Food webs examine energy and nutrient flow and are critical for understanding ecological processes, such as decomposition, trophic cascades, ecological subsidies, and ecosystem stability. In my dissertation, I studied the food webs of small ponds in order to understand how leaf litter and pond biogeochemistry shaped energy flow.
The Role of Terrestrial Leaf Litter
Aquatic consumers derive carbon from two sources: terrestrial leaves (outside subsidy) and algae (internally produced). There is currently debate among aquatic ecologists regarding the extent to which terrestrial carbon can support the food web of lakes and ponds. If terrestrial carbon can support any aquatic food web, one would expect to see it in small ponds where leaf litter inputs are high and water volume is low. We used stable isotope analysis and an isotope tracer to evaluate the role of terrestrial leaf litter in small pond food webs. We found that while leaf litter permeated the entire pond food web, algae provided the dominant food source for most consumers. Check out our study published in Ecology.
Interannual Variability in Food Web Structure
The unique biogeochemistry (high CO2 and CH4; very low O2) of small ponds influences the food web of these systems. Using stable isotope analysis, I found that interannual and seasonal differences in CO2 and CH4 influenced the carbon source for consumers. Specifically, methane provided an additional carbon source to the food web when concentrations were high. I am currently writing this manuscript, so check back to see the final results.