Susquehanna Flats, located at the mouth of the Susquehanna River in Maryland, is a large, shallow mud flat covered with dense populations of freshwater grasses, including wild celery (Vallisneria americana) and water stargrass (Heteranthera dubia). This dynamic ecosystem has long been a popular destination for both fishermen and tourists. Since the 1980s, annual mapping of Susquehanna Flats has been undertaken from aerial photography. However, these once-yearly observations overlook the dramatic seasonal changes in both extent and biomass of the vegetation. In this study we investigated patterns of seasonality on Susquehanna Flats from 2016 to 2023 using imagery from Planet, a commercial satellite company, providing daily coverage of terrestrial and coastal ecosystems at 3 m spatial resolution. We found that grasses on the flats experience a significant die-off during winter months, with aerial coverage reducing from approximately 50 km² in August to 6 km² in December. Estimated above ground carbon biomass in the summer reached as high as 3.5 Gg carbon, declining to less than 0.3 Gg C in the winter, pointing towards a potential carbon export from the flats of ~3 Gg carbon per year. Understanding the seasonal cycle of growth on the flats has important implications for the management and conservation strategies for this unique habitat.

Primary Presenter: Kylie Harrison, Old Dominion University (keharrison01@gmail.com)

Authors:

Kylie Harrison, Old Dominion University  (keharrison01@gmail.com)

Victoria Hill, Old Dominion University  (VHill@odu.edu)

Richard Zimmerman, Old Dominion University  (RZimmerm@odu.edu)