Oxygen dynamics in a well mixed estuary, the lower Delaware Bay, USA

Dissolved oxygen (O2) and other physical and biological factors were monitored in the lower Delaware Bay using an autonomous buoy. Six weeks of data from the summer of 2007 provide insight into the processes occurring in the lower bay. O2 concentrations varied at both tidal and diel periodicities and were super-saturated for most of the summer, with day time maxima of up to 390 µM (140% saturation). Extended periods of high wind speed reduced the O2 concentration to saturation, after which it took up to 4 days for the system to return to a super-saturated state. Air–sea gas exchange rates and net O2 production rates (primary productivity and respiration) were calculated using the measured O2 concentrations, wind speed, and tidal currents. O2 production was modeled using the Delta method and a primary productivity and respiration model. Based on these calculations, the lower Delaware Bay was net autotrophic during the summer of 2007, producing O2 at a rate of 2.8 µM d− 1 over the well-mixed 15 m water column. Additionally, this study provides insight into the complexities present at the interface between estuaries and the coastal ocean.