Scientists develop swarm of tiny underwater robots to study ocean currents and plankton movement

Scientists have created a swarm of tiny underwater robots that will help them to study the currents in the ocean. These little robots will also allow scientists to understand the movement of planktons that are the most abundant life forms in the sea.

The tiny robots are dubbed miniature autonomous underwater explorers (M-AUEs). They will also study the small-scale environmental processes that happen in the ocean.

In order to measure the surrounding ocean conditions, the ocean-probing instruments are equipped with temperature and other sensors. For maintaining a constant depth by adjusting their buoyancy, the robots swim up and down.

In order to fetch a 3D view of the interactions between oceans and marine life, the M-AUEs could potentially be deployed in swarms of hundreds to thousands.

Researchers at Scripps Institution of Oceanography at the University of California San Diego in the US deployed a swarm of 16 grapefruit-sized underwater robots. These robots were programmed to mimic the underwater swimming behaviour of plankton, the microscopic organisms that drift with the ocean currents.

The researchers designed the study to test theories about how plankton create dense patches under the ocean surface, which often later reveal themselves at the surface as red tides.

“These patches might work like planktonic singles bars,” said Peter Franks, a Scripps biological oceanographer who has long suspected that the dense aggregations could aid feeding, reproduction, and protection from predators.

Two decades ago Franks had proposed a theory predicting that swimming plankton would form dense patches when pushed around by internal waves - giant, slow-moving waves below the ocean surface.

Testing his theory would require tracking the movements of individual plankton - each smaller than a grain of rice - as they swam in the ocean, which is not possible using available technology.

Scripps research oceanographer Jules Jaffe instead invented “robotic plankton” that drift with the ocean currents, but are programmed to move up and down by adjusting their buoyancy, imitating the movements of plankton.

A swarm of these robotic plankton was the ideal tool to finally put Franks’ mathematical theory to the test.

“The big engineering breakthroughs were to make the M-AUEs small, inexpensive, and able to be tracked continuously underwater,” said Jaffe.

The low cost allowed researchers to build a small army of the robots that could be deployed in a swarm.

During a five-hour experiment, researchers deployed a 300-metre diameter swarm of 16 M-AUEs programmed to stay 10-metres deep in the ocean off the coast of California.

The M-AUEs constantly adjusted their buoyancy to move vertically against the currents created by the internal waves.

The three-dimensional location information collected every 12 seconds showed where this robotic swarm moved below the ocean surface.

The results of the study were nearly identical to what Franks predicted. The study was published in the journal Nature Communications. 

(With inputs from PTI)