Cultivated seaweed carbon sequestration capacity

Abstract

Abstract The rising of the earth’s temperature and climate change have attracted the attention of many scientists and environmental experts. One of the main strategies being proposed to minimize the acceleration of the earth’s temperature is to increase the potential of carbon sequestration from the atmosphere by taking advantage of the ability of plants, including algae, to utilize carbon dioxide in photosynthetic processes. This study aimed to estimate the carbon sequestration capacity and total carbon sequestration of macroalgae (seaweeds) commonly used in mariculture or in brackish-water pond (tambak) aquaculture. The study was conducted in August 2018 in South Sulawesi Province, Indonesia Carbon sequestration was estimated using the oxygen exchange method. Three maricultured seaweeds ( Kappaphycus alvarezii green and brown strains and Eucheuma spinosum ) and two pond-cultured seaweeds ( Gracilaria verrucosa and Caulerpa racemosa ) were studied. Thallus sections weighing 2.46-4.91 g were inserted into clear bottles (270 mL) filled with seawater and incubated for 3 hours (09.00-12.00), with 5 replicates for each seaweed. The bottles were attached to the seaweed culture lines (maricultured seaweeds) or placed in the ponds (pond-cultured seaweeds). Bottles filled with ambient water (containing phytoplankton) were used as controls. After 3 hours, titration was used to measure the oxygen exchange in each bottle, and the results converted into carbon sequestration. Seaweed productivity ranged from 0.660-11.997 mgCO 2 /gbk/hour with the lowest sequestration by K. alvarezii green strain and the highest by E. spinosum . Carbon sequestration was estimated at 57.64 tons CO 2 /ha/year for maricultured seaweed and 12.38 tons CO 2 /ha/year for pond-cultured seaweeds. The total annual carbon sequestration from seaweed cultivation in South Sulawesi was estimated at 2,656,625 tons CO 2 /year from mariculture and 621,377 tons CO 2 /year from pond culture.

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