ESTIMATES OF ACCRETION RATES OF SALT MARSH ISLANDS IN SOUTHERN NEW JERSEY

Salt marshes are an essential ecosystem for connecting nutrients between coastal and land environments, protecting shorelines from erosion, and providing habitat for various species. Anthropogenic climate change causing sea level rise poses threats to salt marshes and the coastal communities nearby. In southern New Jersey, the relative rate of sea level rise (4.17 ± 0.14 mm/yr from 1911-2022; SLR; NOAA, 2023) is greater than the global average (3.4 ± 0.04 mm/yr). In this study, we measure chronologies, bulk density and organic content (loss on ignition, LOI) from cores collected in 2023-22 at four locations in the Seven Mile Island Innovation Lab (SMIIL) in Stone Harbor, New Jersey to determine the multidecadal accretion rate. Chronologies are developed from a radionuclide dating analysis (using concentrations of ²¹⁰Pb, ²⁴¹Am, ¹³⁷Cs and ⁷Be) following procedures similar to Boyd et al. (2017) and Landis et al. (2016). The accretion rates from 1911-2022 from the first two cores (85 cm and 91 cm long) analyzed are 4.3 ± 0.2 mm/year and 4.1 ± 0.8 mm/year, respectively, which are similar to the local SLR rate. Radionuclide analysis from the other two cores (96 cm and 121 cm long) are currently in progress. The mean LOI for the 4 four cores is 27.2 ± 19.0%, 21.3 ± 8.9%, 20.2 ± 7.5% and 14.2 ± 13%. The mean dry bulk density for the 4 cores is 437 ± 127 kg/m³, 380 ± 103 kg/m³, 415 ± 88 kg/m³, 657 ± 353 kg/m³. The additional information from these cores will add to existing studies of salt marsh accretion in SMIIL in order to measure the threat of sea level rise on the ecosystem.