THE EFFECTS OF OIL SEEPS ON SOUTHERN CALIFORNIA WATERSHEDS

Naturally occurring oil seeps can be found throughout California watersheds. Although natural, oil seeps are sources of organic and inorganic contaminants, such as polycyclic aromatic hydrocarbons (PAHs) and trace metals, that threaten the wildlife in impacted watersheds. Many studies have assessed the environmental impacts of marine oil spills; however, there is limited research on terrestrial oil seeps in riparian habitats. In this project, we analyze water samples from six oil seep-impacted locations in Southern California to investigate the effects of oil-seep contamination on water chemistry. We hypothesize that (1) oil seeps located near or within stream channels introduce metals to water and sediments, and (2) the presence of oil seeps in a channel changes the redox geochemistry of creek sediments and water, liberating additional metals. This redox shift happens when microbes use oxygen to consume the organic carbon in oil. Our results indicate there is a relationship between a sampling site’s proximity to an oil seep and the concentrations of redox sensitive trace metals, such as iron. We also observed an increase in direct oil seep derived trace metals, such as vanadium and chromium, in areas where immediate oil seepage occurs. Future work will include measuring the concentration of metals in stream sediment as well as in oil from the seeps.