Understanding the Connection Between Flash Drought and Harmful Algal Blooms to Assist a Rural Health Department in North Carolina

In the Coastal Plain of the Carolinas, drought manifests differently than it does in the Mountains and Piedmont regions. Chronic droughts and shorter-term flash droughts can increase salinity levels of freshwater bodies through reduced precipitation and decreased stream levels. Flash droughts are characterized by exhibiting a quick onset and rapid intensification over a period of approximately two weeks. Flash droughts historically have a high frequency of occurrence along the Carolina coastlines, and these events are projected to become more frequent throughout the entire southeast United States. If these conditions are combined with increasing temperatures and rising sea levels, there can be a drastic change to salinity levels in estuaries creating cascading impacts to the surrounding environment. One of these threats are harmful algal blooms, which are large toxin-producing colonies of algae that are unsafe for humans and wildlife, and can kill aquatic life through oxygen depletion. The Carolinas Collaborative on Climate, Health and Equity (C3HE), a NOAA Climate Adaptation Partnership (CAP/RISA) and the Albemarle Regional Health Services (ARHS) have identified harmful algal blooms as a key issue in the Coastal Plain region. Past studies have investigated the overlapping relationship of chronic droughts and harmful algal bloom occurrence, however, to our knowledge there are no studies focusing on their relationship with flash droughts. This study will investigate the relationship between flash droughts and harmful algal bloom occurrence to aid in external communications with the ARHS. Flash drought events are classified using the Evaporative Demand Drought Index (EDDI) and the North Carolina Division of Water Resources Fish Kill & Algal Bloom Report Dashboard are used to identify harmful algal bloom occurrence. If a relationship between these two hazards are identified and flash droughts become more frequent, we anticipate more frequent harmful algal blooms in the Coastal Plain of the Carolinas in the future. This would increase the need for urgent and effective communication with residents of the Coastal Plain about the risks to human health and how to identify these harmful algal blooms.