Long-term variations in the dissolved oxygen budget of an urbanized tidal river: The Upper Delaware Estuary

Daniel Tomaso, Penn State University, dantomaso@psu.edu
Raymond Najjar, The Pennsylvania State University, rgn1@psu.edu (Presenter)

The dissolved oxygen budget in the upper Delaware Estuary between 1970 and 2014 was inferred from oxygen concentration measurements using a box-model approach. The region was found to be a net biogeochemical sink of oxygen, with net oxygen consumption greater in the tidal-fresh portion than in the oligohaline portion. Net oxygen consumption decreased from the 1970s to the 1990s by roughly a factor of two before increasing slightly in the 2000s. The dramatic decline in oxygen consumption was presumably due to improvements in wastewater treatment, though a comparison with biological oxygen demand measurements in wastewater was equivocal. Non-algal oxygen consumption (i.e., oxygen consumption due to heterotrophic respiration and nitrication) was computed as the sum of the estimated net oxygen consumption and historical measurements of primary production. Non-algal oxygen consumption was found to be highly seasonal and positively correlated with temperature, with Q₁₀ values ranging between 1.4 and 2.3. Annual non-algal oxygen consumption was found to be several times annual primary production. Exchange with the atmosphere is the main process that balances the net oxygen consumption throughout the study region, with advection also an important process in the tidal-fresh portion. Decadal-scale variability in oxygen concentration, including the recent decline in the 2000s, appears to be mainly driven by biological, not physical, processes.

Presentation Type:  Poster

Session:  Theme 2: Landscapes to coasts: understanding Earth system connections   (Mon 1:30 PM)

Associated Project(s): 

• Related Activity: Related Activity or Previously Funded CC&E Activity not listed ...details

Poster Location ID: 174