While options under (a) have sound footing in biological processes, actions under (b) and (c) are theoretical and the fate of the extra captured carbon is unknown, including potentially harmful disruption in the marine food web (Hoegh-Guldberg et al., 2019). Another is growing macroalgae at very large scales and subsequently dumping it in the deep ocean or converting it to long-lived products such as biochar and thus sequestering CO2 over large time scales (100s – 1000s years).