Area 2: Long-term Patterns of Estuary and Intertidal Variation

Long-term Patterns of Estuary and Intertidal Variation

We track the temporal and spatial variability of the habitats within the GCE study area through a combination of field monitoring and remote sensing in order to evaluate ecosystem responses to long-term change and domain perturbations. The field monitoring program includes regular sampling in both the water column and intertidal habitat at a series of 11 core long-term monitoring sites that range across the domain (Fig. 1).

Research Objectives

A) Field Monitoring

• 2A.1 - Continue the GCE core monitoring program in the water column
• 2A.2 - Measure water exchange between the Duplin River and Doboy Sound
• 2A.3 - Evaluate patterns of dissolved organic matter in the water column
• 2A.4 - Continue the core monitoring program in the marsh and tidal fresh forests
• 2A.5 - Characterize groundwater flow

B) Remote Sensing

• 2B.1 - Continue Phenocam observations
• 2B.2 - Continue regular aerial photographs of the GCE domain
• 2B.3 - Establish drone surveys of selected sites
• 2B.4 - Make use of satellite imagery to scale up observations

Current Progress Report

Below is an update for each of the Area 2 objectives as reported in the most recent annual report. For a list of all reports click here (Annual Reports).

A) Field Monitoring

• 2A.1 - Continue the GCE core monitoring program in the water column

  Activities:  We maintain sondes at 10 sites and collect quarterly or monthly CTD profiles and grab samples for water quality measurements at 12 sites. (Table 1, Fig. 1).

  Significant Results:  GCE monitoring data are being used to calibrate and validate a water quality model for the GCE domain (Sheldon et al. 2021; see Objective 4C).

Fig. 2. The tidal and synoptic transport at the mouth of the Duplin River reveal a consistent net outflow (right axis), which is related to the EOF mode 2 salinity variations (left axis). This is consistent with a southerly buoyant flow that connects estuaries all along the GA coast. Source: D Di Iorio and J. Kelly.

Table 1. Monitoring program for GCE-IV. LTER core areas are 1: primary production, 2: populations, 3: organic matter cycling, 4: inorganic nutrients, 5: disturbance.

• 2A.2 - Measure water exchange between the Duplin River and Doboy Sound

  Activities: The horizontal acoustic profiler in the Duplin River was removed because the dock to which it was mounted is being replaced; we are evaluating options for re-deployment.

  Significant Results:  Data from the horizontal acoustic profiler demonstrate consistent net outflow from the Duplin River, which suggests a southerly buoyant flow (Fig. 2).

Fig. 2. The tidal and synoptic transport at the mouth of the Duplin River reveal a consistent net outflow (right axis), which is related to the EOF mode 2 salinity variations (left axis). This is consistent with a southerly buoyant flow that connects estuaries all along the GA coast. Source: D Di Iorio and J. Kelly.

• 2A.3 - Evaluate patterns of dissolved organic matter in the water column

  Activities:  We conducted a focused study to characterize variability in dissolved organic matter composition in Doboy Sound.

  Significant Results:  Martineac et al. (2021) showed that the dominant pattern of variability in DOM composition occurs at seasonal scales (see also Accomplishments).

• 2A.4 - Continue the core monitoring program in the marsh and tidal fresh forests

  Activities:  We monitor plants, invertebrates and soils in 2 zones at each of our 10 marsh sites and the tidal fresh forest (Table 1, Fig. 4). This past year we replaced SETs at sites 4 and 6, which failed after 20 years. We also monitor vegetation dynamics along the salinity gradient of the Altamaha River estuary (see Obj. 4B1).

  Significant Results:  Adams et al. (2021) analyzed 20 years of data on salt marsh katydid densities at the GCE sites. They found much higher densities of Orchemlium fidicinium at sites with extensive adjacent upland, which may provide habitat for reproduction or escape from predators during extreme high tides (Fig. 3).

Fig. 3. Mean densities of Orchelium fidicinium in GCE marshes with high versus low upland influence. a) data from 7 long-term sites monitored from 2003-19; b) data from a one-time sampling of 34 sites in 2003. Bars represent standard errors. Source: Adams et al. 2021.

• 2A.5 - Characterize groundwater flow

  Activities: We monitor groundwater at a series of wells associated with the high marsh manipulation and at the upland-marsh transition at Marsh Landing. We are also evaluating groundwater patterns across Sapelo Island using water level observations in ponds.

  Significant Results:  We constructed a 2-D variable-density groundwater flow model based on the Marsh Landing site (Sanders 2021), which is currently being refined to improve the match between simulated and observed hydraulic head and groundwater salinity.

B) Remote Sensing

• 2B.1 - Continue Phenocam observations

  Activities:  We continue to maintain the “GCESapelo” Phenocam, which focuses on a Spartina marsh. This year we identified a site for a “GCEJuncus” camera, began field observations, and set up temperature and water level sensors.

