Scientists use tracking underwater crawling robots to collect valuable deep-sea data

Although the deep-sea seabed appears to be isolated from life in other parts of the Earth, it actually plays an important role in the global carbon cycle. Scientists now have a better understanding of this effect, thanks to a tracking robot underwater rover. The deep-sea autonomous vehicle, known as the Benthic Rover II, was designed by a team from the Monterey Bay Aquarium Research Institute (MBARI).

For the past seven years, it has been continuously used at a location called Station M, located 225 kilometers off the central coast of California. There, it has been collecting data on how deep-sea organisms recycle the continuously falling carbon from the bottom of the ocean - which is contained in organic matter such as lifeless plants and animals, as well as excreted waste.

At the beginning of each annual cycle, this roughly titanium rover is placed into the water from the deck of a water supported ship with crew members, then released and allowed to descend to a bottom of 4000 meters - its maximum depth is 6000 meters. Once it lands on its double rubber can like track, it first checks the direction of the water flow and then continues to move towards an undisturbed underwater section.

It then began measuring the number of newly fallen phytoplankton and plant debris in the area, using a blue light to emit fluorescence of chlorophyll. It also records water temperature and oxygen concentration, and measures the oxygen consumption (as well as the resulting carbon dioxide) of organisms living in silt. The latter is achieved by using two transparent breathing chambers, which are placed on mud and left in place for 48 hours. Once the time is up, they are lifted and the rover moves forward 10 meters, repeating all tests - it continues to do so for about a year, during which time it is powered by the onboard battery.

Due to the inability of the rover to transmit directly to the shore (radio waves cannot pass through the water well), the Wave Glider autonomous surface vehicle travels to Station M four times a year. Then, the rover transmits its position and operational status in the form of sound pulses through water, which are received by the Wave Glider - which in turn forwards the information to the shore through satellites.

One year later, the rover was towed back to a ship on the sea surface so that its battery could be replaced, its recorded data could be downloaded, and any necessary maintenance could be carried out. Then, it was sent back to the seabed.

In a recently published paper, MBARI scientists outlined some of the contributions of Benthic Rover II to understanding the deep seabed. Among them, it was found that between November 2015 and 2020, the number of dead phytoplankton and plant matter that sank to the seabed increased significantly, accompanied by a decrease in dissolved oxygen in the water above the seabed.

Researchers say that if traditional short-term data collection devices are used, these changes will not be detected.

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