Isabella Rico, Vassar College

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Abstract:

Methane exists in estuarine sediment in high concentrations due to microbial activity, lack of oxygen, and organic matter availability, but is understudied. Estuarine methane is not a significant source of emissions to the atmosphere, as most of the methane remains in the aquatic environment. Here it can be transferred to the water column, depending on sulfate availability, and oxidized aerobically into carbon dioxide. An influx of CO₂ can lower the pH, causing acidification, which can be harmful to aquatic ecosystems. The primary goals of this study were to quantify the sedimentary methane flux across the salinity gradient of the Patuxent River (PAX) and to determine the impact of the methane on the water column pH. Modeling programs were used to determine flux and subsequent pH changes. Methane flux to the water column of the PAX does not appear to be correlated with the salinity gradient. Further study into the many factors that impact flux and the specific makeup of each station is needed to solidify this conclusion. Current methane concentrations are not impacting the pH in the PAX, but there is potential for heightened methane flux to occur as anthropogenic climate change worsens, leading to the lowering of pH in the water column. When greater methane concentrations were modeled, the pH was lowered by up to 1 unit. Further study of the climate dependent factors that impact methane flux is necessary to make a definite conclusion, however, it’s clear that methane has the potential to reduce pH in marine systems if concentrations increase.