This dataset contains dissolved oxygen, salinity, water temperature and related calculated variables for water quality stations in western Long Island Sound. Additionally, the data set include water level data from an associated NOAA tide gauge. This dataset is associated with the following publication: Duvall, M.S., J.D. Hagy III, J.W. Ammerman, and M.A. Tedesco. High-frequency Dissolved Oxygen Dynamics in an Urban Estuary, the Long Island Sound. Estuaries and Coasts. Estuarine Research Federation, Port Republic, MD, USA, 47: 415-430, (2024).