Research Seminar: Carson Miller

A research seminar from UNC Marine Sciences graduate student, Carson Miller. Presented by the UNC-CH Department of Marine Sciences and UNC’s Institute of Marine Sciences (IMS). The main location of this event will be in seminar room 222 at IMS in Morehead City, NC. The seminar will be streamed live to room G201 on the ground floor of Murray Hall on UNC-CH campus in Chapel Hill, NC. This event will be held on Monday, August 27th at 12:20pm.

Seminar Title: Determining the drivers of saltmarsh transgression across morphological gradients of the upland-forest boundary

Abstract: Saltmarsh provides invaluable ecosystem services such as storm protection, fish habitat, erosion control, water purification, and carbon sequestration. Coastal communities are prioritizing saltmarsh conservation and restoration because stressors such as storms, sea-level rise, and development are decreasing saltmarsh area globally. Loss of fringing saltmarsh occurs because development along the upland boundary prevents landward expansion with sea-level rise, while erosion from waves and boat wakes is occurring at the estuarine edge. Previous studies show that saltmarshes unobstructed by development, migrate landward with sea-level rise at a rate that is proportional to the upland slope. This study aims to understand how an increase in the rate of sea-level rise around CE 1865-1873 and a period of increased storminess from CE 1400-1675 influences the transgression rates of saltmarsh along low-gradient ramped upland morphologies and high-gradient scarped upland morphologies. Saltmarsh landward migration rate and area change based on slope and sea-level rise alone, may be too low if storm waves are eroding the scarped upland boundary. We will examine 4 saltmarsh sites in North Carolina by collecting core transects that sample the contact between upland-forest and overlying saltmarsh sediment.  Transgression rates will be measured by radiocarbon dating the first saltmarsh to colonize the upland forest at multiple locations along the transect. Preliminary data from a ramped site shows saltmarsh peat overlying freshwater peat, above upland clay and the elevation of the saltmarsh-upland contact decreases gradually landward. An additional transect at a scarped site showed saltmarsh overlaying subtidal sandflat from the estuary inland for 89% of the transect. Within 8.5 m of the current upland boundary, the sandflat unit pinched out and only landward of this point did the elevation of the contact between saltmarsh peat and upland sand decrease in elevation. The field work will be completed after sites along the Shallotte River Estuary and Pamlico Sound are sampled.  The data set will be placed in context with that historic stormy period and the recent acceleration in sea-level to evaluate the processes that drive saltmarsh transgression at each morphological boundary.