August 11, 2020

The satellite that dives with its laser to understand the migrations at sea | Science

At nightfall, millions of marine species, such as squid and kriles, rise from the depths of the ocean to the surface to feed on phytoplankton. He satelite Calypso, of the POT and of French National Center for Space Studies, is equipped with a laser that it manages, from space, to penetrate up to 20 meters deep into the sea and offers, for the first time, global data on the greatest animal migration that are essential for the ecosystem and the carbon cycle. Mike Behrenfeld, one of the researchers at the head of the project and professor at the Oregon State University (USA), highlights that this laser, which has been launched 10 years ago, It has the necessary sensitivity to provide scientifically useful ocean measurements from space. The device It allows us to understand the impact of climate change on the marine system over time and, above all, solve mysteries of the ocean.

The squid, one of the animals that feeds on the surface of the sea.

The squid, one of the animals that feeds on the surface of the sea. POT

Calypso It has given information every 16 days for 10 years and is only a first model to make a better analysis in the future and understand the importance of this migration daily vertical (DVM) for the environment, according to Behrenfeld. Thanks to this laser, researchers have tested a curious aspect of the marine world: migrations are not only linked to the amount of food (phytoplankton) to the surface. Tiny animals run away from predators that come out to attack at night. In the clear waters, in which the species become more vulnerable prey, there is less phytoplankton but much more trips to the surface. And similarly, in the more murky waters there is more food but less night migration. The species move both day and night because, in that fuzzier environment, the predator loses power. “This calculation was one of the most amazing things we found throughout our study. It opens a totally new world about the force of migration and the influence of the analyzed area, ”the scientist develops.

On the other hand, researchers observe that climate variation leads to changes in the population of migratory animals. Throughout the study (from 2008 to 2017), the measurements of Calypso reveal an increase in migrations in the subtropical waters of the north and south of the Pacific Ocean, the north of the Atlantic and the south of the Indian Ocean, while in tropical waters the biomass decreases. These changes could be due to the climate that affects phytoplankton production. This species on the sea surface is an important agent in the Earth's carbon cycle and therefore a reference base to understand how climate change affects the planet.

The 'Calypso' laser penetrates up to 20 meters deep into the ocean.

The 'Calypso' laser penetrates up to 20 meters deep into the ocean. POT

This key migration to the ecosystem was discovered about 200 years ago, but the lack of material and techniques prevented obtaining strong data, according to the expert. Two decades ago, things got better thanks to acoustic technology but it still wasn't enough. “This system did not offer us a global image of the process and today, finally, we have achieved it,” he adds.

The device is designed to analyze clouds and gas particles in the atmosphere, but it cannot go beyond 20 meters deep. The next step that Behrenfeld promises to take is to improve this technology. "It has given us a curious result and the greatest hope I have is to be able to go further and thus understand how our natural sources and the climate are changing and will change in the future," he concludes.

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