The role of macroalgae in the global ocean carbon budgetInternal

Activity Overview

Type: Foresight Workshop
Start Date: April 8, 2019
End Date: April 10, 2019
Host: AU
Venue: Carmen de la Victoria, Albaicin, Granada (University of Granada)
Contact: Dorte Krause-Jensen
E-mail: dkj [at]
Funding Call: EuroMarine 2018 call for FWS and WG proposals
Total Budget: €7,500
Funds Granted: €7,500

Recent focus on Blue Carbon strategies, including actions to mitigate and adapt to climate change through conservation and restoration of coastal vegetated habitats, have directed attention to the globally relevant role of vegetated coastal habitats in carbon sequestration in the ocean. However, while the focus has primarily been on angiosperm-dominated systems (salt-marsh, seagrass and mangroves) growing over soft sediments, recent studies have highlighted the potentially highly significant role of macroalgae in this process.

This workshop will address the role of macroalgae in the global ocean carbon budget, with the aim of contributing to a revision of the Blue Carbon agenda, and inform policy and management actions.


The foresight workshop will aim to consolidate the available empirical bases on carbon fluxes supported by macroalgae and to reconcile these with current depictions of the global ocean carbon budget. It will do so through:

  • Synthesis of available estimates of the carbon flux of macroalgal stands (NPP, DOC and POC export, remineralization and grazing) as well as estimates of the contribution of macroalgae to C-sinks; and a
  • Synthesis of available estimates of the area covered by macroalgal stands, along with changes in their area


  1. A review paper on “The role of macroalgae in the global ocean carbon budget” targeting the broad scientific community through a high-profile international journal such as Nature Geoscience
  2. A "Policy brief" communication of key results to inform management/policy agendas, such as those under the UN Framework Convention for Climate Change, Blue Carbon agendas and international conservation units
  3. The workshop may also result in:
    1. A review paper on estimates of area covered by macroalgal globally
    2. A review paper on carbon flux from macroalgal stands


This workshop will contribute to the scientific foundation for a revision of the global ocean carbon budget. Through the policy brief, it will influence policies and management actions to support the conservation of macroalgae and provide knowledge support for including macroalgal C-sequestration as part of Nationally Determined Contributions under the Paris Agreement and in blue carbon scheme initiatives. The workshop will target the UN Framework Convention for Climate Change community with the intent to communicate this information to those responsible for enacting the sustainability agenda.

'The role of macroalgae in the global ocean carbon budget' foresight workshop was held in Carmen de la Victoria, Granada, from April 7-10, 2019. A total number of 22 participants took part in the workshop, with six of those doing so remotely. Most participants came from the academic field (MSc and PhD students, researchers, lecturers), but there were also participants from Norway's NIVA research institute. 


The key outcome of the workshop was the initiation of the first map and estimate of the global extent of macroalgal forests by habitat. Information on changes in macroalgal area cover are key to evaluate potential changes in the sequestration potential over time. The workshop also compiled estimates of carbon fluxes from wild and aquacultured seaweeds, to assess their role in the carbon cycle and their blue carbon potential. The potential carbon sequestration by seaweed aquaculture on the site is significant, as for every 40 tons landed, 60 tons detach and are released in the marine environment during the growth.

Next steps

During the workshop, a number of collaborative products were planned and initiated, which are being developed over the coming months. For each product a lead person/core group has been identified who will coordinate contributions from the workshop participants and ensure progress.

  • Manuscript with the working title “Bio-Geo-Physical Constraints to the Seaweed Panacea” (Target journal: Nature Sustainability)
  • Revised data-paper with the working title “Light at the coastal seafloor” (Target outlet: Data journal (Earth System Science data) and data repository)
  • Manuscript with the working title “Global Patterns of Distribution of Macroalgae” (Global Ecology and Biogeography)
  • Manuscript with the working title “Model-based projections of global changes in macroalgae with climate change scenarios” (Target journal: Nature Climate Change)
  • Manuscript with the working title “The role of macroalgal in the global carbon cycle” (likely to be split into two products) (Target journal: Nature Geoscience?)
  • Possible series of 2020 workshops on macroalgal restoration. Funding options to be explored
  • Possible on-going mapping effort to track changes. Funding options to be explored

Networking effect

The workshop created major networking effects through the participation and interaction of colleagues with key insights in various aspects of macroalgal distribution, production, fate, and modelling. This provided the basis for inspiring and stimulating discussions allowing the various insights to be combined into the above-listed array of draft products. The workshop thereby also served as an important kickstart for continued collaboration.