The salt marshes of Jamaica Bay, managed by New York City Parks and Recreation and the Gateway National Recreation Area (GNRA) of the National Park Service, provide critical ecosystem services including carbon sequestration. Marshes in Jamaica Bay disappeared at an average rate of 33 hectares per year between 1989-2003, resulting in the loss of long-term carbon storage and potentially converting the salt marshes from carbon sinks to sources. The stressors contributing to marsh loss in the estuary include natural (e.g., increased tidal range, sea-level rise, subsidence, hurricanes, and storms) and anthropogenic disturbances (e.g., wastewater treatment and dredging activities). However, the variation in soil organic carbon (SOC) sequestration across the urban estuary and the controlling factors are poorly understood. We collected soil cores to a depth of ~50 cm at twelve salt marsh locations across the estuary in August 2014 to study the chronology of salt marsh vertical accretion, as well as the accumulation of mineral sediment, organic matter, and carbon. The twelve marsh sites were classified as healthy, degraded, and restored. Marsh soil cores were sliced into 2-cm sections and were analyzed for 137Cs and 210Pb activity, bulk density, moisture content, organic matter, total organic carbon, and total nitrogen.
Results/Conclusions
Preliminary results show that geochronology-based sediment accumulation rates (SAR) for Jamaica Bay salt marshes are in the range of 0.41-0.51 and 0.22-0.73, and 0.29-0.49 cm/y for the healthy, degraded, and restored marshes, respectively. The degraded marshes tend to have larger variations in SARs than the healthy and restored marshes. Vertical accretion is driven more by organic matter accumulation than mineral sedimentation. Soil organic carbon (SOC) sequestration in Jamaica Bay salt marshes tends to range from 90 to 233 g C/m2/yr. The SOC sequestration ranges are 125-233, 90-217, and 105-174 g C/m2/y for the healthy, degraded, and restored marshes, respectively. Critical factors affecting the variability in SAR and SOC sequestration rates in Jamaica Bay salt marshes, such as hurricanes and wastewater treatments, are being investigated. Results of this study provide essential sediment data for the development of a numerical wetland morphology model to examine the impact of hurricanes (e.g., Hurricane Sandy) and extra-tropical storms on salt marsh morphological change in this urban estuary. This is an abstract and does not necessarily reflect USGS policy.