The influences of winds on Karenia brevis bloom characteristics along the shoreline of southwest coast of Florida

The recurrent Karenia brevis (K. brevis) blooms along the southwest coast of Florida produce aerosolized toxins that pose respiratory health risk to humans, especially near the beaches. Various past research focused on the timing of the bloom initiation, yet the respiratory impact and duration of the bloom are rarely studied. Using the bloom severity and respiratory irritation matrices quantified by observed cell counts and beach irritation reports (Stumpf, Li et al., in prep.), the influence of winds on the bloom dynamics is further investigated. Results show that wind plays an important role in modulating the bloom in different ways. First, while in general, higher bloom concentrations correspond to higher respiratory irritation near beaches, increased frequency of onshore wind augment the respiratory irritation impact of the bloom. Second, the apparent under-sampling of the bloom in the 1980s (before routine sampling started) coincided with reduced onshore frequency of wind. Third, on weekly to monthly timescales, the southward transport of the bloom followed stronger cumulative northerly winds, suggesting that wind may be used as an indicator of both bloom expansion and duration. The important role of wind in modulating K. brevis blooms implies that wind should be considered directly in predictive models of K. brevis blooms and its respiratory impact.