Using a space-based laser, NASA has managed a close look and monitoring of the largest marine migration known to humankind, and the direct impact it has on the global climate. The 10-year-long study was carried out using an earth-observation satellite managed jointly by American and French national space agencies: Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO).
Researchers from NASA and the French space agency Centre National d'Etudes Spatiales (CNES) used CALIPSO's laser capabilities to track the movement and behavior of small aquatic animals like squids and krill, from hundreds of kilometers in space. They looked specifically at a natural, daily phenomenon that involves zooplankton.
Zooplankton " a group of tiny organisms drifting in oceans, seas, and bodies of freshwater " feed on phototrophic plankton (photoplankton), and together form the base of the entire aquatic food chain. Zooplankton find their way to deep water in the morning and rise as the sun sets " a process known as the 'diel vertical migration', or DVM. This process is carried out all over the world by both marine and freshwater plankton.
So far, it was thought that the DVM was a compromise between finding morsels near the surface, and avoiding turning into tasty morsels for predators themselves. But the researchers found that this kind of migration happens with plenty of small creatures that leave the depths of the ocean to feed on phytoplankton near the surface.
Due to the large number of individual animals participating in the DVM, it is considered the largest migration of living organisms on Earth. Through CALIPSO, researchers were able to monitor this behavior and even keep track of its overall effect on Earth's climate.
"This is the latest study to demonstrate something that came as a surprise to many: that lidars have the sensitivity to provide scientifically useful ocean measurements from space," Chris Hostetler of NASA's Langley Research Center and co-author of the study said in a statement.
"I think we are just scratching the surface of exciting new ocean science that can be accomplished with lidar."
DVM has an effect on climate because, during the day, the phytoplankton near the ocean's surface photosynthesize, which allows them higher levels of carbon dioxide. In turn, phytoplankton would improve/increase the amount of greenhouse gas from the atmosphere absorbed by the ocean. As small animals feed on the surface, they also eat plenty of the phytoplankton-converted solid carbon form.
This food is then defecated into the ocean's depths after the return of the ocean creatures. According to the researchers, this prevents the carbon from being released back into the atmosphere. Due to the large number of animals that participate in DVM, the amount of carbon that is prevented from returning to the atmosphere, thereby slowing down global warming.
"The new satellite data give us an opportunity to combine satellite observations with the models and do a better job quantifying the impact of this enormous animal migration on Earth's carbon cycle," Mike Behrenfeld, lead author of the study, said in a statement.
New satellite data give us an opportunity to combine satellite observations with the models and do a better job quantifying the impact of this enormous animal migration on Earth's carbon cycle. The study carried out by the researchers was published in the journal Nature.