Overall aim: to estimate the amount of macroalgal production that is sequestered in the ocean annually.

Approach: To build off a revised estimate of the global distribution and production of macroalgae from the 2019 Euromarine Workshop, and use a combination of literature surveys, data sets and models to revise and refine the pathways and processes that should be considered in estimates of macroalgal fate for key categories of macroalgae. We will finally use these data sets, maps of predicted carbon sinks, and ocean current models to quantify the amount of macroalgal carbon sequestered globally in the ocean. This approach can help evaluate whether the total carbon stored by macroalgae is relevant on a global scale, and the possible consequences of changes in macroalgal distribution for the global carbon budget. It will also highlight the types of habitats, and the regions of coasts, that contribute the most to macroalgal carbon sinks, and the main sources of uncertainty in our current understanding.

 Outputs: One anticipated manuscript submission to Nature Geosciences and one anticipated methods paper on modelling transport of macroalgae. 

Remember to register on Zoom to access the workshop:

Password: NBFNR0ckS!

WORKSHOP DAY 1: Wednesday 2 December 2020

8:30 to 11:40 CET





Participants join Zoom meeting room, tech check – GRID-A

Introduction & workshop aims – Karen

Update on Euromarine outputs/Nat Geo paper etc. – Dorte/Carlos

5th paper on macroalgal fate – Karen/Dan
– Outlining paper and approach (Karen)
– Introduction to modelling export for different categories of coastlines (Dan C)

15-minute break


Task presentations steps I – III: (SHORT, 5 to 10 min each). Chair: Karen

Each presentation includes:
– Progress to date: general approach, key results so far
– Any issues and assumptions: questions or problems for discussion with group
– Presentation will be followed by questions about issues and assumptions

Step I: establish a starting point of the amount of macroalgae that leaves the coastal habitats

Presentation Task 1: Map of global macroalgal area
Lead: Jorge

Presentation Task 2: Agree on a conceptual diagram of fate
Leads: Dorte, Karen (Morten)

Presentation Task 4: DOC pathway
Lead : Kasper

Presentation Task 3: Collate estimates of NPP (Lead: Albert) and % Export (Lead: Kira)

15-minute break


Step II: obtain key parameters for macroalgal transport (particle properties, and end zones)

Presentation Task 5: Collate estimates of remineralization, decomposition
Lead: Morten (Albert)

Presentation Task 6: Collate sinking rates/buoyancy and how these change over time
Lead: Dan S

Presentation Task 9: Estimate export of POC out of macroalgal habitat and seasonality of export (macroalgae and ocean currents)
Leads: Thomas, (Karen)

Presentation Task 8: Map coastal and oceanic sinks
Leads: Trine, Mike, Hege


Final notes on Day 1 and plans for Day 2. – Karen


WORKSHOP DAY 2: THURSDAY 3 December 2020

8:30 to 12:00 CET



Task presentations continued
Step III. Estimate percent export to deep marine sinks

Presentation Task 11: Macroalgal transport in open oceans and assessment of capabilities and limitations of ocean models (resolution and domain) for use in estimating carbon export
Lead: Dan C

Presentation Task 10: Modelling algal transport below the mixed layer depth – convective cells. Lead: Nobuhiro

Presentation Task 7: Horizontal shelf transport and post depositional processes to consider
Lead: Jack

15-minute break


Round 1 breakout sessions

Goal: Three groups discuss key questions from presentations and begin to work on the following:

– How to deal with any issues raised in presentations or discussions.
– Plan data compilation: ESM tables, methods details
– Task organization: next steps, timeline for completion, appointed people
Group 1. Mapping source and sinks
Trine, Mike, Hege, Jorge, Jean-Pierre, Tomohiro, Heather. Chair: Trine
Task 1: Map of global macroalgal area. Lead: Jorge
Task 8: Map coastal and oceanic sinks. Lead: Trine
*Linking coastal and oceanic sinks to macroalgal distribution
Group 2. Amount of macroalgae that leaves the coastal habitats
Albert, Dorte, Thomas, Kasper, Alasdair, Celina, Kira, Pip, Hirotada, Isabel. Chair: Thomas
Task 3: Collate estimates of NPP (Lead: Albert) and % Export (Lead: Kira)
Task 5: Collate estimates of remineralization, decomposition. Lead: Morten (Albert)
Task 9: Estimate coastal interactions and seasonality. Lead: Thomas, Karen
Group 3. Key parameters for algal transport
Dan C, Ana, Jack, Carlos, Dan S, Karen, Ester, Nobuhiro. Chair: Ester
Task 6: Collate sinking rates/buoyancy and how they change over time. Lead: DanS
Task 7: Horizontal shelf transport and post depositional processes. Lead: Jack
*How do we deal with variation across species and particle sizes?
*Can we use mean values for groups of macroalgae?


Summary of progress to date for each step:

One assigned person give overview from each breakout session

10-minute break


Round 2 breakout sessions
Group 1. Dealing with DOC export
Kasper, Alasdair, Jack, Mike, Pip, Morten, Jean-Pierre, Thomas, Albert, Isabel. Chair: Carlos
Task 4: DOC pathway. Lead: Kasper
Group 2. Percent export model

Kira, Tomohiro, Hege, Dorte, Karen, Celina, Trine, Jorge, Dan S, Ester. Chair: Dan C
Task 10: Identify deep areas below the mixed layer depth that connected to coastlines by surface currents, and test different modes of transport to deep zones. Lead: Dan C
Task 11: Algal transport in open oceans and assessment of capabilities-limitations of ocean models in estimating carbon export. Lead: Dan C

*use models and literature to estimate cross shelf transport and long-term storage for different types of macroalgae and different coastal categories

15-minute break


Summary for each group:

One person give overview from breakout session 2


Address remaining issues:

Open discussion on how to deal with key problems, assumptions, possible approaches and next steps

11:50 – 12:00

Review final timeline and next steps.