Temperature dependence of daily respiration and reaeration rates during baseflow conditions in a northeastern U.S. stream

Study region: Finger Lakes Region, New York, USA. Study focus: The relationship between stream temperature and daily respiration and reaeration rates was investigated from May 2015 - May 2016 for two sites, one in the headwaters and the other near the mouth of a net heterotrophic stream. Daily respiration and reaeration rates were calculated by applying the night time slope method to open-channel diel oxygen concentrations during baseflow conditions. New hydrological insights for the region: Reference values for activation energy (E-a) are presented that could be applicable to lower order streams in temperate climates receiving significant inputs from surface and subsurface flows. There was a sizeable difference in temperature sensitivity between upstream and downstream sites. Ecosystem respiration (ER) exhibited a strong Arrhenius temperature dependence with daily respiration rates of 0.5-9.5 g O-2 m(-2) d(-1) (E-a = 0.61 eV) in the headwaters and 1.8-30.3 g O-2 m(-2) d(-1) (E-a = 0.67 eV) at the downstream location where ER in the headwaters was less sensitive to temperature. E-a for both sites fell within the expected theoretical range for heterotrophic respiration in aquatic ecosystems. Temperature reaeration rate coefficients ranged from 1.011 to 1.020 at the headwaters and from 1.005 to 1.009 downstream suggesting that daily reaeration rates at the headwaters were more sensitive to temperature than the downstream location where reaeration was likely controlled by stream discharge and driven by turbulence.