After years of development and testing, researchers from the University of Hawai‘i (UH) 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 the UH Mānoa 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.
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 over 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 it’s 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.
Testing robots’ tracking abilities
During the Simons Collaboration on Ocean Processes and Ecology (SCOPE) Eddy Experiment in March and April 2018, researchers used satellite imaging to locate an eddy north of the Hawaiian Islands. They deployed a high-tech team of three robots—two long-range autonomous underwater vehicles (LRAUVs) and one Wave Glider surface vehicle—from the Schmidt Ocean Institute’s (SOI) research vessel Falkor.
The LRAUVs were programmed to locate, track, and sample the DCM. Using an onboard 3rd-Generation Environmental Sample Processor (3G-ESP), on robot collected and preserved seawater samples, allowing researchers to capture a series of snapshots of the organisms’ genetic material and proteins.
The researchers determined that over the course of its multi-day sampling missions, one of the LRAUVsaccurately and consistently tracked the DCMand maintained its position within the DCM even as this biological feature moved as much as 118 feet vertically in four hours.
Collaboration fulfilled the vision
“Building an LRAUV with an integrated ESP that could track this feature was a milestone. Combining that sampling power with the agility of three different robots autonomously working together over the course of the experiment is a significant engineering and operations achievement,” said Yanwu Zhang, a senior research engineer at MBARI and the lead author of this study.
“This work is really the fulfillment of a decades-long vision,” said co-author and MBARI President and CEO Chris Scholin. “Coordinating a robotic fleet to show how microbial communities react to changing conditions is a game-changer when it comes to oceanographic research.”
These robotic fleets are now also being used to monitor other key disturbances to ocean health—like harmful algal blooms and oil spills.
“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,” said Karl. “The future is today!”
This research is supported by the National Science Foundation, the Simons Foundation, the Gordon and Betty Moore Foundation, the Schmidt Ocean Institute, the David and Lucile Packard Foundation, and the State of Hawai‘i.