Like The Martian’s Mark Watney, Mike Behrenfeld is a botanist challenging a remote ecosystem. An expert in marine plants, Behrenfeld is leading a $30 million study, and like Watney, he’s funded by NASA. But instead of a dry, deserted planet, this Oregon State botanist is studying a swath of ocean from Greenland to the Gulf Stream. He’s focused on some of the smallest ocean inhabitants—microscopic phytoplankton— and their big impact on the earth’s atmosphere. And here, in the North Atlantic, is one of the biggest plankton blooms on the planet.
This is the first of four sea expeditions planned for the 5-year study, each to catch a different critical moment in the annual cycle of the North Atlantic plankton. November is the point of least bloom activity, and this is when Behrenfeld’s team headed out to sea to deploy a breadcrumb trail of drifting, bobbing sensors that will collect ocean data for the next several years.
Onboard ship, researchers collected information on everything from the types of organisms present to the airborne aerosols linked to plankton activity. Meanwhile, a C-130 Hercules aircraft took measurements of aerosols, clouds, and trace gases in the atmosphere. And above that, satellites provided large-scale observations of plankton populations by measuring shifts in ocean color.
This is NASA’s North Atlantic Aerosols and Marine Ecosystems Study (NAAMES). Information collected at sea, in the air, and from space could potentially change our understanding of how the atmosphere is connected to life in the ocean. “We are investigating the annual cycles of ocean plankton,” Behrenfeld said. “We will address two basic questions. First, what processes allow the plankton blooms to be recreated each year? And second, how do blooms impact atmospheric aerosols and clouds?”
Plant-like phytoplankton are the foundation of the ocean’s food web. They are abundant, especially in springtime in high latitudes, where their populations explode into blooms. For decades, scientists have attributed these blooms to increases in sunlight and warming temperatures. Yet satellite images show phytoplankton concentrations starting to increase in midwinter, when the ocean’s upper waters are stirred by strong winds and cold surface waters sink. It seems these physical forces deepen the upper mixing layers, giving phytoplankton room to slowly spread out and escape being eaten. In this way, phytoplankton out-multiply the grazers, and then stay ahead of the grazers as their photosynthesis continues to accelerate toward a spring bloom climax.
Behrenfeld’s team is examining how much effect phytoplankton abundance can have on the atmosphere. The photosynthesis of these tiny marine plants creates a feast for all kinds of marine bacteria, viruses, and tiny animal zooplankton who, in the process of their feasting, break down carbon molecules. Some of these carbon crumbs filter into the atmosphere and become the nuclei for water vapor to form droplets. Higher droplet concentrations make clouds dense and reflective, which can increase their cooling effects on the climatic thermostat.
So, Behrenfeld and his collaborators are considering the full circle of relationships from physical ocean conditions to plankton, aerosols, clouds, climate, and back to physical ocean conditions. By studying these relationships over the next 5 years, Behrenfeld hopes to better understand how these tiny organisms in this massive ecosystem play a critical role in the Earth’s biosphere.