Historical rates of salt marsh accretion on the outer Bay of Fundy

We examine rates of salt marsh accumulation in three marshes of the outer B ay of Fundy. At each marsh we selected a site in the high marsh with simila r vegetation, and thus similar elevation. Accretion rates were estimated by Cs-137, Pb-210, and pollen stratigraphy to estimate rates of change over p eriods of 30, 100, and similar to 170 years, respectively. These rates are compared with records from the two closest tide gauges (Saint John, New Bru nswick, and Eastport, Maine) to assess the balance of recent marsh accretio n and sea-level change. Averaged marsh accretion rates have ranged from 1.3 +/- 0.4 to 4.4 +/- 1.6 mm.year(-1) over the last two centuries. Recent rat es are similar to the rate of sea-level change recorded at Eastport, Maine, suggesting that they are in step with recent sea-level change but very sen sitive to short-term variation in relative sea level. Based on the pollen s tratigraphy in the marsh sediments, the marsh accretion rate was higher dur ing the late 18th to early 19th century. Higher rates probably were due to local increases in relative sea level as a result of neotectonic activity a nd may have been enhanced by increased sediment deposition through ice raft ing.