Quantifying Disturbance and Recovery in Estuaries: Tropical Cyclones and High-Frequency Measures of Oxygen and Salinity

Tropical cyclones impact estuaries via a variety of mechanisms including storm surge, flooding from precipitation, high winds, and strong wave action. Prior studies have documented disturbances caused by tropical cyclones, including prolonged periods of depressed salinity from high freshwater discharge and increased or decreased dissolved oxygen concentrations from increased loading of organic matter and/or nutrients. However, most studies of disturbance and recovery in estuaries have been limited to one or a few locations or storm events, limiting generalizations about tropical cyclone impacts and characteristic patterns of ecosystem response and recovery. We analyzed responses to 59 tropical cyclones across 19 estuaries in the eastern USA by applying a new method for detecting disturbance and recovery to long-term and high-frequency measurements of salinity and dissolved oxygen from NOAA's National Estuarine Research Reserve System. We quantified disturbance occurrence, timing, recovery time, and severity. Salinity disturbances generally started earlier and lasted longer than dissolved oxygen disturbances. Estuaries usually recovered within days, but some disturbances lasted weeks or months. Recovery time was positively correlated with disturbance severity for both variables. Tropical cyclone properties (especially precipitation) and location characteristics were both related to disturbance characteristics. Our findings demonstrate the power of high-frequency, long-term, and cross-system data, when combined with appropriate statistical methods, for analyzing hurricanes across many estuaries to quantify disturbances. Estuaries are resilient to hurricanes for the variables and time periods considered. However, persistent impacts can potentially damage resources provided by estuaries, eroding future resilience if hurricanes become more frequent and severe.