Ecosystem Modeling of the Oregon Shelf: Everything but the Kitchen Sink

The Oregon coast has long been recognized as a region of strong summer upwelling and rich productivity. Over the last decade several observational programs have begun to unravel the underlying factors controlling observed patterns of primary and secondary production. Key discoveries include the finding that phosphorus availability can control phytoplankton production, despite the common misconception that nitrogen is the sole proximate limiting nutrient. Enhanced field efforts have also revealed frequent summertime episodes of hypoxic and even anoxic bottom waters during the last decade. The severity and duration of these low-oxygen events, as well as their spatial extent along the Oregon shelf vary on an annual basis. Finally, regular blooms of Myrionecta rubra, a “red-tide” forming mixotrophic ciliate, have been recorded within the Columbia River Estuary (CRE) over the last 15 years or so. Incongruously, these red waters persist for months while the residence time of the CRE is a few days. Simple ecosystem and active particle tracking models coupled to circulation models have complemented field experiments tohelp us better understand the dominant forcing (physical and biological)leading to hypoxic/anoxic events, the frequency of phosphorus stressed conditions, and the mechanisms for retention of Myrionecta rubra in the CRE.