Spartina species zonation along the Altamaha River estuary 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 2000-01-01 2004-12-31 Dr. Susan N. White University of Georgia

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

snwhite@uga.edu Graduate research assistant 2000-01-01 2004-12-31 2026

S.N. White (UGA Ph.D. student) and M. Alber (UGA) conducted reciprocal transplant studies, greenhouse experiments, species removals in mixed Spartina stands, and vegetation surveys in the estuary of the Altamaha River, where S. cynosusroides occurs upstream of S. alterniflora. In reciprocal transplant experiments, each plant survived and performed best in its natural habitat. The presence of conspecific neighbors slightly reduced S. alterniflora plant performance in the salt marsh whereas S. cynosuroides showed little response in either environment. The results of these and other experiments suggest the lower estuarine distribution of Spartina cynosuroides is controlled by abiotic conditions (salinity or sulfide concentrations). The upper estuarine distribution of S. alterniflora is not well understood, but seems to also be primarily controlled by abiotic factors (possibly a sulfate requirement). These outcomes challenge results from previous investigations of zonation controls in salt marshes and suggest that modifications to the salt marsh paradigm are necessary when describing vegetation distribution along an estuarine gradient. During an extended drought (2000-2002), Spartina alterniflora density increased to a greater extent than S. cynosuroides in mixed stands and the location where Spartina cover was 50 % S. cynosuroides and 50 % S. alterniflora shifted approximately 3 km upriver, suggesting that Spartina communities can respond rapidly to increasing estuarine salinity. These studies improve our understanding of the ecological linkages in estuaries and can aid coastal policymakers in making better management decisions and predictions concerning how changes in freshwater inflow might impact the distribution of estuarine organisms.

Question 3: What are the underlying mechanisms by which the freshwater-saltwater gradient drives ecosystem change along the longitudinal axis of an estuary? (more information)

salinity LTER NSF Altamaha River Georgia GCE Spartina estuary salt marsh transplant zonation Overall geographic extent of the research project -81.582311 -81.237936 31.401403 31.296034 2000-01-01 2004-12-31

National Science Foundation grant number OCE-9982133

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 Survey sampling locations in 2000 (diamonds), 2002 (circles), and 2004 (triangles), and experimental removal site (black bar) along the Altamaha River estuary. Numbers represent distance from the mouth of the estuary (in km). https://gce-lter.marsci.uga.edu/public/resources/projects/AltamahaSurveyAlberQ3.png White, S.N. and Alber, M. 2009. Drought-associated shifts in Spartina alterniflora and S. cynosuroides in the Altamaha River estuary. Wetlands. 29(1):215-224. (DOI: 10.1672/08-39.1) http://www.bioone.org/doi/abs/10.1672/08-39.1 White, S.N. and Alber, M. 2005. Presentation: The response of Spartina species to prolonged drought in the Altamaha River Estuary, Georgia. 2005 Estuarine Research Federation Meeting. October 16-20, 2005, Norfolk, Virginia. White, S.N. 2004. Spartina species zonation along an estuarine gradient in Georgia: Exploring mechanisms controlling distribution. Ph.D. Dissertation, University of Georgia, Athens, Georgia. 206 pp. http://gce-lter.marsci.uga.edu/public/files/pubs/White_Susan_PhD_2004.pdf White, S.N. and Alber, M. 2003. Spartina species zonation along the Altamaha River Estuary. Hatcher, K.J. (editor). Proceedings of the 2003 Georgia Water Resources Conference. Institute of Ecology, University of Georgia, Athens, Georgia. http://gce-lter.marsci.uga.edu/public/files/pubs/White_gwrc_2003.pdf White, S. and Alber, M. 2003. Poster: Controls of Spartina zonation patterns along the Altamaha River Estuary, GA: Abiotic and biotic mechanisms. 2003 Estuarine Research Federation meeting. Sept. 14-18, 2003, Seattle, WA. White, S.N. and Alber, M. 2003. Presentation: Will the marsh paradigm hold? Spartina distributions along the length of the Altamaha River Estuary, GA. 2003 Ecological Society of America meeting, Aug. 2003, Savannah, GA. White, S. and Alber, M. 2003. Presentation: Salinity, Sulfate, and Competition: Exploring interactions and impacts on Spartina alterniflora and S. cynosuroides growth. Southeastern Estuarine Research Society meeting. March 2003, Atlantic Beach, NC. White, S. and Alber, M. 2001. Presentation: Distribution of two salt marsh bank species along a salinity gradient in the Altamaha River Estuary: A fraction of the sum. Southeastern Estuarine Research Society Meeting. Southeastern Estuarine Research Society, Mar 01, 2001, Charleston, South Carolina. White, S.N. and Alber, M. 2001. Presentation: Distribution of S. alterniflora and S. cynosuroides along the Altamaha River: Potential impacts of competition, salinity and sulfate availability. ERF 2001: An Estuarine Odyssey. Estuarine Research Federation, Nov. 4-8, 2001, St. Pete Beach, Florida.