterogeneity in sedimentary carbon fluxes annually that could help improve coastal wetland restoration and management to minimize the impact of climate change in the future.