On the downswing of the C-SAW: dissolved organic matter losses from the landscape after extreme weather in coastal North Carolina

Estuaries are prominent biogeochemical reactors in the land-ocean-aquatic continuum (LOAC) that provide essential ecosystem services. The increasing frequency of extreme events (e.g., tropical cyclones) are altering the sources and quality of organic matter exported to estuaries from the landscape. We posit that one effect of this symptom of climate change is a saturation of carbon in coastal waters after such events – but the source and fate of the organic matter driving the saturation remain poorly known. Here we present the changes in dissolved organic matter (DOM) quality in the Neuse River Estuary, a major tributary to the nation’s second largest estuarine complex, the Albemarle-Pamlico Sound, in eastern North Carolina, caused by extreme precipitation events. We used a new fluorescence-based approach for estimating DOM sources across the LOAC based on ordinary least squares regression. We found the majority of DOM in the lower estuary and sound was dominated by upstream river, soil leachate, and wetland sources. Further, we estimated that >60% of DOM in the sound originated from riparian wetlands above head-of-tide of the estuary and persisted for months during a period in which we estimated CO₂ supersaturation in this otherwise productive estuary. Our results suggest a new paradigm of Carbon Saturation And Weather (C-SAW) such that extreme rainfall events from tropical cyclones deplete DOM stored in wetlands, saturating estuaries with long-residence times, and leading to dramatic changes to the estuarine carbon sink.

Presentation Preference: Oral

Primary Presenter: Christopher Osburn, North Carolina State University (closburn@ncsu.edu)

Authors:

Christopher Osburn, North Carolina State University  (closburn@ncsu.edu)

Peter Hoff, Duke University  (peter.hoff@duke.edu)

Nathan Hall, University of North Carolina - Institute of Marine Sciences  (nshall@email.unc.edu)

Hans Paerl, University of North Carolina - Institute of Marine Sciences  (hans_paerl@unc.edu)