DOES DIEL NITRATE VARIABILITY INDICATE NITROGEN SATURATION?
Diel nitrate patterns in streams are often attributed to metabolic uptake, with the timing and magnitude of patterns resulting from demands of primary productivity. Recent work however, indicates that this may only be the case when nitrogen is not limiting in a stream, and that the amplitude of diel nitrate signals are dampened when nitrogen limitation exists. Moreover, additional hydrologic and anthropogenic forces also have the capacity to influence diel patterns both in amplitude and in timing of peaks and valleys. Such external forcing would create nitrate patterns which closely correlate with diel discharge. We conducted a synthesis of 83 USGS monitored sites with continuous nitrate and DO data (cumulative 201 years of nitrate and 318 years of DO data) to determine the extent of diel fluctuations across rivers, as well as whether metabolism accurately predicts diel fluctuations without considering nitrogen saturation or external forcing. Using patterns of amplitude and peak timing, we additionally infer how dominant controls may shift through time in any given stream, whether seasonally or in response to distubrance.
Catherine Chamberlin (Primary Presenter/Author), Duke University, email@example.com;
Jim Heffernan ( Co-Presenter/Co-Author), Duke University, firstname.lastname@example.org;