GCE water quality monitoring 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 Dr. Melissa G. Booth University of Georgia Marine Institute

University of Georgia Marine Institute Sapelo Island Georgia 31327 USA

booth@uga.edu Co-investigator Daniel F. Saucedo University of Georgia Marine Institute

University of Georgia Marine Institute Sapelo Island Georgia 31327 USA

dsaucedo@uga.edu Research technician Jacob Shalack University of Georgia Marine Institute

University of Georgia Marine Institute Sapelo Island Georgia 31327 USA

shalack@uga.edu Research technician Kimberley S. Hunter University of Georgia

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

kshunter@uga.edu Research technician 2026

We run regular cruises to measure the surface water concentrations of dissolved and particulate materials at core stations located across the GCE domain. This includes dissolved inorganic nutrients (NO2-, NO3-, NH4+, HPO42-, and H2SiO42-), dissolved organics (DOC, TDN, DON, TDP, and DOP); chlorophyll a samples; total suspended sediment and particulate CN samples. During 2008, the Joye lab (K. Hunter) processed a total of 6,720 samples from the monitoring cruises: 480 samples for determination of concentrations of dissolved inorganic nutrients (NO2-, NO3-, NH4+, HPO42-, and H2SiO42-) and dissolved organics (DOC, TDN, DON, TDP, and DOP); 480 chlorophyll a samples; 480 total suspended sediment and particulate CN samples. Analyses are completed through last spring’s samples; other analyses are in progress.

Table 1 shows the averages and standard deviations for nutrient and DOC concentrations during 2009. As observed in previous years, spatial and temporal variations among the study sites were apparent. The highest NH4 concentrations were observed in Sapelo Sound (GCE 1); the average concentrations in the Altahama (GCE 8 and 9) were half those at GCE 1. However, differences among the stations were not significant because of high variability in NH4 concentration. The highest NOx concentrations were present in Altamaha Sound (GCE 7 and 8). NOx concentrations in Sapelo and Doboy Sounds were significantly lower than those in Altamaha Sound. In Altamaha Sound NOx concentrations usually exceeded NH4 concentration whereas in Doboy and Sapelo Sounds, concentrations of NH4 usually exceeded NOx. DON concentrations were highest in Sapelo Sound (GCE 1). Inorganic (PO4) and organic (DOP) phosphorus concentrations were highest in Sapelo Sound (GCE 1). Phosphorus concentration tended to decrease along the salinity gradient (higher at lower salinity) in Sapelo and Altamaha Sounds. DOC concentrations were highest in Sapelo Sound, followed by Doboy and Altamaha Sounds (which were not different from one another). Silicate concentrations were also highest in Sapelo Sound (GCE 1). The molar ratio of DIN:DIP was significantly below the Redfield Ratio (16:1) in Sapelo and Doboy Sounds, suggesting N limitation of primary production (Table 2). In Altamaha Sound, the DIN:DIP ratio was not significantly different from Redfield at GCE 7 and 8 but was slightly below Redfield at GCE 9. The ratio of DIN:DSi was significantly below Redfield (1:1) at all sites, providing further support for N limitation in these three estuarine systems. The DON:DOP ratio, in contrast, exceeded Redfield at all sites. The high concentrations of DON and DOP in this system suggest that organic N and P fuel a good portion of biological production. Chlorophyll concentrations were highest at GCE 1 in Sapelo Sound, and decreased along the salinity gradient (Table 3). In contrast, chlorophyll concentrations increased with salinity in Doboy and Altamaha Sounds. The pattern of TSS concentration followed that of chlorophyll, with highest concentrations at the freshwater end of Sapelo Sound (GCE 1) and at the seaward stations in the other two Sounds (GCE 6 and 9). Overall concentrations of particulate organic carbon and nitrogen were highest in Altamaha Sound but the maximum concentrations were observed at GCE 1.

Area 2: Patterns within the Domain (more information) 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 GCE Georgia inorganic organic water quality Overall geographic extent of the research project -81.582311 -81.154122 31.559628 31.172459 2001-01-01

