Presenter: Caralyn Grace Rexroad

Faculty Sponsor: Brian Yellen

School: UMass Amherst

Research Area: Geology and Earth Sciences

Session: Poster Session 4, 2:15 PM - 3:00 PM, 163, C2

ABSTRACT

Estuaries and salt marshes provide many benefits to those who rely on them, including wildlife habitat, improved water quality, recreation, and coastal protection. These subtidal ecosystems and their functions are at risk due to accelerated sea level rise, and current projections state that 78% of coastal wetlands globally may become completely submerged by 2100 if they cannot grow vertically with sea level rise. Sediment accumulation is critical for vertical accretion and thus salt marsh resilience. Recent studies highlight the importance of high-energy events for increasing sediment availability and mud organic matter (OM) for its contribution to vertical accretion, but we don’t know the origin of the OM in estuarine sediments in the Northeastern U.S. Carbon and nitrogen stable isotopes in OM can be used to trace the source of sediment, and are particularly useful for differentiating between terrestrial and marine OM. This study applies carbon and nitrogen stable isotopic analysis to eight sediment cores from the lower Connecticut River, CT, lower East River, CT, and Boston Harbor, MA, to determine sediment sources to these estuaries over time. This study will further inform our understanding of the exchange of OM between fluvial and marine sources to estuaries, as well as the delivery of OM from salt marshes to estuaries. We hypothesize that allochthonous marine OM will have the greatest contribution to estuarine sediments throughout time. These processes are key for predicting the resilience of estuaries and salt marshes in the Northeastern U.S. amid accelerating sea level rise.