Kappaphycus alvarezii and Eucheuma denticulatum are important seaweed species cultivated in Karimunjawa National Park, Indonesia, yet their economic viability within a protected area remains understudied. This study evaluated the profitability of seaweed cultivation using production costs, market access, value chain conditions, and three financial indicators: benefit-cost (B/C) ratio, return on investment (ROI), and net present value (NPV). Primary data were collected through questionnaires from 50 cultivators in Mrican, Telaga, and Batulawang beaches. All cultivators recorded positive ROI and NPV values and B/C ratios above 1.0, while 96% achieved a B/C ratio ≥ 2.0. The mean B/C ratio, ROI, and NPV were 6.105, 2,459.96%, and Rp 136,028,118, respectively. These results demonstrate that seaweed cultivation is economically viable and provides an important livelihood for coastal communities in Karimunjawa National Park. However, dependence on a single market, limited bargaining power, price fluctuations, and seasonal production variability remain key constraints. Strengthening market access and production management could further improve the economic resilience of seaweed cultivation while supporting conservation objectives.
