Autonomous submarines set out to collect and analyse ocean microbes

A small fleet of long-range autonomous underwater vehicles (LRAUVs) are being deployed by scientists to automatically collect and archive seawater samples to track and study ocean microbes in unprecedented detail.

A team from the University of Hawai’i at Mānoa (UH Mānoa) and the Monterey Bay Aquarium Research Institute (MBARI) completed the construction and testing of three new LRAUVs in late February and delivered them last week for their first deployment in Hawaiian waters.

Ocean microbes produce at least fifty per cent of the oxygen in our atmosphere while removing large amounts of carbon dioxide. They also form the foundation of marine food webs, including those that support global ocean fisheries.

The project will be used 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.

As the LRAUVs move through the ocean, they collect information about water temperature, chemistry, and chlorophyll (an indicator of microscopic algae) and send this data to scientists on shore or on a nearby ship.

Additionally, a unique aspect of the 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.

The first ESPs developed about 15 years ago were the size of a 55-gallon drum, but the latest models, the third generation, are around one-tenth the original size at 8-10" in diameter and were designed specifically to fit inside an LRAUV.

Jim Birch, MBARI’s lead engineer on the ESP project commented, “When we first talked about putting an ESP in an AUV, I thought to myself, ‘This is never going to happen.’ 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 condition and can stay within the same water mass as it drifts around the open ocean.”

With its surveying ability, the LRAUV allows scientists to discover, track and sample open-ocean eddies, which can be over 100km 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.

“The new LRAUVs can transit for over 600 miles and use their own ‘eyes and ears’ to detect important oceanographic events like phytoplankton blooms,” oceanography professors Edward 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.”

An expeditionary cruise aboard the Schmidt Ocean Institute’s (SOI) research vessel Falkor leaves on March 10 2018 for open-ocean sea trials of MBARI’s newly-designed 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, as well as improving current ocean models, which are critical for developing expectations on the health of future oceans.

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