Uncovering climate-driven salt stress in coastal marsh plants with cutting-edge imaging technology

Mikayla Bechtel wanted to study how increasing salinity caused by climate change affects plants in salt marshes. Her interest led her to a fellowship with the Woods Hole Oceanographic Institution, an organization supporting a wide range of research in ocean and earth science. 

Over the summer of 2024, Bechtel studied salt stress in coastal vegetation at Waquoit Bay National Estuarine Research Reserve in Falmouth on Cape Cod. The area spans 2,700 acres of open waters, barrier beaches, marshlands, and uplands. She used hyperspectral imagery, a remote sensing technique that uses special cameras to capture light reflections across a range of wavelengths. Hyperspectral imagery can show if plants are stressed, which is reflected in a shift in the spectral profile. Among the plants Bechtel studied were the common reed, smooth cordgrass, and red maple. 

Salt marshes on the East Coast are increasingly threatened by saltwater intrusion, a consequence of climate change. Coastal plants, particularly those in the upland areas of the marsh, are sensitive to changes in salinity distributions and concentrations. Bechtel researched the effects of high salt levels on key marshland and upland species.  

“When plants are exposed to excessive salt, it can interfere with their ability to absorb water and nutrients,” said Bechtel. High salt levels can also damage the plant’s cell structure, leading to reduced growth or even death. Salt can affect chlorophyll levels, making it harder for the plant to photosynthesize. “This, in turn, alters how the plant reflects light, which can be detected with hyperspectral imaging. Salt stress can also change the leaf structure, often leading to wilting, leaf discoloration, or other signs of damage,” she said. 

During the two-month fellowship, she made bi-weekly visits to Waquoit Bay, where she collected salinity samples and captured hyperspectral images of each species in the field.  

“I collected samples of pore water, which is the water found in the spaces between soil particles, and measured its salinity, temperature, pH, and more,” said Bechtel. “I also collected leaf clippings from the plants to analyze how they are responding to salt stress, including spectral measurements and instruments to assess changes in their reflectance,” she said.  

Using the salinity data and corresponding imagery, Bechtel and her research team analyzed how the plants’ spectral profiles—the way they reflect light across different wavelengths—changed with varying salinity concentrations. Plants absorb light for photosynthesis, the process by which plants use sunlight to convert water and carbon dioxide into energy, but they also reflect some light. The pattern of reflected light changes depending on the plant’s health and composition of photosynthetic pigments which differ based on the species of plant.  

“Healthy plants tend to reflect more light in the near-infrared region, while stressed plants might reflect less, and this shift can be detected through hyperspectral imaging,” she said. “I learned that upland species show a stronger correlation with porewater salinity changes, suggesting they are more sensitive to salinity fluctuations compared to marshland species,” said Bechtel. 

The opportunity to collaborate with experts in different areas was especially valuable for Bechtel. 

“I received help from many different scientists specializing in various fields. Science is so interconnected, and I greatly valued the discussions I had with others. I gained valuable experience in communicating and collaborating with others, which will be helpful in my future studies,” she said. 

Bechtel, a native of Schenectady, New York, also toured the RV Neil Armstrong, a state-of-the-art research vessel that helps WHOI scientists study the ocean and marine environments.  

“It was super cool seeing the labs inside the ship and advanced equipment. After each eight-hour field day in the hot salt marsh, I got to jump in the ocean! That always made my day,” she said. 

Bechtel will graduate this spring with a Master of Science in Engineering. She is considering pursuing a PhD or working in water quality management as a field technician.

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