Gary S. Caldwell

Macroalgae (seaweeds) are drawing interest as potential tools for climate mitigation within a burgeoning blue carbon agenda. With the high rates of net primary productivity, they are one of the main carbon sinks in the global ocean, both as biomass standing stock and as vectors of carbon export through detritus pathways. When coupled with their intrinsic ecological value, their contribution to coastal economies, and their current and future scope for aquaculture production, it is perhaps unsurprising that macroalgae have become a focus for nature-based carbon sequestration. However, the research community must guard against the hyperbole that is beginning to permeate the conversation, such as that which beset the microalgae biofuel movement. Macroalgae undoubtedly have a role to play in combating carbon pollution, and perhaps before significant investment is committed to ramping up macroalgae aquaculture, a more pragmatic view of its contribution to natural capital is justified. This article takes an objective look at the capacity for macroalgae to fill a global carbon sequestration niche, both as managed natural carbon pools and as deployable carbon capture assets.