INFLUENCE OF VEGETATION TYPE ON THE CARBON CONTENT OF SEDIMENT IN PIERMONT MARSH, HUDSON RIVER ESTUARY

The carbon storage potential of coastal wetlands is high due to rapid sediment accumulation rates and high plant productivity. Carbon sequestration in tidal salt marshes has been estimated at 210 g CO₂ m^-2 yr^-1, an order of magnitude greater than carbon storage per unit area in peatlands (Chmura et al., 2004). We explore the impact of vegetation type and sediment accumulation rate on sediment in brackish Piermont Marsh (73¢ª54’W, 41¢ª02’N), located ~ 50 km above the mouth of New York’s Hudson River Estuary. We compare water and organic carbon content measured by Loss-On-Ignition, (LOI) and bulk density of sediments from the surface to 1 meter depth collected in areas dominated by different plant species today: the invasive grass Phragmites australis(common reed), Typha angustifolia (narrow-leaved cattail), Spartina alterniflora and Spartina patens (native saltwater cordgrasses). We also discuss sediment properties measured along transects that link both stream and Hudson River banks with the interior marsh. Organic carbon in Phragmites-dominated areas increases from 5 % near depositional stream banks up to 34 % near stable pools within the central marsh. Carbon density ranges from 0.01 – 0.04 g C cm^-3. Sediment accumulation rates, measured using the feldspar-marker technique (Cahoon et al., 1989), also allow us to estimate ongoing rates of carbon sequestration in Piermont Marsh. This information improves our understanding of modern carbon cycle dynamics in the Hudson River Estuary, and may enable better global estimates of the role of brackish marshes with shifting vegetation as a future carbon sinks.

All data presented were collected and analyzed as part of Lamont-Doherty Earth Observatory’s Secondary School Field Research Program, which engages NYC public school teachers and students in research projects in the Hudson/Raritan estuarine environment.