Predicting Karenia brevis induced respiratory irritation at individual southwest Florida beaches using cell abundances plus wind direction and speed

Nearly annually, blooms of Karenia brevis along the southwest Florida coast lead to a variety of negative impacts, including respiratory irritation (RI) in humans. To limit these impacts, NOAA's National Centers for Coastal Ocean Science developed a RI model to provide beach-goers with a category-based estimate of RI risk at individual beaches along the Gulf and Florida's East coast. The RI model is based on: 1) K. brevis cell counts collected at individual beaches; 2) high resolution wind direction and speed forecasts and observations; and 3) point-based beach shoreline orientation used to designate onshore and offshore winds at individual beaches. To test the model logic, an analysis of modeled RI was compared to same-day RI reports, based on the frequency of coughs at individual beaches from the Beach Conditions Reporting System (BCRS). Overall, the model proved to be 88% accurate when K. brevis was present along the southwest Florida coastline from 2006-2022. In addition, validation efforts confirmed model assumptions, including: 1) reports of higher RI correlate with higher cell abundances; and 2) when cells are present, onshore winds lead to a higher risk of RI. However, we found that individual model categories ('low', 'moderate') were less robust. Furthermore, BCRS was not a direct measure of toxic aerosol presence, so some coughing (modeled false negatives) may result from other environmental factors. Together, results suggest the RI model accurately predicts 'very low' and 'high' risk, but that additional research is needed to better capture environmental conditions when RI is 'low' or 'moderate'.