Nutrient Stressor-Response Models for Algal Communities in Oregon Streams and Rivers

Excessive algal growth in streams and rivers cause costly human health and environmental problems.  Recent harmful algal blooms and nuisance aquatic weed growth in the Willamette, Deschutes, and Rogue Rivers highlight the need to examine factors influencing primary producer response dynamics in Oregon's river basins.  As part of the Nutrient Scientific Technical Exchange Partnership and Support (N-STEPS) program, the Oregon Department of Environmental Quality is working with the US Environmental Protection Agency and Tetra Tech to link nutrients and other factors with algal community dynamics in Oregon streams and rivers.  We envision that this project will help prioritize water quality management, among other benefits.  Thus far, a conceptual model linking algal communities with nutrients and other factors has been developed, algae and nutrient data from 843 sites across the Pacific Northwest have been compiled, and a stressor-response analysis initiated.  Conceptual model development has shown that complex feedbacks among algal community characteristics (e.g., abundance of nutrient sensitive species), standing stock of algal biomass, and ecosystem function (e.g., gross primary production and respiration) are critical for interpreting results of stressor-response analyses.  Results of this initial analyses will inform a 2016 field study aimed at improving stressor-response models.