Phytoplankton species determine sediment carbon dioxide removal

[Tom Goreau]

NB, Prochlorococcus and Synechococcus are the most abundant plants in the world, and dominate carbon flow in the ocean. Also note that at least 99% of the carbon flow is decomposed on the sea floor.

• Article
• Open access

• Published: 23 May 2026

Synechococcus dominates the sedimentary record of exported picocyanobacteria in the ocean

• Chen Qiu, 
• Jiandong Zhang, 
• Chunshan Li, 
• Lele Lei, 
• Furun Li, 
• Lijuan Long & 
• Sijun Huang 

Communications Earth & Environment (2026) Cite this article

We are providing an unedited version of this manuscript to give early access to its findings. Before final publication, the manuscript will undergo further editing. Please note there may be errors present which affect the content, and all legal disclaimers apply.

Abstract

Picocyanobacteria Prochlorococcus and Synechococcus are the most abundant primary producers in the global ocean, yet their contribution to carbon export has long been overlooked. Based on surveys of picocyanobacterial abundance (by qPCR) and community structure along water-column profiles and sediment cores across the South China Sea and Indian Ocean, here we found that picocyanobacterial abundance were roughly 10–100 cells mL⁻¹ in deep waters, and up to 100000 cells g⁻¹ in surface sediments and 100 cells g⁻¹ at 800 cm below seafloor. Moreover, the export and preservation are strongly lineage-specific: deep-water communities are largely derived from surface Prochlorococcus lineages, whereas sediment communities are overwhelmingly dominated by Synechococcus, particularly clades 5.1-CRD1 and 5.1-I. Furthermore, we estimated that nearly 99% exported picocyanobacterial cells are decomposed in surface sediment. These results suggest that Prochlorococcus may contribute more to supplying organic matter for element recycling, whereas Synechococcus may have greater contribution to carbon sequestration.