Ocean microbes eat a different diet that affects climate change

The beauty of nature lies in its intricate, minute details, and a small yet profoundly significant part of this beauty is owed to the diverse microbes residing in the mysterious depths of our oceans.

These tiny, often-overlooked beings, each with their own unique food preferences, play a crucial role in the vast, complex, and seemingly invisible process of carbon sequestration, a process vital to regulating Earth’s climate and supporting life on the planet.

Recent insights from a Science publication titled “Microbial dietary preference and interactions affect the export of lipids to the deep ocean” shed light on how the dietary preferences of bacteria influence the efficiency of carbon storage in the oceanic depths.

Ocean microbes’ dietary preferences

“In our study, we found incredible variation in what the different microbes preferred to digest. Bacteria seem to have very distinct diet preferences for different lipid molecules,” explained Benjamin Van Mooy, senior scientist at the Woods Hole Oceanographic Institution (WHOI).

“This has real implications for understanding carbon sequestration and the biological carbon pump.”

The biological carbon pump refers to the process where sinking biomass transports carbon from the ocean surface to the deep ocean.

Lipids, carbon-rich fatty acid biomolecules, make up about 5 to 30% of the surface ocean’s particulate organic matter, serving as a crucial component in marine ecosystems.

These lipids not only act as energy storage but also play a key role in facilitating essential cellular functions for the microbes that inhabit the ocean.

As the organic matter sinks to the deep sea, diverse and complex communities of resident microbes degrade and utilize these lipids, significantly influencing global CO2 concentrations and contributing to the regulation of Earth’s climate system.

Understanding this process is crucial to improve our ability to forecast global carbon fluxes in changing ocean regimes.

Microbes and deep ocean carbon regulation

“Bacteria isolated from marine particles exhibited distinct dietary preferences, ranging from selective to promiscuous degraders,” the study explains.

These dietary choices modulate lipid degradation and, consequently, affect how efficiently lipids are transported through the ocean’s mesopelagic zone, which extends about 200-1000 meters below the surface.

“I was thrilled to see how much there is to learn about the functioning of the ocean by combining two technologies — high-end chemical analysis and microscale imaging — that have historically never been used together,” noted co-author Roman Stocker, professor at ETH Zurich.

“I believe that work at the interface between these exciting technologies will continue to yield important insights into how microbes shape our oceans, now and into the future,” he continued.

Lipid preferences in ocean microbes

“Scientists are starting to understand that lipids in the ocean can vary significantly depending on different environments, such as the coast versus the open ocean, and the season,” Van Mooy enthused.

Researchers can now begin to consider whether some regions efficiently sequester lipids, while others may see inefficient sequestration.

“What excites me about this paper is that it shows bacteria are not just eating any type of lipid but are very specialized and, like us, have specific food preferences,” added Lars Behrendt, associate professor at Uppsala University.

“This changes how we think about how microorganisms consume food in their natural environment.”

Bacterial communities and degradation dynamics

The study also examined how multispecies communities of bacteria affect degradation rates, revealing that co-cultures exhibit different dynamics compared to species in isolation.

This complexity emphasizes the importance of understanding microbial interactions in natural environments.

Microbes and the huge carbon sink

“Phytoplankton are the main reason the ocean is one of the biggest carbon sinks, absorbing as much carbon as all the plants on land combined,” said Uria Alcolombri, senior lecturer at The Hebrew University of Jerusalem.

These microscopic organisms and their interactions with deep-sea microbes play a crucial role in regulating global carbon levels.

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This research was funded by a variety of international organizations, including the Moore Foundation, Simons Foundation, and National Science Foundation, underscoring the global recognition of the importance of understanding the role of ocean microbes in carbon sequestration.

The full study was published in the journal Science.

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