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Gussenhoven Seminar: Iris Anderson – VIMS
March 4, 2020 @ 12:30 pm - 1:30 pm
UNC-CH’s Department of Marine Sciences is proud to host a seminar by Iris Anderson. This event is scheduled for Wednesday, March 4th, at 12:30 pm in room G201 on the ground floor of Murray Hall at the University of North Carolina at Chapel Hill. This seminar will also be broadcast live to UNC’s Institute of Marine Sciences room 222.
Presenter Affiliation: Professor, Virginia Institute of Marine Science
Title: Carbon fluxes in microtidal estuaries: Physical vs. biological drivers
Abstract: Most estuaries are thought to be net heterotrophic and, thus, net emitters of CO2 to the atmosphere. Emissions of CO2 are regulated by a combination of physical and biological factors, which vary seasonally, annually, and inter-annually. The objective of this study was to compare CO2 emissions from two microtidal estuaries, the New River Estuary (NRE), NC and York River Estuary (YRE), VA, under dramatically different freshwater (FW) discharge patterns. Discharge in the NRE varied from slightly below average in 2013-14 to slightly above average in 2014-15. Conditions in the YRE during 2018 were dramatically different with average discharge approximately double the long-term average; however, by July – December 2019 discharge had declined to well below average. High resolution surveys of pCO2, DO, and physical parameters were conducted with a Dataflow system during bi-monthly cruises at dawn, dusk, and a second dawn. Grab samples were taken at 10 stations for additional biogeochemical parameters. Annually NEM in the YRE was net heterotrophic varying from -9.24 to -11.77 mol O2 m-2 y-1 in 2018 and 2019, whereas in the NRE NEM varied from -4.5 to +1.8 mol O2 m-2 y-1 in 2013 and 2014. CO2 effluxes were highest during years of high FW discharge: in the YRE fluxes varied from 8.15 to 3.57 mol C m-2 y-1 and in the NRE they ranged from 1.8 to 6.6 mol C m-2 y-1. CO2 fluxes were more strongly related to NEM in the YRE than the NRE with net effluxes when the estuary was net heterotrophic. Effluxes were strongly related to FW age in the YRE and were greatest at short FW ages. The relationship between CO2 flux and both DOC and DIN was strongest during years of high FW discharge. Physical variables were the dominant drivers of CO2 fluxes during years of high FW discharge, whereas biological variables become more important during years of low discharge.