TRacing the fate of Algal Carbon Export in the Ross Sea, Antarctica TRACERS: The NBP13-02 Cruise: Phy-to-plankton

We study phytoplankton! When you hear this, an image of Plankton from Sponge Bob may pop into your head:

Image credit: Sponge Bob’s artist.

But don’t think for a moment that stealing a crabby patty recipe is the extent of the plankter’s purpose of life. It gets much more riveting and exciting than that. The story of life in the ocean begins on the micron scale with strikingly beautiful phytoplankton. No, not fido-plankton. We’re talking gorgeous, sunlight-harvesting life forms!

Diatoms, a type of phytoplankton, are the base of the food chain here in the Ross Sea, Antarctica. While alive, they are collecting energy from the sun (which shines 24 hours a day in the Antarctic summer!), using it for photosynthesis, and creating organic compounds. When phytoplankton are consumed, they are a source of energy for an amazing collection of organisms that live in this icy world. Not only does their presence support the ocean’s food web, but they also play a global role in oceanic carbon export to bottom water. They are found living in salty channels (brine channels) of the ice at the surface, floating in the upper layers of the water column, and it turns out, they can be the primary component of the sediment as well.

Despite their huge role in the ecosystem, these single-celled, plant- like organisms are very small. This makes fieldwork – to be frank – boring. Typically, if the ship instrumentation tells us we have high fluorescence levels in the water, we get a happy rush, knowing there is likely a lot of phytoplankton in the water. We sample seawater from the CTD (contraption with bottles that is lowered into the water to collect at different depths), and filter away. A brown, stinky filter is the slightly anticlimactic result, and the pattern occurs day after day.

Best described as a very cold version of the movie Groundhog’s Day, where the main character wakes up every day to a very similar version of the previous, time here becomes a blur. The disappointment almost makes us wish we worked with charismatic mega fauna (like this beautiful Emperor Penguin who visited us the other day).

The visiting Emperor Penguin who posed for 10 minutes on the ice before jumping in for a swim. Photo credit: R. Dunbar.

But before we let our minds slip too far into this silliness, the monotony of phytoplankter harvesting is broken by Christina Riesselman, Golden Pancakes, and the Smith-MacIntyre Sediment Grab.

Dr. Riesselman, from University of Otago, has been collecting water, ice, and sediment samples for microscopy to identify the species of phytoplankton present. We were caught looking over her shoulder all the time with wide, bright eyes, and were invited to participate in the sampling of ice and sediment.

Image of pancake ice during a sampling trip on the zodiac. The brown color between pancakes is from all of the phytoplankton living in this ice. Photo credit: R. Dunbar.

Amanda and Christina look at some of the water from the sediment grab sample on deck. Photo credits: R. Stevens.

Jacob and Rachel sample the sediment. Photo credits: A. McLenon.

When we helped collect a sediment grab of what looked like clay completely void of structure or life, Dr. Riesselman assured us it was full of diatoms. When she placed the first slide on the microscope and brought it into focus, those of us in the room were amazed at the beauty and intact shapes of various diatoms. Some looked like sand dollars, some like pillboxes, all with detailed silicate “shells” that held together all the way to the bottom of the sea. We have to say it was the highlight of the trip thus far.