I. Data Set Descriptors A. Title: Steven C. Pennings. 2025. RTK survey of permanent monitoring plots at Altamaha plant transition sites conducted between 2015 and 2025.. Georgia Coastal Ecosystems LTER Data Catalog (data set PLT-GCEM-2510; /data/PLT-GCEM-2510) B. Accession Number: PLT-GCEM-2510 C. Description 1. Originator(s): Name: Steven C. Pennings Address: Department of Biology and Biochemistry University of Houston Houston, Texas 77204-5513 Country: USA Email: scpennin@central.uh.edu 2. Abstract: Initial real time kinematic (RTK) GPS survey of ground elevations of GCE permanent monitoring plots at the Altamaha plant transition sites ZSC1 and ZSC2 was conducted in January 2013. RTK survey of permanent monitoring plots at Altamaha plant transition site SCSA was conducted in July 2025. Plots that experienced terminal slump or could not be found for any reason were replaced with a new plot in the same general area with the plot code incremented by 10. For example if plot 3 was lost, it was replaced by 13, and then in turn by 23. This data set will be updated as future RTK measurement of the plots are made. 3. Study Type: Monitoring 4. Study Themes: Plant Ecology 5. LTER Core Areas: Primary Production 6. Georeferences: geographic coordinates as data columns 7. Submission Date: Oct 08, 2025 D. Keywords: Altamaha River, Altamaha Sound, elevation, GCE, Georgia, Georgia Coastal Ecosystems, global positioning system, LTER, plant communities, Primary Production, Sapelo Island, USA II. Research Origin Descriptors A. Overall Project Description 1. Project Title: Georgia Coastal Ecosystems LTER - IV 2. Principal Investigators: Name: Merryl Alber Address: Dept. of Marine Sciences University of Georgia Athens, Georgia 30602-3636 Country: USA Email: malber@uga.edu 3. Funding Period: Feb 01, 2019 to Jan 31, 2025 4. Objectives: The GCE-LTER project has four goals. 1) Track environmental and human drivers that can cause perturbations in our focal ecosystems. This will be accomplished this through continuing long-term measurements of climate, water chemistry, oceanic exchange, and human activities on the landscape. 2) Describe temporal and spatial variability in physical, chemical, geological and biological characteristics of the study system (coastal wetland complexes) and how they respond to external drivers. This will be accomplished through field monitoring in combination with remote sensing and modeling. 3) Characterize the ecological responses of intertidal marshes to disturbance. This will be accomplished by ongoing monitoring and experimental work to evaluate system responses to major perturbations in three key marsh habitats (changes in inundation and predator exclusion in Spartina-dominated salt marshes; increases in salinity in fresh marshes; changes in runoff in high marshes), by implementing standardized experimental disturbances along salinity and elevation gradients, and by tracking responses to natural disturbances. 4) Evaluate ecosystem properties at the landscape level (habitat distribution, net and gross primary production, C budgets) and assess the cumulative effects of disturbance on these properties. The project will also develop relationships between drivers and response variables, which can be used to predict the effects of future changes. This will be accomplished through a combination of data synthesis, remote sensing and modeling. 5. Abstract: The Georgia Coastal Ecosystems (GCE) Long Term Ecological Research (LTER) program, based at the University of Georgia Marine Institute on Sapelo Island, Georgia, was established in 2000 to study long-term change in coastal ecosystems. Estuaries (places where salt water from the ocean mixes with fresh water from the land) and their adjacent marshes provide food and refuge for fish, shellfish and birds; protect the shoreline from storms; help to keep the water clean; and store carbon. The GCE LTER researchers study marshes and estuaries to understand how these ecosystems function, to track how they change over time, and to predict how they might be affected by future changes in climate and human activities. They accomplish this by tracking the major factors that can cause long-term change in coastal areas (e.g. sea level, rainfall, upstream development), and measuring the effects of these factors on the study site. They also conduct focused studies to assess how key marsh habitats will respond to major changes expected in the future, including large-scale experiments to evaluate the effects of a) increases in the salinity of the water that floods freshwater marshes (mimicking drought and/or sea level rise), b) changes in water