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Iron limitation of kelp growth may prevent ocean afforestation
oleh: Ellie R. Paine, Philip W. Boyd, Robert F. Strzepek, Michael Ellwood, Elizabeth A. Brewer, Guillermo Diaz-Pulido, Matthias Schmid, Catriona L. Hurd
Format: | Article |
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Diterbitkan: | Nature Portfolio 2023-06-01 |
Deskripsi
Abstract Carbon dioxide removal (CDR) and emissions reduction are essential to alleviate climate change. Ocean macroalgal afforestation (OMA) is a CDR method already undergoing field trials where nearshore kelps, on rafts, are purposefully grown offshore at scale. Dissolved iron (dFe) supply often limits oceanic phytoplankton growth, however this potentially rate-limiting factor is being overlooked in OMA discussions. Here, we determine the limiting dFe concentrations for growth and key physiological functions of a representative kelp species, Macrocystis pyrifera, considered as a promising candidate for OMA. dFe additions to oceanic seawater ranging 0.01-20.2 nM Fe′ ‒ Fe′ being the sum of dissolved inorganic Fe(III) species ‒ result in impaired physiological functions and kelp mortality. Kelp growth cannot be sustained at oceanic dFe concentrations, which are 1000-fold lower than required by M. pyrifera. OMA may require additional perturbation of offshore waters via dFe fertilisation.