Single Celled Food Factories of the Arctic [ICESCAPE]

Dr. Kevin Arrigo is a Professor in the Department of Environmental Earth System Science at Stanford University. He is the Chief Scientist for NASA’s ICESCAPE (Impact of Climate change on the Eco-Systems and Chemistry of the Arctic Pacific Environment) mission this summer onboard US Coast Guard Cutter HEALY.

The Arctic Ocean. It marks the end of the line for the gray whales’ epic 2-3 month, 5000-7000 mile journey. It’s also where Arctic terns raise their chicks after a grueling 12,000 mile migration.

But why here?

Surprisingly, during its abbreviated spring and summer season, the Arctic Ocean hosts among the most biologically rich waters on Earth. When the sun approaches its zenith and the sea ice begins to wane, the Arctic Ocean teems with life. This frenzy of biological activity is fueled by the rapid growth of phytoplankton, those tiny floating photosynthetic dynamos that turn carbon dioxide into sugary snacks for the rest of the Arctic marine food web.

My research group, along with that of Greg Mitchell (Scripps Institution of Oceanography), is interested in how these amazing single celled food factories grow so quickly under such harsh conditions.

Like the tomatoes in your garden, phytoplankton require both sunlight and nutrients like nitrogen and phosphorus to thrive. A recent up-tick in the amount of phytoplankton, especially in the shallow areas of the Arctic Ocean, indicates that nutrients may now be more abundant than in the past.

So naturally we want to know how well phytoplankton grow under different light and nutrient conditions and where any extra nutrients are coming from.

By working with Bob Pickart (Woods Hole Oceanographic Institution), who is measuring the paths of the major currents in the Chukchi Sea, we hope to get a handle on where the nutrients come from, where they are going, and how much there are.

To measure the growth of phytoplankton, we use a variety of tricks. Gert van Dijken (Stanford University) and Gert van Dijken (Scripps Institution of Oceanography) add radioactive CO2 to water samples and measure how fast it is removed during photosynthesis. They do this both on deck in “incubators” under natural sunlight and in the lab in a “photosynthetron” that exposes the phytoplankton to many different light levels. Molly Palmer (Stanford University) shoves phytoplankton into a Fast Repetition Rate Fluorometer and measures their respond to changes in light. And Matt Mills and Zach Brown (both of Stanford University) assess how phytoplankton behave under altered nutrient concentrations.

Because phytoplankton (and to a lesser degree sea ice algae) provide virtually all the food for Arctic marine ecosystems, it is important to understand what controls their numbers. By surveying a large area of the Chukchi Sea, ICESCAPE should be able to provide unique insight into the growth of these fascinating and ecologically important parts of the Arctic ecosystem.