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Abstract
The Columbia River is a productive, mesotrophic river that traditionally supported some of the largest stocks of Pacific salmon in the world. Recovery efforts have focused on characterizing the habitat of juvenile salmonids prior to ocean entry to better understand threats to salmon survival. Off-channel habitats of the lower Columbia River estuary have been shown to support stocks of juvenile salmonids; yet, little is known about the seasonal or inter-annual variations in plankton populations or food web dynamics in these areas. Since the installation of hydroelectric dams through the early to mid-20th century, changes in the Columbia River ecosystem have resulted in a shift toward larger standing stocks of fluvial phytoplankton relative to macrodetritus inputs, with unknown consequences for the salmon food web. Here, I explore the inter-annual variability in spring phytoplankton populations within two contrasting off-channel habitats (Whites Island and Campbell Slough) to provide context for salmon recovery efforts.