The ocean's role in protecting the environment by serving as a large carbon sink is not clear. Scientists across the globe, however, shed light on how the ocean absorbs carbon from the atmosphere through plankton networks and deposits it in the bottom of water.

The study, published in the journal Nature, shows how the ocean plucks carbon from the atmosphere and keeps it under the ocean through certain mechanisms. The results came from the Tara Oceans Expedition, wherein a team of at least 200 scientists around the globe studied unseen inhabitants in the ocean such as phytoplankton, bacteria and viruses. The expedition collected samples in nutrient-poor regions in oceans, which comprises 70 percent of the ocean's surface area.

"We're trying to understand, 'Does carbon in the surface ocean sink to the deep ocean and, if so, how?'" Matthew Sullivan, an assistant professor of microbiology at The Ohio State University, said.

"It's the first community-wide look at what organisms are good predictors of how carbon moves in the ocean," Sullivan added.

There are two main reasons why the ocean is dubbed as the Earth's major carbon sink. First, it serves as a physical pump because it can pull surface water filled with dissolved carbon dioxide down in deep waters. Second, it acts like a biological pump because of organisms like plankton which take up carbon dioxide through the process of photosynthesis.

The team analyzed data collected by the expedition between 2009 and 2013. They used advanced genetic sequencing to study tiny ocean inhabitants and through an analytical approach, they identified which inhabitants were responsible in depositing carbon in the bottom of the ocean.

They found that phytoplankton absorbs carbon from the atmosphere and transmit it deep into the ocean. They found that viruses are also important, especially those that infect cyanobacteria cells.

"Additionally, we show that the relative abundance of a few bacterial and viral genes can predict a significant fraction of the variability in carbon export in these regions," the researchers wrote in the paper.

The study allowed for a better understanding of the roles of the organisms in the ocean in maintaining a healthy planet and ecosystems.

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