Growth Dynamics and Carbon Content During Red Seaweed Cultivation

The cultivation of Kappaphycus alvarezii, a commercially valuable red macroalga, is increasingly recognized as a cornerstone of sustainable aquaculture and blue carbon strategies, especially in tropical coastal regions like South Sulawesi, Indonesia. This study aimed to evaluate the effects of three planting densities (25g/tie, 50g/tie, 75g/tie) on biomass yield, specific growth rate (SGR), and carbon content in K. alvarezii, with a focus on region-specific cultivation practices in South Sulawesi. Using a completely randomized design and triplicate replications, the study tracked temporal changes across a full 45-day cycle, providing high-resolution insights into growth and carbon dynamics. Biomass yield increased over time across all treatments, with the highest final yield recorded at the 75g/tie density. However, the 50g/tie medium-density treatment achieved the highest SGR throughout the cultivation cycle and maintained stable carbon content, reflecting superior physiological performance. The 25g/tie treatment initially showed high carbon content but underperformed in overall productivity. Statistical analysis confirmed that medium density optimized both growth efficiency and biochemical composition, minimizing the stress effects observed in high-density treatments. The results suggest that medium-density planting offers an optimal balance between resource use, physiological stability, and carbon sequestration—an integrative approach not widely reported in prior regional studies. These findings support the development of climate-smart aquaculture systems and provide actionable guidance for seaweed farmers and policymakers. Optimizing planting density is therefore essential not only for improving productivity but also for enhancing the ecological sustainability of marine farming systems.