Recent increases of rainfall and flooding from tropical cyclones (TCs) in North Carolina (USA) implications for organic matter and nutrient cycling in coastal watersheds

• Published in: Biogeochemistry Vol. 150; no. 2; pp. 197 - 216
• Main Authors: Paerl, Hans W., Hall, Nathan S., Hounshell, Alexandria G., Rossignol, Karen L., Barnard, Malcolm A., Luettich, Richard A., Rudolph, Jacob C., Osburn, Christopher L., Bales, Jerad, Harding, Lawrence W.
• Format: Journal Article
• Language: English
• Published: Cham Springer Science + Business Media 01.09.2020; Springer International Publishing; Springer Nature B.V
• Subjects: Atmospheric precipitations; Biogeosciences; Brackishwater environment; Carbon; Carbon sources; Catastrophic events; Coastal ecology; Coastal waters; Cyclones; Discharge; Earth and Environmental Science; Earth Sciences; Ecological conditions; Ecosystems; Environmental Chemistry; Estuaries; Estuarine dynamics; Fisheries; Flooding; Floods; Freshwater; Habitats; Hurricanes; Hydrology; Inland water environment; Life Sciences; Loads (forces); Microprocessors; Mineral nutrients; Nitrogen; Organic matter; ORIGINAL PAPERS; Phosphorus; Precipitation; Rain; Rainfall; Storms; Submarine pipelines; Tropical climate; Water quality; Watersheds; North Carolina; United States > US; Organic carbon; Nutrient cycling; Tropical cyclones; Phytoplankton; Coastal; Flooding; North carolina; Estuarine
• ISSN: 0168-2563; 1573-515X
• DOI: 10.1007/s10533-020-00693-4

Coastal North Carolina experienced 36 tropical cyclones (TCs), including three floods of historical significance in the past two decades (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 United States. 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 in this > 120-year record occurred in the past two decades, identifying a period of elevated precipitation and flooding associated with recent TCs. 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 loads depending on antecedent conditions and storm-related flooding. Depending on the magnitude of freshwater discharge, the NRE either acted as a “processor” to partially assimilate and metabolize the loads or acted as a “pipeline” to transport the loads to the APS and coastal Atlantic Ocean. Under base-flow, terrestrial sources dominate riverine carbon. During storm events these carbon sources are enhanced through the inundation and release of carbon from wetlands. These findings show that event-scale discharge plays an important and, at times, predominant role in C, N and P loadings. We appear to have entered a new climatic regime characterized by more frequent extreme precipitation events, with major ramifications for hydrology, cycling of C, N and P, water quality and habitat conditions in estuarine and coastal waters.