Life in the Dead Zone

It’s about 5 am central time, we’re on our last transect of this cruise, Neil Young is ‘Rockin’ in the Free World’, and the Late-Night watch is feeling contemplative. As we turned the corner and deployed the CTD for our last transect, the seas laid down to a gentle roll for the final push. The data are still coming in, and we’re continuing to see some interesting patterns in the oxygen and CDOM – multiple layers of low oxygen that correspond to the fluorescence signals. The Mini-OPC is cranking along, churning out plankton patterns that also seem to have some correspondence with the physical features, but the details will have to wait for the post-cruise processing on dry land. Our water-catchers, who have been sampling the smallest organisms, including bacteria and micro-plankton, have almost exhausted their supply of sample vials, just in the nick of time. Upper trophic level sampling – meaning fish – has taken a break due to bad weather that interfered with the acoustic signals used to identify fish targets in the water column. The companion vessel that was shadowing us and trawling for fish had headed for home after filling their freezer and suffering through a long night of rough seas.

That’s where we’re at, but the work is not done yet. We’ll finish up the transect after day break, secure the gear on deck and begin our transit home. On the way back to Cocodrie, LA, we’ll start to pack up the labs and prepare our stuff for shipment back to Corvallis, OR, Cambridge, MD, Akron, OH, Dauphin Island, AL, Baton Rouge, LA, and Ann Arbor, MI. Once we hit the protection of Terrebonne Bay, we’ll have to calibrate the fish acoustics gear. This entails dangling two different tungsten carbide spheres from a fishing rod as standard targets for the acoustics instruments. In other words, the metal balls act as fake fish with known size and weight. After running the instrument with the simulated fish hanging below it, the operator can go back through the collected data and determine the density of fish at any given time and depth.

All in all it has been quite an eventful cruise. The OPC has been rebuilt twice and replaced once. The TAPS (a high frequency acoustic instrument used to measure zooplankton abundance) was fixed on day one as well. The 15 year old Scanfish tow cable, tired and frayed after so many years of service, had to be mended. The fisheries acoustics on the other hand, was brand-spanking new at the beginning of the cruise and had a successful shakedown after working out some kinks on the first couple of days. One other casualty, besides the OPC which is still here, is the ship’s gaff, which was lost at sea while retrieving the Scanfish in rough weather. ‘Twas a good gaff too, and will be sorely missed.

Much of our success would not have been possible without the experience and expertise of the RV Pelican crew. They have had a very busy summer, thanks in large part to the flurry of activity around the oil spill, but were nonetheless always ready to make sure the science happened. And we were well fed. Very well fed. Some highlights included sushi (!), carrot cake, tiramisu, eggs benedict, egg rolls, gumbo, and various baked goods, all homemade. Oscar Wilde once said something like, ‘The only difference between going to sea and prison is the added risk of drowning’, but I think the food probably elevates research cruising even more.

Speaking of food, it’s almost breakfast time. I wonder what we’ll have this morning?

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Some content in this post provided by a ghost writer who shall remain nameless.

I’ve been quiet for a few days, mainly because of equipment problems that have kept me busy, but we also encountered some inclement weather last night that was not conducive to sitting at a computer. The equipment problems have been continuing with the Scanfish OPC, so we took a very drastic move of trying to rig up a different instrument onto the Scanfish – a mini-OPC. This is exactly the same technology, but in a smaller package. It’s a newer piece of gear – 10 vs. 15 years old, and has usually been mounted on a different towing package called an Acrobat.  The Acrobat is smaller and has fewer bells and whistles than the Scanfish, namely meaning it doesn’t ‘fly’ itself like the Scanfish does. We bring the Acrobat out just incase we have problems with the Scanfish – as my advisor used to say, when you go to sea you bring one of everything for you, and one for Davy Jones.

In this instance, we were able to take the mini-OPC off the Acrobat, and with the help of the ship’s engineers and technicians, we got it mounted onto the Scanfish.  The engineers and tech actually scoured the ships nooks and crannies to fine a piece of aluminum that could be drilled out to accommodate mounting on the Scanfish and attachment to the mini-OPC. Then we had to make a cable to plug the mini-OPC into the Scanfish. Fortunately, this was foreseen before we lit out for the bayou, and one of the Scanfish technicians ordered some spare ‘pig tails’, which are just pieces of wire with the proper moulded fittings on them. We took an old cable that had the proper fitting on the other end, cut it, and made an underwater splice with the pigtail and the old cable. This of course required us to make sure we had the correct wires connected. Probably the most nerve-wracking part for the planktoneer, who actually made the splice. I learned how to do this watching some of my mentors who resurrected failing equipment on some of my earliest cruises. There are a lot of different ideas about how to do this, and having only done it once before on my own, I was a bit anxious, and probably went overkill with the splicing tape, ScotchKote, and heat-shrink tubing, but so far so good.  It’s not a particularly ‘supple’ splice, meaning it’s pretty rigid because I layered so much material, but it’s watertight so far and fits in the Scanfish body, which is all that really matters. Here’s a picture of our newly mounted mini-OPC on the Scanfish, and stay tuned for a data update, once I get the stuff analyzed.