Objective 1: Investigate carbon pool characteristics in glacially fed streams
The purpose of my first objective was to characterize the organic carbon pool in four glacially fed streams using absorbance parameters and carbon isotopes in order to (1) assess whether the stream organic carbon pool appeared more glacial or terrestrial in character and (2) to investigate how the carbon pool changed with changing hydrological inputs, distance away from glacier and between rivers. Overall, the stream organic carbon pools showed a mixture of glacial characteristics (low amounts of humic components (A254) and low amounts of organic carbon (DOC)) and terrestrial characteristics (high molecular weight compounds (S275-295) and d13C values) (Table 5). Additionally, the carbon pools were found to vary significantly with month sampled, between rivers, and depending on proximity to glacier (Figure 16-18). Although organic carbon characteristics were significantly different between May and August (Figure 15), these characteristics still showed a mixture of glacial and terrestrial characteristics which was not expected. Finally, sites near and far away from glaciers were found to have significantly different carbon pools (Figure 17). Sites near glaciers displayed characteristics similar to glacial meltwater samples, which was expected. Sites far away from glaciers displayed a mixture of glacial and terrestrial characteristics which was unexpected.
Objective 2: How do Microbial Communities Vary Spatially and Temporally?
The purpose of my second objective was to investigate if microbial communities showed temporal and spatial variation within and between my four study rivers. I hypothesized that the microbial communities would follow similar trends in the organic carbon pool variation. Meaning that, if the organic carbon pool varied spatially and temporally then the microbial communities would as well. It was found that microbial communities varied 12% with month sampled, 10% between rivers rivers and 6% with distance from glacier (Table 11). This was expected as organic carbon pools also vary between months, rivers, and distance from glacier. Microbial community samples collected in May varied relative to other months (Table 8). Samples between sites near and far away from glaciers (Table 9) also varied significantly. This is the same trend that was observed between organic carbon pool characteristics and was expected. Microbial communities were also found to vary significantly between Bow River and all other rivers (Table 10). This does not follow the same trend as carbon pool variation and was unexpected.
Objective 3: Are properties of the organic carbon pool creating variation in microbial communities?
The purpose of my third objective was to investigate if differences carbon pool characteristics would lead to difference in microbial communities. I hypothesized that organic carbon parameters would explain variation between microbial communities. To achieve this a distance based redundancy analysis was performed, and it was determined that organic carbon absorbance parameters did not significantly explain microbial community variation (Table 11).
Future Directions
One of the main goals of the first data chapter of my MSc thesis was help plan an incubation experiment to test whether microbial communities preferentially consume glacially derived carbon over terrestrial carbon. This will be achieved by mixing together different stream microbial communities with different organic carbon pools (water from different sites) and then observing how the organic carbon pool characteristics change over time. The research done for this project has helped guide the 2021 experimental design by (1) the decision to include other carbon parameters such as carbon fluorescence characteristics to provide more specific details on carbon pool properties (compared to absorbance parameters used in this study which are more general), (2) the decision to conduct the incubation experiment in late summer which had both unique microbial communities and carbon pool characteristics compared to spring, and (3) that an incubation experiment comparing carbon pools with microbial communities near the glacier to carbon pools with microbial communities far away from glaciers, since these distance ranges are significantly different from each other.