runoff from land into the upland marsh border (mimicking drought or upland development), and c) exclusion of larger organisms in the salt marsh (mimicking long-term declines in predators). During this award they will initiate additional studies to systematically evaluate how coastal wetlands respond to disturbances. Disturbances, or disruptions in the environment, are particularly important to understand in the context of long-term background changes such as increasing sea level, and GCE researchers are working to assess the cumulative effects of multiple disturbances on the landscape. The GCE education and outreach program works to share an understanding of coastal ecosystems with teachers and students, coastal managers, citizen scientist and the general public. 6. Funding Source: NSF OCE 1832178 B. Sub-project Description 1. Site Description a. Geographic Location: SCSA -- SCSA Altamaha Plant Transition Site, Georgia, USA ZSC1 -- ZSC1 Altamaha Plant Transition Site, Georgia, USA ZSC2 -- ZSC2 Altamaha Plant Transition Site, Georgia, USA Coordinates: SCSA -- NW: 081 22 34.61 W, 31 19 25.64 N NE: 081 22 16.54 W, 31 19 25.64 N SE: 081 22 16.54 W, 31 19 20.07 N SW: 081 22 34.61 W, 31 19 20.07 N ZSC1 -- NW: 081 27 11.04 W, 31 19 47.07 N NE: 081 26 54.01 W, 31 19 47.07 N SE: 081 26 54.01 W, 31 19 37.01 N SW: 081 27 11.04 W, 31 19 37.01 N ZSC2 -- NW: 081 27 18.91 W, 31 20 31.29 N NE: 081 27 05.14 W, 31 20 31.29 N SE: 081 27 05.14 W, 31 20 19.92 N SW: 081 27 18.91 W, 31 20 19.92 N b. Physiographic Region: SCSA -- Lower coastal plain ZSC1 -- Lower coastal plain ZSC2 -- Lower coastal plain c. Landform Components: SCSA -- Estuarine tidal marsh ZSC1 -- Estuarine tidal marsh ZSC2 -- Estuarine tidal marsh d. Hydrographic Characteristics: SCSA -- Site borders the Altamaha River, and is subject to 2-3m semi-diurnal tides ZSC1 -- Site borders the Altamaha River, and is subject to 2-3m semi-diurnal tides ZSC2 -- Site borders the Champney River, and is subject to 2-3m semi-diurnal tides e. Topographic Attributes: SCSA -- Flat, with elevations ranging from 0-3m above mean low tide ZSC1 -- Flat, with elevations ranging from 0-3m above mean low tide ZSC2 -- Flat, with elevations ranging from 0-3m above mean low tide f. Geology, Lithology and Soils: SCSA -- unspecified ZSC1 -- unspecified ZSC2 -- unspecified g. Vegetation Communities: SCSA -- Spartina alterniflora and Spartina cynosuroides ZSC1 -- Spartina cynosuroides and Zizaniopsis miliacea ZSC2 -- Spartina cynosuroides and Zizaniopsis miliacea h. History of Land Use and Disturbance: SCSA -- Oct 14, 2013: Plots were examined for signs of disturbance by wrack inundation, animal activity, and creek bank erosion. The following plots were disturbed by wrack: C1. The following plots are located on creek bank areas that are collapsing: C1, C4. Oct 17, 2014: Plots were examined for signs of disturbance by wrack inundation, animal activity, and creek bank erosion. The following plots are on creekbank areas that are collapsing: C4, C7. The following plots were lost and replaced: C1 (replaced with C11). Oct 22, 2015: Plots were examined for signs of disturbance by wrack inundation, animal activity, and creek bank erosion. The following plots are on creekbank areas that are collapsing: C5. The following plots were lost due to creekbank erosion (terminal slump) and replaced: C11, C4, C7, C8 (replaced with C21, C14, C17, C18 resp). ZSC1 -- Oct 14, 2013: Plots were examined for signs of disturbance by wrack inundation, animal activity, and creek bank erosion. No disturbance was observed, and no plots were replaced. Oct 17, 2014: Plots were examined for signs of disturbance by wrack inundation, animal activity, and creek bank erosion. No disturbance was observed, and no plots were lost and replaced. Oct 22, 2015: Plots were examined for signs of disturbance by wrack inundation, animal activity, and creek bank erosion. No disturbance was observed, and no plots were lost and replaced. ZSC2 -- Oct 14, 2013: Plots were examined for signs of disturbance by wrack inundation, animal activity, and creek bank erosion. No disturbance was observed, and no plots were replaced. Oct 17, 2014: Plots were examined for signs of disturbance by wrack inundation, animal activity, and creek bank erosion. The following plots were disturbed by wrack: C3 (no plants). No plots were lost and replaced. Oct 22, 2015: Plots were examined for signs of disturbance by wrack inundation, animal activity, and creek bank erosion. The following creekbank plots are on creekbank areas that are collapsing (slump): C3. Not plots were lost and none were replaced. i. Climate: Climate summary for