National Science Foundation grant numbers OCE-9982133 and OCE-0620959

estuary marsh complex Altamaha River - Altamaha River transect used for GCE quarterly hydrographic monitoring surveys. Nominal profiling stations are defined every 2km from -4km to 40km (relative to station 0km at the line of demarcation), based on an estimated Thalweg line running up the main river channel. -81.582311 -81.237936 31.401403 31.296034 Doboy Sound - Doboy Sound transect used for GCE quarterly hydrographic monitoring surveys. Nominal profiling stations are defined every 2km from -2km to 12km and at 12.6km (relative to station 0km at the line of demarcation), based on an estimated Thalweg line running up the main sound channel. -81.368240 -81.242954 31.455664 31.340942 Duplin River - Duplin River transect used for GCE quarterly hydrographic monitoring surveys. Nominal profiling stations are defined at various locations along the Duplin River west of Sapelo Island, Georgia. -81.301987 -81.263124 31.486493 31.410854 Intracoastal Waterway - Intracoastal Waterway transect used for GCE quarterly hydrographic monitoring surveys. Nominal profiling stations are defined at varying distances from -28km to 32km (South to North, relative to station 0km at the sourthernmost tip of Wolf Island near the mouth of the Altamaha River), based on an estimated Thalweg line running up the main channel. -81.439160 -81.257748 31.546850 31.172459 Sapelo River - Sapelo River transect used for GCE quarterly hydrographic monitoring surveys. Nominal profiling stations are defined every 3-4km from 0km to 36km (relative to station 0km at the line of demarcation), based on an estimated Thalweg line running up the main river channel. -81.431980 -81.154122 31.559628 31.516636 Lehmann, M.K., Gurlin, D., Pahlevan, N., Binding, C., Fichot, C., Gitelson, A., Mishra, D., Schalles, J.F., Simis, S., Smith, B. and Spyrakos, E. 2023. GLORIA - A globally representative hyperspectral in situ dataset for optical sensing of water quality. Nature - Scientific Data. 10:1130958, 6 April 2023(100 (2023)):13 p. (DOI: doi.org/10.1038/s41597-023-01973-y) https://www.nature.com/articles/s41597-023-01973-y Schaeffer, B., Neely, M., Spinosa, A., Serafy, E., Odermatt, D., Weathers, K., Barracchini, T., Bouffard, D., Carvalho, L., Comny, R., De Keukelaere, P., Hunter, P., Jamet, C., Joehnk, K., Johnston, J., Knudby, A., Minaudo, C., Pahlevan, N., Rose, K., Schalles, J.F. and Tzortziou, M. 2021. Integrating inland and coastal water quality data for actionable knowledge. Special Issue: Big Earth Data and Remote Sensing in Coastal Environments. Remote Sensing. 13; 23 July 2021(15):24 p. (DOI: doi.org/10 https://www.mdpi.com/2072-4292/13/15/2899 NUT-GCEM-1609 - Long-term water quality monitoring in the Altamaha, Doboy and Sapelo sounds and the Duplin River near Sapelo Island, Georgia from November 2013 to December 2022 https://gce-lter.marsci.uga.edu/public/app/dataset_details.asp?id=616 NUT-GCEM-2105 - Dissolved Inorgainic Carbon concentration and Total Alkalinity from surface water samples collected in the GCE LTER domain near Sapelo Island, Georgia between May 2014 and December 2022. https://gce-lter.marsci.uga.edu/public/app/dataset_details.asp?id=760 PHY-GCEM-1506a - Monthly vertical profiles of salinity, temperature, pressure, oxygen and photosynthetically-available radiation in Sapelo River, Doboy Sound, Duplin River and Altamaha River transect surveys from April 2008 to April 2015 https://gce-lter.marsci.uga.edu/public/app/dataset_details.asp?id=565 NUT-GCEM-0909a - Long-term water quality monitoring in the Altamaha, Doboy and Sapelo sounds and the Duplin River near Sapelo Island, Georgia from May 2001 to August 2009 https://gce-lter.marsci.uga.edu/public/app/dataset_details.asp?id=316 CHM-GCEM-0501 - Surface water DIC, total alkalinity, and pH for the September 2002 through December 2004 Georgia Coastal Ecosystems LTER oceanographic surveys https://gce-lter.marsci.uga.edu/public/app/dataset_details.asp?id=461 Table 1. Dissolved inorganic and organic nutrients. https://gce-lter.marsci.uga.edu/public/resources/projects/Table1JoyeQ2.png Table 2. Molar ratios of nutrients. https://gce-lter.marsci.uga.edu/public/resources/projects/Table2JoyeQ2.png Table 3. Chlorophyll and particulates. https://gce-lter.marsci.uga.edu/public/resources/projects/Table3JoyeQ2.png Document: Dissolved Inorganic Carbon and Total Alkalinity Processing Protocols https://gce-lter.marsci.uga.edu/public/app/resource_details.asp?id=975 Document: Cruise Sampling Protocol https://gce-lter.marsci.uga.edu/public/app/resource_details.asp?id=488