Salinity intrusion in estuarine sediments 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 2005-01-01 2006-12-31 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 2005-01-01 2006-12-31 Ray E. Dixon University of Georgia

Undergraduate research assistant 2005-01-01 2006-12-31 2026

N. Weston (Ph.D. student, UGA) and S. Joye (UGA) evaluated the effects of upriver salinity intrusion on the biogeochemistry of sediments from the tidal freshwater portion of the Altamaha River. Methanogenesis, which dominated in the freshwater sediments, declined quickly following salinity intrusion. Sulfate reduction was the dominant pathway of microbial organic matter mineralization within two weeks of salinity intrusion, although increased iron-oxide availability during initial salinity intrusion appears to have stimulated high rates of microbial iron reduction for a short period. Salinity-driven desorption of ammonium and increased rates of silica and phosphorus mineral dissolution following salinity intrusion increased overall export of ammonium, phosphate and silicate from salinity-impacted sediments.

Question 3: What are the underlying mechanisms by which the freshwater-saltwater gradient drives ecosystem change along the longitudinal axis of an estuary? (more information)

LTER NSF GCE biogeochemistry freshwater intrusion salinity sediments tidal Overall geographic extent of the research project -81.493498 -81.475900 31.348774 31.334364 2005-01-01 2006-12-31

National Science Foundation grant number OCE-9982133

estuary marsh complex Carrs Island - Freshwater marsh site along the northern bank of Hammersmith Creek at the south end of Carrs Island. Upland area is heavily forested. Northern 3/4 of the island was diked for rice agriculture, but the southern 1/4 is undisturbed. A hydrographic sonde is deployed in the Altamaha River near Hammersmith Creek, adjacent to this site. -81.493498 -81.475900 31.348774 31.334364 Edmonds, J.W., Weston, N.B., Joye, S.B., Mou, X. and Moran, M.A. 2009. Microbial Community Response to Seawater Amendment in Low-Salinity Tidal Sediments. Microbial Ecology. 58(3):558-568. (DOI: 10.1007/s00248-009-9556-2) http://www.springerlink.com/content/44411m5237863955/ Weston, N.B., Vile, M.A., Velinksy, D.J., Joye, S.B. and Neubauer, S.C. 2007. Presentation: Shifting pathways and magnitude of organic matter mineralization in tidal freshwater marshes following sea-level rise. Estuarine Research Federation 2007 Annual Meeting, 4-8 November 2007, Providence, Rhode Island. Weston, N.B., Vile, M.A., Velinksy, D.J., Joye, S.B. and Neubauer, S.C. 2007. Presentation: Rising sea levels and salinity intrusion into tidal freshwater marshes: Shifting microbial communities and pathways of organic matter mineralization. ASLO Aquatic Sciences Meeting, Santa Fe NM, February 2007. Weston, N.B., Dixon, R.E. and Joye, S.B. 2006. Ramifications of increased salinity in tidal freshwater sediments: Geochemistry and microbial pathways of organic matter mineralization. Journal of Geophysical Research. 111:G01009. (DOI: 10.1029/2005JG000071) https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2005JG000071 Edmonds, J.W., Weston, N.B., Joye, S.B. and Moran, M.A. 2004. Presentation: Changes in Microbial Community Structure and Activity in Response to Fluctuations in Organic Carbon Pools in Salt Marsh Sediments. Annual Meeting of the American Society of Microbiology. American Society of Microbiology, June, 2004, Atlanta, Georgia.