Natural petroleum seeps release equivalent of 8 - 80 Exxon Valdez oil spills

Washington, May 14 (ANI): A new study has shown that the amount of oil residue in seafloor sediments that result from natural petroleum seeps off Santa Barbara, California, is the equivalent of approximately 8-80 Exxon Valdez oil spills.

Researchers at Woods Hole Oceanographic Institution (WHOI) and the University of California, Santa Barbara (UCSB), did the study.

It shows the oil content of sediments is highest closest to the seeps and tails off with distance, creating an oil fallout shadow.

It estimates the amount of oil in the sediments down current from the seeps to be the equivalent of approximately 8-80 Exxon Valdez oil spills.

"Farwell developed and mapped out our plan for collecting sediment samples from the ocean floor," said WHOI marine chemist Chris Reddy, referring to lead author Chris Farwell, at the time an undergraduate working with UCSB's Dave Valentine.

"After conducting the analysis of the samples, we were able to make some spectacular findings," he added.

There is an oil spill everyday at Coal Oil Point (COP), the natural seeps off Santa Barbara, California, where 20-25 tons of oil have leaked from the seafloor each day for the last several hundred thousand years.

Based on their previous research, Valentine and Reddy surmised that the oil was sinking "because this oil is heavy to begin with."

"It's a good bet that it ends up in the sediments because it's not ending up on land. It's not dissolving in ocean water, so it's almost certain that it is ending up in the sediments," said Valentine.

To conduct their sampling, the team used the research vessel Atlantis, the 274-foot ship that serves as the support vessel for the Alvin submersible.

The research team sampled 16 locations in a 90 km2 (35 square mile) grid starting 4 km west of the active seeps.

Sample stations were arranged in five longitudinal transects with three water depths (40, 60, and 80 m) for each transect, with one additional comparison sample obtained from within the seep field.

"The instrument reveals distinct biomarkers or chemical fossils - like bones for an archeologist - present in the oil. These fossils were a perfect match for the oil from the reservoir, the oil collected leaking into the ocean bottom, oil on the sea surface, and oil back in the sediment," said Reddy.

"We could say with confidence that the oil we found in the sediments was genetically connected to the oil reservoir and not from an accidental spill or runoff from land," he added. (ANI)