Salt marsh fluxes of halocarbons

Coastal salt marsh measurements in the United States occurred on the west coast (Rhew and Mazéas, 2010), east coast (Jiao et al., 2018; Wang et al., 2016) and Gulf Coast (Rhew et al., 2014). Our group also conducted the first net ecosystem flux measurements of methyl halides using micrometeorological techniques at a brackish salt marsh, and a compilation of published salt marsh emissions provided a geographically weighted global salt marsh source estimate (Deventer et al., 2018).

Background: Coastal salt marshes may be the largest known natural terrestrial sources of methyl halides. While smaller emissions were reported from mid- to high-latitude salt marshes in Scotland, Australia and northern California, subtropical salt marshes found the highest reported flux per unit area from a natural terrestrial ecosystem, demonstrating the importance of geographic coverage for field studies. To measure at larger spatial scales, our group developed a Relaxed Eddy Accumulation system to measure ecosystem-scale fluxes at a brackish salt marsh in the San Francisco estuary at Rush Ranch / Suisun marsh (Deventer et al., 2018). These first ecosystem-wide flux measurements of methyl halides from a terrestrial ecosystem showed temporal correspondence with flux chamber results but provided better spatial coverage, and this study demonstrated the nonlinear impact of climatic factors in determining emissions.