Sapelo Research Application Form
Research Application ID: GCE-147-2025 (submitted: 12/17/2025, status: approved)
Provide a brief title for web display
Interactive effects of precipitation and wrack disturbance in the high marsh
Investigator Information
On Island Sponsor: GCE SINERR UGAMI GADNR
| Principal Investigator: | Steven C. Pennings | ||
| Home Institution: | University of Houston | ||
| Award Information: | GCE-LTER core project | ||
| Mailing Address: | Department of Biology and Biochemistry | Phone Number: | (713) 743-2989 |
| University of Houston | E-mail Address: | scpennin@central.uh.edu | |
| Houston, Texas 77204-5513 | |||
| Co-investigators: | |||
Briefly describe the project goals and methodology
Our goal is to understand how high marsh plant communities respond to different levels of precipitation by simulating drought and abnormally wet conditions. We hypothesize that these infrequently flooded plants will respond positively to increased freshwater input due to decreased porewater salinity. Conversely, decreased rainfall will lead to negative outcomes in the plants. We will establish no more than 10 replicates in three plant zones in the high marsh: Batis maritima, Juncus roemerianus, and short-form Spartina alterniflora. Each replicate has three plots: decreased precipitation (drought), increased precipitation (flood), and ambient.
To simulate drought, we will build a rainout shelter with transparent plastic shingles on top to exclude rain and redirect it via a gutter and downspout to the neighboring plot, which will serve as the "flood" treatment. Each rainout shelter will be made of 1.25" diameter PVC and will measure 1.5 m tall, 2 m wide, and 2 m long. We will establish a control plot next to the two experimental plots. Both control and increased rainfall treatment plots only need four 0.75" diameter PVC poles standing 1 m tall to mark the corners.
A pilot study (approved by CRD) was performed in 2025 with this design in multiple plant zones. The full study will only be conducted in the three zones listed above since this is where the effect of the treatment appeared to be greatest. The materials from the pilot study will be removed in March 2026 when the new rainout shelters are constructed.
We will add wrack disturbance as an additional treatment in the full study. We will follow Merryl Alber's (2013) methodology: fill a mesh "pillow" (approximately 0.6 m x 0.6 m) with wrack and fasten it to four PVC poles with zip ties to allow the pillow to rise and fall with the tide (See attached materials). These pillows will be deployed in May 2026 (8 weeks following rainout shelter construction) and plant mortality will be monitored bi-weekly until all plants are dead, at which point all wrack packets will be removed to allow for recovery to begin synchronously. We will establish an undisturbed plot under each precipitation treatment for comparison. In the first year of the experiment, each replicate will have six plots: Drought-Disturbed, Drought-Undisturbed, Flood-Disturbed, Flood-Undisturbed, Ambient-Disturbed, Ambient-Undisturbed. In May 2027, the disturbance treatment will be repeated in a different quadrant (See attached plot layout).
At the end of each growing season, above- and belowground biomass will be collected in an undisturbed quadrant of each plot to assess the impact of the precipitation treatments. The experiment will conclude at the end of 2027. We anticipate removing all materials from the marsh in 2028.
Where will the project be located?
The west side of Sapelo Island within the SINERR, a little to the North of the barge landing. See attached map.
How will you provide GPS coordinates for study sites?
I will provide a provisional map and arrange with my sponsor to collect and register GPS coordinates
What are the expected start and end dates of the project?
Start Date: 03/01/2026 End Date: 05/01/2028
How many people will access the site and at what frequency?
Up to five people will assist in building the shelters in March 2026. For monitoring three people will access each plot weekly or less often depending on how rapidly vegetation changes.
Keywords that describe your project
What equipment will be deployed in the field?
Each rainout shelter will be made of 14 pieces of PVC (1.25" diameter) and 16 plastic shingles. Six legs will be driven 30cm into the ground to hold structure in place. Each shelter will stand 1.5 m tall and have an area of 2 m x 2 m. A gutter will collect rainwater from the rainout shelters and deliver it via downspout to the neighboring plot. The other two plots for each replicate (increased rainfall and control) will be marked by one PVC pole (0.75" diameter) standing 1 m tall at each corner.
Will plants or animals be collected as part of this study?
Plant belowground and aboveground biomass. No animals will be collected. UGAMI collection permit will cover this activity.
What are the likely impacts of the project on the site?
The experimental treatments (decreased and increased rainfall, wrack disturbance) are likely to fall within the range of what these marshes have experienced and withstood in the past. In the short term, we expect biomass production to be diminished in drought conditions and enhanced in rain addition plots, and all aboveground biomass to be killed under the wrack treatment.
Will the project design include boardwalks? If not, explain why not.
How long will impacts persist after the research is concluded?
We know from previous experiments that Spartina and Batis recover quickly from wrack disturbance (several months to two years), while Juncus can take longer (up to 10 years) with lots of variation. Where destructive sediment cores are taken to collect belowground biomass, we expect roots and sediment to be replaced within one year.
Files attached to this application
GCE-147-2025_Documents_Supporting_materials_interactive_effects_precipitation_and_wrack.docx (MS Word file, 1388.43 kb, submitted 12/17/2025)
