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Global Carbon Cycle and Ocean Health – Robotic floats

Robotic floats for use in ocean primary productivity [Image source:SOCCOM]


The overall microscopic sea life is vital for the marine environment, including the oceans and the subsequent planet’s health. Additionally, through photosynthesis, the plants on earth and the minute phytoplankton convert carbon dioxide to biological matter and oxygen. Marine primary productivity is a term that refers to this natural transformation.

Effects of changes in healthy marine productivity

Any disruption in the healthy production of phytoplankton may lead to dire side-effects, ranging from changes to the regular capabilities of the ocean to handle carbon volumes and changing ocean food chains. It is critical to comprehend the ocean’s role in removing carbon from the atmosphere and storing it for extended periods with a changing climate.

Roles of Phytoplankton in marine life

From numerous marine studies done by diverse marine scientists, phytoplankton normally produce organic matter which they later use as their food which is vital for their subsequent growth and production. Zooplankton then consume phytoplankton, small fish consume zooplankton, and so on up to whales.

Phytoplanktonconsume carbon dioxide and emit oxygen in a specific ratio during photosynthesis. Researchers can estimate the amount of carbon phytoplankton produce and the amount of carbon dioxide they consume by measuring the amount of oxygen phytoplankton release over time. Oxygen levels rise during the day as a result of photosynthesis and fall during the night as a result of respiration—if you can obtain the daily cycle of oxygen, you have a measure of primary productivity.

While it’s a well-known phenomenon, this is the first time it has been analyzed quantitatively at the global scale using instruments rather than estimated using modeling and other tools.

Global primary marine productivity studies

According to Scientist Mariana Bif, a biogeochemical oceanographer, approximately half of the earth’s primary productivity occurs in the ocean. However, the scarcity of measurements prevents us from providing a reliable global estimate for the ocean at the moment.

The estimates on primary marine productivity are further facilitated through the use of satellites which eliminate the hectic manual measurements. The satellites have made it easier to collect marine data and analyze it for subsequent marine productivity studies; for instance, up to thousands of free to roam robots navigate the vast ocean waters for research purposes.

Studies by Ken Johnson and Mariana Bif for the Monterrey Bay Aquarium Research Institute showed that the use of self-navigating robots could boost studies on marine productivity to a higher level. More importantly, the study funded by The National Science Foundation, concluded that robots were versatile and could be used on a vast worldwide scale.

Johnson and Bif were able to quantify ocean primary productivity using an innovative way of evaluating the float data.  Initial experiments concluded that each robot float could help determine daily oxygen cycles, that is, the increase and decrease of oxygen levels. These conclusions were drawn from over 300 floats which were calculated at various times daily.

Benefits of using oceanic robotic floats

With the addition of hundreds, and possibly thousands, of robotic profilers, a new understanding of the seas has been established, just like an array-based approach to understanding how the oceans interact within the climate system. With the information the robot floats provide the marine scientists, it becomes much easier to calculate the carbon levels from the oceans to grasp a new understanding of the worldwide carbon dioxide levels.


Researchers place a robotic float into the water. (Image Credit: SOCCOM)


How do profiling marine productivity robots work?

For instance, the BGC-ARGO robotic floats are commonly used to calculate the ocean’s salinity, pH, chlorophyll, nutrients, and temperature. They can sink up to 1,000-3,000 meters below the ocean level. With the help of self-navigation and advanced programming setup, they provide correct data for analysis.  Once the required data volumes are obtained, they float to the water’s surface and link with satellites to send the same data to the marine scientists; a procedure is always done for at least ten consecutive days.

Over the last decade, an expanding fleet of BGC-Argo floats has been collecting data from the world’s oceans. Each year, the floats catch thousands of profiles. Ken Johnson and his counterpart Bif relied on these floats and methods to develop the correct analyses of estimates for long. From the floats’ data, they obtained overall worldwide marine primary productivity by analyzing oxygen production patterns.

Accuracy of BGC-Argo floats (BATS)

Two different ship-related data samples from two diverse locations were compared against each other. The samples were collected from Hawaii Ocean Time Series (HOT) and Bermuda Atlantic Time Series stations. The data was collected mainly to compare the accuracy of the primary marine productivity information analyzed from previous BGC-Argo floats.

The comparison results

They obtained the following form comparing data from the regions as mentioned earlier.

  • The data collected from profiling floats near those regions produced identical results to those obtained from monthly sampling from ships at these two locations for many years.
  • As per conclusions by both Johnson and Bif, a minimum of 53 petagrams of carbon dioxide was emitted by phytoplankton yearly. Which is the same range estimated through advanced computers.
  • For calculation figures, they concluded that one petagram is equivalent to 1 000,000,000,000 Kilograms/gigaton, which is the same as the weight of 200 mature elephants.

This study confirmed recent biogeochemical models and demonstrated their increasing robustness.

Cited Works

Hurley, Billy. “Robotic Floats Measure Primary Factor in CLIMATE Picture: Oxygen in the Ocean.” Tech Briefs, 23 Aug. 2021,

“Robotic Floats Provide New Look at Ocean Health and Global Carbon Cycle.” Dossier News.,

“Robotic Floats Provide New Look at Ocean Health and Global Carbon Cycle.” NSF,

“Robots to Fan out across World’s Oceans to Monitor Their Health.” GO,

staff, E&T editorial. “Robotic Floats Provide New Insight into Ocean Health.” RSS, 17 Aug. 2021,