Algal survey and light availability experiment along salinity gradient Dr. Christopher B. Craft Indiana University at Bloomington

Indiana University - School of Public and Environmental Affairs Room 408. MSB II. 702 N. Walnut Grove Ave. Bloomington Indiana 47405 USA

ccraft@indiana.edu https://orcid.org/0000-0002-6225-786X 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. Christopher B. Craft Indiana University at Bloomington

Indiana University - School of Public and Environmental Affairs Room 408. MSB II. 702 N. Walnut Grove Ave. Bloomington Indiana 47405 USA

ccraft@indiana.edu https://orcid.org/0000-0002-6225-786X Principal investigator Owen Langman Indiana University

School of Public and Environmental Affairs Indiana University Bloomington Indiana 47405 USA

olangman@indiana.edu Co-investigator 2026

I will conduct a novel survey of algal diversity and productivity along the salinity gradient which will provide baseline data for future algal work relating the algal community to sea-level rise. The second portion of the research is an experiment toward that end; I will thin stands of vegetation in several sites along the salinity gradient to simulate a disturbance on marsh vegetation and test hypotheses of increased productivity and shifts in relative abundance of algal species due to increased light penetration to the benthos. I will collect samples for determining chlorophyll a, species identification, light and nutrient availability, and a number of other environmental characteristics.

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

marsh biomass chlorophyll land cover nutrients population density population diversity radiation salinity sedimentology LTER NSF GCE algae other phytoplankton productivity Overall geographic extent of the research project -81.493498 -81.264378 31.546750 31.304063 2013-06-01 2013-08-26

GCE LTER

estuary marsh complex Eulonia - Transitional salt marsh/upland forest site at the upper reach of the Sapelo River near Eulonia, Georgia. The main marsh area is to the north of the channel where the upland is controlled by DNR. Several small creeks lie within the study area. Residential development is increasing on the upland areas south of the channel. A hydrographic sonde is deployed within this site attached to a private dock to the south of the main channel near the HW-17 bridge. The sonde is accessed from a dock on a private residence off of highway 17. As of late 2017 the property is owned by Linda Hornby. She asks that we notify her by text about an hour before arriving to service the sondes. There is no reason to go to this property other than for sonde work. -81.428481 -81.410732 31.546750 31.533963 Meridian - Inland marsh and tidal creek site near Meridian, Georgia. The primary marsh site is to the south of the dock in front of the Sapelo Island Visitor Center. Some small creeks and one large creek (Hudson Creek) are present. Upland is heavily forested. Marsh to the north of the dock can be used for additional studies if larger areas are required. Upland to the North is being developed for residential use, so future access is uncertain. The USGS super station site (weather station plus multiple-sensor sonde) is deployed off the ferry dock. Salinity is similar to seawater because there is little freshwater input from the upland. -81.370752 -81.357256 31.463533 31.448419 Dean Creek - Doboy Sound/salt marsh site at the southern end of Sapelo Island near Dean Creek and the Sapelo lighthouse. A few small creeks are present, but a large creek (Dean Creek) is easily accessed. Upland is composed of small hammocks and some constructed causeways, with sand dune complexes east of Dean Creek and extending to the beach. Upper end of the watershed is affected by a culvert at Beach Road and heavy student use of marsh immediately adjacent to culvert. A hydrographic sonde is deployed in Doboy Sound near Commodore Island approximately 1.5km from this site. GCE6 is also the focus of Sapelo Island Microbial Observatory research on microbial diversity and genomics (http://simo.marsci.uga.edu) -81.299522 -81.264378 31.394072 31.371003 Carrs Island - Freshwater marsh site along the northern bank of Hammersmith Creek at the south end of Carrs Island. Upland area is heavily forested. Northern 3/4 of the island was diked for rice agriculture, but the southern 1/4 is undisturbed. A hydrographic sonde is deployed in the Altamaha River near Hammersmith Creek, adjacent to this site. -81.493498 -81.475900 31.348774 31.334364 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 Rockdedundy Island - Lower estuary tidal creek and marsh site at Rockdedundy Island west of Wolf Island. A hydrographic sonde is deployed approximately 2km from this site in the Altamaha River near Rockdedundy Island, attached to the US Coast Guard Daymarker 201 pilings. -81.346730 -81.326495 31.358142 31.339173 GPS data file (Trimble, Excel) https://gce-lter.marsci.uga.edu/private/registration/files/gps_data/GCE-44-2013_GPS_Clipping_Sites_-_Proposed.kmz

The clipping experiment will take place at six GCE sites: GCE site 7, GCE site 8, GCE site 9, GCE site 1, GCE site 4, and GCE site 6.

PAR sensors will be deployed for 24 hours at each site. - Short PVC pipes will be used to mark plot corners. Due to the nature of the experiment (clipping), two PVC pipes per plot will be sufficient to delineate. Plot corners will be removed during the August visit.

Approximately six 100 sq cm of epiphytic algal scrapes will be taken from the vegetation at each site in a non-destructive manner. Shallow 5 cm diameter benthic cores will be taken for soil analyses and benthic algae and diatoms. Sampling will be replicated in June and August.