THE RESILIENCE AND RECOVERY OF SALT MARSHES TO LANDFALLING STORMS, NEW JERSEY, USA

It is socially, economically, and ecologically important to protect, conserve, or restore coastal wetlands in light of the growing risks from hurricanes. But instrumental and observational records of landfalling storms (e.g., hurricanes and extratropical) are too short to adequately estimate the recurrence of such events, particularly for rare, high magnitude events. Fortunately, the sediment preserved beneath coastal wetlands in New Jersey provides a 2,500 year long archive of when storms impacted the coast and how long it takes for wetlands recovery from storm-induced erosion.

Here, we describe late Holocene sediments beneath the Sea Breeze salt marsh on the New Jersey side of Delaware Bay from more than 200 gouge cores positioned along seven transects. The stratigraphic record documents at least seven depositional sequences consisting of salt-marsh peat and mud couplets that represent dramatic changes in sedimentation regime. There are number of processes that could cause this salt-marsh erosion including lateral migration of tidal creeks, rapid relative sea‑level rise, tsunamis, formation and expansion of salt pans, and storms. The abrupt contacts between the salt-marsh peat and overlying intertidal mud suggest that erosion of the peat was followed by rapid infilling of accommodation space. Correlation of erosional surfaces across 2.5 km suggests a common mechanism and we propose that the erosion was caused by hurricanes and/or large winter storms. Further, the changes in salt-marsh sedimentation documented at several sites on the north shore of Delaware Bay were synchronous and broadly correlate with storm over-wash deposits and historical record of hurricane landfalls in New Jersey.

We estimated wetland recovery time from hurricane-induced erosion using radiocarbon dates that bracket the erosive event in the sedimentary record. Following erosion and lowering of the marsh surface into the tidal frame a low-marsh ecosystem recolonizes the site, followed by recovery to a high salt-marsh environment. We estimate that this ecological and sedimentary succession can take up to 200 years.