Microscopic marine organisms can create parachute-like mucus structures that block the absorption of CO₂ from the atmosphere

New Stanford-led research reveals a hidden factor that could change our understanding of how oceans mitigate climate change. The study, published October 11 in Sciencereveals never-before-seen mucus “parachutes” produced by microscopic marine organisms that dramatically slow their sinking, curbing a crucial process for removing carbon dioxide from the atmosphere.

This surprising finding implies that previous estimates of the ocean’s carbon sequestration potential may have been overestimated, but it also paves the way for improving climate models and informing policymakers in their efforts to slow the climate change.

“We haven’t been looking in the right direction,” said the study’s lead author, Manu Prakash, associate professor of bioengineering and oceans at the Stanford School of Engineering and the Stanford Doerr School of Sustainability.

“What we discovered highlights the importance of fundamental scientific observation and the need to study natural processes in their true environments. This is essential to our ability to mitigate climate change.”

The biological pump

Marine snow – a mixture of dead phytoplankton, bacteria, fecal pellets and other organic particles – absorbs about a third of the human-made carbon dioxide in the atmosphere and transports it to the bottom of the ocean. ocean where it is locked for millennia.

Scientists have known about this phenomenon, known as the biological pump, for some time. However, exactly how these delicate particles fall (the average depth of the ocean is 4 kilometers) has remained a mystery until now.

Researchers unraveled the mystery using an unusual invention: a rotating microscope developed in Prakash’s lab that turned the problem on its head. The device moves as organisms move through it, simulating vertical movement over infinite distances and adjusting aspects such as temperature, light and pressure to mimic specific ocean conditions.

Over the past five years, Prakash and members of his lab have brought their custom-made microscopes aboard research vessels to every major ocean in the world, from the Arctic to the Antarctic.

On a recent expedition to the Gulf of Maine, they collected marine snow by suspending traps in the water, then quickly analyzed the particle sinking process in their rotating microscope.

As marine snow is a living ecosystem, it is important to carry out these measurements at sea. The rotating microscope allowed the team to observe marine snow in its natural environment for the first time in exquisite detail, instead of a remote laboratory.

The results stunned the researchers. They revealed that marine snow sometimes creates parachute-like mucus structures that effectively double the length of time organisms stay in the upper 100 meters of the ocean.

This prolonged suspension increases the likelihood that other microbes will break down the organic carbon contained in marine snow particles and convert it back to organic carbon readily available to other plankton, thereby blocking the uptake of carbon dioxide from the atmosphere.

Beauty and complexity in the smallest details

The researchers present their work as an example of observation-based research, essential for understanding how even the smallest biological and physical processes work within natural systems.

“Theory shows you what a flow around a small particle looks like, but what we saw on the boat was radically different,” said the study’s lead author, Rahul Chajwa, a postdoctoral researcher at the Prakash Lab. . “We are beginning to understand these complex dynamics.”

This work exposes an important fact. For the past 200 years, scientists have studied life, including plankton, in a two-dimensional plane, trapped in small slides under a microscope.

In contrast, doing high-resolution microscopy is very difficult in the open ocean. Chajwa and Prakash emphasize the importance of leaving the laboratory and making scientific measurements as close as possible to the environment in which they occur.

Supporting research that prioritizes observation in natural environments should be a priority for public and private organizations that fund science, researchers say.

“We can’t even ask the fundamental question of what life does without mimicking the environment in which it evolved,” Prakash said. “In biology, removing it from its environment has deprived us of any ability to ask the right questions.”

Beyond its importance in directly measuring marine carbon sequestration, the study also reveals the beauty of everyday phenomena. Much like sugar dissolving in coffee, the descent of marine snow into the depths of the ocean is a complex process influenced by factors we don’t always see or appreciate.

“We take certain phenomena for granted, but the simplest set of ideas can have profound effects,” Prakash said. “Observing these details, like the mucus tails of marine snow, opens new doors to understanding the fundamentals of our world.”

The researchers are working to refine their models, integrate the datasets into Earth-scale models, and publish an open dataset from the six global expeditions they have conducted so far. This will be the world’s largest dataset of direct measurements of marine snow sedimentation. They also aim to explore factors that influence mucus production, such as environmental stressors or the presence of certain species of bacteria.

Although the researchers’ discovery represents a significant shock to the way scientists think about tipping points in ocean sequestration, Prakash and his colleagues remain hopeful. During a recent expedition off the coast of Northern California, they discovered processes that could accelerate carbon sequestration.

“Every time I observe the plankton world through our tools, I learn something new,” Prakash said.