The ocean’s twilight zone (TZ), as the name suggests, is defined by the amount of light that penetrates the water above it, as opposed to any specific depth reading. It starts at approximately 200 meters below the surface and continues down to 1,000 meters, after which the so-called Midnight Zone begins. The twilight zone is home to abundant and diverse sea life, but it also plays a vital—and under-studied—role in removing carbon from the atmosphere, which in turn regulates the planet’s climate.
Therefore, amid the mounting concern for ocean sustainability, an ongoing commitment to the scientific exploration and analysis of the ocean’s twilight zone is of critical importance. But studying such vast expanses—over two-thirds of Earth’s surface—poses obvious operational challenges. Recent advances in marine robotics look set to provide new solutions.
ROBOTIC SURVEILLANCE
One such robotic device is Mesobot, a new hybrid platform (which essentially means it can be piloted manually via a lightweight tether or autonomously without) that has been engineered to render a completely new perspective on life in the twilight zone by enabling operators to deploy cameras and lights to quietly shadow individual animals.
At 1.5 meters in length, Mesobot’s streamlined form and quiet propellers allow the unit to hover and transit with minimal disturbance, ideal for tracking and recording slow-moving and fragile zooplankton, gelatinous animals, and particles in mesopelagic habitats, while its red lights—imperceptible to most species—enable authentic in-situ behavioral observation.
In addition to capturing high-quality images, Mesobot can carry a sampler as part of its payload to gather important scientific samples, such as environmental DNA (eDNA), which it collects by pumping seawater through filters.
Mesobot is housed in an hydro-dynamically efficient yellow case and outfitted with a suite of oceanographic and acoustic survey sensors that allow it to track a target at depths of up to 1,000 meters (3,300 feet). This ability to follow a specific species for over 24 hours without the need for human intervention will deliver invaluable insight into animal behavior during diel vertical migration, known as “the greatest migration on Earth” because of the vast number and diversity of creatures that undertake it each night.
Speaking exclusively to ON&T, WHOI senior scientist Dana Yoerger said that Mesobot would prove instrumental to advancing scientific knowledge of the twilight zone:
“The need to better understand the specific behaviors, interactions, morphological structures, and the use of bioluminescence of midwater organisms for extended periods called for the custom design and development of a platform that was truly fit-for-purpose. Mesobot’s unique ability to survey, track, and record compelling HD imagery will help us decipher the role these creatures play in transporting carbon dioxide from the atmosphere to the deep sea, as well as how the commercial exploitation of TZ fisheries might impact the marine ecosystem.”
Mesobot is a collaborative initiative between Woods Hole Oceanographic Institution (WHOI), the Monterey Bay Aquarium Research Institute (MBARI), Stanford University, and the University of Texas Rio Grande Valley, and funded by the National Science Foundation and the Ocean Twilight Zone project.
Find out more here: www.whoi.edu
This story was originally featured in ON&T Magazine’s August 2021 issue. Click here to read more.
