Modeling study on the physical and biogeochemical controls of Chesapeake Bay hypoxia from interannual to decadal time scales

The seasonal depletion of dissolved oxygen (DO) in the coastal and estuarine environment is a worldwide problem due to the anthropogenic nutrient loading. The Chesapeake Bay has been experiencing more severe seasonal hypoxia (DO<2mg/L) with increased nutrient loading during the past decades. On the shorter time scales, the Chesapeake Bay hypoxia also showed strong interannual variability controlled by both physical and biogeochemical processes. In order to fill the knowledge gap of previous studies that dedicated on either the interannual or long-term time scales, this study utilized a well-developed coupled hydrodynamic-biogeochemical model (ROMS-RCA) to implement hindcast simulation of the Chesapeake Bay hypoxia from 1950-1970 the time period when the nutrient loading was relative low, and1985-2016 when nutrient level was high, to closely inspect the physical and biogeochemical control on the oxygen depletion quantitatively. Preliminary results indicated the role of physical transport (i.e. advection and diffusion) to the interannual variation of bottom oxygen relied on the riverine nutrient concentration level. This research has significant implications for developing effective nutrient management strategies to restore the bay water quality by better understanding the relative contributions of physical and biogeochemical processes on hypoxia with the changing nutrient loads.