CTD's, Carboys, and Colin's Critters
This morning, we are sitting on sampling station 2. It’s going to be a busy day, starting with a CTD at 0600. But as I’m up well before 0500 and sitting at my desk on the main deck, an albatross glides by my porthole. I stumble up to my stateroom, throw on my parka, grab the camera, and speed up the next four flights of rocking stairs to the bridge deck. Climbing stairs is one of the fun aspects of living on a ship on the wild Southern Ocean. As you step up, you find yourself alternatively heavier than usual on one stair then nearly weightless on the next few. It makes me chuckle each time. My mad dash to the top of the ship is rewarded with not just one but two albatrosses this morning.
Once the CTD returns to the surface, prior to breakfast, there’s a flurry of activity. The team takes samples of the water for various purposes. I help Colin fill three 60 liter carboys (large clear plastic jugs). It’s a mixture of seawater from 25 meters deep—where there’s ample sunlight for diatoms to photosynthesize, grow, and reproduce—and of 1500 meters deep, where nutrients are dense. Colin’s goal is to provide a great environment for the diatoms to grow in.
Tubing is attached to a valve at the base of the Niskin bottle. You allow the water to flow through the tube into your collection container and then shut it off and cap your container. Sounds simple, right?
Things I learn:
Don’t let the tubing touch the water.
If you accidentally touch the inside of the cap with your gloved hands, make sure you flush it out with seawater before you put it on the carboy/container.
The valve at the top of each Niskin bottle is for controlling the water pressure, not to start and stop the flow.
Gloves used to handle seawater don’t go in the “chemical waste only” bin.
Scientists are very patient with outreach people.
Colin takes these three large carboys and places them in their racks in the cool room. Diatom Alley’s first residents have moved in!
Their artificial sun (fluorescent lights) are on and will stay on, mimicking the Antarctic summer where the sun never sets. Now they are ready to be “fed.” (No one else calls it that, but I like to think of it as Colin feeding his critters.) He mixes up a solution of nitrate, silicate, phosphorus, vitamins, and trace metals such as iron, copper, and zinc—all the nutrients diatoms need to thrive and reproduce—and “spikes” the seawater. This is the only time they’ll be “fed” while they live in Diatom Alley; with the nutrients already in the seawater, they should have all they need for some time.
Once he has spiked the water, Colin turns on the magnetic plate beneath each carboy, which turns the magnetic blade inside each one. This mimics the turbulent motion of the waters of the Southern Ocean and keeps the nutrients circulating. He also sets up an aquarium air pumps so they have adequate oxygen. The cool room in which they’re housed will stay at a constant 3 degrees Celsius, which is slightly warmer than the water than they were taken from, which will encourage the diatoms’ growth.
Now we wait. At Site 6, Colin will start the same experiment in the other three carboys. Station 2 is located in the Antarctic Zone and has seasonal sea ice coverage. Station 6 in at the Antarctic Polar Front, between the Antarctic and Subantarctic zones, and is in the permanently open ocean. This should give us a good idea of how two different sets of diatoms react.
I’m really interested to see what diatoms we have and how they’ll grow over the course of our cruise.
Exactly why is Colin growing diatoms on our cruise? He’s agreed to tell us all about it tomorrow!