Coastal Upwelling Equatorward winds along a coastline lead to offshore Ekman transport Mass conservation requires these waters replaced by cold, denser waters Brings nutrients to the surface increasing rates of primary production Creates dynamic height gradients - currents

Coastal Upwelling

CalCoFI Cruise 9804

Coastal Upwelling Changes Density Line 90

Density & Currents for Line 90 Negative currents to south

Primary Production Phytoplankton h CO 2 O2O2 PlantsNUTS Light, carbon & nutrients make plants & O 2

Respiration & Remineralization remineralizers h CO 2 O2O2 PlantsNUTS Biological processes consume plants & O 2 to make CO 2 & nutrients

Euphotic Zone Euphotic Zone – PP happens Aphotic Zone - Respiration & Remineralization Depth of Euphotic Zone is f(water clarity) 100% Light1% Light

Euphotic Zone Defined as the depth where the light = 1% of the surface value A function of plant biomass or chlorophyll concentration Varies from 10 to 130 m Typically, Z eu = 3 * Secchi depth

CalCoFI Light Profiles % surface light Depth (m) Secchi = 7 m Secchi = 18 m

Primary Production Phytoplankton h CO 2 O2O2 PlantsNUTS Light, carbon & nutrients make plants & O 2

Facts & Predictions CO 2 will not be limiting In euphotic zone … – NUTS will be consumed – O 2 & plants will grow (high chlorophyll) In aphotic zone … – Remineralization produces CO 2 & NUTS – Consumes O 2 & plants

Facts & Predictions KEY: Upper layer biology is controlled by supply of nutrients to euphotic zone Upwelling is dominate process regulating primary production

Density & Currents for Line 90 Negative currents to south

NUTS for Line 90

Line 90 Results In euphotic zone … – NUTS are low – O 2 & plants are high (O 2 is supersaturated) In aphotic zone … – NUTS are high – O 2 & plants are low Pattern follows physical inflow

CalCoFI Cruise 9804

Link to Physical Process April 1978 AVHRR - SST CZCS Chlorophyll SST Chl

Coastal Upwelling

The Upwelling Conveyor Belt Highest NUTS & CO 2 High NUTSLow NUTS High ChlLow ChlLower Chl Sinking Flux of Carbon

Biological Water Masses Residence time in euphotic zone controls nutrient concentrations Source characteristics are also important

Primary Production Simple light-NUT model explains basic features regulating primary production Physical processes drive nutrient supply to euphotic zone & primary production Concept of “upwelling conveyor belt” Water mass characteristics