Seagriculture EU
29 - 30 June 2022
Bremerhaven, Germany


Aquafarming the open ocean by combining floating seaweed and artificial upwelling

Mar Fernandez-Mendez, Chief Scientific Officer, Marine Researcher, Seafields, UK; Junior Professor, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, DE

About the speaker:

Dr Mar has an MSc in Marine Microbiology and a PhD in Biological Oceanography. She has worked at the Norwegian Polar Institute and at GEOMAR Helmholtz Centre for Ocean Research Kiel, and now leads her own research group at the Alfred Wegener Institute Helmholtz Center for Polar and Marine Research. Her expertise covers a broad range from phytoplankton ecology and primary productivity, marine carbon dioxide removal, artificial and natural upwelling systems, climate change impacts on ecosystems, carbon and nutrient biochemistry, carbon export and microbial functional diversity. She has participated in several sea-going research expeditions from the Arctic to the Tropics, is a member of the Ocean Artificial Upwelling project and a co-founder of Seafields and their current Lead Scientific Advisor.

Company info: 

Seafields aims to develop offshore farms for the floating seaweed Sargassum, which it will then bale and sink in the deep ocean in order to lock away carbon.

The Alfred Wegener Institute is an internationally respected centre of expertise on polar and marine research and is a member of the Helmholtz Association, the largest scientific organization in Germany.

Presentation:Farming the open ocean to produce seafood and raw materials will reduce pressure on coastal natural ecosystems and their biodiversity, while providing economic growth and employment in the global South. In addition, the combination of seaweed aquafarming with artificial upwelling in the subtropical gyres can contribute to ocean Carbon Dioxide Removal  (CDR) at scale.

In this presentation I will talk about the innovative approach proposed by Seafields to establish seaweed farms in the oceans’ deserts by irrigating them with nutrient-rich deep water. Sargassum fluitans and natans grow naturally floating in the ocean doubling its biomass every 11 days when provided with enough nutrients. Sargassums very high carbon to nutrient ratio (28-50), makes it ten times more efficient at carbon capture than phytoplankton. Sargassum biomass, harvested with solar powered autonomous drones, can be processed to extract high-value and fossil-fuel replacing products (eg. fertilizers, emulsifiers, bioplastic, biofuel..) and the remaining carbon-rich biomass compressed into bales to prevent microbial breakdown on selected sites of the abyssal plain.

The aquafarms will be located in the largest unused spaces of the planet: the subtropical gyres, where upwelling of nutrient-rich deep water will be achieved by harnessing the density gradients in the water column. Deep cold nutrient-rich water will rise in thin-walled inner pipes by warming them with high-salinity, surface water. The Sargassum aquafarms will not only contribute to long-term carbon sequestration, but also serve as a habitat for high-protein crustaceans and as nursery for fish, increasing oceanic productivity and benefiting open ocean fisheries.

Keywords: open ocean, aquafarming, sargassum, artificial upwelling