Short-term evaluation of "Cajun coating," a capsaicin-enhanced copper antifouling coating for reducing marine biofouling.

Marine biofouling imposes significant operational and ecological costs for the maritime industry, including increased hydrodynamic drag, material degradation, and the spread of non-native species. This study investigated the use of cayenne pepper to reduce fouling on submerged hard substrate - a method sometimes used by recreational boat owners for anti-fouling and referred to as "Cajun coating." We ran a preliminary short-term efficacy study to evaluate whether capsaicin, the active ingredient in cayenne pepper, enhances the effectiveness of traditional copper-based antifouling coatings under in-situ conditions. Fiberglass-coated tiles were assigned six treatments (copper only, copper with 0.5%, 1%, or 2% capsaicin, copper plus methylated seed oil, and an uncoated tile control) and were deployed in the marine environment for six weeks in coastal Alabama. Nine taxa were recorded, with taxa richness highest on controls and lowest on 2% capsaicin tiles. Community composition differed significantly among treatments, with soft-bodied taxa (e.g. soft tube-dwelling polychaetes, hydroids) declining in response to capsaicin, whereas barnacles showed minimal response. Detritus and bare space generally increased with capsaicin concentration. Notably, bare space - perhaps the most relevant indicator of antifouling efficacy - was significantly greater in the 2% capsaicin treatment than in the copper treatments, indicating enhanced antifouling performance with incorporation of capsaicin. Largest differences were also seen between 1% and 2% capsaicin treatments, particularly in total mean taxa abundance and percent detritus. Overall, capsaicin enhanced antifouling performance in a concentration-dependent manner, particularly against soft-bodied taxa and increasing bare space, suggesting this approach has potential as an environmentally benign antifouling option. Our results provide preliminary in-situ research-based evidence for this low-technology and cost-effective approach to reduce marine biofouling on infrastructure and recreational vessels.