Chlorophyll distributions Dr. Merryl Alber University of Georgia

Dept. of Marine Sciences University of Georgia Athens Georgia 30602-3636 USA

malber@uga.edu https://marsci.uga.edu/directory/people/merryl-alber https://orcid.org/0000-0002-9467-4449 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. Merryl Alber University of Georgia

Dept. of Marine Sciences University of Georgia Athens Georgia 30602-3636 USA

malber@uga.edu https://marsci.uga.edu/directory/people/merryl-alber https://orcid.org/0000-0002-9467-4449 Principal investigator Joan E. Sheldon University of Georgia

Dept. of Marine Sciences University of Georgia Athens Georgia 30602-3636 USA

jsheldon@uga.edu https://orcid.org/0000-0002-6409-9500 Research professional 2026

Joan Sheldon (Research Professional, UGA) and Merryl Alber (UGA) completed an analysis in which chlorophyll a concentrations measured along the Altamaha River estuary during 10 sampling periods were compared to transit times through the entire estuary as well as through the tidal freshwater, oligohaline, mesohaline, and polyhaline zones. Overall, total transit time is a good predictor of average estuary chlorophyll concentration, location of the chlorophyll peak, and salinity at the peak location. With increasing transit time, chlorophyll concentrations increase and the peak moves upstream and occurs at lower salinities. However, zone transit times can be better predictors of zone chlorophyll concentrations. At high flows, the tidal freshwater zone is long (>35 km) but transit time through it is very short (<1 d), and chlorophyll concentrations are nearly zero except in the lower estuary. As flows decrease, most of the extra transit time is spent in higher-salinity zones, and chlorophyll increases in these zones. Chlorophyll in tidal freshwater remains minimal until the freshwater zone transit time surpasses 1.3 d, then rises rapidly, suggesting that net phytoplankton production has overcome flushing

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 chlorophyll mesohaline oligohaline phytoplankton polyhaline tidal freshwater Overall geographic extent of the research project -81.582311 -81.237936 31.401403 31.296034 2005-01-01 2005-12-31

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 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 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.