  Significant Results: Narron et al. (submitted) leveraged the multi-year archive of PhenoCam observations to develop an algorithm that detects flooding in Landsat imagery (see Accomplishments).

• 2B.2 - Continue regular aerial photographs of the GCE domain

  Activities:  We use aerial photographs of the domain to evaluate patterns in creek configuration, creekbank slumping, shoreline armoring, and shifts in tidal marsh distribution.

  Significant Results:  High resolution orthoimagery of the GCE domain was used in delineating and training image classifiers in support of Objectives 2B.4 and 4B.1.

• 2B.3 - Establish drone surveys of selected sites

  Activities:  We are using the drone to conduct monthly flyovers of selected marshes to track disturbances (see Area 4A). We have also added an annual survey of high marsh transitional areas.

  Significant Results: Monthly drone imagery is revealing high resolution patterns of Spartina biomass (Fig. 4) (See also Obj. 4A4).

Fig. 4. Spatio-temporal patterns of biomass of Spartina at the Dean Creek disturbance site, based on relationship between NDVI from drone observations and ground-truthed clip plot data. Source: J. Schalles.

• 2B.4 - Make use of satellite imagery to scale up observations

  Activities:  We are using salinity data collected by the sondes to develop tools to predict sea surface salinity from the Sentinel-2 satellite. We are also using satellites to aid in habitat classification (Obj. 4B1) and to track Spartina biomass at large spatial scales.

  Significant Results: Biomass estimates derived from Sentinel 2 show strong coherence across the Georgia coast and are similar to estimates derived from Landsat.

Area 2 Publications from GCE-IV

Narron, C., O'Connell, J.L., Mishra, D., Cotten, D.L., Hawman, P. and Mao, L. 2022. Flooding in Landsat across tidal systems (FLATS): An index for intermittent tidal filtering and frequency detection in salt marsh environments. Ecological Indicators. 141:109045. (DOI: 10.1016/j.ecolind.2022.109045)

Robinson, M., Alexander, C.R. Jr. and Venherm, C. 2022. Shallow Water Estuarine Mapping in High-Tide-Range Environments: A Case Study from Georgia, USA. Special Issue: Shallow Water Mapping. Estuaries and Coasts. 45:980-999. (DOI: https://doi.org/10.1007/s12237-021-01032-y)

O'Connell, J.L., Alber, M. and Pennings, S.C. 2020. Microspatial differences in soil temperature cause phenology change on par with long-term climate warming in salt marshes. Ecosystems. 23:498–510. (DOI: https://doi.org/10.1007/s10021-019-00418-1)

Alber, M. and O'Connell, J.L. 2019. Elevation drives gradients in surface soil temperature within salt marshes. Geophysical Research Letters. 46:5313-5322. (DOI: https://doi.org/10.1029/2019GL082374)

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)

Liu, W. and Pennings, S.C. 2019. Self-thinning and size-dependent flowering of the grass Spartina alterniflora across space and time. Functional Ecology. 33:1830-1841. (DOI: 10.1111/1365-2435.13384)

Miklesh, D.M. and Meile, C. 2018. Controls on porewater salinity in a Southeastern salt marsh. PeerJ. 6:e5911. (DOI: 10.7717/peerj.5911)

Schalles, J.F., Hladik, C.M., O'Donnell, J., Miklesh, D.M., Pudil, T. and Nealy, N. 2021. Presentation: Satellite and drone remote sensing to study decadal scale and high resolution spatial-temporal patterns and declines of Spartina alterniflora above-ground biomass in Georgia, USA salt marshes. Session 2. 1st International Symposium on Coastal Ecosystems and Global Change (CoEco1), April 18, 2021, Xiamen University, Xiamen, China.

Schalles, J.F., Hladik, C.M., O'Donnell, J., Miklesh, D.M., Pudil, T., Nealy, N. and Currin, H. 2021. Presentation: Serious multidecadal declines in aboveground biomass of the keystone salt marsh species, Spartina alterniflora, are related to climate change in coastal Georgia, USA. Wetlandscapes: Understanding the Large-scale Wetland Functions in the Landscape Symposium. 11th INTECOL International Wetlands Conference, October 14, 2021, Christchurch, New Zealand (virtual, prerecorded).

O'Connell, J.L., Alber, M., Mishra, D. and Byrd, K. 2020. Presentation: Structural heterogeneity in above vs belowground biomass pools differ for Spartina alterniflora monocultures, with consequences for forecasting ecosystem resiliency. Ecological Society of America.

