For the first time, scientists from the University of Hawaiʻi at Mānoa and the Monterey Bay Aquarium Research Institute (MBARI) will track and study ocean microbes in unprecedented detail using a small fleet of long-range autonomous underwater vehicles (LRAUVs) that have the ability to collect and archive seawater samples automatically.
Ocean microbes produce at least fifty percent of the oxygen in our atmosphere, remove large amounts of carbon dioxide and form the foundation of marine food webs. Edward DeLong and David Karl, oceanography professors in the UH Mānoa School of Ocean and Earth Science and Technology, have been studying these microbes for decades.
For this project, UH Mānoa teams are collaborating with engineers from MBARI to test new ways of adaptively sampling oceanographic features such as open-ocean eddies, swirling masses of water that move slowly across the Pacific Ocean, which can have large effects on ocean microbes.
“The new LRAUVs can transit for over 600 miles, and use their own ‘eyes and ears’ to detect important oceanographic events like phytoplankton blooms,” DeLong explained. “These new underwater drones will greatly extend our reach to study remote areas, and also will allow us to sample and study oceanographic events and features we can see by remote satellite imaging, even when ships are not available.”
A valuable collaboration
MBARI engineers completed the construction and testing of three new LRAUVs in collaboration with UH Mānoa scientists, and delivered them last week for their first deployment in Hawaiian waters.
As the LRAUVs move through the ocean, they collect information about water temperature, chemistry and chlorophyll, which is an indicator of microscopic algae, and send these data to scientists on shore or on a nearby ship. Additionally, a unique aspect of these vehicles is an integrated Environmental Sample Processor (ESP), a miniature robotic laboratory that collects and preserves seawater samples at sea, allowing researchers to capture a snapshot of the organisms’ genetic material and proteins.
MBARI has been developing ESPs for about 15 years. The first instruments were about the size of a 55-gallon drum. These latest ESPs, the third generation, are eight to ten inches in diameter—one-tenth the original size—and were designed specifically to fit inside a LRAUV.
Commented Jim Birch, MBARI‘s lead engineer on the ESP project, “When we first talked about putting an ESP in an autonomous underwater vehicle, I thought to myself, ‘This is never going to happen.’ But now I really think this is going to transform oceanography by giving us a persistent presence in the ocean—a presence that doesn’t require a boat, can operate in any weather conditions, and can stay within the same water mass as it drifts around the open ocean.”
Tracking open-ocean eddies
With its surveying ability, the LRAUV allows scientists to discover, track and sample open-ocean eddies, which can be over 100 kilometers across and last for months. When these eddies spin counterclockwise they bring water from the depths up toward the surface. This water often carries nutrients that microscopic algae (phytoplankton) need to survive.
An expeditionary cruise aboard Schmidt Ocean Institute’s research vessel Falkor leaves on March 10 for open-ocean sea trials of MBARI‘s newly outfitted LRAUVs. During this cruise, the researchers will locate an eddy using satellite data and then deploy the LRAUVs to survey the feature and collect water samples.
When the robots return to the surface and are recovered, UH Mānoa researchers will extract DNA from the filters. This information will provide unique insight into the eddy’s duration, stability and influence on the ocean systems; and will improve current ocean models, which are critical for developing expectations on the health of future oceans.
“Although this fleet of autonomous underwater vehicles will never replace our need for a capable research vessel, it will provide much needed access to the sea and the collection of novel data sets that would not otherwise be possible,” said Karl.
This research is supported by the Simons Foundation, National Science Foundation, Schmidt Ocean Institute, David and Lucile Packard Foundation, and State of Hawaiʻi.
Joint news release by the University of Hawaiʻi and MBARI