Contrasting decadal-scale changes in elevation and vegetation in two Long Island Sound salt marshes

Area of Science:

• Coastal ecology
• Geomorphology
• Environmental science

Background:

• Northeastern US salt marshes face co-stressors like sea level rise, nutrient enrichment, and low sediment supply.
• Understanding marsh surface elevation response is critical for predicting coastal ecosystem stability.

Purpose of the Study:

• To evaluate how salt marsh surface elevations respond to relative sea level rise (RSLR) and other co-stressors.
• To compare elevation changes and vegetation patterns in two distinct salt marshes.

Main Methods:

• Utilized surface elevation tables (SETs) and surface elevation pins to measure marsh surface elevation changes.
• Analyzed long-term historical vegetation data alongside elevation measurements.
• Compared marsh elevation gain rates with local rates of RSLR.

Main Results:

• Barn Island marsh is not keeping pace with RSLR (2.3 mm yr⁻¹), while Mamacoke Marsh shows increased elevation gain (4.2 mm yr⁻¹) to keep pace.
• Vegetation patterns at Barn Island shifted towards lower-elevation species, indicating stress.
• Mamacoke Marsh vegetation showed minimal change, suggesting greater stability.

Conclusions:

• Marsh elevation dynamics and vegetation responses to RSLR vary significantly, even within close proximity.
• Differences in sediment availability, salinity, and elevation capital likely drive contrasting marsh resilience.
• Findings emphasize that not all salt marshes in the region may respond uniformly to accelerated RSLR.