Impacts of Hurricanes on Nutrient Export and Ecosystem Metabolism in a Blackwater River Estuary Complex

Abstract

Hurricanes have the ability to export uncharacteristically large amounts of nutrients from terrestrial systems into riverine and estuarine networks, altering rates of ecosystem metabolism throughout the aquatic continuum. In order to explore these impacts and compare these values to common precipitation events, water quality and chemistry data from the National Estuarine Research Reserve’s System Wide Monitoring Program (NERR-SWMP) were combined with discharge data from the United States Geological Survey (USGS) to calculate biogeochemical export from a Florida coastal blackwater river. This analysis was focused on the years 2016–2020, when Hurricanes Matthew, Irma, and Dorian impacted the landscape of Florida’s Atlantic coast. Hurricane Irma, the only hurricane to occur after especially wet summer conditions, dwarfed the other two hurricanes in the export of dissolved organic carbon (DOC), with an increase from <5 kg DOC day−1 to approximately 250 kg DOC day−1. Soluble reactive phosphorus (SRP) and most nitrogen species export exhibited similar trends. Additionally, other spikes in export occurred during non-hurricane months, and no significant differences between monthly export values were found between hurricane and non-hurricane months. However, net ecosystem metabolism (NEM) was calculated at similar intervals and revealed significantly lower NEM during months of hurricane passage. On monthly timescales, this work suggests that lower-category hurricanes might not significantly impact organic matter export, but the shortened export interval associated with hurricane impacts produces significant implications for NEM.