Oral Presentation Society for Freshwater Science 2026 Annual Meeting

Pinpointing drivers of covariance, persistence, and synchrony in stream metabolism across a heterogeneous watershed (136014)

Jonathan Behrens 1 , Robert Brown 1 , Natalie Griffiths 1 , Scott Brooks 1 , Erin Hotchkiss 2 , Saubhagya Rathore 1 , Marie Kurz 1
  1. Oak Ridge National Laboratory, Oak Ridge, TN, United States
  2. Virginia Tech, Blacksburg

Differences in light, temperature, and discharge lead to distinct rates of gross primary production (GPP) and ecosystem respiration (ER) in stream ecosystems. As such, within-day, magnitudes of metabolism and its drivers may covary across sites (spatial covariance) and within a site over time (temporal covariance). We examined how spatial and temporal covariance, spatial persistence, and temporal synchrony of metabolism drivers (light, temperature, and discharge) align with GPP and ER in East Fork Poplar Creek in Oak Ridge, TN, a 4th order river (77 km2) that drains heterogenous landcover. On a given day, an analyte has high spatial persistence when the ranked ordering of each site’s magnitude of the analyte on that day is nearest to the median site ranked ordering calculated from the ranked order of each day with complete data (n = 100+ days). At a given site, an analyte has high temporal synchrony when the ranked ordering of each day’s magnitude of the analyte at that site is nearest to the median ranked ordering of days across each individual site (n = 12 sites). We sampled across two years at 9 main channel sites and 3 tributaries. Seasonal shifts in light and temperature reduced spatial persistence of GPP and ER. As the canopy closed and light availability differed across sites, spatial covariance of light and GPP increased; this period had low spatial persistence relative to the full time series (i.e., site rank shifted). Temporal synchrony of light and GPP were lowest at the sites with little to no canopy cover due to low temporal covariance in GPP and light (and limited shifts in ordering of days). GPP and ER were not always correlated with one another, leading to differences in covariance, spatial persistence, and temporal synchrony. In the fall, consistent leaf inputs but variable light are associated with higher spatial covariance for GPP relative to ER. By investigating covariance, persistence, and synchrony independently, we can pinpoint specific sites or time periods for further analysis to explore the complex interplay of metabolic drivers or other drivers not commonly included in analysis (e.g., nutrients).