Autonomous robotic rover helps scientists with long-term monitoring of deep-sea carbon cycle and climate change

Date:
November 3, 2021
Source:
Monterey Bay Aquarium Research Institute
Summary:
For the past seven years, an autonomous robotic rover, Benthic
Rover II, has been continuously operational 225 kilometers off the
coast of central California and 4,000 meters below the ocean's
surface. This innovative mobile laboratory has further revealed
the role of the deep sea in cycling carbon. The data collected by
this rover are fundamental to understanding the impacts of climate
change on the ocean.



FULL STORY ==========================================================================
The sheer expanse of the deep sea and the technological challenges of
working in an extreme environment make these depths difficult to access
and study.

Scientists know more about the surface of the moon than the deep seafloor.

MBARI is leveraging advancements in robotic technologies to address
this disparity.


==========================================================================
An autonomous robotic rover, Benthic Rover II, has provided new insight
into life on the abyssal seafloor, 4,000 meters (13,100 feet) beneath
the surface of the ocean. A study published today in Science Robotics
details the development and proven long-term operation of this rover. This innovative mobile laboratory has further revealed the role of the deep
sea in cycling carbon. The data collected by this rover are fundamental
to understanding the impacts of climate change on the ocean.

"The success of this abyssal rover now permits long-term monitoring of
the coupling between the water column and seafloor. Understanding these connected processes is critical to predicting the health and productivity
of our planet engulfed in a changing climate," said MBARI Senior Scientist
Ken Smith.

Despite its distance from the sunlit shallows, the deep seafloor is
connected to the waters above and is vital for carbon cycling and sequestration. Bits of organic matter -- including dead plants and
animals, mucus, and excreted waste -- slowly sink through the water
column to the seafloor. The community of animals and microbes on and in
the mud digests some of this carbon while the rest might get locked in
deep-sea sediments for up to thousands of years.

The deep sea plays an important role in Earth's carbon cycle and climate,
yet we still know little about processes happening thousands of meters
below the surface. Engineering obstacles like extreme pressure and the corrosive nature of seawater make it difficult to send equipment to the
abyssal seafloor to study and monitor the ebb and flow of carbon.

In the past, Smith and other scientists relied on stationary instruments
to study carbon consumption by deep seafloor communities. They could
only deploy these instruments for a few days at a time. By building
on 25 years of engineering innovation, MBARI has developed a long-term
solution for monitoring the abyssal seafloor.



========================================================================== "Exciting events in the deep sea generally occur both briefly and at unpredictable intervals, that's why having continuous monitoring with
Benthic Rover II is so crucial," explained Electrical Engineering Group
Lead Alana Sherman. "If you're not watching all the time, you're likely
to miss the main action." Benthic Rover II is the result of the hard
work of a collaborative team of MBARI engineers and scientists, led by
Smith and Sherman.

Engineers at MBARI designed Benthic Rover II to handle the cold,
corrosive, and high-pressure conditions of the deep sea. Constructed
from corrosion-resistant titanium, plastic, and pressure-resistant
syntactic foam, this rover can withstand deployments up to 6,000 meters
(about 19,700 feet) deep.

"In addition to the physical challenges of operating in these extreme conditions, we also had to design a computer control system and software reliable enough to run for a year without crashing -- nobody is there
to press a reset button," explained MBARI Electrical Engineer Paul
McGill. "The electronics also have to consume very little power so that
we can carry enough batteries to last for a year. Despite all it does,
the rover consumes an average of only two watts -- about the same as
an iPhone." Benthic Rover II is about the size of a small car -- 2.6
meters (8.5 feet) long, 1.7 meters (5.6 feet) wide, and 1.5 meters (4.9
feet) high -- and treads gently over the muddy bottom on a pair of wide,
rubber tracks.



========================================================================== Researchers deploy Benthic Rover II from MBARI's vessel, the R/V Western
Flyer.

The ships' crew gingerly lowers the rover into the water and releases
it to free-fall to the ocean floor. It takes the rover about two hours
to reach the bottom. Once it lands on the seafloor, the rover can begin
its mission.

First, sensors check the currents flowing along the seafloor. When they
detect favorable currents, the rover moves up or across the current to
reach an undisturbed site to begin collecting data.

Cameras on the front of the rover photograph the seafloor and measure fluorescence. This distinctive glow of chlorophyll under blue light
reveals how much "fresh" phytoplankton and other plant debris has landed
on the seafloor.

Sensors log the temperature and oxygen concentration of the waters just
above the bottom.

Next, the rover lowers a pair of transparent respirometer chambers
that measure the oxygen consumption of the community of life in the
mud for 48 hours. As animals and microbes digest organic matter, they
use oxygen and release carbon dioxide in a specific ratio. Knowing how
much oxygen those animals and microbes use is crucial for understanding
carbon remineralization -- the breakdown of organic matter into simpler components, including carbon dioxide.

