Brian von Herzen(1), Joseph Rauch(2), Eric Smith(2), Will White(2), Sam Donohue(2), Perfecto Tubal(2), Theresa Theuretzbacher(3), Sam Zak(3), CM Wang(4)
1.Climate Foundation Australia, Ltd, Woodford, QLD, Australia
2.Climate Foundation Inc., Compostela, Cebu Philippines
3.Climate Foundation, Woods Hole, Massachusetts, USA
4.University of Queensland, Brisbane, QLD, Australia
Climate warming and marine heatwaves have raised epipelagic ocean temperatures and lowered nutrient levels associated with upwelling in [sub]tropical and seasonally temperate regions. This environmental disruption reduces the extent and growth of seaweeds underpinning marine ecosystems, e.g. (Macrocystis pyrifera) forests in Tasmania have declined by ~95%.
Renewable energy can be harnessed to restore natural upwelling by regenerative upwelling or deep-cycling of seaweeds accessing nutrients from the mesopelagic zone, reducing ocean stratification and primary production loss. Results from deep-cycling trials and regenerative upwelling show significant restoration of growth rates of multiple macroalgal species consistent with pre-industrial production rates. Measured monthly growth rates of 100-300% per month for red seaweeds and much higher growth for green seaweeds clearly demonstrate production increases under deepwater irrigation. Such approaches have reached fractional-hectare scale under field conditions offshore so that; production can extend across countries with marine EEZs and landlocked countries can apply these techniques in international waters.
Measurements of the significant percentage of seaweed falling off platforms during growth, sinking to the seafloor at rates >1000m/day. Ample physical oceanographic evidence shows that once the biomass reaches such depths it is sequestered for hundreds to thousands of years, even if remineralized into abyssal CO2. Green seaweeds show particularly high potential. Deep-cycled pneumatocyst seaweeds sink rapidly, unlike their surface-irrigated counterparts.
Regenerating primary seaweed production at scale can address key needs for; Food security in a climate-disrupted world, marine ecosystem services including temperate kelp-forest regeneration, measurement of carbon export and long-term sequestration of carbon dioxide.