Biogeochemical Transformations and Dissolved Oxygen Dynamics along the Urban Watershed-Estuary Continuum
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Dissolved oxygen is a common metric of water quality that is sensitive to various factors. While predicting dissolved oxygen has been identified as a crucial objective for managing water quality in both freshwater and coastal ecosystems, making accurate predictions has been challenging. Uncertanties exist within and across ecosystems due to differences in habitat such as shallow versus deep water, which are compounded by high spatial and temporal variability. This project seeks to understand dynamics along flowpaths connecting nontidal and tidal ecosystems. This research leverages continuous and discrete water quality data from collected from the Potomac and Anacostia watersheds of the eastern US to explore drivers of longitudinal patterns in water quality and diurnal variability in dissolved oxygen along the urban watershed-estuary continuum. We conducted longitudinal stream synoptic (LSS) monitoring across different streamflow conditions ranging from drought to storms. We observed longitudinal changes in organic matter concentrations quantity and quality, and significant relationships between organic matter and salinity were observed across sites (p < 0.05). Longitudinal patterns changed in response to climatic events, and there were relationships between organic matter quality and salinity along the urban watershed-estuary continuum. Continuous dissolved oxygen data showed differences in the amplitude of daily and seasonal cycles along longer flowpaths from rivers to estuaries. Future work will combine sensor data, routine sampling, and longitudinal steam synoptic monitoring to better understand drivers and longitudinal patterns in dissolved oxygen, salinity, and organic matter.