Event Title

The Response of Whole Stream Metabolism to Global Increases in Temperature is Confounded by Variation in Hydrology and Resource Supply?

Location

Eccles Conference Center

Event Website

http://water.usu.edu/

Start Date

4-3-2009 2:40 PM

End Date

4-3-2009 3:00 PM

Description

The International Panel on Climate Change predicts - 3 °C change in surface temperature by 2100. Streams will likely respond to increased surface temperatures because they are well-mixed, turbulent systems. Laboratory-based measures of benthic respiration with increasing temperature have found that an increase in stream temperature by 2.5 °C will increase respiration by 18-23 %. It is unclear whether stream metabolism will respond similarly to increases in temperature under field conditions. Two years of continuous measures of gross primary production (GPP) and ecosystem respiration (ER) have been collected in Walker Branch, a first-order forested stream in Tennessee (USA). We used this dataset to 1) quantify the temperature dependence of whole stream metabolism for Walker Branch, 2) compare observed scaling relationships between temperature and GPP or ER to those predicted by metabolic theory, and 3) estimate how increased global temperature could alter whole stream C dynamics. We found that GPP and ER are dependent on temperature in manner described by the Arrhenius equation; but this pattern is often masked by variation in hydrology or resource supply (light or carbon [C]). The temperature dependence of GPP most closely approximated predicted values under stable hydrologic flow and high light availability. Under variable flow conditions, GPP was independent of temperature. The temperature dependence of ER most closely approximated predicted values under two different types of conditions: 1) stable flow combined with C supply largely derived from GPP or 2) variable flow combined with C supply primarily derived from leaf litter. Both ER and GPP should increase with increased temperature with greater increases in ER relative to GPP, according to metabolic theory. In Walker Branch, an increase in stream temperature by 3 °C would result in an increased P:R ratio and decreased net C deficit (the quantity of C consumed by ER that is not derived from GPP), patterns opposite of those predicted by metabolic theory. These results should be interpreted with caution because 1) Walker Branch is fed by ground water and thus likely to be buffered from increases in temperature and 2) the temperature-dependence of whole-stream metabolism may not be predictable, if two or more factors interact. More high-resolution data on whole stream metabolism, hydrology, and resource supply is needed from streams in a variety of systems to better assess the effect of global increases in temperature on streams C dynamics.

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Apr 3rd, 2:40 PM Apr 3rd, 3:00 PM

The Response of Whole Stream Metabolism to Global Increases in Temperature is Confounded by Variation in Hydrology and Resource Supply?

Eccles Conference Center

The International Panel on Climate Change predicts - 3 °C change in surface temperature by 2100. Streams will likely respond to increased surface temperatures because they are well-mixed, turbulent systems. Laboratory-based measures of benthic respiration with increasing temperature have found that an increase in stream temperature by 2.5 °C will increase respiration by 18-23 %. It is unclear whether stream metabolism will respond similarly to increases in temperature under field conditions. Two years of continuous measures of gross primary production (GPP) and ecosystem respiration (ER) have been collected in Walker Branch, a first-order forested stream in Tennessee (USA). We used this dataset to 1) quantify the temperature dependence of whole stream metabolism for Walker Branch, 2) compare observed scaling relationships between temperature and GPP or ER to those predicted by metabolic theory, and 3) estimate how increased global temperature could alter whole stream C dynamics. We found that GPP and ER are dependent on temperature in manner described by the Arrhenius equation; but this pattern is often masked by variation in hydrology or resource supply (light or carbon [C]). The temperature dependence of GPP most closely approximated predicted values under stable hydrologic flow and high light availability. Under variable flow conditions, GPP was independent of temperature. The temperature dependence of ER most closely approximated predicted values under two different types of conditions: 1) stable flow combined with C supply largely derived from GPP or 2) variable flow combined with C supply primarily derived from leaf litter. Both ER and GPP should increase with increased temperature with greater increases in ER relative to GPP, according to metabolic theory. In Walker Branch, an increase in stream temperature by 3 °C would result in an increased P:R ratio and decreased net C deficit (the quantity of C consumed by ER that is not derived from GPP), patterns opposite of those predicted by metabolic theory. These results should be interpreted with caution because 1) Walker Branch is fed by ground water and thus likely to be buffered from increases in temperature and 2) the temperature-dependence of whole-stream metabolism may not be predictable, if two or more factors interact. More high-resolution data on whole stream metabolism, hydrology, and resource supply is needed from streams in a variety of systems to better assess the effect of global increases in temperature on streams C dynamics.

https://digitalcommons.usu.edu/runoff/2009/AllAbstracts/28