After our last core of the day yesterday, we once again hove to,this time at a site 20 miles due east of the Deepwater Horizon site. At that time (midnight), the winds were calm and no oil or odor were evident. At 04:00, the winds picked up from the west and a sheen of oil arrived and, along with it, a distinctive hydrocarbon odor. From there to our next station, sited at 2 miles due south of the DH rig, we recorded observations of the oil characteristics every 15 minutes (see attached “oil observations” table). As this table records, we passed through some areas of very high concentrations of oil while others were moderate or clear. The skimmer fleet was north of us during this transit so we presume that the oil was even heavier in that area.
We acquired cores at 4 additional sites starting near the DH rig (site 24) and progressing in to a site near the Southwest Pass of the Mississippi River (site 27). Nothing anomalous was seen in or on any of these sediment cores with the possible exception of roughly 6 dead euphausids at site 24. Although this is an unusual find and we find no definitive link to the oil, we do intend to follow up on this observation by acquiring an additional sample from this location for the express purpose of carefully preserving such organisms for further study.
The shallow site (27) was in only 17m of water and was adjacent to one of the areas in Louisiana where oil had been reported as washing ashore. Our intent here was to investigate whether oil had also been deposited on the seafloor but we saw none either on the surface or on the sediments. This site is characterized by rather fresh water (11ppt salinity) due to the river discharge both to the west and to the east. It can be expected that this discharge will displace the ocean surface water and help to buffer the shoreline from oil deposition except during strong southerly winds.
As before, the attached table and map image list all of the stations visited to date, including the 4 cores obtained today. We are currently headed back to Cocodrie (expected eta 06:30) where we will exchange personnel and pick up new equipment for the second leg. This will include a towed package (Acrobat) with CDOM fluorometer tuned to detect hydrocarbons, an ROV for investigating subsurface oil aggregates, a multispectral sensor for ground-truthing NASA flyovers, an innovative pCO2 sensor, an acoustic recorder intended to monitor marine mammals, and a collection of supplies for preserving plankton, water, and sediment samples.