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Variability of greenhouse gas fluxes in wetlands and importance to blue carbon assessments
Citation:
Wigand, C., D. Perry, J. Loffredo, J. Bishop, S. Ayvazian, D. Cobb, N. Schafer, P. Colarusso, AND R. Martin. Variability of greenhouse gas fluxes in wetlands and importance to blue carbon assessments. NEERS Spring Meeting 2023, Brooklyn, NY, April 27 - 29, 2023.
Impact/Purpose:
The rate of carbon storage in wetlands is higher than storage rates in forests. Wetland plants use carbon dioxide in the air to photosynthesize and store carbon in the soil. It is a benefit to people that wetlands can transform the greenhouse gas, carbon dioxide, to stored carbon in the soil. However, somtimes wetlands may also release other greenhouse gases such as methane and nitrous oxide. Release of these other greenhouse gases could offset the benefit of the stored carbon in the soil. We examined greenhouse gas uptake and release from a variety of wetlands, including healthy, impacted, and restored sites. The balance of greenhouse gas release was greater at sites in more polluted sites than in less impacted ones. We also found higher rates of greenhouse gas emissions at recently restored sites that received dredged materials than reference wetlands. Understanding the variability in greenhouse gas emissions in healthy, impacted, and restored wetlands is important for managing carbon storage.
Description:
Blue carbon (C) represents long-term C storage in wetlands and rivals C stored in land forests. Methane (CH4) and nitrous oxide (N2O) emissions from wetlands may offset C stored. We examined greenhouse gas (GHG) fluxes associated with elevation enhancement, urbanization, and proximity to oyster aquaculture. Placement of sediments on drowning salt marshes is a restoration approach to build elevation. In a lab study, additions of 5 and 10 cm of dredged sand to the marsh surface resulted in short-term increases in CH4 and N2O emissions. Along an urbanization gradient in the San Juan Bay Estuary (PR), CH4 emissions from urbanized mangrove sites were five times greater than less urbanized sites. GHG fluxes in eelgrass beds near and distal to oyster aquaculture are now being studied. Using carbon dioxide (CO2) equivalent coefficients for CH4 and N2O, the balance between wetland CO2 uptake and CH4 and NO2 fluxes are assessed. Consideration of anthropogenic stressors on GHG fluxes in wetlands is important to better understand blue C sinks.
