We are still in the vicinity of Ground Zero and are continuing to collect sediment samples on several transects from the spill site to points north and west. We are looking for the effects of the oil with seems to be leaving the surface and settling towards the seafloor at an unknown rate. I have attached two photos: The first (6891) shows the NIUST team in action, recovering the box corer. This is a very heavy device that is more complicated than it looks and these guys are experts at making it work so we have had 100% success in obtaining useful cores. Each core takes about 2-3 hours because of the time it takes to lower this device to 1500m, recover it, remove the box from beneath it, sub-sample the mud in the box, clean all of the excess mud up, and re-load it for the next core. Pictured are, from left to right, Chris Berkey (the freelance photojournalist who has promised to give us copies of his excellent photos), Matt Lowe (from Ole Miss; a genius at getting things into and out of the water), Dr. Arne Diercks (USM grad and current employee, also Chief Scientist for the cruise), and Andy Gossett (also Ole Miss; can make anything or make anything work). These guys are all masters at what they do and the coring operation always runs safely and without a hitch.
The second photo (6887) shows the surface of the water at the current sampling location. Okay, so it’s not all that photogenic but it gives you a really good idea of what we’re seeing out here. On the surface is a very light sheen of oil, as you’d expect to see with an oil spill. Along with that are the tan clumps of oil ranging in size from pea to pancake. Some of these can be very filamentous in shape but others are just ragged clumps of oil, appearing almost as if there were some kind of fiber involved. Most interesting to us, however are the smaller clumps (I’m calling them oil aggregates) that appear below the surface. It’s counter-intuitive to see “oil” sink below the surface but you have to remember that this isn’t motor oil, it’s crude oil and there are all kinds of compounds in it, including many that are heavier than water. Apparently, the dispersants that they are spreading on the surface (using C-130’s and ancient DC-3s that have been retrofitted with turbo-prop engines) are causing this oil to coagulate into these relatively large clumps. This reduces the amount of surface area, which causes drag, for the amount of oil volume, so if they’re heavier than water, they’ll sink more rapidly than they would have, had they not aggregated. The question is, what happens to this oil after it leaves the surface? How rapidly does it sink? How far down has it been able to travel so far? What effect is it having on the midwater ecosystem? What will its ultimate fate be? We are planning to bring some novel gear along next time to investigate some of these questions but it’s clear that some long term monitoring will be required to address many of these issues.
One of the instruments that we’ll bring along next time is a small (some call it “micro”) Remotely Operated Vehicle (ROV). We’ll use this to qualitatively describe the concentration of oil aggregates in the surface layer down to about 75m, which is as far as it can go. We’ll also be looking at the plankton in the water and maybe even the nekton (fish) if any come around. In addition, NIUST has a really large ROV that is capable of placing and recovering relatively large instruments on the sea floor and we expect to have that on site in the weeks to come but not for the next leg.
A final note: I’ve been surprised by the total absence of dead animals out here. Granted, it’s an “oligotrophic” environment (blue water, low nutrients, sparse concentration of anything living) but still, I was expecting to see the occasional dead fish, oiled bird, rotting jellyfish. Instead, we’ve seen flying fish that skim along the surface, and schools of needle fish and others that seem oblivious to the oil and that’s a surprise. It’s still early so the toxic effects may not have had their full effect but this clearly demands some closer investigation.