Liquid Smoke as a Biofertilizer and Ice-Ice Disease Suppressant in the Cultivation of Kappaphycus striatus

Graphical Abstract Highlight Research Liquid smoke improved growth and biomass of Kappaphycus striatus. A concentration of 2.67 mL L⁻¹ yielded the highest specific growth rate and weight gain. All treatments maintained 100% survival throughout the culture period. Liquid smoke reduced ice-ice disease incidence, indicating biostimulant potential.   Abstract Liquid smoke (LS) is an organic product derived from the condensation of natural wood smoke and is widely applied in agriculture as a fertilizer, growth enhancer, and disease-control agent. However, its potential application in seaweed farming, particularly for improving growth performance and mitigating ice-ice disease, remains poorly explored. This study aimed to evaluate the effects of different liquid smoke concentrations on the growth performance, weight gain, survival rate, and ice-ice disease occurrence in the cultured macroalga Kappaphycus striatus. A 45-day culture experiment was conducted under controlled conditions using a Randomized Completely Block Design (RCBD) with five treatments in triplicate: a control without liquid smoke (T1) and four liquid smoke concentrations, 0.67 mL L⁻¹ (T2), 1.33 mL L⁻¹ (T3), 2.00 mL L⁻¹ (T4), and 2.67 mL L⁻¹ (T5). Liquid smoke treatments were prepared by dissolving the required volume in seawater, and seaweed seedlings were soaked in the respective solutions for 10 minutes and covered overnight before deployment. Higher liquid smoke concentrations significantly enhanced seaweed performance. The highest concentration (2.67 mL L⁻¹) resulted in the greatest specific growth rate (5.70 ± 0.04% day⁻¹), which was significantly higher (p<0.05) than the control (3.41 ± 0.16% day⁻¹), and produced the highest weight gain (207.94 ± 1.96 g). Survival remained at 100% across all treatments, while ice-ice disease incidence was markedly reduced in higher liquid smoke treatments, decreasing from 28.00 ± 0.00% in the control to 6.00 ± 0.00% at the highest liquid smoke concentration, with improvements observed as early as day 15. Liquid smoke, particularly at a concentration of 2.67 mL L⁻¹, effectively enhances growth performance, biomass production, and disease resistance in Kappaphycus striatus. Further studies under field conditions are recommended to validate its long-term effectiveness and practical application in commercial seaweed farming.