Area 1: External Drivers of Change

Objectives Progress Report Publications Show All  

External Drivers of Change

Our goal for this area is to characterize external drivers such as climate change, sea-level rise, and human alterations of the landscape in terms of long-term trends, spatio-temporal variability, and occurrence of extreme events (e.g., storms, droughts) so that we can investigate the links between external drivers and ecosystem response. This includes collecting ongoing information on climate and oceanographic conditions, sea level, and river discharge (Fig 1).

Research Objectives

A) Environmental Drivers

  • 1A.1 - Collect ongoing information on climate and oceanographic conditions, sea level, and river discharge
  • 1A.2 - Maintain eddy covariance tower in Duplin River
  • 1A.3 - Monitor Altamaha River water entering the GCE domain
  • 1A.4 - Conduct dendrochronology analysis

B) Human Drivers

  • 1B.1 - Assess Native American oyster harvesting practices
  • 1B.2 - Evaluate how human activity relates to marsh inundation patterns
  • 1B.3 - Track shoreline armoring

Current Progress Report

Below is an update for each of the Area 1 objectives as reported in the most recent annual report. For a list of all reports click here (Annual Reports).

A) Environmental Drivers

Area1 Figure 1

Fig. 1. Locations of observing stations used for boundary conditions (ML is Marsh Landing; UGAMI is UGA Marine Institute).

  • 1A.1 - Collect ongoing information on climate and oceanographic conditions, sea level, and river discharge

      Activities and Accomplishments:  A series of meteorological stations are used to characterize the GCE domain (Fig. 1). The station at Marsh Landing serves as our primary station for ClimDB. We now also generate 15-minute summaries from our eddy covariance flux tower. Long-term sea-level data come from the NOAA 8670870 gage at Ft. Pulaski, offshore wind forcing from the NOAA 41008 NDBC buoy at Gray’s Reef; river discharge from the USGS gage at Doctortown. The GCE also co-funds USGS station 022035975 at Meridian, but it is about to be disrupted by a dock renovation so we are testing a Campbell Water Level Sensor as a potential replacement. An analysis of sea-level rise rates at NOAA buoys near GCE shows that rates were 2x higher from 1999-2019 than from 1940-1999 (Fig. 2, Crotty et al. 2020).

  • 1A.2 - Maintain eddy covariance tower in Duplin River

      Activities and Accomplishments:  The GCE eddy covariance flux tower on the Duplin River measures CO2 and H2O fluxes, weather conditions, radiation, water levels, and soil temperature. Maintenance is conducted on a regular basis including replacement of thermocouples, sensor cleaning and calibration. In 2019 we installed additional radiation sensors to improve our estimations of nighttime respiration and daytime fAPAR (fraction of absorbed PAR) for accurate GPP modeling, along with a second soil temperature and water level gauge in order to measure spatial variation in these parameters. We have implemented a data integration methodology to gap-fill and combine CO2 flux data from two different CO2 sensors and have now produced a continuous 30-min NEE dataset from 2014 to the present that provides information on marsh productivity over time. We are working to estimate respiration using a novel machine learning model so that we can partition NEE into gross primary production (GPP) and ecosystem respiration (R). As noted below in the “Cross-site” section, we plan to compare GPP annual budgets with other salt marsh flux tower sites in the east and the Gulf coast (Plum Island LTER, North Inlet, SC, and Grand Bay, MS).

Area 1 Figure 2

Fig. 2. Relative sea level rise recorded by NOAA tide stations from 1940-2019. Trend lines for 1940-1998 and 1999-2019 shown separately. Source: Crotty et al, 2020, PNAS.

  • 1A.3 - Monitor Altamaha River water entering the GCE domain

      Activities and Accomplishments:  We increased our monthly sampling of Altamaha River water to weekly from Apr 2020 through Oct 2020 to capture potential changes in water quality associated with COVID19. Letourneau and Medeiros (2019) recently completed a directed study in which they evaluated the DOM signatures of water entering the system. They found increased biodegradation of DOC when the discharge of the Altamaha River was high, and the DOM composition was more terrigenous in character. This paper, in JGR Biogeosciences, was featured as an EOS research spotlight.

  • 1A.4 - Conduct dendrochronology analysis

      Activities and Accomplishments:  Activities and Accomplishments: Napora et al. (2019; Napora 2020) analyzed bald cypress tree ring data to document variation in tree growth from the last 5,117 years, providing insight into long-term fluctuations in climate (Fig. 3). This is now the longest dendrochronological record east of the Mississippi River.

