Most of our view of the ocean is of a flat blue expanse, only every once in a while, a whale breaching the surface to give us some clue to the mysterious and wonderful creatures lurking in the vast deep waters beyond our vision. But the true mystery is not elusive because it is hidden under the waves, but rather by its size. The ocean is teeming with life, the great bulk of it microscopic. In just one milliliter (about a teaspoon) of seawater, hundreds of thousands of phytoplankton thrive. Phytoplankton are tiny algae that use photosynthesis to grow, living off the energy from sunlight and the nutrients dissolved in seawater. Historically, scientists have used microscopes to probe their world, but cataloguing their diversity can be tedious and difficult, and can miss either rare species or ones that are too small for even a powerful microscope. Advances in technology, pioneered by the biomedical industry, are now being used by marine scientists to overcome the limitations of the microscope. With an device called a flow cytometer, a water sample is illuminated by a laser as it passes by in a narrow chamber surrounded by light detectors. Depending on the instrument, this technique can be used to detect and identify particles from as small as individual bacteria, up to many of the largest phytoplankton. And it can do it up to 5,000 times per second! For this project, we are using two types of flow cytometer, one back at the Bigelow Laboratory for Ocean Sciences in Maine that can quantify the smallest cells, and another here on board that we use to take pictures of the larger phytoplankton.
My role in the Arctic Integrated Ecosystem Survey is to identify the phytoplankton and measure how active they are. From a microscopic view, this basically translates to who and how much is there, and what they are doing. This information is critical to understanding any ecosystem. Phytoplankton growth sets the baseline for how strong a food web is. By studying their growth, termed primary production, we can know how much nutrition is available for larger organisms that graze on the phytoplankton. These larger organisms are then eaten by fish, and then bigger fish, ultimately ending up as a rich nutritional resource for people, and a vital global industry. Any phytoplankton that escape being eaten tend to settle on the seafloor, providing food for abundant groups of commercially and ecologically important organisms that inhabit or feed on the bottom, such as crabs and walruses.