deep sea technology

Using Sound as Sight: acoustic technology finds hidden deep sea creatures

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Mizuno, K., Nomaki, H., Chen, C. et al. Deep-sea infauna with calcified exoskeletons imaged in situ using a new 3D acoustic coring system (A-core-2000). Sci Rep 12, 12101 (2022).

Photo 1: a person looking through a port window underwater. Source: Teo D.

Studying the deep sea is not unlike exploring a foreign planet; its environment is wildly different from our own, its inhabitants are otherworldly, and conditions are adverse to human existence. Making the journey requires innovative methods, and the desire for discovery pushes technological advancements to new levels. A new technology recently tested in Japan is one such advancement that allows the study of deep sea organisms invisible to the human eye.

Deep sea researcher Katsunori Mizuno and colleagues successfully used their acoustic device, the A-core-2000, to visualize hidden deep sea clams off the coast of Japan. The device produces a 3d rendered image of organisms buried in sediment without extracting them or disturbing their environment. This novel tool will be incredibly useful to get a better understanding of the distribution and behavior of deep sea organisms that are indicators of ocean health, as well as visualizing the unseen world of the deep seafloor.

Sonar Discovery

Photo 2: an image of the A-Core 2000. Source: Mizuno et al.

Acoustic technology uses the power of sonar for locating objects in the ocean as well as mapping the seafloor. When soundwaves are emitted from an acoustic device in a focused direction, they bounce off or “reflect” an object in the ocean, like a wrecked ship or coral reef. In this project, the A-core-2000 uses the power of a 3d acoustic “coring” system for the magical ability to detect benthic or buried organisms. The submersible device (Photo 2) has a control unit and a focusing probe that receives soundwaves reflected off buried organisms with calcium-rich skeletons. It then renders these waves into 3d images of the organisms in their natural habitat. Thus this device can “core” through the ground in order to take a peek at hidden deep sea creatures without disturbing an inch of sediment.

The researchers used this clever machine to detect vesicomyids, deep sea clams that live buried by hydrothermal vents over 1200 meters deep in the Off Hatsushima hydrocarbon seep site in Sagami Bay, Japan. Using ultrasound waves of around 500 Hz, they were able to successfully “reflect” or visualize the clams in their natural positions and distribution by the vents. 

Photo 3: 3D rendered image from the A-core-2000 of vesicomyid clams in their natural environment. Source: Mizuno et al.

These 3D rendered images give a good depiction of what the clams look like in their natural state. Moreover, the depth and distribution this device displays can help deep sea researchers learn more about the geological and chemical structure of the sediments making up the seafloor. Creatures like these clams disturb and mix up the sediments while burrowing, allowing other small organisms to access important minerals and fresh organic matter like marine snow.

The success of this technology excites a lot of members of the ocean science community, especially those studying the deep sea. Understanding the nature of ocean infauna, organisms that live buried in the seafloor, is crucial to the understanding of deep sea life. These creatures are vital in the biodiversity and health of the deep sea, and they offer important insights into how these ecosystems work. By having the ability to capture their behavior without the need for disturbance, Mizuno and fellow researchers believe they are “making sure the deep-sea infauna are no longer ‘out of sight, out of mind.’” Advancements like this not only make it possible for groundbreaking discovery, but also bring the alien world of the deep sea a little closer than before.

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