Sapelo Island, Georgia, based on NWS data from 1980-2010: Daily-aggregated Values: Mean (sample standard deviation) mean air temperature: 20.09°C (7.28°C) minimum air temperature: 15.02°C (7.96°C) maximum air temperature: 24.82°C (6.98°C) total precipitation: 3.26mm (10.3mm) Yearly-aggregated Daily Values: Mean (sample standard deviation) total precipitation (1980-2010): 1124mm (266mm) 2. Experimental or Sampling Design a. Design Characteristics: We established permanent vegetation monitoring plots in creekbank at plant transition zones along the Altamaha River 2012. b. Permanent Plots: Active plots were measured at each survey. Some plots were lost and replaced with a new plot in the same general area with the plot code incremented by 10. For example if plot 3 was lost, it was replaced by 13, and then in turn by 23. c. Data Collection Duration and Frequency: Initial real time kinematic (RTK) GPS survey of ground elevations of the permanent monitoring plots at GCE Altamaha plant transition sites ZSC1 and ZSC2 was conducted in January of 2013. Initial real time kinematic (RTK) GPS survey of ground elevations of the permanent monitoring plots at GCE Altamaha plant transition sites SCSA was conducted in July of 2025. In survey, the location was measured at the mid-point of the plot edge furthest from the creek. Beginning of Observations: Jan 14, 2013 End of Observations: Jul 01, 2025 3. Research Methods a. Field and Laboratory Methods: Method 1: 2013 RTK Survey -- At each sampling location the RTK Rover foot was placed flush with the marsh surface and care was taken to leave the sediment and vegetation undisturbed. The measurements were taken at the mid-point of the plot edge furthest from the creek. For each sampling location, the RTK was set to record 5 sec readings, with a logging interval of 1 sec. Other RTK settings included: 10 degree elevation mask, PDOP mask of 6, minimum vertical precision of 0.015 m and a minimum horizontal precision of 0.020 m. All RTK observations were automatically stored in the handheld Trimble Survey Controller and uploaded to the LTER GIS computer using the Trimble Geomatics Office Software. Method 2: 2025 RTK Survey -- At each sampling location the RTK Rover foot was placed flush with the marsh surface and care was taken to leave the sediment and vegetation undisturbed. The measurements were taken at the center point of the plot. All RTK observations were automatically stored in the handheld Trimble Survey Controller and uploaded to the LTER GIS computer using the Trimble Geomatics Office Software. b. Protocols: Method 1: none Method 2: none c. Instrumentation: Method 1: RTK GPS Manufacturer: Trimble (Model: R6) Parameter: Elevation (Accuracy: 20mm + 1 ppm RMS, Readability: 1mm, ) Protocol: Base receiver is placed on a permanent cement base installed near each field site, connected to GLONASS satellite services via mobile 3G Internet connection, and allowed to establish a stable benchmark positional fix. A portable wireless rover unit is then used to collect and log horizontal position and vertical elevation data for sites being surveyed. Parameter: Latitude (Accuracy: 10 mm + 1 ppm RMS, Readability: 1mm, Range: 0-90 degrees) Protocol: Base receiver is placed on a permanent cement base installed near each field site, connected to GLONASS satellite services via mobile 3G Internet connection, and allowed to establish a stable benchmark positional fix. A portable wireless rover unit is then used to collect and log horizontal position and vertical elevation data for sites being surveyed. Parameter: Longitude (Accuracy: 10 mm + 1 ppm RMS, Readability: 1mm, Range: 0-180 degrees) Protocol: Base receiver is placed on a permanent cement base installed near each field site, connected to GLONASS satellite services via mobile 3G Internet connection, and allowed to establish a stable benchmark positional fix. A portable wireless rover unit is then used to collect and log horizontal position and vertical elevation data for sites being surveyed. Method 2: RTK GPS Manufacturer: Trimble (Model: R12i) Parameter: Elevation (Accuracy: 15mm + 0.5ppm RMS, Readability: 1mm, ) Protocol: Base receiver is placed on a permanent cement base installed near each field site, connected to GLONASS satellite services via mobile 3G Internet connection, and allowed to establish a stable benchmark positional fix. A portable wireless rover unit is then used to collect and log horizontal position and vertical elevation data for sites being surveyed. Parameter: Latitude (Accuracy: 8mm + 0.5ppm RMS, Readability: 1mm, Range: 0-90 degrees) Protocol: Base receiver is placed on a permanent