The identity of the mysterious plume spotted in the depths of the Gulf of Mexico has been confirmed: it is oil.

As reporter Mark Schrope reported from the research vessel Pelican in the early days of the Deepwater Horizon disaster, researchers had identified a huge plume of something. Now the detailed findings on that something have been released.

Yesterday researchers confirmed that “distinct layers of degraded oil” had been found at depth in the Gulf of Mexico (University of South Florida press release).

Samantha Joye, a professor of marine sciences at the University of Georgia, told reporters that around a kilometre from the well head, “there’s a huge signal, and that signal is between 11,000 1,100 metres and 13,000 1,300 metres water depth”.

Analysis of samples collected by the Weatherbird II research vessel by NOAA has failed to conclusively link this oil to the leaking Deepwater Horizon well though (NOAA). However, Joye said the data on particles and chemical analysis in the water column collected on the cruise provided “strong evidence that the plume does derive from the Deepwater Horizon”.

The plumes have proven controversial with BP chief executive Tony Hayward saying last week, “There aren’t any plumes.” BP’s chief operating officer Doug Suttles said today that there are no plumes in “large concentrations” and it “may be down to how you define what a plume is here” (NY Times).

NOAA Administrator Jane Lubchenco said yesterday, “We have always known there is oil under the surface; the questions we are exploring are where is it, in what concentrations, where is it going, and what are the consequences for the health of the marine environment?”