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Research Spending & Results

Award Detail

Awardee:UNIVERSITY OF GEORGIA RESEARCH FOUNDATION, INC.
Doing Business As Name:University of Georgia Research Foundation Inc
PD/PI:
  • Jay Brandes
  • (912) 598-2361
  • jay.brandes@skio.uga.edu
Co-PD(s)/co-PI(s):
  • William B Savidge
  • Aron Stubbins
  • Catherine R Edwards
Award Date:09/16/2012
Estimated Total Award Amount: $ 699,971
Funds Obligated to Date: $ 699,971
  • FY 2012=$699,971
Start Date:09/01/2012
End Date:08/31/2016
Transaction Type:Grant
Agency:NSF
Awarding Agency Code:4900
Funding Agency Code:4900
CFDA Number:47.050
Primary Program Source:040100 NSF RESEARCH & RELATED ACTIVIT
Award Title or Description:Tempo and mode of salt marsh exchange
Federal Award ID Number:1234704
DUNS ID:004315578
Program:Chemical Oceanography
Program Officer:
  • Henrietta Edmonds
  • (703) 292-7427
  • hedmonds@nsf.gov

Awardee Location

Street:310 East Campus Rd
City:ATHENS
State:GA
ZIP:30602-1589
County:Athens
Country:US
Awardee Cong. District:10

Primary Place of Performance

Organization Name:Skidaway Institute of Oceanography
Street:10 Ocean Science Circle
City:Savannah
State:GA
ZIP:31411-1011
County:Savannah
Country:US
Cong. District:01

Abstract at Time of Award

Intellectual Merit: Salt marshes are critical mediators of the flux of material between the terrestrial and marine realms. The balance of material import, export, and transformation affects both the marsh itself and the surrounding estuary. Previous efforts to understand the role of marshes have concentrated either on examining temporal changes (often at low resolution) of bulk exports, or compositional changes in exported material with little regard for its temporal variability. Researchers working at the Skidaway Institute of Oceanography contend that both the quantity and quality of materials exchanged between marsh and estuary in tidally-dominated systems along the southeastern US coast vary significantly in response to semidiurnal, diurnal, tidal, meteorological and seasonal forcing, and that this variability must be included when considering the total contributions of marshes to carbon cycling along the land-ocean boundary. This study will utilize a three-pronged strategy to assess both the quantity and quality of dissolved organic matter (DOM) and particulate organic matter (POM) exported from Groves Creek, a well-characterized meso-tidal salt marsh in coastal Georgia. In particular, by evaluating how marsh function responds to a full spectrum of present environmental conditions, this project will provide tangible insight into how carbon cycling in these critical regions will respond to anticipated changes in those conditions. Broader Impacts: The broader scientific significance of the study will be an improved understanding of DOM and POM exchange and transformation in the salt marsh-estuarine region. This study will also provide valuable opportunities to undergraduate interns to experience interdisciplinary research. Results of this work will be disseminated to scientific researchers, regional environmental managers, and the public on the web, in print, and through Skidaway Institute's programs of public outreach.

Publications Produced as a Result of this Research

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Powers, L. C., J. A. Brandes, W. L. Miller, and A. Stubbins. "Using liquid chromatography-isotope ratio mass spectrometry to measure the ?13C of dissolved inorganic carbon photochemically produced from dissolved organic carbon." Limnol. And Ocean. Methods, v., 2016, p.. doi:dx.doi.org/10.1002/lom3.10146 

Tait, Z. S., M. Thompson, and A. Stubbins. "Chemical fouling reduction of a submersible steel spectrophotometer in estuarine environments using a sacrificial zinc anode." Journal of Environmental Quality, v., 2015, p.. doi:10.2134/jeq2014.11.0484 

Tait, Z. S., M. Thompson, and A. Stubbins. "Chemical fouling reduction of a submersible steel spectrophotometer in estuarine environments using a sacrificial zinc anode." Journal of Environmental Quality, v., 2015, p.. doi:doi:10.2134/jeq2014.11.0484 

