Speaker: Dr. Jon Benstead
Seasonality is a fundamental natural phenomenon that drives annual cycles of ecosystem production as a function of distance from Earth’s equator. Despite its familiarity, exploring the consequences of seasonality for ecosystem function at appropriate spatial scales is complicated, particularly by coupling annual light and temperature regimes, two key direct drivers with effects that are challenging to tease apart. Arctic spring-fed streams are thermally stable ecosystems embedded in an intensely seasonal light environment, and so represent rare exceptions to the tight coupling of annual light and temperature cycles that characterize most ecosystem types.
For several years, my colleagues and I have been leveraging these unusual habitats to explore seasonal ecosystem dynamics, focusing on the metabolic consequences of stable temperature in the face of dramatic annual cycles in carbon fixation at the base of their food webs. In my seminar, I will summarize our earlier work in a single spring-stream, Ivishak Spring on the North Slope of Alaska, before introducing a new project, the fieldwork for which we recently completed. This new project expanded our investigation to five spring-streams that vary in source temperature. We also extended our study of seasonal metabolism beyond our past focus on communities and ecosystem processes to the physiological status and performance of individual organisms.
Our results highlight how the effect of stable temperatures on metabolism exacerbate the consequences of seasonal light limitation of primary production for ectothermic consumers, leading to severe winter carbon limitation of trophic level production. These special challenges shed light on the potential significance of the coupled light-temperature cycles experienced by most ecosystem types for stabilizing food-web and ecosystem energetics over annual cycles.