Microbial Ecotones in the Oregon Coast System

Melissa Steinman, United States, Beatrice Pickett, Portland State University, Portland, OR, United States, Samantha Ward, Portland State University, United States and Anne Thompson, Portland State University, Biology, Portland, OR, United States
Surface waters influenced by nutrient influx from upwelling fuel productivity in the Oregon Coastal Upwelling System. Previous work suggests an ecotone transition across the continental shelf boundary, with low abundance of cyanobacteria and picoeukaryotes in shelf regions with high nutrient levels and a negative relationship between small-sized phytoplankton abundance and nutrient concentration. Impacts of seasonal dynamics and upwelling strength along onshore / offshore transects remain unknown. In this study phytoplankton community structure was measured in the surface waters across the shelf boundary, in two upwelling systems (persistent and intermittent), over a two year period, during two seasons (winter and summer). Understanding the impact of ecotones like this on phytoplankton community structure is important as their effects may cause a bottom-up trophic cascade, impacting Pacific fisheries.