After 48 hours, the rover raises the respirometer chambers and moves
10 meters (32 feet) forward, careful not to cross its previous path,
and selects another site to sample. It repeats this sampling pattern
over and over for the duration of deployment, typically a full year.

At the end of each deployment, the R/V Western Flyer returns to recover
the rover, download its data, swap out its battery, and return it to the
deep seafloor for another year. Within each year-long deployment, the
MBARI team launches another autonomous robot -- the Wave Glider -- from
shore to return quarterly to check on Benthic Rover II's progress. "The
rover can't communicate with us directly to tell us its location or
condition, so we send a robot to find our robot," explained McGill. An
acoustic transmitter on the Wave Glider pings the rover on the seafloor
below. The rover then sends status updates and sample data to the glider overhead. The glider then transmits that information to researchers on
shore via satellite.

"Data from the Benthic Rover II have helped us quantify when, how much,
and what sources of carbon might be sequestered, or stored, in the
abyssal seafloor," said MBARI Senior Research Specialist Crissy Huffard.

For the past seven years, Benthic Rover II has been continuously
operational at Station M, an MBARI research site located 225 kilometers
(140 miles) off the coast of central California. Station M lies 4,000
meters (13,100 feet) below the ocean's surface -- as deep as the average
depth of the ocean -- making it a good model system for studying abyssal ecosystems.

Over the past 32 years, Smith and his team have constructed a unique
underwater observatory at Station M. Benthic Rover II and a suite of
other instruments operate there 24 hours a day, seven days a week,
for a full year without servicing.

"The rover's reliable performance over seven years, spending 99 percent
of its life on the seafloor, is a result of many years of testing, troubleshooting, and developing the best techniques to maintain the
vehicle," said Sherman.

"It's a great example of what's possible when applying technology to challenging problems in science." Data collected at Station M show that
the deep sea is far from static.

Physical, chemical, and biological conditions can change dramatically
over timescales ranging from hours to decades.

The surface waters of the California Current over Station M teem
with phytoplankton in the spring and summer. These seasonal pulses in productivity cascade from the water column to the seafloor. Much of this sinking organic matter -- known as "marine snow" -- originated as carbon dioxide in the atmosphere.

Over the past decade, MBARI researchers have observed a dramatic increase
in large pulses of marine snow falling to the seafloor at Station M. These episodic events account for an increasing fraction of the yearly food
supply at this site. In seven years of operation at Station M, Benthic
Rover II recorded significant weekly, seasonal, annual, and episodic
events -- all providing data that help MBARI researchers understand the deep-sea carbon cycle.

Between November 2015 and November 2020, Benthic Rover II recorded
a substantial increase in the rain of dead phytoplankton and other
plant-rich debris (phytodetritus) landing on the abyssal seafloor from
the waters overhead. A decrease in the concentration of dissolved oxygen
in the waters just above the deep seafloor accompanied this windfall of
organic matter.

Traditional short-term monitoring tools would not have detected the fluctuations that drive long-term changes and trends. Benthic Rover
II has revealed a more complete picture of how carbon moves from the
surface to the seafloor.

"Benthic Rover II has alerted us to important short- and long-term
changes in the deep sea that are being missed in global models,"
underscored Huffard.

The success of Benthic Rover II and MBARI's ongoing work at Station
M highlight how persistent platforms and long-term observations can
further our understanding of the largest living space on Earth. With more companies looking to extract mineral resources from the deep seafloor,
these data also give valuable insights into the baseline conditions in
areas under consideration for industrial development or deep-sea mining.

The ocean is also a crucial component in Earth's carbon cycle and
climate. The ocean and its biological communities are a sink for carbon dioxide. Burning fossil fuels, raising livestock, and clearing forests
release billions of tons of carbon dioxide into our atmosphere every
year. The ocean has buffered us from the worst impacts by absorbing more
than 25 percent of this excess carbon dioxide. Facing a changing climate, understanding how carbon flows between the ocean's sunlit surface and
its dark depths is more important than ever.

Video of autonomous robotic deep-sea rover:
https://www.youtube.com/ watch?v=Nqe6tKIn628&t=6s ========================================================================== Story Source: Materials provided by
Monterey_Bay_Aquarium_Research_Institute. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. K. L. Smith, A. D. Sherman, P. R. McGill, R. G. Henthorn,
J. Ferreira, T.

P. Connolly, C. L. Huffard. Abyssal Benthic Rover, an autonomous
vehicle for long-term monitoring of deep-ocean processes. Science
Robotics, 2021; 6 (60) DOI: 10.1126/scirobotics.abl4925 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/11/211103150809.htm

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