Robot swarm measures the motion of the ocean

Oceanographers dropped mini underwater drones off the coast of California and found they congregated like plankton.

An artist's depiction of the near-shore deployment of the robot swarm off the coast of San Diego.
Jaffe et al, 2017 / DOI: 10.1038/ncomms14189

A swarm of robots that swim like plankton have mapped underwater currents in 3-D in the first such deployment between a metre and a few kilometres below the surface.

Jules Jaffe from the University of California San Diego and colleagues dropped 16 mini autonomous underwater explorers off the coast of San Diego for five hours to monitor ocean dynamics.

Each of the robots was tracked in 3-D, allowing the researchers to calculate subsurface flows. They published their work in Nature Communications.

Duck just a few metres below the ocean surface and you enter a whole new world.

This is where sea creatures – including microscopic organisms such as plankton – live, breed and hunt. But not much is known about the strong ocean currents that push life around.

Large patches of plankton are often found under the surface as kilometre-long bands, parallel to shorelines.

Plankton are thought to swim against subsurface currents to eventually accumulate in regions where current converge.

To see if this was the case, Jaffe and his crew programmed a swarm of small robots, each only around 1.5 litres in volume, to copy the vertical swimming patterns of plankton.

When the robots were deployed in a square kilometre for five hours, they grouped together – just like plankton – suggesting that subsurface currents do indeed affect plankton commute.

While this research focuses on plankton encounters, the results should help study other processes in the ocean that depend on encounter rates, such as mating and predation.

Watch a graphical representation of the swarm moving in the video below.

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Vishnu Varma R Vejayan is a physics student from Queen Mary University of London with an interest in scientific writing and research in physics. He interned at Cosmos in early 2017.