Scientists use space lidar to track the largest migration of marine animals on Earth

A joint study by NASA and CNES is the first global study to track large-scale marine animal migration using space lasers, conducted twice a day. Using the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite, launched in 2006, this unprecedented 10-year study could provide new insights into the Earth’s climate.

Scientists use space lidar to track the largest migration of marine animals on Earth

When we think of animal migration, we usually think of animals such as antelopes on the African savannah, but the migration of marine animals is different. Animals in the ocean perform large-scale movementtwice (at sunrise and sunset) twice a day. In terms of quantity and biomass, it is known as the “Day and Night Vertical Migration” (DVM) (DVM) and is the largest known marine animal migration. DVM is performed on a wide variety of animals such as krill, squid, juvenile crabs and small fish, but because these animals are small – mostly microscopic, we usually don’t notice it.

Simply put, at night, some marine animals rise to the surface of the ocean, feeding on tiny plankton. Before sunrise, the animals dive deep into the ocean and hide in dark waters. This huge migration is significant in many areas, so NASA and CNES used CALIPSO light detection and ranging (LIDAR) lasers to detect and study these phenomena from 2008 to 2017.

“Lidar from space allows us to sample these migratory animals globally every 16 days for up to 10 years,” said study leader Professor Mike Behrenfeld, a senior researcher at Oregon State University’s Corwallis. We have never had such extensive global coverage of the behaviour, distribution and number of these animals that cannot be studied. “

Scientists use space lidar to track the largest migration of marine animals on Earth

For decades, the world’s leading navies have wanted to learn more about this layer of migratory animals because of its noise and ability to reflect sonar signals, making it an ideal place for submarines to hide. In addition, zooplankton are one of the main sources of food for large fish, and larger DVM signals indicate that large fish stocks can be maintained in the area.

DVM is also important in terms of climate. Because phytoplankton capture large amounts of carbon dioxide through photosynthesis. When zooplankton eat them, they bring them into the deep sea, and when animals defecate or die, they are captured. The results may be an important factor in understanding the Earth’s carbon cycle and how it affects climate models.

“These modelers don’t have a global dataset to calibrate these models, so they can tell them where these migrations are most important, where they are most abundant, and how they change over time,” says Behrenfeld. The new satellite data provide us with an opportunity to combine satellite observations with models and better quantify the impact of this huge animal migration on the Earth’s carbon cycle. “

The study was published in Nature.

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