A Simple Method to Clear Harmful Algal Blooms: Sprayable Foams with Algaecides and Flocculants

Harmful algal blooms (HABs) pose significant challenges to coastal communities and economies worldwide. The annual occurrence of “red tide” along the Gulf of Mexico is caused by Karenia brevis (KB) during periods of eutrophication. KB produces brevetoxins that harm marine life and human health. Current mitigation methods are limited, especially with regard to their scalability. Here, we describe a new technology where a surfactant-based foam is delivered to the surface of a bloom. The foam carries hydrogen peroxide producing algaecides (soluble gallic acid or particulate calcium peroxide) and/or a flocculant such as polyaluminum chloride (PAC). The release of hydrogen peroxide onto the surface of the water column results in high algaecide concentrations in surface layers with dilution further down the water column to potentially minimize impact to off-target organisms. PAC integrates easily into the foams and transports uniformly into the water column, leading to effective cell flocculation. Eco-friendly foams can thus be a practical way to clear HABs over large areas since they remain localized at the water surface, targeting the bloom, and eventually dissipate, leaving no residue. Our findings highlight the potential of surfactant foams as a versatile and effective delivery system for mitigating harmful algal blooms.