Short-term responses of tidal low-salinity marsh vegetation to saltwater intrusion Dr. Steven C. Pennings University of Houston

Department of Biology and Biochemistry University of Houston Houston Texas 77204-5513 USA

scpennin@central.uh.edu https://uh.edu/nsm/biology-biochemistry/people/profiles/steven-pennings/ https://orcid.org/0000-0003-4757-7125 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. Steven C. Pennings University of Houston

Department of Biology and Biochemistry University of Houston Houston Texas 77204-5513 USA

scpennin@central.uh.edu https://uh.edu/nsm/biology-biochemistry/people/profiles/steven-pennings/ https://orcid.org/0000-0003-4757-7125 Principal investigator Fan Li University of Houston

Department of Biology and Biochemistry 369 Science and Research Bldg 2 University of Houston Houston Texas 77204-5001 USA

lifan.uh@gmail.com Co-investigator 2026

In 2013, the Georgia Coastal Ecosystems Long Term Ecological Research program will initiate a long-term experiment of saltwater intrusion, using constant and episodic saltwater addition to mimic effects of sea level rise and drought. To help explain the results of this field manipulation, I (Fan Li, PhD student with Steven Pennings) will conduct a lab experiment to compare the detailed, short-term responses of freshwater and brackish plants to multiple saltwater intrusion scenarios. The goals of this experiment will be 1) to test the hypothesis that brief saline pulses will increase plant biomass by releasing nutrients from soils [9], and 2) to rank the six common species with respect to tolerance to saline pulses. This information will allow me to predict how saltwater intrusion in nature, and in the GCE experiment, is likely to change plant community structure. Methods: I will grow six common tidal marsh plants in the experiment: Zizaniopsis miliacea, Pontederia cordata, and Sagittaria lancifolia from fresh marshes; and Juncus roemerianus, Spartina cynosuroides and Schoenoplectus tabernaemontani from brackish marshes. Healthy plants with soil blocks (~20 cm × 20 cm × 20 cm) will be collected in March 2013 near the Altamaha River estuary, GA, and acclimated in fresh water before treatments start. In the greenhouse, plants will receive different schedules of saline (0, 1, 2, 4, 8, 16, 31 days per month, n=5 replicates per species per treatment) versus fresh water. Porewater salinity will be raised from zero to 5 psu for the saline treatment. Water will be added on a semi-diurnal tide cycle to 5 cm above the soil surface, and then allowed to drain. Treatments will run from May to September, and I will measure plant growth rate by taking periodic measurements of photosynthesis, height, and leaf number. In the end, I will harvest above- and below-ground biomass, and collect leaf samples for organic carbon, nitrogen and phosphate analysis. Data will be analyzed with ANCOVA among treatments and species.

Area 3: Responses to Salinity and Inundation (more information)

freshwater wetlands marsh biomass gas exchange LTER NSF GCE Juncus plants Spartina Zizaniopsis plant ecology primary production Overall geographic extent of the research project -81.466637 -81.278834 31.398877 31.304063 2013-03-10 2013-12-01

GCE-LTER graduate student support for project related to SALTEX, about $25k for one year.

estuary marsh complex Alligator Creek - Mid-estuary/salt marsh site on the west side of Friday Cap Creek along the Altamaha River. This is a brackish marsh with salinities around 14 PSU during drought, less than 5 PSU normally. A hydrographic sonde is deployed adjacent to this site in the Altamaha River near Alligator Creek, attached to the US Coast Guard Daymarker 2 pilings. -81.426272 -81.410634 31.317808 31.304063 UGA Marine Institute - The University of Georgia Marine Institute is located on the southern end of Sapelo Island, a barrier island off the central Georgia coast. -81.282950 -81.278834 31.398877 31.395295 SALTEx_Well1 - Groundwater monitoring well for the GCE SALTEx research project -81.466637 -81.466637 31.339439 31.339439

In the greenhouse at UGAMI. No field component other than collecting the plants, which will be done near to GCE 8 (brackish plants) and near to the SALTEX site (freshwater plants).

Yes, 40 individuals each of 6 species, we are covered by the UGAMI collection permit.