Area1 Figure 3

Fig. 3. Dendochronology from bald cypress tree cookies collected at the mouth of the Altamaha River, Georgia, USA, showing changes in annual tree rings over 5177 years (left axis) along with the number of radii available for each year (right axis). Source: Napora 2020

B) Human Drivers

  • 1B.1 - Assess Native American oyster harvesting practices

      Activities and Accomplishments:  Thompson (2019) and Thompson et al. (2020) measured 37,805 oysters from Late Archaic and Mississippian archaeological sites along the coasts of GA and SC, along with radiocarbon and climate data. They demonstrated that oyster reefs were an integral part of the Native American landscape and that their sustained presence over long periods of time were likely due to the sophisticated cultural systems that governed harvesting practices. We have also mapped all oyster reefs in the GCE domain in order to connect these baseline data with paleobiological information and to assess the trajectory of modern oyster reefs.

  • 1B.2 - Evaluate how human activity relates to marsh inundation patterns

      Activities and Accomplishments:  We are developing a detailed land use history of the Hog Hammock Community on Sapelo Island to examine how property ownership and potential development interfaces with flooding patterns during extreme high tides. As part of this we have deployed data loggers in drainage ditches to evaluate salt water incursion into populated areas. A new ROA supplement will extend our ethnographic research to incorporate information on traditional ecological knowledge of coastal resources. Heynen and colleagues published both technical and popular articles on the history of land use on Sapelo Island (Heynen 2020; Bailey and Heynen 2020; Hardy and Heynen, in press).

  • 1B.3 - Track shoreline armoring

      Activities and Accomplishments:  We used aerial photography from 2018 to update our coastal armoring analysis and found a 15% increase in revetments and 23% increase in bulkheads in McIntosh County over the past 6 years (2012-2018) (see Table 1).

Area1 Table 1

Table 1. Number and length of shoreline armoring structures in McIntosh County (where most of the GCE is located) and in all counties along the GA coast. Source: C. Alexander

Area 1 Publications from GCE-IV

Hardy, D. and Heynen, N. (in press). "I am Sapelo": Racialized Uneven Development and Land Politics within the Gullah/Geechee Corridor. Environment and Planning E: Nature and Space. (DOI: 10.1177/2514848620987366)

Burns, C., Alber, M. and Alexander, C.R. Jr. 2020. Historical Changes in the Vegetated Area of Salt Marshes. Estuaries and Coasts. (DOI: https://doi.org/10.1007/s12237-020-00781-6)

Crotty, S.M., Ortals, C., Pettengill, T.M., Shi, L., Olabarrieta, M., Joyce, M.A., Altieri, A.H., Morrison, E., Bianchi, T.S., Craft, C.B., Bertness, M.D. and Angelini, C. 2020. Sea-level rise and the emergence of a keystone grazer alter the geomorphic evolution and ecology of southeast US salt marshes. PNAS. 117:17891-17902. (DOI: https://doi.org/10.1073/pnas.1917869117)

Heynen, N. 2020. A plantation can be a commons: Re-Earthing Sapelo Island through Abolition Ecology. Antipode. 0(0):20. (DOI: 10.1111/anti.12631)

Ritchison, B.T., Thompson, V.D., Lulewicz, I.H., Tucker, B. and Turck, J.A. 2020. Climate Change, Resilience, and the Fisher-Hunter-Gatherers of Late Holocene Georgia Coast. Quaternary International. (DOI: 10.1016/j.quaint.2020.08.030)

Thompson, V.D., Rick, T., Garland, C.J., Thomas, D.H., Smith, K.Y., Bergh, S., Sanger, M., Tucker, B., Lulewicz, I.H., Semon, A.M., Schalles, J.F., Hladik, C.M., Alexander, C.R. Jr. and Ritchison, B.T. 2020. Ecosystem stability and Native American oyster harvesting along the Atlantic Coast of the United States. Science Advances. 6. (DOI: 10.1126/sciadv.aba9652)

Letourneau, M.L. and Medeiros, P.M. 2019. Dissolved organic matter composition in a marsh-dominated estuary: Response to seasonal forcing and to the passage of a hurricane. Journal of Geophysical Research: Biogeosciences. 124:1545-1559. (DOI: 10.1029/2018JG004982)

Napora, K., Cherkinsky, A., Speakman, R.J., Thompson, V.D., Horan, R. and Jacobs, C. 2019. Radiocarbon Pretreatment Comparisons of Bald Cypress (Taxodium distichum) Wood Samples from a Massive Buried Deposit on the Georgia Coast, USA. Radiocarbon. 61:1755-1763.

