SHORT- AND LONG-TERM EFFECTS OF HURRICANES ON LAKE OKEECHOBEE WATER QUALITY AND CYANO-HABs

Hurricanes are natural disturbance events that have a significant impact on aquatic systems by drastically changing their biogeochemistry, habitats, and geomorphology. Understanding the impacts of individual hurricanes and the cumulative impacts of recurring hurricanes is essential for managing these systems. A series of hurricanes that impacted Florida provide a unique opportunity to explore the direct and indirect effects that these extreme events have on Lake Okeechobee’s water quality and cyano-HABs. Since the 1800s, the lake has been impacted by 17 major hurricanes, with 3 directly crossing the lake. Hurricanes Frances and Jeanne (2004), Wilma (2005), Irma (2017), and Ian and Nicole (2022) caused significant alteration of the lake’s water quality, sediment distribution and thickness, cyano-HAB dynamics, and vegetation cover. High winds generated by these events produced large seiches, and strong waves and currents, which eroded and redistributed bottom sediments and uprooted aquatic vegetation in the littoral zone. The large transport of suspended particles and nutrients from the surrounding watershed further exacerbated water quality issues in the lake. These poor water quality conditions lasted more than 4 years following hurricanes Frances, Jeanne, and Wilma, and for at least 3-6 months following hurricanes Irma, Ian, and Nicole. Significant reduction of water column transparency inhibited phytoplankton growth directly after the hurricanes, but high external and internal nutrient inputs during the events often resulted in extensive cyano-HABs in the following years.

Primary Presenter: Anna Wachnicka, South Florida Water Management District (awachnic@sfwmd.gov)

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