Tiny plankton play a big role in the global carbon cycle

Photosynthesis is not the only carbon accumulation technique employed by diatoms living in the ocean, according to a new study. These single-cell plankton have now been found to accumulate carbon by directly feeding on organic carbon dispersed throughout the ocean.

This discovery has the potential to significantly revise our current understanding of the amount of carbon dioxide that diatoms can eliminate from the atmosphere.

Consequently, this finding could lead to a redefinition of the global carbon cycle, which is a critical consideration as we continue to grapple with the challenges posed by climate change.

The research was conducted by a team of bioengineers, genomics experts, and bioinformatics researchers at the University of California San Diego.

Photosynthesis and direct eating

The study was focused on the diatom species Cylindrotheca closterium, which is found globally in oceans. The results revealed that this particular diatom can perform both photosynthesis and direct carbon consumption simultaneously.

Remarkably, these findings were consistent in over 70% of the water samples the team analyzed from oceans worldwide.

Interestingly, this species exhibits significantly faster growth when it consumes organic carbon in addition to performing photosynthesis.

Even more exciting is the possibility that certain bacteria are directly feeding organic carbon to a substantial percentage of these diatoms dispersed across global waters, further enhancing their role in carbon sequestration and impacting marine ecosystems on a broad scale.

Diatoms consuming carbon

An essential tool employed in the process was a genome-scale metabolic modeling approach. This tool helped the experts decipher the metabolism of Cylindrotheca closterium.

The researchers incorporated global gene expression data obtained from the TARA ocean expedition into their genome-scale metabolic model, which was a first in this field.

Adding to the growing body of knowledge, the metabolic modeling data supported recent lab experiments which suggest that diatoms may not rely solely on photosynthesis. Instead, they might adopt different strategies to ingest the necessary carbon.

Tackling the diatom paradox

Upon examining the physical and chemical parameters of their ocean water samples, the team found no correlation between these factors and the tendency of diatoms to divert from photosynthesis to direct feeding strategies.

Yet, a pattern emerged when the team studied specific bacterial populations co-existing with Cylindrotheca closterium.

This discovery hints at the prevalence of mixotrophy – a phenomenon that blends photosynthesis and direct organic carbon consumption.

The research team proposes that specific bacteria may be fueling diatoms, thereby aiding these diatoms in becoming one of the most successful and vital microbes in terms of oxygen production, carbon sequestration, and supporting almost all oceanic life.

New perspectives on global carbon cycling

“Diatoms are major contributors to marine food chains and key drivers of the global carbon cycle. Previously, we have estimated all carbon cycling models on the assumption that the only role that diatoms play is in carbon dioxide fixation,” noted Karsten Zengler, a professor at UC San Diego.

“Our findings demonstrate that this is not the case, but that diatoms simultaneously also eat organic carbon. We believe these results will have major implications for our understanding of global carbon cycling.”

The team hopes this insightful revelation will encourage a closer examination of the global carbon cycle and prompt further research on the symbiotic relationship between diatoms and bacteria.

Dual carbon strategies of diatoms

Understanding the dual carbon accumulation strategies of diatoms opens new avenues for climate change mitigation. Given their significant role in sequestering carbon, diatoms could become focal points in efforts to reduce atmospheric CO2 levels.

Enhancing conditions that promote both photosynthesis and organic carbon consumption by diatoms in oceanic environments might amplify their carbon sequestration capabilities.

This innovative approach could be integrated into broader climate action strategies, highlighting the critical intersection of marine biology and environmental science in addressing global warming.

The insights from this study emphasize the need to delve deeper into the interactions between oceanic microbes and their environment, fostering a more comprehensive approach to managing Earth’s carbon cycle.

By fully understanding the dual roles of these organisms, researchers can ultimately contribute to global sustainability efforts and environmental resilience.

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