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Phytoplankton Carbon Dioxide Removal

What is Phytoplankton-Based Carbon Dioxide Removal?

Phytoplankton-Based Carbon Dioxide Removal is a group of mCDR approaches that would enhance the ocean’s natural carbon sequestering processes through the biological carbon pump, the process being characterized by: 

Microscopic marine plants called phytoplankton absorb CO2 as they grow

Phytoplankton are the base of the marine food web and are mostly consumed by larger marine life, but a portion of phytoplankton escape consumption and sink into the deep ocean

Once in the deep ocean, carbon can be stored for hundreds to thousands of years

Could Phytoplankton-Based Carbon Dioxide Removal Matter at Climate Scale?

If key risks and uncertainties can be addressed, phytoplankton based approaches may be capable of removing on the order of one gigaton of CO2 per year a meaningful contribution to addressing climate change. Critical open questions include:

Effectiveness
How much additional CO2 can phytoplankton based approaches really remove?
Durability

How long is that carbon stored?

Acceptability

Are environmental and social
impacts acceptable and equitable?

Ocean Visions’ Phytoplankton-Based Carbon Dioxide Removal Project

In 2025, Ocean Visions launched a year-long project to assess the state of knowledge on phytoplankton-based carbon dioxide removal, identify critical knowledge gaps, and recommend priorities for responsible research, development, and demonstration (RD&D). The project included literature review, expert interviews and workshops, and guidance from an international advisory board.

Key Takeaways Included: 

  • There is strong evidence that phytoplankton-based approaches could meaningfully contribute to closing the global CDR gap
  • Continued research and testing are appropriate to determine whether phytoplankton-based carbon dioxide removal should be pursued at scale
  • Any decisions on deployment must be guided by evidence, ethics, and public engagement
  • Across all phytoplankton-based pathways, priority needs include:
    • Improving quantification of net CDR via phytoplankton-based pathways by identifying the largest sources of uncertainty in these estimates and setting clear targets to reduce this uncertainty
    • Improving ocean biogeochemical models to understand long-term storage and large-scale impacts
    • Strengthening understanding of the ocean’s biological carbon pump, including how climate change is already altering it
    • Advancing carefully designed field trials that maximize learning while addressing environmental and social concerns
  • Pathway-specific insights include:
    • Models suggest Southern Ocean iron fertilization may be the most scalable, but real-world feasibility and impacts remain unclear
    • New iron-based approaches that stimulate nitrogen fixation in tropical regions could expand scalability, but are very early stage
    • Approaches that help phytoplankton carbon reach the deep ocean more efficiently may improve viability as a climate solution, yet remain underexplored
Read the Report

The Case for an International Phytoplankton-Based Carbon Dioxide Removal Research Program

A dedicated phytoplankton based carbon dioxide removal RD&D program could:

  • Coordinate research to ensure funding is used strategically
  • A pply a stage gate framework, with clear decision points to advance, refine,
    pause, or stop work
  • Ensure transparency, inclusivity, and ethical standards
  • Mobilize sustained funding and global collaboration

Work Already Underway

Ocean Visions supports related efforts, including:

  • A co-designed South Pacific research partnership led by AltaSea’s Growing Oceans team to assess the carbon sequestration and ecosystem benefits of naturally stimulated phytoplankton growth, while building trusted scientific and sovereign partnerships—beginning with Tonga—to inform the viability and governance of phytoplankton-based approaches.
  • The Exploring Ocean Iron Solutions (ExIOS) program, hosted at Woods Hole Oceanographic Institution, investigates the feasibility, impacts, and governance of ocean iron fertilization. Its research focuses on stimulating phytoplankton blooms to enhance the biological bump and increase the long-term storage of atmospheric carbon dioxide in the deep ocean.
  • A partnership between NASA’s Jet Propulsion Laboratory at Caltech and San Jose State University is using satellite observations of marine ecosystems to improve ocean biogeochemical models, with an eye towards improving CDR measurements for phytoplankton-based pathways.

Project Advisory Board

  • Mattias Cape, Marine Biogeochemical Scientist, Environmental Defense Fund
  • Leticia Cotrim da Cunha, Associate Professor and Coordinator of Laboratório de Oceanografia Química, Universidade do Estado do Rio de Janeiro
  • Anna-Maria Hubert, Assistant Professor, University of Calgary Faculty of Law
  • Tom Lawton, Senior Staff Scientist, John Hopkins Applied Physics Laboratory
  • Terre Satterfield, Professor of Culture, Risk and the Environment, The University of British Columbia
  • Brad Warren, Chief Executive Officer, Global Ocean Health
  • Angelicque White, Associate Professor, University of Hawai i at Mānoa
Project Team Leads
  • Eric Schwaab, Senior Fellow, Ocean Visions, formally Senior Vice President at Environmental Defense Fund and Assistant Administrator at NOAA
  • Lydia Kapsenberg, Senior Associate, CEA Consulting, PhD, Marine Ecology, Evolution, and Marine Biology