This report includes observations from an EcoRigs scuba sampling trip, on the east side of the Mississippi, to Main Pass (MP) 311 on August 8th 2010. We were surprised by what we found, the subsurface plume layer was larger, the water more turbid and currents were swifter than we normally encounter. We periodically saw scummy foam and oil sheen on the surface and oil on the pilings and the heavy murky plume for the upper 40 to 45 feet. The water cleared up at about 45 feet and we saw white noodles at 45 to 60 feet. Noodles are stringy white materials that fall out of subsurface plumes that are located in the upper water column. We caught a few on tape, but we missed catching a flurry of them on film when the noodles were coming down like snow.
The currents were extraordinarily swift, 5 mph down to 60 feet (the extent of our dive). I was holding on to a pipe and the current forced me horizontal like a flag in a strong wind. The plume was much more turbid than any other time in the past, with the exception of a dive on Mississippi Canyon (MC) 194 on June 24. (Aug. 8 video here.)
On a previous visit to MP 311 on June 6th, we observed a similar phenomenon and was described on the scene as big balls of brown “snot” and can be seen on video here.
We also have a video of MP 311 on May 19th and you can see materials from globules, flakes and small particulates to fine materials and dissolved oil and dispersants. You can view that here.
The May 19th video at MP 311 shows particulate oil and dispersants moving down the water column. The oil has not broken down to fine materials yet, as seen in the June 6th and August 8th video. The oil appears to be in transition to finer materials which may be caused by agitation from the wave action and currents. The water is relatively clear and fish do not appear to avoid the areas.
Finally, a video from October 2008 is presented for reference to view water conditions before the Deepwater Horizon spill.
I should note that MP 311 is on the east side of the river in 250 ft (76 m) of water and in a marine transition area, where the water is sometimes green due to freshwater flows on the surface of the ocean (freshwater floats) from the Mississippi. When wind and currents blow from a southerly direction, as it often does during the summer, blue ocean currents prevail and the water conditions around MP 311 are blue and clear. When fresh water prevails, there is greenish layer in the upper 10 -20 feet called murk. The fresh water gets pushed east and west of the Mississippi depending on prevailing wind and currents. When the winds are from the easterly direction, the surface water is blue at MP 311 and the murk is on the west side of the Mississippi.
We are very cognizant of the fact that we may be mistaking the oil and dispersant plume for a freshwater plume. There are characteristics that distinguish the two, first, the presence of the noodles or snot falling down the water column indicates that the plume is not just fresh water. Secondly, plume has a different mixing pattern than a freshwater layer. Looking at the oil and disperant plume from below, the underside of the plume billows and is not as even a layer like fresh water. The fresh water and the oil plume can both be present, however, the combination is much darker than freshwater alone. A freshwater layer was present on August 8th and May 19th but not so prevalent as in October 2008. We are presently collecting water samples and testing for Total Petroleum Hydrocarbons (TPH) & Trace Metals to verify our observations.
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