Greenhouse gases, which warm the Earth’s atmosphere, specifically methane, ethane, propane, and butane, are emitted from natural marine hydrocarbon seeps around the world. These greenhouse gases do not receive as much attention as carbon dioxide, but they are up to 26 times more detrimental than carbon dioxide as a greenhouse gas, and their effect on the marine environment is uncertain. Coal Oil Point, CA, the largest known marine seep field, releases more than 100 billion kg of gas each year. Gas released from this seep dissolves into the water column, giving microbes an opportunity to oxidize these natural gases before they are released into the atmosphere. In this study, we investigate the effects of microbial consumption on the ratio of carbon-13 to carbon-12 in the dissolved hydrocarbon plume in order to explore how microbial metabolism controls this ratio. Assuming that the lighter isotope is metabolized at a faster rate, the relative change of these isotope values can provide insight into the microbial activity around hydrocarbon seeps, and an advanced understanding of the down plume flow of the dissolved gases.