Cabomba caroliniana and Schoenoplectus californicus as Antifouling Candidates: Anti-Attachment and Toxicological Effects in Aurelia coerulea (Cnidaria, Scyphozoa).

Biofouling on artificial surfaces in aquatic ecosystems leads to significant economic losses. Current antifouling paints, while effective, often harm the aquatic environment. This study explores ecologically safe antifouling alternatives derived from plants, focusing on the aquatic macrophytes Cabomba caroliniana (CC) and Schoenoplectus californicus (SC). While these macrophytes have shown promise against microfouling, their effectiveness against marine macrofouling remains underexplored. For marine macrofouling tests, Aurelia polyps have been recommended due to their availability and handling. Using the marine cnidarian Aurelia coerulea (AC) as a model organism, the ability of CC and SC extracts to inhibit polyp attachment was evaluated as well as their toxicological effects on polyps and ephyrae. Additionally, the sensitivity of AC to substances (surfactant, zinc, and copper) was assessed to determine its sensitivity compared to other organisms. A dose-dependent inhibition of polyp attachment was observed, with up to 65% efficacy. Toxicity tests indicated low toxicity at concentrations of up to 5% for CC and 20% for SC. The main compounds identified were n-nonadecanol-1 for CC and eicosane for SC. Additionally, AC proved to be a versatile anti-attachment assay model, offering advantages such as sensitivity to chronic and acute tests, dual life stages, and short assay times of up to 72 h. These results suggest the biotechnological potential of CC and SC as natural antifouling agents and highlight their suitability for developing environmentally friendly antifouling applications.