Sapelo Research Application Form
Research Application ID: GCE-136-2024 (submitted: 05/20/2024, status: approved)
Provide a brief title for web display
Disturbance-mediated changes to habitat connectivity and ecological interactions
Investigator Information
On Island Sponsor: GCE SINERR UGAMI GADNR
| Principal Investigator: | James Byers | ||
| Home Institution: | University of Georgia | ||
| Award Information: | GCE-LTER sub-award and GRFP NSF award | ||
| Mailing Address: | Room 194B, Ecology Bldg. | Phone Number: | (706) 583-0012 |
| Odum School of Ecology | E-mail Address: | jebyers@uga.edu | |
| Athens, Georgia 30602 | |||
| Co-investigators: | Matthew Pierce (University of Georgia) | ||
Briefly describe the project goals and methodology
To better understand the ecological interactions that occur due to the presence of slump blocks I will perform multiple field and aquaria studies. Although it has been shown that creekbank slumping (Li and Pennings 2016) and slump blocks (Nelson et al. 2019) affect marsh ecology and the movement of energy through the system the studies above focused on occurrence of slumping and nutrient-induced slumping, respectively. I aim to build on this work and expand our knowledge and understanding about the effect of slumping on ecosystem function and how slump blocks mediate/influence ecological interactions. In the case that no effect of slumping is observed the information collected during this study will provide key insight on small-scale patterns in predation and access between creeks with different edge morphologies and the marsh platform during neap tides (periods of limited marsh access) and spring tides (periods of greater marsh access). This provides important information related to the movement of energy and physical access on the marsh platform for larger nekton.
Methodology:
Question: Does altered creekbank morphology affect densities of marsh plants and macroinvertebrates? How far into the marsh do these effects occur?
Creekbank and Slumping Surveys: Across 2-3 creeks (Dean Creek, Duplin River, and Oakdale Creek) on Sapelo Island, GA I will perform a survey of slumping activity. This will be done by walking along creekbanks and quantifying the occurrence of slumping and cracking along a predetermined distance (~200 m) (Lesser et al. 2020). Once I have quantified the slumping activity, I will select ~4 pairs of slump and non-slumping sites along each creek. Each set will be ≥25 m away from one another for independence. At each pair I will set up a ~ 50 m transect that runs from the creekbank edge into the marsh. Along this transect I will set up permanent 0.25 m2 plots every 5 m and will survey plant stem density, average stem height (10 stems), mud crab density, adult and juvenile fiddler crab density, adult and juvenile snail density, amphipod density, and soil shear strength. The elevation of each permanent plot will be taken using an RTK. Moving down towards the channel from the creekbank edge (along the transect line), I will perform surveys on slump blocks to quantify variables listed above. Using HOBO water level loggers, I will record water depth along the transect from the mudflat/slump block to the furthest permanent plot along the transect. At least one array of ~3-4 loggers will be placed at each creek.
Question: How does the ephemeral structure affect predation risk in an otherwise unstructured system?
Predation Assays: Along the permanent transects described above I will perform predation assays via tethering to quantify differences in predation behind slumping and non-slumping creekbanks. To assess predation across differently sized predators I will use 3-4 differently sized prey items: squid squares, amphipods, periwinkle snails, and mud crabs(Duffy and Harvilicz 2001, Bullard and Hay 2002, Duffy et al. 2015). These prey items capture many of the possible items that transient nekton predators would be consuming on the marsh platform. These predation assays will be performed during monthly neap (2x) and spring (2x) tides to assess changes in in the effects and/or strengths of effects by water depth and creekbank geomorphology. Adjacent to each permanent plot ~8 prey items will be tethered to acrylic rods or lawn staples. Predation will be assessed by presence/absence (1/0) of prey items after the tidal cycle is complete. Prey items that are partially consumed will be considered absent and notes will be taken representing partial consumption. Predation trials will also be performed in the same manner described above on creekbank edges, slump blocks, and mud flats to assess predation on and off channel and creekbank edges experiencing slumping and non-slumping.
