Fleet of robots successfully tracks, monitors marine microbes

University of Hawaiʻi
robot in water
LRAUV, Aku. (Photo credit: Elisha Wood-Charlson)

After years of development and testing, researchers from the University of Hawaiʻi at Mānoa, Monterey Bay Aquarium Research Institute (MBARI) and Woods Hole Oceanographic Institution have successfully demonstrated that a fleet of autonomous robots can track and study a moving microbial community in an open-ocean eddy. The results of this research effort were recently published in Science Robotics.

Edward DeLong and David Karl, oceanography professors in UH Mānoa’s School of Ocean and Earth Science and Technology (SOEST) and co-authors of the study, have been researching open-ocean microbes for decades using research vessels, buoys, satellite observations, automatic samplers and on-shore laboratories.

Autonomous robotic fleets enable researchers to observe complex systems in ways that are otherwise impossible with purely ship-based or remote sensing techniques.

robot in water
MBARI engineers dunk-test a long-range AUV in Honolulu Harbor. (Photo credit: Chris Preston © 2018 MBARI)
graphic of robots in water
Two LRAUVs (Aku and Opah) and a Wave Glider (Mola) coordinated to study the DCM.

Tracking a moving target

Phytoplankton (photosynthetic microbes) are essential players in the global climate system, producing roughly half of the world’s oxygen, removing carbon dioxide and forming the base of the marine food web. There is a “sweet spot” in the ocean, where light from above and nutrients from below converge to create an ideal environment for phytoplankton. The plethora of microbes in this layer form a ubiquitous open-ocean feature called the deep chlorophyll maximum (DCM).

Open-ocean eddies, swirling pools of water, can be more than 60 miles across and last for months. Phytoplankton thrive when these eddies spin counterclockwise in the Northern Hemisphere and bring nutrient-rich water from the depths up toward the surface.

“The research challenge facing our interdisciplinary team of scientists and engineers was to figure out a way to enable a team of robots-communicating with us and each other-to track and sample the DCM,” said Brett Hobson, a senior mechanical engineer at MBARI and co-author of this study.

The DCM is typically found at depths of more than 300 feet, so it can’t be tracked with remote sensing from satellites, and its position can shift more than 100 feet vertically in just a few hours. This variability in time and space requires technology that can embed itself in and around the DCM and follow the microbial community as it drifts in the ocean currents.

DeLong noted that these teams of coordinated robotic vehicles offer a vital step toward autonomous and adaptive sampling of oceanographic features. “Open-ocean eddies can have a huge impact on microbes, but until now we haven’t been able to observe them in this moving frame of reference,” he explained.

“There is no limit to what can be achieved when you mate a team of collaborative scientists and engineers with a co-ordinated fleet of smart robots,” added Karl. “The future is today!”

This research is an example of UH Mānoa’s goal of Excellence in Research: Advancing the Research and Creative Work Enterprise, one of four goals identified in the 2015–25 Strategic Plan, updated in December 2020.

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