Wednesday, Nov. 30
Lat: 35.23 N
Long: 21.48 E
Air temp: 16.2°C, 61.7°F
Bar. pressure: 1024.1 mbar
Sea surface temp: 19.2°C, 66.5°F
Winds: ENE; 21.3 knots
Jason and the chamberpots
November 30, 2011 (posted December 1, 2011)
by Cherie Winner
You’ve planned for more than a year to go on a research cruise and get samples from the bottom of the sea. Once you are at sea, you only have two weeks to accomplish your goals. So you want to get the most you can out of every single dive.
WHOI geobiologist Joan Bernhard came on the cruise to study the
benthos, the organisms that live on or in the seafloor in Deep Hypersaline Anoxi Basins, or DHABs. Benthic organisms play a big role in cycling carbon, nitrogen, and other elements around different parts of the planet. On this cruise, she wants to learn what organisms are living in the DHAB sediments, and how they are able to survive in such a harsh environment with high salt levels and no oxygen.
So before we set sail, Joan and the Jason team loaded Jason’s basket with three different kinds of samplers that would bring back sediments from the DHABs. She started with many samplers of each kind, to be sure of getting the material she requires. When working by remote control with equipment 3.5 kilometers beneath sea surface, it’s best to bring backups.
“The general rule of thumb is, ‘Take two times as many as you want, and you’ll end up with what you need,” she says.
The basic sampler is the pushcore, which you can see in action in this video from Jason’s hi-definition video camera. The advantage of the pushcore is that it keeps the sediment layers intact, rather than smushing them all together. Also, they can be directed to a very specific spot, which is important when the area you want to sample is small, like the bathtub ring of a DHAB. When pushcore samples are returned to the ship, Joan and her team slice them into segments and study the chemistry and biology of each thin segment. We’ll talk more about that work tomorrow.
The second kind of sampler is the injection core, which looks and works just like a pushcore, except there’s a valve and tubing at the top through which the scientists can squirt various chemicals. They might inject a preservative like RNALater or formaldehyde, or a marker like CellTracker Green® (CTG), which only labels living cells. CTG gets into living cells, where enzymes called esterases clip off the end of the CTG, which then fluoresces green. It’s a way to find out if cells were alive when you found them. Sometimes dead cells can look like they’re alive, especially in a place like a brine basin where the high salt concentration essentially pickles the cells. But dead cells don’t have esterases, so no matter how good they look, if they are dead, they won’t clip CTG and they won’t glow green under fluorescent light.
Then there are the chamberpots. They have much larger diameters than pushcores and they sit front and center on the Jason basket. They receive big scoops of sediment from ice scoops wielded by Jason’s arm. In these samples the sediment gets all stirred up, so you can’t do the thin slices you can with pushcores and injection cores. But you get more starting material. On this cruise, some chamberpots will get a dose of RNALater, which we talked about in Dispatch 2. Others will receive fixatives that will preserve cells for examination with different kinds of microscopes.