HUMAN IMPACTS IN A TRANSECT OF HUDSON RIVER MARSH SEDIMENT CORES – WHAT IS OUR SIGNATURE AND LEGACY?

A south-north transect of Hudson River marsh sediment cores (Jamaica Bay, Staten I., Piermont, Croton, Iona, Constitution, Tivoli, Stockport) are analyzed for pollen, plant macrofossils, C and N isotopes, as well as bulk chemistry. Pollen stratigraphy in all of the cores show a striking shift with European impact, including the increase of ragweed and other weedy species from the uplands, along with a decline in tree pollen due to clearing of the landscape by the settlers. Subsequent reforestation in the twentieth century is sometimes seen with the resurgence of upland tree species, but typically the stratigraphy reveals a dramatic increase of first invasive Typha (cattail) and then Phragmites (common reed) throughout the marshes with the decline of native sedges such as Schoenplectus americanus (chairmaker’s bulrush). Macrofossil analysis indicates the dominance of these invasive species throughout the marshes, and the loss of plant diversity, probably due to increased nitrogen and expansion of Phragmites throughout the estuary. Carbon and nitrogen isotopes are correlated with these major shifts. X-ray fluorescence (XRF) data reveal increases in upland input to the marshes due to European impact, as well as increases in heavy metals.