Using δ13C and δ15N signatures to identify carbon and nitrogen sources in the Lower Cape Fear River and Estuary, NC

The Lower Cape Fear River basin spans the coastal plains of southeastern North Carolina and extends to the Atlantic Ocean. The river basin is characterized by a variety of ecosystems, with wetlands being the dominant feature. In recent years, more than half of these wetlands have been converted for agricultural and residential use, disrupting local environments and affecting waterways. In this study, δ¹³C and δ¹⁵N signatures were analyzed to better understand the fate, transport, and sources of carbon and nitrogen in the Lower Cape Fear River Basin and Estuary. Water samples were collected seasonally and after storm crests from eleven sites, including five along the mainstem of the Cape Fear River (from inland to the estuary mouth), one on the Black River, and one on the Northeast Cape Fear River. Additionally, two pristine control sites and two agricultural end-member sites were included. Particulate organic matter (POM) was filtered from water samples and analyzed using an isotope ratio mass spectrometer (IRMS). Results showed that δ¹³C signatures became heavier downstream as open ocean influence increased. One agricultural site exhibited some of the lightest signatures observed in this study, while the other displayed some of the heaviest. The control sites displayed δ¹³C and δ¹⁵N signatures consistent with natural baselines. After storm events, elevated water levels and runoff caused shifts in dominant carbon sources.

Presentation Preference: Poster

Primary Presenter: Mia Carulli, University of North Carolina Wilmington (mcc2768@uncw.edu)

Authors:

Mia Carulli, University of North Carolina Wilmington  (mcc2768@uncw.edu)

Ai Ning Loh, University of North Carolina Wilmington  (lohan@uncw.edu)