Bittar, T. B., S. A. Berge, L. M. Birsa, T. L Walters, M. E. Thompson, R. G. M. Spencer, E. L. Mann, A. Stubbins, M. E. Frischer, and J. A. Brandes "Seasonal dynamics of dissolved, particulate and microbial components of a tidal saltmarsh-dominated estuary under contrasting levels of freshwater discharge." Est. Coast. &Shelf Sci., v.182 A, 2016, p.72. doi:dx.doi.org/10.1016/j.ecss.2016.08.046 


Project Outcomes Report

Disclaimer

This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.

Spartina-dominated marshes are a dominant environment along the southeastern US coast. They perform a variety of very important environmental functions, from serving as habitat for the young of many fish species, as stopovers for migratory birds, and as an interface between inland river systems and the coastal ocean.  Significant tides, as much as 3 meters in some regions, move waters back and forth between estuarine rivers and the marshes though intricate networks of channels. The continuous exchange of water between the deep river channels and the shallow marsh surface allows marshes efficiently create, modify and remove organic matter in the water column as it is repeatedly exposed to the marsh surface.  The balances among these processes determine what is ultimately exported from the land into the coastal ocean.  tHow environmental factors such as day/night cycles, temperature, rainfall, and the timing of tidal cycles, affect this balance are very much open questions. The goal of this project was to examine carbon and water balances within a small but typical spartina-dominated salt marsh near Savannah, Georgia.  In order to do so, we instrumented the dominant tidal creek feeding the marsh with a variety of devices designed to measure salinity, temperature, water color and fluorescence (measures of dissolved organic matter concentrations), water current movements, and oxygen content.  This was done over a period of 18 months, from July 2013 to January 2015.

 

            Because these tidally-influenced salt marshes are very active biologically, one of our challenges was to ensure that our instruments were faithfully recording their individual signals, which required swapping our many of them every 2-3 weeks for cleaning and re-calibration. Even with that effort, the data from our instruments required significant cleanup to remove dropouts (in one case, a fish took up residence in the intake port of an instrument). Calibration was also cross-checked with water samples taken during these instrument swapouts. In addition, we periodically collected water samples using an automated sampler for those types of measurements that cannot be measured optically or electronically in place, like particulate organic matter, chlorophyll and cell counts. And every 4 months we sampled the marsh waters by hand, for very time-sensitive samples like RNA and dissolved gasses. So in all we were able to gain a very detailed picture of how Groves Creek, and by extension the marshes dominating the Georgia and South Carolina Coastlines, function in terms of carbon, oxygen and other elements.

 

            With this data in hand, what did we learn? First, that this marsh is mostly ‘net heterotrophic’, meaning that it burns more organic matter than it produces. We see that in a net overall consumption of oxygen, chlorophyll, and dissolved organic matter over the study period.  However there are times of the year and even parts of a particular month, where this is reversed and the marsh becomes an exporter of dissolved organic matter. And even though the marsh as a whole may be a net importer, complex circulation of water on the marsh surface means  that certain conduits and tributaries within the marsh may axt as net local exporters.   Interestingly, although Spartina grass visually dominates the marsh ecosystem, it contributes relatively little towards carbon export. Instead, it is the very highly biologically active marsh muds that appear to strongly influence marsh particulate carbon exports, and possible also dissolved organics as well (that part will be resolved in the future as we finish sample analysis and data workup).

 

            We also observed several environmental events, including a pulse of water from an up-state dam release that left a pool of terrestrially-derived dissolved organic matter sloshing back and forth in the local estuaries for weeks. Also during our sampling period Georgia went from a dry-drought period to a wet period. These types of climatic shifts were recorded in both organic and inorganic carbon compositions and concentrations, as well as salinity and temperature records, and are the subjects of continued interpretation as we complete the latest rounds of manuscript writing. 

 


Last Modified: 12/02/2016
Modified by: Jay Brandes

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