Growth and Survival of the Seaweed Eucheuma cottonii Cultivated Using a Verticulture System

Abstract

Eucheuma cottonii is one of the most widely cultivated seaweeds in the Asia–Pacific region, including Indonesia. Various farming techniques have been developed to enhance its production, yet the use of verticulture—multi-tiered cultivation structures—remains limited for this species. This study is one of the first to systematically evaluate the application and effectiveness of a multi-tiered verticulture system for E. cottonii cultivation, specifically analyzing the effect of depth gradient within this novel structure. The experiment was conducted from June to September 2025 in Kodek Bay, North Lombok, Indonesia, using a completely randomized design with four depth treatments and three replicates: 0 m (P0), 1 m (P1), 2 m (P2), and 3 m (P3). Seedlings with an initial weight of 30 g were used. The measured parameters included absolute weight gain, specific growth rate, thallus length, thallus number, survival rate, and water quality. Data were analyzed using analysis of variance (ANOVA) followed by Duncan’s multiple range test in SPSS. The results showed that depth treatments had a significant effect on absolute weight gain, specific growth rate, thallus length, thallus number, and survival of E. cottonii. Water-quality parameters remained within optimal ranges across all treatments, with temperature 27–28°C, pH 8.06–8.07, salinity 34–35 ppt, and light intensity 3,061–5,607 lux. The best performance was obtained at the 0-m depth (P0), yielding an absolute weight gain of 29.29±2.14 g, thallus length of 1.1±0.12 cm, 67±1.53 thalli, a specific growth rate of 2.27±0.12% day⁻¹, and a survival rate of 88.9±0.58%. Based on these findings, the 0-m depth (water surface) is definitively recommended for E. cottonii farming using the verticulture system in Kodek Bay and similar shallow waters with equivalent oceanographic conditions.