Patterns of mud snail and ribbed mussel abundance Dr. Brian R. Silliman Duke University

135 Duke Marine Lab Rd. Duke University Marine Lab Beaufort North Carolina 28516-9721 USA

brian.silliman@duke.edu https://nicholas.duke.edu/people/faculty/silliman https://orcid.org/0000-0001-6360-650X 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. Brian R. Silliman Duke University

135 Duke Marine Lab Rd. Duke University Marine Lab Beaufort North Carolina 28516-9721 USA

brian.silliman@duke.edu https://nicholas.duke.edu/people/faculty/silliman https://orcid.org/0000-0001-6360-650X Principal investigator 2026

In 2008 the Silliman lab conducted a one-time survey of densities of mud snails and ribbed mussels at all GCE sites. These species are not included in (mud snails) or are poorly sampled by (ribbed mussels) our routine monitoring protocol. We found no clear off-shore, on-shore gradient in density of mud snails or ribbed mussels. Densities of both species roughly mirrored each other. Both were rare at some sites (7, 8, 9), present at others (2, 3, 4, 5, 6) and were most abundant at site 10. Both species also displayed a highly patchy distribution. These data provided good baseline data for long term monitoring, and shed insight into the patchy nature of the animals, but lacked sufficient replication to rigorously test whether there was a pattern in densities across the barrier island - mid-estuary - mainland gradient. To assess this possibility, in the fall of 2009, we will enumerate densities of these species and the other dominant marsh invertebrates in a highly replicated transect with 8 barrier island marshes, 8 mid-estuary marshes, and 8 mainland marshes.

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 Georgia GCE island marsh mainland marsh mid-estuary marsh mud snail ribbed mussel Overall geographic extent of the research project -81.493498 -81.195661 31.552554 31.304063 2008-01-01 2008-12-31

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

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 Hunt Camp - Barrier island/marsh site on western Sapelo Island. This site is located at the upper reaches of the Duplin River, and is within the Sapelo Island National Estuarine Research Reserve. Existing well fields border small marsh area to northwest, some wells have been installed to south end of hammock where marsh is more extensive and permanent plots are located. Two existing hydrographic sondes and weather stations within this site are operated by SINERR (Hunt Camp dock) and UGAMI (flume dock). -81.295506 -81.258908 31.497026 31.462320 Four Mile Island - Low salt marsh/estuary site encompassing the southwestern end of Four Mile Island and the Sapelo River near Sapelo Sound. The large island is totally marsh, with no upland, and no development. Nearby areas, like "Sutherland Bluff", are developing with golf courses. A hydrographic sonde is deployed within this site attached to channel marker 4 (under U.S. Coast Guard permit). Salinity regime is similar to seawater. -81.318961 -81.292844 31.552554 31.533604 North Sapelo - High salinity marsh/Sapelo Sound site. Few or no small creeks, but one large creek is easily accessed. Further upstream upland drainage is affected by culvert at Reynolds' duck pond. Upland is heavily forested. Hydrographic sonde is deployed adjacent to this site attached to a channel marker (under U.S. Coast Guard permit). A huge mud flat is present at the northern tip of Sapelo Island. -81.233249 -81.195661 31.546868 31.515188 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 Folly River - Salt marsh/tidal creek site at the Folly River near Doboy Sound. No upland areas present. The north side of Doboy Sound immediately opposite is similar, but creeks are not as nice. No existing markers are close enough for sonde deployment, so we will initially use the existing sonde at Marsh Landing operated by UGAMI for surrogate hydrographic data. -81.354413 -81.327201 31.442538 31.417640 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 INV-GCES-0906 - Population Study of Geukensia demissa and Ilyanassa obsoleta at the Georgia Coastal Ecosystems LTER site in April 2008 https://gce-lter.marsci.uga.edu/public/app/dataset_details.asp?id=471 Mud snails and ribbed mussels densities https://gce-lter.marsci.uga.edu/public/resources/projects/MudSnailsRibbedMussels.png