Today’s highlight was the discovery of a feature that could be the most important finding of the trip. We have been hypothesizing that some of the oil that is coming out of the well is most likely not getting to the surface so we engaged in two efforts to find subsurface oil. The first effort was a shallow survey with the Acrobat that lasted all night. We towed the package in a 10 x 10 mile box around the well, surveying from the surface (6m) to 47m which was as deep as the acrobat would go. The first leg was to the south of the well and we saw no oil on the surface and no indication from the fluorometer on the Acrobat package although there was some increased fluorescence at the bottom of our survey depth, near the thermocline. At the top of the eastern leg heading north, we started seeing an increase in fluorescence just below the surface and this was related to a marked increase in oil on and near the surface so we are confident that the signal it is producing relates, at least qualitatively, to the abundance of oil.
Following the Acrobat survey, we mad a CTD cast, collected a box core, and completed the small boat and ROV sampling. The fluorometer on the CTD rosette revealed the presence of several layers of CDOM fluorescence at depths varying from 700 to more than 1300m. These layers also exhibited increased optical beam attenuation and reduced oxygen content to we decided to investigate the source of the material. We completed two more stations on the same bearing (246 degrees) but at 2.5 and then 1.25 miles from the well. Each of these revealed increasing signal so we concluded that the well was the source of the material and decided to spend the rest of the day mapping these layers. We proceeded to the south and then east of the well and the signal quickly faded so we moved around to the northwest, in very heavy oil (site 39) where the signal was also considerably reduced. As of this writing, we have completed site 39, where the signal was again present, and are about to start a CTD cast at site 40. We will report on these findings and provide more detail regarding possible mechanisms to generate these signals when we know more. Our preliminary working hypothesis is that this is hydrocarbon material that was produced by the well but that did not reach the surface, perhaps due to the deep injection of dispersants which BP has stated that they are conducting. We will continue to map these plumes with the techniques available to us but we suggest that a more thorough investigation of the composition and trajectories of this material is warranted.
As always, we have attached a table with all stations occupied and most activities engaged in to date and we have also posted some new photos on the ftp site. Two curiosities are included there; the first is a photograph of some of the ships spraying water into the air, an activity that several ships engaged in for hours, and the second is the collection of pyrosomas that were swept out of the water by the acrobat.