Growth and product quality of the seaweed Kappaphycus alvarezii from different farming locations in Indonesia

Abstract Indonesia is now the largest producer of carrageenophyte seaweeds, particularly Kappaphycus alvarezii (‘cottoni’ in the industry). Although it is widely acknowledged that there is substantial seasonal and regional variation in production and product quality of farmed K. alvarezii, this variability has not previously been systematically assessed in terms of production (growth and survival) and product quality (carrageenan content, gel strength and viscosity) in Indonesia. This study evaluated K. alvarezii cultured using standard techniques at 10 different geographic locations in Indonesia. Production over the 45-day trial period was highly variable, ranging from a high of (mean ± SE) 2819 ± 124 g.m−1 per rope (Bontang site) to (mean ± SE) 848 ± 66.7 g.m−1 to 495 ± 25.2 g.m-1 for the poorest-performing sites (Mamuju, Gorontalo, Manado and Banten). Carrageenan content of cultured K. alvarezii also varied between sites, from 26.4 % (Mamuju site) to 8.6–11.7 % (Lombok and Bantaeng sites). Gel strength ranged from 735.2 g.cm-2 (Manado) to 291.5 g.cm-2 (Bantaeng), and viscosity from 138.8 cP (Lombok) to 30.0 cP (Gorontalo). Overall, the sites with the ‘best’ product quality from culture K. alvarezii were Banten and Mamuju, and the ‘worst’ was Bantaeng. This variability in product quality data across growing regions is widely acknowledged by the industry but, to date, had not been evaluated using standardised approaches to farming. These results can be utilised to select and evaluate better-performing K. alvarezii cultivars, with a view to improving overall productivity of seaweed farming in Indonesia.