Carbon sequestration and physiological conditions of Kappaphycus Alvarezii: Toward sustainable seaweed cultivation in coastal waters of Mattirobaji Village, Takalar, South Sulawesi, Indonesia

A particular species widely cultivated in Indonesia, that contributes to biomass-based carbon storage and coastal social-ecological systems is Kappaphycus alvarezii . This study evaluated the physiological characteristics of K. alvarezii and carbon sequestration in Mattirobaji Village, Takalar Regency, South Sulawesi, Indonesia, with water temperature, salinity, and pH being monitored weekly, while nutrients, biomass, and physiological traits were assessed monthly (n = 9 thalli plot –1 month –1 ). Optimal growth and physiological performance were observed between July and September, with maximal chlorophyll, carotenoids, and photosynthetic efficiency (Fv/Fm = 0.75). Biomass increased steadily, reaching 430.22 ± 0.53 g plot –1 in October (Plot 2), with a maximum carbon sequestration of 116.10 ± 0.10 g C plot –1 . Monthly mean carbon sequestration was positively correlated with water temperature (r = 0.872, 95% CI: 0.208–0.986; p = 0.023; n = 6), with regression explaining 76.1% of variation (R 2 = 0.761). Relationships with nitrogen (N) and phosphorus (P) were moderate but not empirically significant. The results showed that temperature-mediated enhancement of photosynthetic performance and biomass accumulation triggered variation in biomass-based carbon sequestration. This also included outlining the significance of site-specific environmental and physiological monitoring. The essence is to support evidence-based farm management aimed at sustaining productivity and carbon sequestration in coastal seaweed farming systems.