Nichole Price1, Samual Tan1,2, Emma Jourdain1,2,3, Aurora Ricart1,4, Peter D Countway1, David Emerson1, Shane Farrell1,2, Brittney Honisch1, Manoj Kamalanathan1, Sean O’Neill2, Douglas Rasher1, Robin S Sleith1, Dara Yiu1,2, Jeremy Rich2
1Bigelow Laboratory for Ocean Sciences, United States, 2School of Marine Sciences, University of Maine, United States, 3Department of Botany, University of British Columbia, Canada, 4Institute of Marine Sciences, Spanish National Research Council, Spain
Correspondence: Nichole N. Price, nprice@bigelow.org
Sequestration of carbon dioxide (CO2) captured from the atmosphere is recognized by the International Panel on Climate Change as a fundamental requirement to limit global warming below 2°C by 2100. Metabarcoding and stable isotope data have revealed that traces of seaweeds can be found in deep, offshore marine sediments. As a consequence, it is proposed that farmed seaweeds may contribute to a blue carbon climate mitigation solution. Fragments of farmed seaweed biomass fall from the subsurface farms as detritus or sloughed particulates during the growth phase and also as culled holdfasts and biofouled blades during harvest. A portion of this discarded seaweed biomass may be buried in marine sediments where it would essentially be removed from the global carbon cycle. However, peer-approved methods for quantifying and verifying whether and how much carbon is captured and subsequently shed during these standard farming operations, and how much becomes transported, remineralized, or buried in the benthic sediment, do not yet exist. We review customized oceanographic sensor technology to quantify inorganic and organic carbon fluxes and species-specific DNA-based quantitative tools to attribute carbon flux to farmed sugar kelp (Saccharina latissima). We present preliminary data for inorganic carbon uptake and organic carbon deposition rates measured at sugar kelp farms in coastal Maine, USA, and discuss the limitations and advantages of various approaches. Tools and protocols such as these will be critical to providing realistic and robust sequestration rate estimates, and to allow seaweed famers to capitalize on carbon offsets and volunteer markets.