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2014-2016 Research Projects: The Coastal and Ocean Landscape

Project: Clonal aging and the molecular basis for sudden marsh dieback

Principal Investigator

James Morris, University of South Carolina

Project Number

R/CP-20

Research Description

Sudden marsh diebacks, or brown marsh, occur throughout the range of Spartina alterniflora, threatening the health and ecosystem services of salt marshes. The causes of sudden marsh dieback are controversial, and despite widespread interest, little progress has been made in identifying them. The researchers propose a generalized mechanism of increasing stress susceptibility with stand age. They will conduct experimental and observational studies to test if sudden marsh dieback is impacted by epigenetic changes that accumulate with stand age. This work focuses on testing assumptions and developing methods necessary to investigate the role of genetic determinants in marsh dieback and to assess how they influence the susceptibility of marsh environmental stress. Namely, the research team will quantify epigenetic modifications in plants using the level of DNA methylation in plant tissues.

The researchers plan to (1) assess the variation in genome-wide DNA methylation among different tissue types in Spartina ramets, (2) measure the spatial variation in genome-wide DNA methylation across a marsh landscape, (3) measure the genome-wide DNA methylation across asexual generations (different ages) of Spartina alterniflora, (4) test for an association between methylation and salinity tolerance, predicting that higher methylation leads to a smaller range of salinity tolerance, and (5) develop a diagnostic technology which can report on the status of the epigenetic aging process in salt marsh stands.

Research Results

Agrelius, Trenton, Jeffry L. Dudycha, and James T. Morris. “Global DNA cytosine methylation variation in Spartina alterniflora at North Inlet, SC ,” PLOS One, September 10, 2018.

Agrelius, Trenton. Master’s thesis, “Global Methylation of DNA among Spartina alterniflora Clones Differing in Age at North Inlet, SC ,” December 2015, University of South Carolina.

Contact for Questions

James Morris (morris@inlet.geol.sc.edu)

Project: Developing water runoff metrics for reference watersheds: Francis Marion National Forest

Principal Investigator

Tim Callahan, College of Charleston

Project Number

M/PM- 2UU

Research Description

This study characterized conditions of three forested watersheds, examining the effects of spatial scaling on outflow and runoff behavior. It also expanded the existing database on hydrology of low-gradient forested watersheds like those in the coastal plain of the southeastern United States.

Stream flow in the larger Turkey Creek watershed, covering about 12,800 acres, was comprised of about 47% groundwater discharge. Two small first-order watersheds showed greater runoff moving relatively quickly through the system. Two smaller watersheds, 520 acres and 300 acres, had averages of 38% and 33%, respectively, of stream flow comprised of groundwater discharge. Both small watersheds had a larger proportion of low-permeability soils compared to the soil makeup in the Turkey Creek watershed, so the difference in runoff behavior cannot be solely attributed to the size of the watershed. It should be noted that most land development projects are relatively small in area, on scale with the two small watersheds studied for this project. Those results may be most useful to predict runoff changes as development in the southeastern U.S. coastal plain continues to encroach into forested areas.

These results are useful for scientists who need direct measurements of watershed conditions for forecasting future conditions, either in natural systems subject to changes in weather patterns or due to extreme events, or for landscapes that have or may soon change due to land development in support of increasing populations. Low-impact development practices have been modeled and tested in certain settings, and these ecological engineering approaches may serve as useful proxies of natural processes to reduce the negative impacts of stormwater runoff.

Research Results

Callahan, Tim, Peter Stone, and Devendra Amatya. “Coastal Forests and Groundwater: Using Case Studies to Understand the Effects of Drivers and Stressors for Resource Management ,” Sustainability, Vol. 9, Issue 3, 2017

Contact for Questions

Tim Callahan (callahant@cofc.edu)

Project: Nonstationary and trend assessment of hydrological extremes in the southeastern catchments: A pilot study

Principal Investigator

Seyedehzahra Samadi, University of South Carolina

Research Description

Human activities change the atmospheric composition by increasing greenhouse gases. These changes have subsequently increased global temperatures, surface evaporation and atmospheric water holding capacity. As a result, climate change may increase the amount of water available for precipitation in the atmosphere as well as increase the probable maximum precipitation or expected extreme precipitation. Those changes in turn would increase the risk of climatic extremes that can cause flash floods and severe damages to human lives, society and infrastructure.

Focusing on different extreme distributions, two different modeling frameworks (stationary vs. non- stationary) were constructed in this research to capture the time-dependent location, scale and shape parameters of floods. The models indicate that increasing trends in monthly and seasonal floods could be explained by the influences of large-scale features such as the El Nino-Southern Oscilation, but changes in vegetation dynamics and in other atmospheric variables such as relative humidity cannot be excluded as influences.

Contact for Questions

Seyedehzahra Samadi (samadi@cec.sc.edu)

Project: Genomic signals of local adaptation in the salt marsh plant Spartina alterniflora

Principal Investigator

Erik Sotka, College of Charleston

Research Description

Spartina alterniflora is a dominant plant species of salt marsh habitats along the South Carolina coastline. Because of historical and recent destruction and die-off of Spartina marshes, restoration of Spartina marshes remains a top priority. Restoration efforts have greatest success when Spartina genotypes are selected that thrive in restored areas, but our understanding of this genetic variation is poor. This project addressed that gap.

Using genotypes from more than 11,000 single-nucleotide polymorphisms from 340 Spartina plants, our study distinguished Spartina among biogeographic zones separated by hundreds of miles, river systems within a single state separated by tens of miles, and tall vs. short-form Spartina separated by tens of yards. The results have important consequences for restoration managers, as there is a strong likelihood that adaptation to local salinity, temperature, and soil conditions is commonplace. When plants are moved away from their sources, even those that are a few hundred feet away, the survivorship, growth, or reproductive fitness of these plants likely is lowered, making restoration efforts less productive and more inefficient than they could be.

Contact for Questions

Erik Sotka (sotkae@cofc.edu)