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Hurricanes are typically seen as harmful to both human and natural systems. This is particularly true when considering coastal freshwater wetlands (CFW). Due to the saltwater intolerance of many CFW plant species, hurricane induced storm surges have the potential to cause considerable damage if they reach CFWs. Coastal baldcypress swamps are a type of CFW where the canopy is dominated by baldcypress trees (Taxodium distichum). With a saltwater tolerance of 2 ppt (seawater is 35 ppt) there is considerable concern when hurricanes are expected to make landfall near baldcypress swamps. The assumption that groundwater salinity in these systems will always increase as the result of a hurricane is not well supported. Data from 22 conductivity-temperature-depth (CTD) groundwater wells located in coastal baldcypress swamps in east Texas and the Florida Big Bend region indicate the impacts of hurricanes on these systems are not easily predictable or uniform. This observation is best realized when looking at the groundwater salinity of the swamps. Hurricanes Hermine (2016) and Irma (2017) both made landfall on Florida impacting the Big Bend coast. Hurricane Hermine increased groundwater salinity in the swamps along the Suwannee River, whereas Hurricane Irma decreased groundwater salinity for those same swamps. However, these trends were not uniform across all sites; there existed a range of increased salinization and freshening that varied spatially. In addition, the acute impact of hurricanes varied temporally for each site. Hurricanes can act as drivers of salinization or freshening to these systems, but they can also do neither. Hurricane Harvey (2017) made landfall in coastal southwest Texas and shifted to east Texas. Beaumont, TX saw historic levels of flooding along the Neches River and its surrounding coastal baldcypress swamp floodplain. Groundwater sensors in the area showed no immediate response to nearly 5 m of additional freshwater. Hurricanes have the potential to wreck CFWs via storm surge induced salinization, relieve them of existing salinization, or have no impact at all. Knowing and understanding the system at homeostasis can give better insight into how hurricanes impact CFW groundwater. |
