Researchers have confirmed that two large plumes in the Gulf of Mexico consist, as suspected, of dissolved hydrocarbons. Early analyses of samples from recent cruises have found hydrocarbons up to 78 kilometers from the leaking well, as well as encouraging signs that microbes are already degrading components of the oil. Although Jane Lubchenco, head of the National Oceanic and Atmospheric Administration (NOAA), describes the concentrations as "very low," she and other researchers caution that there still may be ecological impacts.
One cruise was led by Ernst Peebles, a biological oceanographer at the University of South Florida in St. Petersburg. He and colleagues aboard the Weatherbird II took samples in late May to the north of the Deepwater Horizon wellhead. Yesterday, they described at a news conference finding hydrocarbons in two layers (pdf), one 400 meters deep and another between 1000 and 1400 meters deep. The compounds were present in both layers at several hundred parts per billion.
Peebles's team gave portions of the water samples to NOAA, which ran its own tests. NOAA released an analysis yesterday, which describes similar concentrations.
The report notes that the 16 polycyclic aromatic hydrocarbons tested were all below ecotoxicological benchmarks. "That does not mean [the oil] doesn’t have significant impact," Lubchenco said at a press conference yesterday. "The impact that it has we remain to understand."
Read the complete story at Science Magazine.