[Coral-List] Re-post Observations of Sub-surface Oil
stevekolian at hotmail.com
Wed Jul 21 22:49:32 EDT 2010
Hello, this is a cleaned up, annotated version of the report posted earlier this week.
Report July 19th 2010: Observations of Sub-surface Oil south of the Mississippi River
On July 15th 2010, a new type of subsurface oil and dispersant signature was observed by Paul Sammarco and Scott Porter (Louisiana Universities Marine Consortium – LUMCON). It consisted of a large plume of white stringy mucus-like material. It was detected at two locations (Grand Isle (GI) 93C & GI-90A) occurring between 0 ft and 120 ft below the surface and beyond. The substance varied in size from small flakes to long strings that extended up to 6 feet (Sammarco and Porter 2010).
They observed two distinct plumes of oil and dispersants on July 15th at these sites. There was the more common greenish cloudy sub-surface plume consisting of fine particulate matter in the upper 30 ft of the water column. The last time GI 93 was visited, on June 16, 2010, the same type of turbidity was observed, except that it was confined to the upper 20 feet of the water column. White mucus-like flocculent material was not observed during the June 16 dive and the depth of the more common greenish plume did not appear to be as large. There was no surface oil or sheen on either day (EcoRigs 2010a). At this point, it is not known whether the white flocculent material was derived from an oil and dispersant mixture or organic material discharged within the Mississippi River plume, known to often sweep through this sector.
A common nepheloid layer was observed near the bottom – a turbid area, probably comprised mostly of suspended sediment and organic material. Because of the limited visibility, it was not possible to tell whether there was accumulated oil covering the bottom, most likely composed of high molecular weight hydrocarbons (e.g., PAHs – Polycyclic aromatic hydrocarbons). This is a highly sedimented area, due to contributions from the Mississippi River and its distributaries, near the Mississippi Canyon area.
Similar flocculent material has been observed before; however, it was brown and not as persistent. At Main Pass (MP) 311, on June 6, 2010, large pieces of semi-translucent mucus-like materials were present below the brown particulate type of plume. On this day, the brown oil and dispersant plume occupied the upper 20 feet of the water column (EcoRigs 2010b).
Finally, some base-line data of water conditions were collected at GI-93. The video captured in July of 2009 at GI-93 by Toby Armstrong (2009) suggests that thespecies composition of fishes observed during pre-spill conditions from the current composition. A large population of fish at GI-93 and -90 still remains, however. Red snapper and amberjack were present on July 15th in greater populations than previously observed, although red snapper are known to be transient. Video and analysis of fish and invertebrate populations are forthcoming.
Report by Paul W. Sammarco, Scott Porter, Toby Armstrong, and Steve Kolian.
Armstrong, Toby 2009. Video footage taken by Toby Armstrong July 2009. Project supported by EcoRigs staff, self-funded.
EcoRigs 2010a. Video footage taken by Scott Porter, June 16th 2010 at GI 93. Project supported by EcoRigs staff, self-funded.
EcoRigs 2010b. Video footage taken by Allen Walker, June 16th 2010 at GI 93. Project supported by staff of EcoRigs, self-funded.
Sammarco, P. and S. Porter, 2010. ROV video, Sammarco LUMCON, Chauvin, LA, (7/15/10); project supported by Louisiana State University Coastal Marine Institute/U.S. Dept. of Interior – Minerals Management Service (MMS).
Best Regards, Steve Kolian 225-910-0304 cell
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