Closing in

Happy Memorial Day.  Today we’ve been trying to trace the deepwater plume as close as possible to the leaking wellhead.  Finally, after about 14 hours of searching and 5 unsuccessful CTD casts, we closed in on the source of the plume.  After a very long day, we finally have this feature well constrained.  We found more visible oil in the deepwater today – at different sites from yesterday – which increases our confidence in this finding. Several people have asked me how much methane versus oil is in these plumes.  We can’t answer that question yet.  But, the plumes are very much enriched in gas.  After we complete the sample analysis, we’ll be able to do this calculation.  I’ll try to make some rough calculations tomorrow to get a feel for the volume and magnitudes we are dealing with.

Three people asked whether we plan to fingerprint the oil from the deep plumes.  Yes, we will be doing that as it is the only way to concretely link the plume oil to the oil leaking from the wellhead. Four others asked whether we are measuring the dissolved inorganic carbon (DIC) concentration in the plume waters.  Yes, we are measuring DIC concentration.  In addition, we are measuring the stable carbon isotopic composition of methane, DIC, oil, and microbial biomass and the radiocarbon content of methane, oil and particulate organic carbon (POC).  This way, we can use the unique isotopic signatures of oil and gas to track these compounds into the microbial food web. Multiple people have asked about oxygen depletion and whether oxygen depletion will become a big problem out here.  We do not know the answer to this question.  Oxygen is depleted but it is not at dangerously low levels and we don’t know the rate of depletion yet.  We will know this in a few days.  If oxygen gets too low (less than 2 mg/L), organisms that can flee or avoid low oxygen waters will do so.  The problem would be for the organisms that are sessile and cannot flee. We’ve also gotten a lot of questions about what the surface oil looks like. Today, we have been within 3 miles of the leaking wellhead.  In here, the distribution, texture, and extent of surface oil slicks are extremely variable but there was oil at every site we visited. In places, there was a thin oily sheen on the water (see image).  In other places there were odd-looking ‘pancakes’ of oil floating on the surface (see image).  In these same places, there were bizarre orange and black stringers, some 10’s of cm long, as deep in the water column as you could see.  These stringers looked like mucous strings but they were the color of oil.  We don’t know what they are but they are abundant as far as you can see into the water column.  There are mats of oil (see image) and then there are thick ropey sea rows of oil (see image). There were a lot of surface burns today, more than we’ve seen since we got out here.  When it got dark, you could actually see the flames reaching high into the air. We got to enjoy a beautiful sunset tonight and pretty soon the sun will be rising again.  Before the sun rises, we’ll begin another day of plume chasing.