Life in the deepest parts of the ocean may have access to more food than scientists once believed. A new study has found that the huge pressure found several kilometres below the ocean surface squeezes nutrients out of sinking organic particles, giving deep-sea microbes a fresh source of food.The discovery could also change how scientists understand Earth’s carbon cycle. If more carbon escapes from these sinking particles before reaching the seabed, the ocean may store carbon differently than researchers had previously thought.The study, led by researchers at the University of Southern Denmark (SDU), was published in the journal Science Advances.
What is Marine snow
The food source comes from what scientists call marine snow. Despite its name, it is not made of ice. Marine snow is a constant shower of tiny bits of dead algae, microbes and other organic material that slowly sink from the ocean’s surface to the deep sea.For years, scientists believed these particles mainly carried food and carbon to the ocean floor. But the new study suggests something important happens while they are still sinking.According to the researchers, when marine snow reaches depths of about 2 to 6 kilometres, the enormous water pressure begins forcing dissolved carbon and nitrogen out of the particles.“The pressure acts almost like a giant juicer,” said Peter Stief, the study’s first author and Associate Professor at the research centres Nordcee and the Danish Center for Hadal Research. “It squeezes dissolved organic compounds out of the particles, and microbes can use them immediately,” he said as quoted by Science Daily.The team estimated that sinking marine snow can lose up to 50% of its original carbon and 58% to 63% of its original nitrogen before reaching the deep ocean floor.
Why does this matter?
The leaked carbon and nitrogen become an instant food source for microbes living in the surrounding seawater. The researchers found that these nutrients helped microbes grow quickly instead of surviving in what was once thought to be a nutrient-poor environment.This finding also affects scientists’ understanding of the carbon cycle. Earlier, researchers believed that much of the carbon carried by marine snow eventually became buried in deep-sea sediments, where it could remain trapped for millions of years. The new study suggests that a significant amount of this carbon leaks into deep ocean water before reaching the seabed.That dissolved carbon can stay in deep waters for hundreds or even thousands of years before slowly returning to the ocean surface and, eventually, the atmosphere. “This process affects how much carbon the ocean can store and for how long,” Stief said. “It’s relevant for understanding climate processes and for improving future models.”
How researchers tested it
To study the process, the team recreated marine snow in the laboratory using diatoms, microscopic algae that naturally stick together as they sink through the ocean.The researchers placed these artificial particles inside specially designed rotating pressure tanks. The tanks kept the particles suspended while exposing them to pressures similar to those found in the deep ocean.The experiments showed that nearly half of a particle’s carbon could leak out during its journey. Most of the released material consisted of proteins and carbohydrates, which deep-sea microbes can easily consume.Within two days, the number of bacteria increased 30-fold, and their respiration rates also rose sharply, showing that the leaked nutrients were quickly being used as food.The researchers now plan to test whether the same process happens in the real ocean. During a future expedition to the Arctic aboard the German research vessel Polarstern, they will look for molecular signs of this nutrient leakage in both surface and deep waters. Finding those signs would help confirm that the process observed in the laboratory is also taking place naturally in the deep ocean.
