Algaecide-Releasing Buoys for Sustained Harmful Algal Bloom Control

Cyanobacterial harmful algal bloom (CHAB) management is challenging, costly, and often requires repeated algaecide application. To this end, here we develop and characterize reusable buoy-like devices that can sustain algaecide release over periods exceeding one month. Using a commercial H2O2-based, water-soluble algaecide and a polyacrylate-based hydrogel as a diffusion barrier, we demonstrate that release rates from these buoys can be predictably controlled by varying gel thickness, initial algaecide concentration, and the gel surface area-to-buoy volume ratio, and that release follows first-order kinetics accurately predicted from known gel, buoy, and H2O2 properties. Microcosm testing on cyanobacteria-laden Lake Erie water indicates that this technology (at least over the 14-day time scale of this initial algicidal activity experiment) produces a sustained algicidal effect during early-stage CHABs. Moreover, the buoys can undergo buoyancy-driven changes in their orientation, enabling sensing of when they must be refilled. Overall, these findings suggest that these reusable, algaecide-releasing devices could enable sustained and targeted algicidal effects in lakes, ponds, and reservoirs, which could facilitate early-stage CHAB treatment. Other possible applications of this sustained release technology (e.g., pest control in rice fields or sustained disinfection) are also briefly discussed.