USF’s R/V Weatherbird II Detects Invisible Hydrocarbons in Gulf Waters
By Vickie Chachere
St. Petersburg, Fla. (May 28, 2010) – Researchers aboard the University of South Florida’s R/V Weatherbird II conducting experiments in a previously unexplored region of the Deepwater Horizon oil spill have discovered what initial tests show to be a wide area with elevated levels of dissolved hydrocarbons throughout the water column, possibly indicating that a limb of an undersea oil plume has spread northeast toward the continental shelf.
(A June 7, 2010 report by CNN.com covers the findings of USF scientists and researchers. Click here to view the report.)
The Weatherbird II deployed a variety of instruments to detect the signature of hydrocarbons, which will undergo further testing to verify if it Deepwater Horizon oil. The probable concentration of dissolved hydrocarbons was highest at 400 meters below the surface.
"The ramification is that what we see at the surface is not the entire story," said Ernst Peebles, a biological oceanographer who was aboard the Weatherbird II and is one of the lead researchers on the project.
"This is not a big glob of oil drifting," he said. "These are layers. They show up on sonar as layers with clear water in between."
The discovery is significant because it verifies the presence of dissolved hydrocarbons in the deep recesses of the Gulf of Mexico that cannot be seen with the human eye but could eventually become a threat to marine life and habitats.
Samples and data gathered during the voyage are now undergoing additional testing. Given the "insidious" nature of dissolved hydrocarbons on marine environments, the discovery has scientists concerned.
The R/V Weatherbird II made its discovery on Tuesday afternoon while performing tests along a series of stations east and northeast of the collapsed Deepwater Horizon rig. The researchers returned to the area on Wednesday and performed a precise repeat of their experiments which produced the same results.
The researchers’ preliminary findings came from water sampling using three separate technologies: a CDOM Fluorometer, the ship’s sonar and gliders which are able to assess water conditions as they move through the water column.
“Our concern regarding these contaminants is they have the potential to be incorporated in the food web,” said David Hollander, a chemical oceanographer who is a lead investigator in the research mission.
“The first ecological impact of this spill is the effect on coastal habitats, including marshes, beaches and estuaries. The second threat to nature would be the impact on the food webs. That is what’s at risk.”
The R/V Weatherbird II’s journey in the gulf did have some bright findings for the state of Florida. Several stations where water testing was completed between the Loop Current and the Florida coast showed currently clean water, no weathered oil on the surface and no record of dissolved hydrocarbons at depth.
The researchers were investigating the area northeast of the leaking well after models created by USF’s Ocean Circulation Group Director Robert H. Weisberg indicated that oil plume from the spill might have spread underwater in that direction.
The underwater discovery of dissolved hydrocarbons came in area that is 35 kilometers northeast of the ruptured wellhead and in an area roughly south of Mobile, Alabama.
Scientists will need to conduct further tests to determine whether the suspected dissolved hydrocarbons were caused by dispersants or the emulsification of the oil as it moved through the water away from the leaking well.
The R/V Weatherbird II departed May 22 for the spill zone on the six-day mission. Seven scientists from USF and the Florida Fish and Wildlife Conservation Commisson's research institute and six crew members are on board.
Video by USF News Intern Amy Mariani.