UVM Theses and Dissertations
Format:
Print
Author:
Cappelletti, Carl
Dept./Program:
Rubenstein School of Environment and Natural Resources
Year:
2006
Degree:
M.S.
Abstract:
Global warming may significantly alter whole--stream metabolism (WSM) in Arctic rivers, which may change net COz fluxes on an ecosystem scale. However, the whole--stream metabolism method has not been applied in high--latitude regions because it has been assumed that the 24--hour photoperiod during the summer would preclude accurate estimate of ecosystem respiration (ER) in the dark and subsequent calculation of gross ecosystem production (GEP) in the light. We found that --- with some modification --- the WSM method is applicable in Arctic streams near the Toolik Lake Field Station, Alaska (68° N latitude). Global warming will likely increase water temperatures, discharge, and SRP (soluble reactive phosphorous) in Arctic rivers and these physical and chemical drivers may influence WSM. By examining the influence of light, temperature, discharge, photosynthetic biomass, and nutrients on WSM, we can develop predictive models of photosynthesis and respiration based on which driving variables are important.
Ecosystem respiration (ER) was not significantly different among any of the study reaches. In all reaches, ER was weakly correlated with temperature, discharge, and SRP. However, ER showed a positive response to temperature and a negative response to discharge in the fertilized reaches, most likely due to the extensive bryophyte and epiphyte biomass that have accumulated there. Analysis of multiple linear models using information theory suggests that ER in the fertilized reach was best described by temperature; ER in the reference reach was less well explained by temperature. SRP was of low to moderate importance among all reaches as a descriptor of ER. The combined influence of increased water temperature, discharge, and SRP will decrease NEM, meaning that carbon sequestration in streams is expected to increase, although not substantially, in the future. This means that the net C0₂ flux out of these rivers and into the atmosphere will likely decrease.
Ecosystem respiration (ER) was not significantly different among any of the study reaches. In all reaches, ER was weakly correlated with temperature, discharge, and SRP. However, ER showed a positive response to temperature and a negative response to discharge in the fertilized reaches, most likely due to the extensive bryophyte and epiphyte biomass that have accumulated there. Analysis of multiple linear models using information theory suggests that ER in the fertilized reach was best described by temperature; ER in the reference reach was less well explained by temperature. SRP was of low to moderate importance among all reaches as a descriptor of ER. The combined influence of increased water temperature, discharge, and SRP will decrease NEM, meaning that carbon sequestration in streams is expected to increase, although not substantially, in the future. This means that the net C0₂ flux out of these rivers and into the atmosphere will likely decrease.