Small Portion of Prokaryoplankton Consume Most of the Oxygen in the Ocean

December 10, 2022

A new study led by researchers from Bigelow Laboratory for Ocean Sciences found that a small fraction of marine microorganisms is responsible for most of the consumption of oxygen and release of carbon dioxide in the ocean.

Key Findings of the Study

The researchers made use of a novel method that provided unprecedented insights into the marine microorganisms that help govern the carbon dioxide exchange between the ocean and the atmosphere.
It examined marine organisms called prokaryoplankton – a large group of bacteria and archaea that account for 90 per cent of the cells in the ocean.
Prokaryoplanktons make use of organic matter to generate energy through the process called cellular respiration. The process of cellular respiration involves consuming oxygen and releasing carbon dioxide.
The researchers found that less than 3 per cent of prokaryoplankton cells accounted for up to a third of all oxygen consumed by these microorganisms.
This conclusion has major implications for the understanding of how the carbon cycle in the ocean work since this process is dominated by a very small fraction of microbes.
Generally, to estimate how much marine microorganisms respire, researchers divide the sum of their respiration by the number of microbes. However, this method does not take into account the diversity of marine prokaryoplankton population and their different features.
The recent study takes into account some of the differences in the marine prokaryoplankton population.
The researchers developed a new method that involves linking the functions and genetic codes (blueprint of the organism’s capability) of individual cells of the organisms to gain insights into the microbes’ unique role in the environment.
The new method makes use of florescent probes to observe the behaviour of prokaryoplankton. These fluorescent probes will become brighter the more these microbes respire. The researchers measured the fluorescent signal and used it to categorize the cells for subsequent genetic analysis.
The researchers found a thousand-fold difference from one type of marine prokaryoplankton to another. They found that microbes that consume the highest amount of oxygen releases the most carbon dioxide. These microbes are not the dominant in the oceans.
Organisms that do not respire more are more successful. Most prolific of these organisms may draw energy from sunlight, which could explain their large-scale presence in the ocean ecosystem.

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