Benthic fluxes 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 2001-01-01 2006-12-31 William P. Porubsky University of Georgia

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

newcastl@uga.edu Graduate research assistant 2026

W. Porubsky (Ph.D. student, UGA), N. Weston (PhD student, UGA) and S. Joye (UGA) examined patterns of benthic metabolism and the relative importance of assimilatory and dissimilatory processes as sinks for nitrate (NO©ý?) in intertidal sediments. We determined patterns of benthic metabolism and examined the relative importance of denitrification (DNF) and dissimilatory nitrate reduction to ammonium (DNRA) as sinks for nitrate (NO3-) in intertidal sediments in the presence and absence of benthic microalgal (BMA) activity. By influencing the activity of BMA, light regulated the metabolic status of the sediments, and, in turn, exerted strong control on sediment nitrogen dynamics and the fate of inorganic nitrogen. A pulsed addition of 15N labeled NO3- tracked the effect and fate of dissolved inorganic nitrogen (DIN) in the system. Under illuminated conditions, BMA communities influenced benthic fluxes directly, via DIN uptake, and indirectly, by altering the oxygen penetration depth. Under dark hypoxic and anoxic conditions, the fate of water column NO3- was determined largely by three competing dissimilatory reductive processes; DNF, DNRA, and, on one occasion, anaerobic ammonium oxidation (anammox). Mass balance of the added 15N tracer illustrated that DNF accounted for a maximum of 48.2 % of the 15NO3- reduced while DNRA (a minimum of 11.4 %) and anammox (a minimum of 2.2 %) accounted for much less. A slurry experiment was employed to further examine the partitioning between DNF and DNRA. High sulfide concentrations negatively impacted rates of both processes, while high DOC:NO3- ratios favored DNRA over DNF.

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 benthic metabolism nitrate sediment sinks Overall geographic extent of the research project -81.299522 -81.258908 31.497026 31.371003 2001-01-01 2006-12-31

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 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 Porubsky, W.P., Weston, N.B. and Joye, S.B. 2009. Benthic metabolism and the fate of dissolved inorganic nitrogen in intertidal sediments. Estuarine Coastal and Shelf Science. 83(4):392-402. (DOI: 10.1016/j.ecss.2009.04.012) http://dx.doi.org/10.1016/j.ecss.2009.04.012 Porubsky, W.P., Weston, N.B. and Joye, S.B. 2003. Poster: Examination of denitrification and dissimilatory nitrate reduction to ammonium as pathways for the reduction of inorganic nitrogen in saltmarsh sediment. 17th Biennial Conference of the Estuarine Research Federation. September 2003, Seattle, WA. Porubsky, W.P., Weston, N.B., Lee, R. and Joye, S.B. 2003. Poster: Diel and seasonal patterns of benthic fluxes of nutrients, gases, and dissolved organics from temperate intertidal sediments of Georgia and South Carolina. Long Term Ecological Research All Scientists Meeting. September 2003, Seattle, WA. Porubsky, W.P., Weston, N.B., Lee, R.Y. and Joye, S.B. 2003. Poster: Diel and seasonal patterns of benthic fluxes of nutrients, gases, and dissolved organics from temperate intertidal sediments of Georgia and South Carolina. SECOS Meeting. January 2003, Charleston, SC. Porubsky, W.P., Weston, N.B. and Joye, S.B. 2002. Presentation: Redox control of benthic fluxes of nutrients and dissolved organics from coastal sediments. ASLO Summer Meeting. American Society of Limnology and Oceanography, June, 2002, Victoria, British Columbia.