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Future of Aquatic Flows

ACRC Postdoctoral Researcher Megan Behnke models the future of Alaska rivers

Through a new project with the Alaska Climate Adaptation Science Center, the University of Alaska Southeast, and the Forest Service Pacific Northwest Research Station, Megan Behnke is working to understand the impacts of changing river conditions on aquatic flows and freshwater habitat quality for fish across Alaska. Behnke rejoined ACRC last year as a postdoctoral researcher funded through the Coastal Rainforest Margins Research Network over five years after first engaging with ACRC as a research technician. In the fall of 2022, she began a new postdoctoral position with the Climate Adaptation Science Center Future of Aquatic Flows cohort, which is bringing early career researchers together to explore the effects of climate change on aquatic flows across the nation and how climate can be integrated into aquatic ecosystem management.

As a member of the Future of Aquatic Flows cohort, Behnke will explore the impacts of changing river conditions on aquatic food webs and fish populations in Alaska. Behnke is working with resource managers, scientists, non-profit, and tribal partners across Alaska to select a range of future scenarios to model downstream changes in river food webs using an ecosystem simulation tool. Behnke will be using theAquatic Trophic Productivity (ATP) Model, which links river food web dynamics and the biomass of fish and invertebrates with the physical conditions of a stream and the inputs of nutrients and organic matter from the surrounding areas.

Behnke will input changes that Alaskan communities are already seeing in their watersheds, such as increased shading from vegetation, warmer temperatures, and more plant material inputs for permafrost streams, and see how they impact the riverine food web over cycles of 10 years. It will give users a sense of the timing and size of fish runs, and how the resulting food webs compare to a stream without those changes.

“For each of those systems, we’re anticipating different primary drivers of change. With the model, we’ll explore what changes like glacial melt or permafrost thaw will do physically to the streams,” said Behnke.

While climate projections show the magnitude of change in temperatures and precipitation across the state, there are few tools to help resource managers model the downstream impacts of the shifting watershed conditions they are already seeing. Behnke’s research will explore the connections between river characteristics such as flow, turbidity, temperature, and shading and the ultimate impact on river food webs. 

“There are many projections for what the range of impacts of climate change will be in 2100, and we need those in order to plan ahead. But streams are changing right now, and managers need to be able to assess what that means for fish populations and aquatic ecosystems.”

The resulting model scenarios could act as a guidebook, where communities can track how the changes they are seeing in their streams now may play out in the coming decades. For land managers, the project could help prioritize the monitoring of characteristics like nutrient levels and turbidity that can indicate changes in the aquatic system.

In this work, Behnke brings together her past research experience studying what happens when warming temperatures release carbon that has been stored in permafrost, glaciers, and wetland soils in both coastal temperate rainforests and around the pan-Arctic.

“It is a statewide project, which is exciting for me to be able to link my previous work on permafrost and work on Southeast Alaska and think about Alaska more holistically,” said Behnke.