Observations of Persistent Upwelling Structures

Project Description
A significant proportion of global primary production occurs in the coastal ocean where the biological pump exports carbon to deep water. The pump's efficiency depends on the fraction of carbon fixation that escapes recycling within the mixed layer, i.e. new production, which is supported by nutrient influx (e.g. nitrate or silicate) to the euphotic zone. Wind-driven coastal upwelling provides nutrient enrichment that creates high rates of new production in eastern boundary ocean margins, which will be described here using historical data collected by our group in a variety of upwelling areas. These include data from Peru, northwest Africa and Baja, California collected during the 1970's as part of the Coastal Upwelling Ecosystem Analysis (CUEA) Program, in the 1980's at Point Conception, CA during the Organization of Persistent Upwelling Structures (OPUS) Project, in the 1990's in Monterey Bay, CA and more recently off Bodega Bay California during the Coastal Ocean Processes Wind Events and Shelf Transport (CoOP-WEST) program. In all studies, the percent of new production or "f ratio" was calculated using the same approach, from nitrate uptake measured using the stable isotopic tracer, 15N. A common feature in these systems, is the need for a brief window of relaxed winds (3-5 days) following an upwelling event, to enable new production rates to increase, as phytoplankton biomass accumulates. More recently, the importance of the larger sized fraction of phytoplankton (mainly diatoms) to new production in these ecosystems has been documented. The significance of this diatom dominance to carbon flux and sinking export within these productive coastal ecosystems will be discussed.