Another Day, Another Core
Unlike the Kasten core, which is a single 3-meter long barrel, the megacore has 12 short tubes.
Each tube has the potential to capture up to 60 cm of water and sediment right at the seafloor - many of the researchers here are interested in studying that sediment-water interface.
The 12 tubes are loaded into the megacore rig and it is lowered off the stern of the ship with the same winch that is used for the Kasten core.
Depending on the water depth, it can take over an hour to send the megacore down to the bottom and bring it back up. The researchers don their safety gear and head out on deck to detach the new samples from the rig once it is back onboard.
Each tube has a shutter at the bottom which is triggered to close when the full core lifts off the seafloor – sometimes not every core closes. In this video (courtesy of Santi Munevar), 10 of 12 tubes were sealed and now contain a sediment sample. The shutter did not close on the other two.
Video by Santi Munevar:
Before a megacore tube can be brought inside, it has to be detached from the rig – and to do that, the shutter that is holding in the cylinder of sediment has to be replaced with a thick rubber stopper called a bung. This invariably requires someone to lie down on the deck in a muddy puddle of ice cold water and attempt to shove a stopper into a tube of mud that is working with the force of gravity to spill out everywhere. Also, often when you shove the bung into the bottom, seawater spills out the top of the tube, typically soaking the person trying to insert the bung. Bunging is the number one reason people’s safety gear looks like they rolled in dirt at some point on this expedition (because they kind of did).
Megacore tubes that have been bunged and capped are placed in a carrying case to be brought inside.
One of my favorite things to do is to inspect the water-sediment interface for signs of life - this is where we discovered Bruce the Antarctic Sea Anemone.
We then begin processing the core samples by slicing off one centimeter of sediment at a time and placing each slice in its own baggie.
Santi Munevar pulls the core tube down to reveal 1 cm of sediment, which Elaine slices off using “Mr. Slicey” and Rachel catches in a plastic bag. A typical core is 40 cm long, so when all 12 tubes successfully trigger and are filled, it can take a while to process all of them. The majority of these samples will be shipped to different research institutions at the end of this expedition.