Using macroalgae to address UN Sustainable Development goals through CO2 remediation and improvement of the aquaculture environment

Abstract

Among efforts to explore ways to achieve carbon neutrality globally or regionally, photosynthetic carbon sequestration by algae has been identified as having immense potential. Algae play a crucial role in providing the base of aquatic ecosystems, driving important biogeochemical cycles in oceans and freshwaters and, in so doing, act as a critical component for CO2 drawdown from the atmosphere and ameliorating global change. Furthermore, algae are used extensively in some societies as a source of food and have potential as feedstock for biofuels and as sources of bioactive chemicals. Such activities align strongly with a number of the United Nations Sustainable Development Goals (SDGs). Here we discuss how marine macroalgae might contribute to several of these goals by exploring their potential to enhance aquaculture, contribute to “Blue Carbon” drawdown of CO2 to ameliorate climate change (UN SDGs 13,14) and provide biomass as feedstock for biofuels (UN SDG 7) to reduce reliance on fossil fuel combustion. Though further work is required, we suggest that farming macroalgae in air has great potential for mitigation of CO2 emissions and improvement of aquaculture environments. Summary: Photosynthetic activity of macroalgae, in addition to driving biosynthesis and biomass accumulation, can cause arise in pH due to CO2 depletion/HCO3–. This can buffer the pH decrease associated with anthropogenic CO2 increases and ameliorate the effects of ocean acidification. Though increasing in magnitude, macroalgal aquaculture still represents only asmall fraction of the Cdrawdown by wild macroalgae populations and currently accounts for drawdown of an even lower fraction of global CO2 emissions. Nonetheless, scaling up of intensive macroalgal aquaculture could be one approach to contribute more to ameliorating anthropogenic CO2 emissions and ocean acidification. Modification of IMTA involving growth of the algae in air rather than in seawater could prove auseful means to help stabilize fluctuations in oxygen and pH in aquaculture operations.