Turck, J.A. and Thompson, V.D. 2019. Human-Environmental Dynamics of the Georgia Coast. In: Reeder-Myers, L., Turck, J. and Rick, T. (editors). The Archaeology of Human-Environmental Dynamics on the North American Atlantic Coast. University Press of Florida, Gainesville, GL.

Napora, K. 2021. Refining cultural and environmental temporalities at the late Archaic-early woodland transition along the Georgia coast, UGA. Ph.D. Dissertation. University of Georgia.

Bailey, M. and Heynen, N. 2020. Sweet (and sticky) redemption. In: Scalawag Magazine.

Area 1 Publications from GCE-III

Journal Articles

Nahrawi, H.B., Leclerc, M.Y., Pennings, S.C., Zhang, G., Singh, N. and Pahari, R. 2020. Impact of tidal inundation on the net ecosystem exchange in daytime conditions in a salt marsh. Agricultural and Forest Meteorology. 294:108133. (DOI: https://doi.org/10.1016/j.agrformet.2020.108133)

Dugan, J., Emery, K., Alber, M., Alexander, C.R. Jr., Byers, J., Gehman, A., McLenaghan, N.A. and Sojka, S. 2018. Generalizing Ecological Effects of Shoreline Armoring Across Soft Sediment Environments. Estuaries and Coasts. 41(1):180-196. (DOI: 10.1007/s12237-017-0254-x)

Gehman, A., McLenaghan, N.A., Byers, J., Alexander, C.R. Jr., Pennings, S.C. and Alber, M. 2018. Effects of small-scale armoring and residential development on the salt marsh-upland ecotone. Estuaries and Coasts. 41(1):54-67. (DOI: 10.1007/s12237-017-0300-8)

O'Connell, J. and Alber, M. 2016. A smart classifier for extracting environmental data from digital image time-series: Applications for PhenoCam data in a tidal salt marsh. Environmental Modelling & Software. 84:134-139. (DOI: 10.1016/j.envsoft.2016.06.025)

Sheldon, J.E. and Alber, M. 2006. The calculation of estuarine turnover times using freshwater fraction and tidal prism models: a critical evaluation. Estuaries and Coasts. 29(1):133-146.

Sheldon, J.E. and Alber, M. 2002. A comparison of residence time calculations using simple compartment models of the Altamaha River estuary, Georgia. Estuaries. 25(6B):1304-1317.

Conference Papers (Peer Reviewed)

Sheldon, J.E. and Alber, M. 2005. Comparing Transport Times Through Salinity Zones in the Ogeechee and Altamaha River Estuaries Using SqueezeBox. In: Hatcher, K.J. (editor). Proceedings of the 2005 Georgia Water Resources Conference. Institute of Ecology, University of Georgia, Athens, Georgia.

Sheldon, J.E. and Alber, M. 2003. Simulating material movement through the lower Altamaha River Estuary using a 1-D box model. Hatcher, K.J. (editor). Proceedings of the 2003 Georgia Water Resources Conference. Institute of Ecology, University of Georgia, Athens, Georgia.

Blanton, J.O., Alber, M. and Sheldon, J.E. 2001. Salinity response of the Satilla River Estuary to seasonal changes in freshwater discharge. Pages 619-622 in: Hatcher, K.J. (editor). Proceedings of the 2001 Georgia Water Resources Conference. Institute of Ecology, University of Georgia, Athens, Georgia.

Conference Posters and Presentations

Dugan, J., Alber, M., Alexander, C.R. Jr., Byers, J., Emery, K., Gehman, A., Lawson, S. and McLenaghan, N.A. 2015. Poster: A conceptual model for predicting the ecological effects of coastal armoring in soft-sediment environments. Coastal and Estuarine Research Federation Biennial Meeting, August 30 - September 2, 2015, Estes Park, CO.

Dugan, J., Alber, M., Alexander, C.R. Jr., Byers, J., Emery, K., Gehman, A., Lawson, S. and McLenaghan, N.A. 2015. Poster: A conceptual model for predicting the ecological effects of coastal armoring in soft-sediment environments. Coastal and Estuarine Research Federation Biennial Meeting, November 8-12, 2015, Portland, OR.

