Organic matter cycling and iron reduction Dr. Samantha B. Joye University of Georgia

Dept. of Marine Sciences University of Georgia Athens Georgia 30602-3636 USA

mjoye@uga.edu http://www.marsci.uga.edu/directory/samantha-b-joye Georgia Coastal Ecosystems LTER Project

Dept. of Marine Sciences University of Georgia Athens Georgia 30602-3636 USA

gcelter@uga.edu https://gce-lter.marsci.uga.edu/ Dr. Samantha B. Joye University of Georgia

Dept. of Marine Sciences University of Georgia Athens Georgia 30602-3636 USA

mjoye@uga.edu http://www.marsci.uga.edu/directory/samantha-b-joye Principal investigator 2002-01-01 2004-12-31 Dr. Nathaniel B. Weston University of Georgia

Dept. of Marine Sciences University of Georgia Athens Georgia 30602-3636 USA

nweston@uga.edu Graduate research assistant Tiffany Roberts University of Georgia

Dept. of Marine Sciences University of Georgia Athens Georgia 30602-3636 USA

Undergraduate research assistant 2026

Under the direction of S. Joye, an undergraduate in the Dept. of Biochemistry at UGA did an honors thesis evaluating time courses of metabolite concentrations to estimate of rates of terminal metabolism over time. Rates of potential denitrification were highest in surface sediments and decreased over depth. Rates of iron reduction were very high at depth and dominated DIC production at depths below the denitrification zone. Sulfate reduction rates increased deeper in sediments, where the abundance of bioavailable iron oxyhydroxides was reduced. An inverse reaction transport model was applied in order to estimate rates of net rates of oxygenic photosynthesis (NOP) from pore water oxygen profiles and gross rates of oxygenic photosynthesis (GOP). The depth profile of NOP was similar to that of GOP; however, NOP rates were typically 40-50% less than GOP rates. This suggests that intertidal sediments are a source of oxygen to the overlying water and that a significant fraction of oxygen is consumed in the sediments by biogeochemical processes (e.g., sulfide, ammonium, or methane oxidation).

Question 2: How do the spatial and temporal patterns of biogeochemical processes, primary production, community dynamics, decomposition, and disturbance vary across the estuarine landscape, and how do they relate to environmental gradients? (more information)

LTER NSF Georgia GCE biogeochemical cycling denitrification iron metabolite organic matter oxygenic photosynthesis sulfate Overall geographic extent of the research project -81.295506 -81.258908 31.497026 31.462320 2002-01-01 2004-12-31

National Science Foundation grant number OCE-9982133

estuary marsh complex Hunt Camp - Barrier island/marsh site on western Sapelo Island. This site is located at the upper reaches of the Duplin River, and is within the Sapelo Island National Estuarine Research Reserve. Existing well fields border small marsh area to northwest, some wells have been installed to south end of hammock where marsh is more extensive and permanent plots are located. Two existing hydrographic sondes and weather stations within this site are operated by SINERR (Hunt Camp dock) and UGAMI (flume dock). -81.295506 -81.258908 31.497026 31.462320