Terminal metabolism 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 2000-01-01 2005-12-31 Dr. Vladimir Samarkin University of Georgia

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

samarkin@uga.edu Research scientist Dr. Steven E. MacAvoy University of Georgia

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

sem7e@hotmail.com Post Doctoral Associate Matthew Erickson University of Georgia

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

rambler@uga.edu Research technician William P. Porubsky University of Georgia

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

newcastl@uga.edu Graduate research assistant 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 2026

Porewater equilibration samplers were used to obtain porewater inventories of inorganic nutrients (NH4+, NOx, PO43-), dissolved organic carbon (DOC) and nitrogen (DON), sulfate (SO42-), dissolved inorganic carbon (DIC), hydrogen sulfide (H2S), chloride (Cl-), methane (CH4) and reduced iron (Fe2+) in intertidal creek-bank sediments at eight sites in three estuarine systems over a range of salinities and seasons. Sulfate reduction (SR) rates and sediment particulate organic carbon (POC) and nitrogen (PON) were also determined at several of the sites. Four sites in the Okatee River estuary in South Carolina, two sites on Sapelo Island, Georgia and one site in White Oak Creek, Georgia appeared to be relatively pristine. The eighth site in Umbrella Creek, Georgia was directly adjacent to a small residential development employing septic systems to handle household waste. The large data set (> 700 porewater profiles) offers an opportunity to assess system-scale patterns of porewater biogeochemical dynamics with an emphasis on DOC and DON distributions. SO42- depletion (SO42-)Dep was used as a proxy for SR, and (SO42-)Dep patterns agreed with measured (35S) patterns of SR. There were significant system-scale correlations between the inorganic products of terminal metabolism (DIC, NH4+ and PO43-) and (SO42-)Dep, and SR appeared to be the dominant terminal carbon oxidation pathway in these sediments. Porewater inventories of DIC and (SO42-)Dep indicate a 2:1 stoichiometry across sites, and the C:N ratio of the organic matter undergoing mineralization was between 7.5 and 10. The data suggest that septic-derived dissolved organic matter with a C:N ratio below 6 fueled microbial metabolism and SR at a site with development in the upland. Seasonality was observed in the porewater inventories, but temperature alone did not adequately describe the patterns of (SO42-)Dep, terminal metabolic products (DIC, NH4+, PO43-), DOC and DON, and SR observed in this study. It appears that production and consumption of labile DOC are tightly coupled in these sediments, and that bulk DOC is likely a recalcitrant pool. Preferential hydrolysis of PON relative to POC when overall organic matter mineralization rates were high appears to drive the observed patterns in POC:PON, DOC:DON and DIC:DIN ratios. These data, along with the weak seasonal patterns of SR and organic and inorganic porewater inventories, suggest that the rate of hydrolysis limits organic matter mineralization in these intertidal creek-bank sediments.

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 Okatee River Sapelo Island South Carolina GCE biogeochemical porewater Overall geographic extent of the research project -81.299522 -81.258908 31.497026 31.371003 2000-01-01 2005-12-31

National Science Foundation grant number OCE-9982133. Additional funding from 2000-2002 by Georgia Sea Grant: 'The role of intertidal sediment processes in mediating coastal ecosystem health'.

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 Dean Creek - Doboy Sound/salt marsh site at the southern end of Sapelo Island near Dean Creek and the Sapelo lighthouse. A few small creeks are present, but a large creek (Dean Creek) is easily accessed. Upland is composed of small hammocks and some constructed causeways, with sand dune complexes east of Dean Creek and extending to the beach. Upper end of the watershed is affected by a culvert at Beach Road and heavy student use of marsh immediately adjacent to culvert. A hydrographic sonde is deployed in Doboy Sound near Commodore Island approximately 1.5km from this site. GCE6 is also the focus of Sapelo Island Microbial Observatory research on microbial diversity and genomics (http://simo.marsci.uga.edu) -81.299522 -81.264378 31.394072 31.371003 Edmonds, J.W., Weston, N.B., Joye, S.B. and Moran, M.A. 2008. Variation in Prokaryotic Community Composition as a Function of Resource Availability in Tidal Creek Sediments. Applied and Environmental Microbiology. 74(6):1836-1844. (DOI: 10.1128/AEM.00854-07) http://aem.asm.org/cgi/content/abstract/74/6/1836 Weston, N.B., Porubsky, W.P., Samarkin, V., MacAvoy, S.E., Erickson, M. and Joye, S.B. 2006. Porewater stoichiometry of terminal metabolic products, sulfate, and dissolved organic carbon and nitrogen in estuarine intertidal creek-bank sediments. Biogeochemistry. 77:375-408. https://link.springer.com/article/10.1007/s10533-005-1640-1 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. Weston, N.B., Porubsky, W.P., Joye, S.B., Samarkin, V. and Erickson, M. 2003. Poster: Porewater Stoichiometry of Terminal Metabolic Products, Sulfate, and Dissolved Organic Carbon and Nitrogen in Estuarine Sediments. Long Term Ecological Research Program All Scientists Meeting. September 2003, Seattle, WA. Weston, N.B., Porubsky, W.P. and Joye, S.B. 2002. Presentation: Seasonal patterns of porewater nutrients, dissolved organics, redox species and gases in estuarine sediments. ASLO Summer Meeting. American Society of Limnology and Oceanography, June, 2002, Victoria, British Columbia. POR-GCED-0210 - Porewater nutrients, dissolved organics, redox species, and gasses in estuarine intertidal sediments at sites on Sapelo Island and near the Satilla River from Fall 2000 through Fall 2002 https://gce-lter.marsci.uga.edu/public/app/dataset_details.asp?id=22