Persistent Aquatic Living Sensors

Building the Internet of Underwater Things (IoUT) comes with special challenges, and researchers continue to seek comparable network methods to those on land. Meanwhile, the military strives for more efficient methods of detecting underwater enemy vehicles. The U.S.’s Defense Advanced Research Projects Agency (DARPA) is researching the use of live fish as an alert system through a program called Persistent Aquatic Living Sensors (PALS).

Marine Life as Natural Sensors

Marine organisms respond to various stimuli underwater, including visual, acoustic, electrical, magnetic and chemical. Understanding these responses could provide more observational capabilities than conventional surveillance systems. Marine life requires no external power supply, is self-replicating and self-sustaining, provides wide-scale coverage and can’t be easily identified as defense assets by adversary surveillance. Marine life also has the ability to thrive in environments humans and technology struggle to survive, including extreme underwater temperatures, currents and darkest depths.

The PALS project involves five research teams focusing on the following study areas:

• Bioluminescent microbes luminesce in response to water flow changes and may also respond to those caused by underwater vehicles, which could serve as a method of detection.
• Certain microbes are known to swim toward low magnetic signatures, such as those caused by submarines, and would also provide detection.
• Goliath grouper emit low-frequency distress calls when approached by divers and could be used to detect underwater drones and submarines.
• Snapping shrimp emit a 200-decibel popping noise that travels long distances. These sounds could be used like sonar and bounce off enemy vehicles, providing detection and classification.
• Schools of seabass change speed and direction when disturbed, which may provide detection of underwater vehicles.

The researchers’ goals are to observe and categorize these behaviors – paying specific attention to differences in responses to natural disturbances versus underwater vehicles. The next step is to design hardware, software and analytic systems capable of observing behaviors, filtering them to exclude false positives, and sending underwater threat alerts.

Each team on the PALS project will use equipment such as hydrophones, sonar and cameras to study their subject’s behavior. The project has the potential for low environmental impact due to passive listening and observation devices. Announced in 2018, PALS is a four-year program with significant implications for military defense, marine life behavior research and the technological development of the Internet of Underwater Things.