<p>Freshwater scarcity, exacerbated by climate change, population growth, and industrialization, has emerged as a critical global challenge. Solar desalination offers a promising and environmentally friendly approach to freshwater production. Recurring green tides in coastal areas of China caused by Enteromorpha prolifera (E. prolifera) result in severe ecological damage and substantial economic losses, while conventional disposal methods such as landfilling not only waste resources but also cause secondary pollution. To simultaneously address marine pollution and freshwater shortages, we developed a regenerative, eco-friendly, and cost-effective hydrogel-based solar evaporator using polysaccharides extracted from E. prolifera. The evaporator exhibited a high solar energy absorption rate (~ 91%), excellent hydrophilicity, and effectively reduced salt deposition during desalination. Under 1 sun irradiation, it achieved an evaporation rate of 1.53 kg·m⁻²·h⁻¹ and maintained stable performance over 15 solar evaporation cycles. Continuous seawater evaporation for 8 h under the same illumination demonstrated its excellent salt resistance. Outdoor experiments further confirmed its ability to efficiently remove K⁺, Ca²⁺, Na⁺, and Mg²⁺ ions, with removal efficiencies as high as 99%. The recyclability of the evaporator was also confirmed. The integration of E. prolifera-based hydrogels in solar desalination systems provides a sustainable strategy for freshwater production while mitigating environmental issues caused by E. prolifera blooms and minimizing secondary pollution from materials.</p> Graphical abstract <p></p>