Fossil Carbon in Particulate Organic Matter in the Gulf of Mexico following the Deepwater Horizon Event

In 2010, the Deepwater Horizon event released large quantities of natural gas into the Gulf of Mexico in addition to oil. Several studies have reported evidence of the introduction of petro-based carbon into the Gulf planktonic foodweb. This study reports results consistent with the hypothesis that methane-derived carbon entered the food web through small particles indicative of methanotrophy. Suspended particulate organic carbon (POCsusp), collected from the Gulf water column in 2011 and 2012, was depleted of δ13C and Δ14C relative to surface planktonic production. The suspended particulate organic fraction was as depleted as −37‰ in δ13C and −618‰ in Δ14C. The 13C and 14C values were strongly correlated and indicated the admixture of modern surface carbon with a depleted radiocarbon source that had a δ13C value indicative of methane input. Mixing models indicated that 28–43% of the POCsusp may have been derived from fossil CH4.