Every night, under the cover of darkness, near countless small sea creatures, such as squid and krill, swim from the ocean depths to near the surface to feed. This vast animal migration, the largest on Earth and a critical part of Earth’s climate, has now been observed globally for the first time thanks to the unexpected use of a space-based laser.
The decade 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).
Lidars have the sensitivity to provide scientifically useful ocean measurements from space
NASA's Chris Hostetler
NASA researchers used CALIPSO’s laser capabilities to track the movement and behaviour of small aquatic animals, from hundreds of miles in space.
The scientist looked specifically at a natural, daily phenomenon involving zooplankton, a group of tiny organisms drifting in oceans and bodies of freshwater.
Zooplankton feed on phototrophic plankton, and together form the base of the entire aquatic food chain.
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NASA has tracked the greatest animal migration in Earth's oceans using as space laser (Image: NASA)
This vast animal migration is the largest on Earth and a critical part of Earth’s climate (Image: Getty)
Zooplankton sink in the morning and rise to the surface as the sun sets — a process known as the “diel vertical migration” (DVM).
This process occurs around the world by both marine and freshwater plankton.
It was believed the DVM was a compromise between finding morsels near the surface, and avoiding being eaten by predators.
However, the researchers discovered this kind of migration happens with plenty of small creatures that leave the depths of the ocean to feed on phytoplankton near the surface.