WHOI geochemist Ken Buesseler heads to the North Pacific in July to lead a cruise to track “marine snow” through the “twilight zone.” This little-known but fundamental process could play a key role in understanding and mitigating global warming.
“Marine snow” consists of tiny particles—composed of decomposed microscopic plants, animals, and fecal pellets—that “rain” from sunlit surface waters to the deep ocean. On the way, the particles sink through the “twilight zone,” a dim, little-studied ocean region that ranges from the surface down to between 450 to 900 meters (1,500 to 3,000 feet).
Blooms of photosynthetic phytoplankton draw huge amounts of carbon from the atmosphere to live and grow. When they die or are eaten, a small portion of that carbon, in the form of marine snow, is delivered into long-term storage in the deep ocean or buried on the seafloor. This “biological pump” already helps to reduce the buildup of atmospheric carbon dioxide, a greenhouse gas, and it has sparked controversial proposals to add more nutrients to the oceans—to stimulate plankton growth, rev up the biological pump, and curtail global warming.
Buesseler was chief scientist for two cruises north of Oahu in 2004 aboard R/V Kilo Moana. Using a variety of instruments, a multi-institutional and multidisciplinary array of scientists and engineers collected specimens and data to learn where marine particles come from, how fast and deep they sink, and how they break apart or are consumed by animals or bacteria on the way down. The project, dubbed VERTIGO (VERtical Transport In the Global Ocean), continues in June with a cruise near Japan aboard R/V Revelle, this time studying a contrasting ocean setting in the northwest Pacific.
VERTIGO has been supported primarily by the U.S. National Science Foundation, in collaboration with the Antarctic Climate & Ecosystems Cooperative Research Centre, the U.S. Department of Energy, Woods Hole Oceanographic Institution, the Fund for Scientific Research in Flanders (Belgium), and other national and international sponsors.
To sample zookplankton at various depths in the ocean, scientists use MOCNESS (the Multiplie Opening and Closing Net Envirnmental Sampling System). Towed by a vessel, MOCNESS has 10 separate nets that scientists can open and close using a shipboard computer. (Photo by Ken Buesseler, WHOI)