Biogeochemical and ecological impacts of ~30 years of elevated tropical cyclone activity on North Carolina’s estuarine and coastal waters

Coastal North Carolina has experienced 39 tropical cyclones (TCs), including three floods of historical significance since the mid-1990’s (Hurricanes Floyd-1999, Matthew-2016 and Florence-2018). These events caused catastrophic flooding and major alterations of water quality, fisheries habitat and ecological conditions of the Albemarle-Pamlico Sound (APS), the second largest estuarine complex in the USA. Continuous rainfall records for coastal NC since 1898 reveal a period of unprecedented high precipitation storm events since the late-1990s. Six of seven of the wettest storm events occurred in the past two decades. We examined storm-related freshwater discharge, carbon (C) and nutrient, i.e., nitrogen (N) and phosphorus (P) loadings, and evaluated contributions to total annual inputs in the Neuse River Estuary (NRE), a major sub-estuary of the APS. These contributions were highly significant, accounting for >50% of annual nutrient loads. Depending on the magnitude of freshwater discharge, the NRE either acted as a “processor” partially assimilating/metabolizing loads or as a “pipeline” transporting loads to the APS and coastal ocean. Storm discharge events followed by dry periods supported eutrophication, algal bloom events and hypoxia. Event-scale discharge plays an important and, at times, predominant role in C, N and P loadings. We have entered a new climatic regime characterized by more frequent extreme precipitation events, with major ramifications for hydrology, C, N and P cycling, water quality and habitat conditions in NC estuarine and coastal waters.

Presentation Preference: Oral

Primary Presenter: Hans Paerl, University of North Carolina - Chapel Hill (hans_paerl@unc.edu)

Authors:

Hans Paerl, UNC-Chapel Hill, Institute of Marine Sciences  (hans_paerl@unc.edu)

Nathan Hall, UNC-Chapel Hill, Institute of Marine Sciences  (nshall@email.unc.edu)

Christopher Osburn, North Carolina State University, Dept. of Marine, Earth and Atmospheric Sciences  (closburn@ncsu.edu)

Jeremy Braddy, UNC-Chapel Hill, Institute of Marine Sciences  (jbraddy@email.unc.edu)

Eero Asmala, Geological Survey of Finland  (eero.asmala@stk.fin)