Area 2 Publications from GCE-III

Journal Articles

Liu, W. and Pennings, S.C. 2021. Variation in synchrony of production among species, sites and intertidal zones in coastal marshes. Ecology. (DOI: 10.1002/ECY.3278)

Liu, W. and Pennings, S.C. 2019. Self-thinning and size-dependent flowering of the grass Spartina alterniflora across space and time. Functional Ecology. 33:1830-1841. (DOI: 10.1111/1365-2435.13384)

Peterson, R.N., Meile, C., Peterson, L., Carter, M. and Miklesh, D.M. 2019. Groundwater discharge dynamics into a salt marsh tidal river. Estuarine, Coastal and Shelf Science. 218:324-333. (DOI: 10.1016/j.ecss.2019.01.007)

Damashek, J., Tolar, B., Liu, Q., Okotie-Oyekan, A., Wallsgrove, N.J., Popp, B.N. and Hollibaugh, J.T. 2018. Microbial oxidation of nitrogen supplied as selected organic nitrogen compounds in the South Atlantic Bight. Limnology and Oceanography. 64:982-995. (DOI: 10.1002/lno.11089)

Li, S., Hopkinson, C.S., Schubauer-Berigan, J.P. and Pennings, S.C. 2018. Climate drivers of Zizaniopsis miliacea biomass in a Georgia, U.S.A. tidal fresh marsh. Limnology and Oceanography. 63:2266-2276. (DOI: 10.1002/lno.10937)

Liu, Q., Tolar, B., Ross, M., Cheek, J., Sweeney, C., Wallsgrove, N.J., Popp, B.N. and Hollibaugh, J.T. 2018. Light and temperature control the seasonal distribution of Thaumarchaeota in the South Atlantic Bight. ISME Journal. 12:1473-1485. (DOI: 10.1038/s41396-018-0066-4)

Takagi, K., Hunter, K.S., Cai, W.-J. and Joye, S.B. 2017. Agents of change and temporal nutrient dynamics in the Altamaha River Watershed. Ecosphere. 8(1):33. (DOI: 10.1002/ecs2.1519)

Wang, Y., Castelao, R. and Di Iorio, D. 2017. Salinity Variability and Water Exchange in Interconnected Estuaries. Estuaries and Coasts. (DOI: 10.1007/s12237-016-0195-9)

Whitby, H., Hollibaugh, J.T. and van den Berg, C.M. 2017. Chemical speciation of copper in a salt marsh estuary and bioavailability to Thaumarchaeota. Special Issue: Organic ligands - A key control on trace metal biogeochemistry in the ocean. Frontiers in Marine Sciences. 4. (DOI: 10.3389/fmars.2017.00178)

Caffrey, J.M., Hollibaugh, J.T. and Mortazavi, B. 2016. Living oysters and their shells as sites of nitrification and denitrification. Marine Pollution Bulletin. (DOI: 10.1016/j.marpolbul.2016.08.038.)

Li, S. and Pennings, S.C. 2016. Disturbance in Georgia salt marshes: variation across space and time. Ecosphere. 7(10):e01487. (DOI: 10.1002/ecs2.1487)

Tolar, B., Wallsgrove, N.J., Popp, B.N. and Hollibaugh, J.T. 2016. Oxidation of urea nitrogen in marine nitrifying communities dominated by Thaumarchaeota. Environmental Microbiology. (DOI: 10.1111/1462-2920.13457)

Conference Papers (Peer Reviewed)

Weston, N.B., Hollibaugh, J.T., Sandow, J.T. Jr. and Joye, S.B. 2003. Nutrients and dissolved organic matter in the Altamaha river and loading to the coastal zone. In: Hatcher, K.J. (editor). Proceedings of the 2003 Georgia Water Resources Conference. Institute of Ecology, University of Georgia, Athens, Georgia.

Conference Posters and Presentations

Craft, C.B., Stahl, M. and Widney, S. 2017. Presentation: Tidal freshwater forests: sentinels for climate change. 10th International Workshop on Nutrient Cycling and Retention in Natural and Constructed Wetlands, September 21-24, Trebon, Czech Republic.

Hollibaugh, J.T., Bratcher, A., Cheek, J., Liu, Q., Malagon, E., Popp, B.N., Ross, M., Schaefer, S.C., Sweeney, C., Tolar, B., van den Berg, C.M., Wallsgrove, N.J. and Whitby, H. 2017. Poster: LIGHT AND TEMPERATURE CONTROL THE SEASONAL DISTRIBUTION OF THAUMARCHAEOTA IN THE SOUTH ATLANTIC BIGHT. Fifth International Conference on Nitrification and Related Processes (ICoN5)23-27 July, 2017, 23-27 July, 2017, Vienna, Austria.

Peterson, R.N., Meile, C., Carter, M., Peterson, L., Waldorf, A. and Miklesh, D.M. 2017. Poster: Groundwater inputs to a back-barrier salt marsh tidal river. 2017 Chemical Oceanography Gordon Research Conference, July 2017, Holderness, NH.

