The coastal ocean plays a key role in global biogeochemical cycles. In the Pacific Northwest, the coastal waters are strongly influenced by freshwater inputs from the Strait of Juan de Fuca (fed by the Fraser River and the rivers of Puget Sound) and the Columbia River. These rivers act as a conduit for land-derived nutrients and as a facilitator for entraining ocean-derived nutrients into the coastal euphotic zone. Riverine delivery of nutrients to the coastal ocean may play an important role in winter and spring phytoplankton blooms along the Washington and Oregon coasts. In the Strait of Juan de Fuca, freshwater flow influences estuarine exchange, where deep, high-nutrient waters are upwelled from a submarine canyon and entrained into surface waters. Additionally, the Columbia River plume modifies flow on the shelf and can play a significant role in the retention and transport of phytoplankton communities along the coast. Here, we present results from a four-box (NPZD) model of planktonic nutrient cycling coupled to a high-resolution circulation model of the Washington and Oregon coasts developed as part of the PNWTOX (Pacific Northwest Toxins) Project. Specifically, we consider a numerical simulation of the year 2005 forced with realistic bathymetry, tides, and climatology with a special model case in which we turn off the Columbia, Fraser, and Puget Sound rivers to examine the role of freshwater inputs on regional patterns of phytoplankton biomass and productivity. Results from the biophysical model are also compared to physical, chemical, and biological data from two recently completed observational studies – The Ecology and Oceanography of Harmful Algal Blooms in the Pacific Northwest (ECOHAB) and River Influences on Shelf Ecosystems (RISE).
Wednesday, April 10, 2013 - 2:00pm
Croul Hall, Room 3101