Gehman, A., McLenaghan, N.A., Byers, J., Alexander, C.R. Jr., Pennings, S.C. and Alber, M. 2015. Poster: Effects of development and shoreline armoring on the high marsh ecosystem. Benthic Society Ecology Meeting 2015, March 4-7, 2015, Quebec City, CN.

Sheldon, J.E. and Burd, A.B. 2009. Presentation: An In-depth Look at Alternating Effects of Climate Signals on Freshwater Delivery to Coastal Georgia, U.S.A. Hydrologic Prediction in Estuaries and Coastal Ecosystems. CERF 2009: Estuaries and Coasts in a Changing World, November 1-5, 2009, Portland, OR.

Sheldon, J.E. and Burd, A.B. 2007. Poster: Detecting climate signals in river discharge and precipitation data for the central Georgia coast. 2007 AERS/SEERS Meeting, March 15-17, 2007, Pine Knoll Shores, NC.

Alber, M. and Sheldon, J.E. 2006. Calculating estuary turnover times during non-steady-state conditions using freshwater fraction techniques. Southeastern Estuarine Research Society meeting, Ponte Vedra Beach, Florida.

Alber, M. and Sheldon, J.E. 2006. Presentation: Simple tools for assessing coastal systems: can we get there from here? Coastal Observing Systems Workshop, LTER All Scientists Meeting, September 20-24, 2006, Estes Park Colorado.

Sheldon, J.E. and Alber, M. 2005. Poster: New and improved: Modeling mixing time scales in the Altamaha River estuary. GCE-LTER 2005 Annual Meeting. GCE-LTER, Feb. 11-12, 2005, Athens, Georgia.

Sheldon, J.E. and Alber, M. 2005. Presentation: Beyond whole-estuary flushing times: Using transport times through salinity zones to explain chlorophyll patterns in the Altamaha River estuary (Georgia, USA). Estuarine Interactions: biological-physical feedbacks and adaptations. 2005 Estuarine Research Federation Meeting. October 16-20, 2005, Norfolk, Virginia.

Sheldon, J.E. and Alber, M. 2004. Presentation: SqueezeBox: Flow-scaled 1-D box models for estuary residence time estimates. NOS Workshop on Residence/Flushing Times in Bays and Estuaries. National Oceanic and Atmospheric Administration, June 8-9, 2004, Silver Spring, Maryland.

Sheldon, J.E. and Alber, M. 2004. Presentation: SqueezeBox: Flow-scaled 1-D box models for estuary residence time estimates. Spring 2004 meeting. Southeastern Estuarine Research Society (SEERS), October 14-16, 2004, Wilmington, North Carolina.

Sheldon, J.E. and Alber, M. 2003. Poster: Modeling mixing time scales and transport of dissolved substances in the Altamaha River estuary. 2003 LTER All Scientist's Meeting, "Embarking on a Decade of Synthesis". LTER, Sept. 18-21, 2003, Seattle, Washington.

Sheldon, J.E. and Alber, M. 2003. Presentation: The equivalence of estuarine turnover times calculated using fraction of freshwater and tidal prism models. 2003 Estuarine Research Federation meeting, Sept. 14-18, 2003, Seattle, WA.

Sheldon, J.E. and Alber, M. 2001. Poster: Any way you slice it: A comparison of residence time calculations using simple compartment models of the Altamaha River estuary. ERF 2001: An Estuarine Odyssey (16th Biennial Conference of the Estuarine Research Federation). Freshwater Inflow: Science, Policy and Management. Estuarine Research Federation, Nov. 4-8, 2001, St. Pete Beach, Florida.

Alber, M. and Sheldon, J.E. 2000. Presentation: Residence times in the Altamaha River Estuary: a progress report. Southeastern Estuarine Research Society Meeting. Southeastern Estuarine Research Society, Oct 01, 2000, Tampa, Florida.

Newsletter and Newspaper Articles

Sheldon, W.M. Jr. 2006. Mining and Integrating Data from ClimDB and USGS using the GCE Data Toolbox. In: DataBits: An electronic newsletter for Information Managers: Spring 2006. Long Term Ecological Research Network, Albuquerque, NM.

 
LTER
NSF

This material is based upon work supported by the National Science Foundation under grants OCE-9982133, OCE-0620959, OCE-1237140 and OCE-1832178. Any opinions, findings, conclusions, or recommendations expressed in the material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.