REGIONAL VARIABILITY OF ACCRETION RATES IN NORTHEASTERN USA SALT MARSHES IN RELATION TO UNVEGETATED TO VEGETATED RATIO (UVVR)

This study examines the connection between sediment accretion and tidal marsh health as indicated by unvegetated to vegetated ratio (UVVR). The wide range of oceanographic conditions and geomorphic settings of northeastern U.S. tidal marshes makes the region an excellent setting for assessing multiple stressors to marsh health. We compiled over 300 published rates of marsh accretion and elevation change, including information on the location, methods of data collection and rate calculation and, where available, dominant vegetation cover. Published accretion rates were derived from radiometric dating of sediment cores (n = 208), surface elevation tables (SET; n = 26), and measurements of sediment accumulation over marker horizons (n = 43). In addition to published data, we determined our own marsh accretion rates derived from seasonal sediment trap deployments in 12 marshes (n = 43). Marsh accretion rates range from 0.5 mm/year to 17.1 mm/year, with a median rate 3.2 mm/year for studies using short-term radiometric dating of sediment cores; a median rate of 3.1 mm/year for studies using marker horizons; and a median rate of 2.6 mm/year for studies utilizing measurements from SET stations. Ongoing analyses seek to evaluate the relationship between sediment accretion and marsh health as indicated by UVVR using USGS 30 m resolution data for coastal wetlands of the contiguous United States for the years 2014-2018. Quantifying the relationship between sediment accretion and marsh health will help to inform conservation and management efforts in the future.