Study finds large-scale seaweed cultivation offers low carbon removal potential with significant ecological costs
By
Prima Anugerahanti, Julien Palmiéri, Chelsey A. Baker, Ekaterina Popova, and Andrew Yool
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Summary
This study uses a new macroalgae aquaculture module within the NEMO-MEDUSA ocean biogeochemistry model to assess the potential of large-scale macroalgae cultivation as a marine carbon dioxide removal (mCDR) strategy. The research finds that while cultivation enhances air-sea CO2 uptake by 11.0 Pg C yr−1, only about 27% of macroalgal production results in additional CO2 uptake. Significant negative consequences include nearly 50% suppression of phytoplankton and zooplankton biomass, widespread oxygen depletion with suboxic conditions at the seafloor, and a 74% decline in production when iron micronutrient supplementation is not provided. The authors conclude that large-scale macroalgal cultivation offers low mCDR potential with substantial unintended biogeochemical consequences.
Key quotes
· 5 pulledOverall cultivation enhances air–sea CO2 uptake by 11.0 Pg C yr−1, but only ∼ 27 % of macroalgal production results in additional CO2 uptake.
Phytoplankton and zooplankton biomass is suppressed by almost 50 % and is geographically displaced by significant surface nutrient changes.
Sinking of harvested biomass increases oxygen demand during remineralisation, leading to widespread oxygen depletion and the emergence of suboxic conditions at the seafloor in deposition regions.
When macroalgal growth is not supplemented with iron micronutrient, its production declines sharply (−74 %), revealing a significant limitation for large-scale feasibility.
Our findings highlight the urgent need to assess nutrient constraints and ecological trade-offs before considering this method as a viable large-scale mCDR strategy.
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