Factors affecting dissolved oxygen metabolism in coastal streams of Virginia

We investigated seasonal and inter-site variation in factors influencing diel dissolved oxygen (DO) metabolism at four streams in the Virginia Coastal Plain.  Data were collected monthly from January to August 2008 to characterize DO metabolism (diel amplitude, production, respiration), incident solar radiation (PAR), dissolved nutrients, fine benthic materials (mass, C:N, Chlα) and hydrology (discharge, water transit time, transient storage).  Reach-scale metabolism estimates were determined using the one-station diurnal DO technique and transit time and transient storage were determined by conservative tracer additions.  Incident solar radiation was the primary determinant of DO metabolism as streams experiencing higher light levels (Herring and Powell Creeks) exhibited greater diel DO amplitudes, production and respiration.  Streams with greater riparian shading (Courthouse and Crump Creeks) exhibited lower DO metabolism despite their higher nutrient concentrations.  Higher incident solar radiation was associated with greater benthic algal biomass at some (Herring) but not all (Powell) sites.  Diel DO amplitudes were found to be significantly and positively correlated with benthic Chlα and incident solar radiation at these sites.  These factors were not significant predictors of DO amplitude, production or respiration at the more shaded sites.