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River Ecosystems in a Changing Arctic

Michael Kendrick, SC DNR

14 April 2017

Significant changes in seasonality and nutrient supply are anticipated for arctic river ecosystems due to climate warming. However, our understanding of the effects of such changes is poor. For instance, the ‘shoulder seasons’ (periods shortly after the spring thaw and then before autumn freezing) have been historically under-represented in sampling regimes, but they have the potential to play important roles as climate warming extends the length of the Arctic growing season. To better understand should-season processes, an assessment of the algal and invertebrate productivity was conducted throughout the open-water period. This study revealed significant seasonal patterns with the highest levels of algal production, and lowest levels of invertebrate production, occurring during the shoulder-seasons. Relatively high rates of algal production during the cool shoulder seasons demonstrate that these under-sampled periods are likely important to the overall energetics of arctic river ecosystems. Next, as a means to assess the importance of changing nutrient supplies on arctic rivers, a whole-river nutrient addition experiment was conducted and revealed strong responses throughout the food web, including shifts in life cycle phenology of an important grazing insect. Analyses show that invertebrates in the Arctic can have substantial effects on the seasonal patterns of algal productivity under ambient and nutrient-enriched conditions. Given the multitude of changes predicted to occur in arctic environments, it will be important to understand how shifts in biotic interactions, seasonality and nutrient availability will affect arctic river ecosystems.