Questions: How does a disturbance-mediated change in edge morphology affect the movement of organisms across habitat boundaries?
Does the change in habitat connectivity affect the growth of organisms reliant on forage area and refugia provided by the secondary habitat?
Trapping and Video Assays: Along the permanent transects and adjacent to the monitoring plots, minnow traps will be placed out to collect macroinvertebrates and mummichogs during high tides. These samples will be used to generate species size-structure distributions for each creek, quantify changes between creekbank morphologies, and sample gut contents (mummichogs only). Along each transect 2 Breder larval traps will be placed on the marsh platform (distance from creekbank edge to be determined later: most likely within ~5 m of edge). One will face the marsh platform to collect organisms as they exit the marsh platform (during ebb tide) and the other will face the creekbank edge to collect as organisms move onto the marsh platform (during flood tide). The Breder traps select for larval shrimp and fish to allow for quantification with reduced risk of predation induced biases from minnow traps. I will quantify biomass-per-unit-effort (BPUE), catch-per-unit-effort (CPUE), and abundance per species using the minnow and larval traps. I will also calculate community metrics such as richness, diversity, and evenness between creeks. I will generate size-structure distributions for each creek and between sites within a creek to assess differences in sizes as a qualitative approach to assessing resource use (larger sizes = higher protein, smaller sizes = less protein). Samples will be saved to perform gut content analyses and stable isotope analyses during Fall 2024 in Athens.
In each creek GoPro cameras will be set up during a flooding tide at 4 zones: creekbank edge behind slump, creekbank edge behind non-slump mudflat, mudflat, and on a slump block. Videos will be recorded to assess movement of organisms onto the marsh platform and activity as the tide rises towards the creekbank. The videos will specifically be used to assess the ability of nekton to move onto the marsh platform and how they interact with the ephemeral structure (slump blocks) before access to the marsh platform is available.
Where will the project be located?
Dean Creek Marsh: 31°23'16.2"N 81°16'47.7"W Oakdale Creek Marsh: 31°24'21.0"N 81°17'43.8"W Airport Marsh/Duplin River: 31°25'22.9"N 81°17'38.6"W
How will you provide GPS coordinates for study sites?
GPS coordinates are listed in the project location field
What are the expected start and end dates of the project?
Start Date: 06/02/2024 End Date: (ongoing)
How many people will access the site and at what frequency?
2 people for 8 days every month.
Keywords that describe your project
What equipment will be deployed in the field?
3 water level wells will be setup per marsh. Wells will be constructed using 4 inch diameter and 3 ft. long pvc pipes. PVC flag stakes will be put out at each permanent monitoring plot (~40 total). Temperature loggers will be deployed at each marsh site. All deployed equipment will be left for the length of the experiment and will be removed at the end of the study.
Will plants or animals be collected as part of this study?
Yes, snails, amphipods, and mud crabs will be collected and used in tethering predation assays. Approximately 200-300 of each species will be collected. In each creek 60 mud crabs and 60 mummichogs will be collected for stable isotope and gut content analysis. A GCE collection permit will be used for collections. In each creek Spartina alterniflora samples will be collected for stable isotope analysis. Minnow traps will be deployed along transects and captured organisms will be measured and released.
What are the likely impacts of the project on the site?
Minor trampling during monitoring of plots will occur and placement of wells (~9) and pvc stakes (~40) will lead to minor impacts to marsh vegetation. 200-300 snails, mud crabs, and amphipods will be collected and used for predation assays. 60 mud crabs and 60 mummichogs per creek will be collected and used for gut content and stable isotope analysis.
Will the project design include boardwalks? If not, explain why not.
How long will impacts persist after the research is concluded?
Impacts will most likely persist for no more than 1 year after the last monitoring.
