Tiny Cyanobacteria May Be the Secret Heroes of Ocean Carbon Sequestration
Even when larger phytoplankton produce more carbon, much of it is lost on the journey to the ocean floor.
Tiny cyanobacteria may hold the key to ocean carbon sequestration, according to new research published in AGU Advances. Scientists have long believed that larger phytoplankton were more efficient at moving organic carbon from the ocean surface to the deep sea, where it can be stored for centuries. However, a study led by Zhang et al. challenges this notion, showing that about two thirds of the carbon sequestered in the ocean actually comes from cyanobacteria, not from the larger microalgae.
Using sediment traps in the South China Sea and observations of surface phytoplankton communities over multiple years, the researchers found that cyanobacteria play a far greater role in carbon sequestration than previously thought. This is because more carbon from cyanobacteria makes it to the deep ocean compared to microalgae, which often loses much of its carbon along the way.
The study also highlights the importance of carbon isotope signatures in tracing the carbon back to its source among the surface phytoplankton groups.
The findings have implications for ocean carbon sequestration models and understanding how the biological carbon pump may respond to climate change. The study also reveals that the efficiency and origin of carbon collected at depth remain relatively stable throughout the year, regardless of seasonal variations in production and nutrient availability.
This efficiency is attributed to the aggregation and ballasting processes, which help cyanobacteria carbon sink more effectively and reduce its loss through microbial degradation.
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