Comparative Vegetation History, Sea Level Change, and Human Impact in Housatonic and Connecticut River Marshes with Linkages to Long Island Sound

Coastal New England tidal marshes are remnant wetlands today which continue to protect our coastlines from storms and provide biodiversity, water purification, and carbon sequestration. Establishing a detailed valid chronology through multidisciplinary sediment analysis allows us to link anthropogenic impacts to future vulnerability of the marshes and their value to humans in the future, including their role in carbon cycling. We examined the upper sediments from three Connecticut watershed marshes along the Housatonic and Connecticut Rivers - Great Meadows, Nells Island, and Ragged Rock. Loss-on-ignition (LOI), stable isotope ratios, pollen and spore analysis, foraminifera, and x-ray fluorescence (XRF) analyses were utilized. Foraminifera and plant macrofossils identify local shifts in marsh fauna and flora, and pollen analysis provides the regional vegetation history. Inorganic sediments declined toward the present, except in cases of human disturbance, reflecting dam capture of upriver sediment. The history of nitrogen and wastewater in sediments varies with the watershed, but major increases are documented with population increase. Industrialization in the early to mid 1800s leads to the rise in lead, copper, and zinc, followed by the decline in recent decades with federal controls. The implications of increases in nitrogen isotopes recorded by the marshes to water quality in Long Island Sound at present and in the future is explored as we link these records to remote sensing of water quality shifts including hypoxic intervals in Long Island Sound. We use these comparisons to estimate future Long Island Sound health with further population increase, vegetation change, and marsh loss.