Stahl, M., Widney, S. and Craft, C.B. 2017. Presentation: Tidal freshwater forests: a sentinel for climate change. SPEA Ph.D. Students' 17th Annual Conference, February 24, 2017, Bloomington, IN.

Widney, S., Stahl, M. and Craft, C.B. 2017. Presentation: Tidal forests: sentinels for climate change. Society of Wetland Scientists Annual Meeting, June 8, 2017, San Juan, Puerto Rico.

Hollibaugh, J.T., Liu, Q., Ross, M., Cheek, J., Sweeney, C., Tolar, B., Hagan, P., Whitby, H., Bratcher, A., Malagon, E., Lynn-Bell, N., Shalack, J., Reddy, C.M. and Walker, J.T. 2016. Poster: Coupling between Sediment and Water Column Populations of Ammonia Oxidizing Thaumarchaeota in a Salt Marsh Estuary.

Alber, M., Schaefer, S.C., Pomeroy, L.R., Sheldon, J.E. and Joye, S.B. 2008. Presentation: Nitrogen inputs to the Altamaha River estuary (Georgia, USA): a historic analysis. American Society of Limnology and Oceanography, 3/08, Orlando, FL.

Alber, M., Schaefer, S.C., Pomeroy, L.R., Sheldon, J.E. and Joye, S.B. 2008. Presentation: Nitrogen inputs to the Altamaha River estuary (Georgia, USA): a historic analysis. American Society of Limnology and Oceanography, 3/08, Orlando, FL.

Seay, J.E., Bishop, T.D. and Tilburg, C.E. 2006. Poster: Spatial and temporal variations of Porcelain Crab larval abundance in a Georgia Estuary. Southeastern Estuarine Research Society Fall 2006 Meeting, 19 October - 21 October 2006, Savannah, Georgia.

Pennings, S.C. 2005. Presentation: Physical forcing and variation in salt marsh plant productivity at multiple time scales. Ecological Society of America 2005 Meeting - Ecology at multiple scales, August 7-12, 2005, Montreal, Canada.

Shalack, J. and Bishop, T.D. 2004. Poster: Spatial and temporal variability in recruitment of decapod megalopae in the Duplin River, Georgia. Semiannual Meeting of the Southeastern Estuarine Research Society. Invertebrates - Poster Session. Southeastern Estuarine Research Society, 15-17 April 2004, Ft. Pierce, FL.

Bishop, T.D. 2003. Presentation: Invasive biology and status of the green porcelain crab (Petrolisthes armatus) in Georgia waters. South Georgia Invasive Species Workshop, sponsored by The Nature Conservancy and Sapelo Island National Estuarine Research Reserve. October 2003, Brunswick, GA.

Bishop, T.D. and Hurley, D. 2003. Poster: The non-indigenous porcelain crab, Petrolisthes armatus: population trends in the Sapelo Island National Estuarine Research Reserve. 2003 Estuarine Research Federation meeting. September 2003, Seattle, WA.

Bishop, T.D. and Hurley, D. 2003. Poster: The non-indigenous porcelain crab, Petrolisthes armatus: population trends in the Sapelo Island National Estuarine Research Reserve. National Estuarine Research Reserve System / National Estuarine Research Reserve Association Annual Meeting. October 2003, Charleston, S.C.

Bishop, T.D., Hurley, D. and Alber, M. 2003. Presentation: An inventory of the macroinvertebrate fauna of oyster reefs in the Duplin River, Georgia, with emphasis on non-indigenous species occurrence. 2003 Estuarine Research Federation meeting. Sept. 14-18, 2003, Seattle, WA.

Ogburn, M.B., Bishop, T.D. and Alber, M. 2003. Poster: Population dynamics of two salt marsh snails in three Georgia estuaries. Southeastern Estuarine Research Society meeting. March 2003, Atlantic Beach, NC.

Bishop, T.D., Alber, M. and Wiegert, R.G. 2001. Poster: Macrofaunal population shifts and changing coastal salinity regimes. ERF 2001: An Estuarine Odyssey. Estuarine Research Federation, Nov. 4-8, 2001, St. Pete Beach, Florida.

Goodbody, G., Bishop, T.D. and Alber, M. 2001. Presentation: Distribution of snails in the Satilla and Altamaha River Estuaries. Southeastern Estuarine Research Society Meeting. Southeastern Estuarine Research Society, Mar 01, 2001, Charleston, South Carolina.

Pennings, S.C., Bertness, M.D., Donnelly, J.P., Ewanchuk, P.J., Silliman, B.R. and Callaway, R.M. 2001. Presentation: Impacts of global change on coastal salt marshes. Keynote address to the German Limnological Association, September 17-21, 2001, Kiel, Germany.