cement base installed near each field site, connected to GLONASS satellite services via mobile 3G Internet connection, and allowed to establish a stable benchmark positional fix. A portable wireless rover unit is then used to collect and log horizontal position and vertical elevation data for sites being surveyed. Parameter: Longitude (Accuracy: 8mm + 0.5ppm RMS, Readability: 1mm, Range: 0-90 degrees) Protocol: Base receiver is placed on a permanent cement base installed near each field site, connected to GLONASS satellite services via mobile 3G Internet connection, and allowed to establish a stable benchmark positional fix. A portable wireless rover unit is then used to collect and log horizontal position and vertical elevation data for sites being surveyed. d. Taxonomy and Systematics: Method 1: not applicable Method 2: not applicable e. Speclies List: f. Permit History: Method 1: not applicable Method 2: not applicable 4. Project Personnel a. Personnel: 1: Steven C. Pennings 2: Christine M. Hladik 3: Emily Pace b. Affiliations: 1: University of Houston, Houston, Texas 2: Georgia Southern University, Statesboro, Georgia 3: University of Georgia Marine Institute, Sapelo Island, Georgia III. Data Set Status and Accessibility A. Status 1. Latest Update: 09-Oct-2025 2. Latest Archive Date: 09-Oct-2025 3. Latest Metadata Update: 09-Oct-2025 4. Data Verification Status: Reviewed by IM B. Accessibility 1. Storage Location and Medium: Stored at GCE-LTER Data Management Office Dept. of Marine Sciences Univ. of Georgia Athens, GA 30602-3636 USA on media: electronic data download (WWW) or compact disk 2. Contact Person: Name: Adam Sapp Address: Department of Marine Sciences University of Georgia Athens, Georgia 30602 Country: USA Email: asapp@uga.edu 3. Copyright Restrictions: not copyrighted 4. Restrictions: This information is licensed under a Creative Commons Attribution 4.0 International License (see: https://creativecommons.org/licenses/by/4.0/). The consumer of these data ("Data User" herein) has an ethical obligation to cite it appropriately in any publication that results from its use. The Data User should realize that these data may be actively used by others for ongoing research and that coordination may be necessary to prevent duplicate publication. The Data User is urged to contact the authors of these data if any questions about methodology or results occur. Where appropriate, the Data User is encouraged to consider collaboration or co-authorship with the authors. The Data User should realize that misinterpretation of data may occur if used out of context of the original study. While substantial efforts are made to ensure the accuracy of data and associated documentation, complete accuracy of data sets cannot be guaranteed. All data are made available "as is." The Data User should be aware, however, that data are updated periodically and it is the responsibility of the Data User to check for new versions of the data. The data authors and the repository where these data were obtained shall not be liable for damages resulting from any use or misinterpretation of the data. a. Release Date: Affiliates: Oct 08, 2025, Public: Oct 08, 2025 b. Citation: Data provided by the Georgia Coastal Ecosystems Long Term Ecological Research Project, supported by funds from NSF OCE 1832178 (data set PLT-GCEM-2510) c. Disclaimer: The user assumes all responsibility for errors in judgement based on interpretation of data and analyses presented in this data set. 5. Costs: free electronic data download via WWW, distribution on CD may be subject to nominal processing and handling fee IV. Data Structural Descriptors A. Data Set File 1. File Name: PLT-GCEM-2510_1_0.CSV 2. Size: 24 records 3. File Format: ASCII text (comma-separated value format) 3a. Delimiters: single comma 4. Header Information: 5 lines of ASCII text 5. Alphanumeric Attributes: 6. Quality Control Flag Codes: Q = questionable value, I = invalid value, E = estimated value 7. Authentication Procedures: 8. Calculations: 9. Processing History: Software version: GCE Data Toolbox Version 3.9.10 (23-May-2022) Data structure version: GCE Data Structure 1.1 (29-Mar-2001) Original data file processed: PLT-GCEM-2510.txt (24 records) Data processing history: 09-Oct-2025: new GCE Data Structure 1.1 created ('newstruct') 09-Oct-2025: 24 rows imported from ASCII data file 'PLT-GCEM-2510.txt' ('imp_ascii') 09-Oct-2025: 13 metadata fields in file header parsed ('parse_header') 09-Oct-2025: data structure validated ('gce_valid') 09-Oct-2025: automatically assigned study date metadata descriptors based on the range of date values in date/time