Methane emissions from three lagoonal estuaries in southern Texas, northwest Gulf of Mexico, were investigated from May 2008 to May 2021 to evaluate the contributions from different sources and factors influencing CH₄ transport. Although the estuaries were connected, there were high spatial variations in CH₄ emissions due to diverse vegetation, hydrological processes, and influences of extreme weather and human activities. More CH₄ was released from the seagrass-dominated lagoon than from the tidally controlled mangrove estuary and the bay with open water. Seagrass meadows unexpectedly emitted more CH₄ (221.1±190.7 µmol/m²·d) than mangrove creeks (94.7±81.3 µmol/m²·d), at least partly due to tidal processes. Tides could reduce CH₄ emissions by decreasing dissolved CH₄ concentrations by exporting CH₄ from mangrove creeks to the outer bay during ebbs and diluting CH₄ concentrations using floods. The highest daily CH₄ flux appeared in the channel of the lagoon dominated by seagrass, suggesting that the disturbance of vegetated sediment could severely enhance CH₄ emissions. In addition, gas leakages from a petroleum platform were observed to be a direct anthropogenic CH₄ input to the atmosphere. Moreover, mangrove dieback caused by extreme cold events and riverine transport of CH₄ due to heavy rains significantly enhanced local CH₄ emissions. This study indicated diverse sources and complicated factors that impacted CH₄ emissions in coastal areas, which needs thorough consideration.

Primary Presenter: Hao Yu, Texas A&M University-Corpus Christi (hao.yu@tamucc.edu)

Authors:

Richard Coffin, Texas A&M University-Corpus Christi  (richard.coffin@tamucc.edu)

Derry Xu, Texas A&M University-Corpus Christi  ()

Hannah Organ, Texas A&M University-Corpus Christi  ()