Harmful algal blooms (HABs) have been observed across the globe in both freshwater and marine areas. In addition to severe impacts on aquatic ecosystems, HAB-related toxins, such as cyanotoxins and brevetoxins, may be aerosolized and inhaled by human or animals. The inhalation of airborne algal toxins causes respiratory irritation, acute or chronic illnesses, disruption of activities, and economic damages. Therefore, a framework to forecast, quantify, and mitigate the risk associated with toxins from HABs seems necessary. Here, as an example, we quantitatively show that the general population highly value a forecast model for air quality conditions associated with the Florida red tide (<i>Karenia brevis</i>). Specifically, using a survey-based stated preference method, we estimated an annual willingness-to-pay of $17-$45 per household for such a forecast model. This aggregates to approximately $14.5-$37 million per year across just five counties in western Florida. A key component of a forecasting framework would be an atmospheric model capable of predicting spatiotemporally variable airborne toxin concentrations based on environmental factors. Such a model should represent the HAB aerosolization process via a physics-based parameterization similar to sea spray aerosol (SSA) models. However, a number of complexities arise when going beyond the well-established SSA source functions. HAB concentrations are spatiotemporally variable in waterbodies and their incorporation either into SSAs or freshwater aerosols (also known as lake spray aerosols; LSAs) are governed by complex physical, chemical, and biological phenomena at the interface air and water. To address these challenges, we developed two drone-based systems for fast and low-cost sampling of HABs in water and air, enabling high-resolution characterization in response to HAB heterogeneity. Using these systems, we characterized surface water and air samples from two HABs in Grand Lake St Marys and Lake Erie, Ohio USA. Furthermore, we investigate the physics of HAB aerosolization at the air-water interface to understand mechanistic differences between spray aerosols from saltwater and freshwater. Through a series of laboratory experiments, we developed the first physics-based LSA source function and implemented it in an atmospheric chemistry model. Regional atmospheric simulations show that LSA particles generated from the Great Lakes can be transported hundreds of kilometers inland.

Value and challenges of a forecast model for aerosolized toxins from harmful algal blooms

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