columns (add_studydates) 09-Oct-2025: deleted column Site from data structure ('ui_editor') 09-Oct-2025: copied/reordered columns Location, Site_name, Zone, Plot, Description, UTM_Zone, UTM_Northing, UTM_Easting, UTM_Datum, Longitude, Latitude, Elevation, Elevation_Datum, Date_Measured and Duplicate ('copycols') 09-Oct-2025: updated 1 metadata fields in the Dataset section(s) ('addmeta') 09-Oct-2025: imported Dataset, Project, Site, Study, Status, Supplement metadata descriptors from the GCE Metabase ('imp_gcemetadata') 09-Oct-2025: updated 57 metadata fields in the Dataset, Project, Site, Status, Study, Supplement section(s) ('addmeta') 09-Oct-2025: updated 6 metadata fields in the Data section(s) ('addmeta') 09-Oct-2025: updated 15 metadata fields in the Status, Data sections to reflect attribute metadata ('updatecols') 09-Oct-2025: parsed and formatted metadata ('listmeta') B. Variable Information 1. Variable Name: column 1. Location column 2. Site_name column 3. Zone column 4. Plot column 5. Description column 6. UTM_Zone column 7. UTM_Northing column 8. UTM_Easting column 9. UTM_Datum column 10. Longitude column 11. Latitude column 12. Elevation column 13. Elevation_Datum column 14. Date_Measured column 15. Duplicate 2. Variable Definition: column 1. Geographic location code in the GCE Metadata Database for the sampling plot column 2. GCE LTER sampling site name column 3. Nominal marsh zone column 4. Permanent plot number column 5. Location description column 6. UTM zone column 7. UTM northing column 8. UTM easting column 9. UTM datum column 10. Longitude in decimal degrees column 11. Latitude in decimal degrees column 12. Plot elevation in meters column 13. Elevation datum column 14. Date of location measurement column 15. Duplicate measurement of previously measured plot (0 = no, 1 = yes) 3. Units of Measurement: column 1. none column 2. none column 3. none column 4. none column 5. none column 6. none column 7. m column 8. m column 9. none column 10. degrees column 11. degrees column 12. m column 13. non column 14. YYYY-MM-DD column 15. none 4. Data Type a. Storage Type: column 1. string column 2. string column 3. integer column 4. integer column 5. string column 6. string column 7. floating-point column 8. floating-point column 9. string column 10. floating-point column 11. floating-point column 12. floating-point column 13. string column 14. string column 15. integer b. Variable Codes: Zone: 1 = creek bank zone, 2 = mid-marsh zone, 3 = additional Juncus zone in high marsh c. Numeric Range: column 1. (none) column 2. (none) column 3. 1 to 1 column 4. 1 to 8 column 5. (none) column 6. (none) column 7. 3465459.459 to 3467522.051 column 8. 456713.28 to 464474.187 column 9. (none) column 10. -81.4551 to -81.3734 column 11. 31.323 to 31.3413 column 12. 0.652 to 1.22 column 13. (none) column 14. (none) column 15. 0 to 0 d. Missing Value Code: 5. Data Format a. Column Type: column 1. text column 2. text column 3. numerical column 4. numerical column 5. text column 6. text column 7. numerical column 8. numerical column 9. text column 10. numerical column 11. numerical column 12. numerical column 13. text column 14. text column 15. numerical b. Number of Columns: 15 c. Decimal Places: column 1. 0 column 2. 0 column 3. 0 column 4. 0 column 5. 0 column 6. 0 column 7. 3 column 8. 3 column 9. 0 column 10. 6 column 11. 6 column 12. 3 column 13. 0 column 14. 0 column 15. 0 6. Logical Variable Type: column 1. free text (none) column 2. free text (none) column 3. coded value (discrete) column 4. nominal (discrete) column 5. free text (none) column 6. free text (none) column 7. geographic coordinate (continuous) column 8. geographic coordinate (continuous) column 9. free text (none) column 10. geographic coordinate (continuous) column 11. geographic coordinate (continuous) column 12. geographic coordinate (continuous) column 13. free text (none) column 14. datetime (none) column 15. logical (discrete) 7. Flagging Criteria: column 1. none column 2. none column 3. none column 4. none column 5. none column 6. none column 7. none column 8. none column 9. none column 10. none column 11. none column 12. none column 13. none column 14. none column 15. none C. Data Anomalies: V. Supplemental Descriptors A. Data Acquisition 1. Data Forms: 2. Form Location: 3. Data Entry Validation: B. Quality Assurance/Quality Control Procedures: C. Supplemental Materials: D. Computer Programs: E. Archival Practices: F. Publications: not specified G. History of Data Set Usage 1. Data Request History: not specified 2. Data Set Update History: none 3. Review History: none 4. Questions and Comments from Users: none