Biological Oceanography

(^) Nitrate appears to be the most limiting nutrient in all four EBCS. In the CCS,
surface nitrate ranges from 2–30 μM over the inner and outer shelves (Corwith &
Wheeler 2002). Offshore nitrate concentrations are <0.1 μM. Iron can also limit
primary production in EBCS subregions. In the CCS iron is replete off the coasts of
Washington and Oregon, presumably due to wide shelves and significant river inputs
(Chase et al. 2007), but is limiting beyond the 200 m isobath in the central region
(Kudela et al. 2008).
(^) Carr and Kearns (2003) combined a hydrographic and nutrient climatology with
primary production modeled from ocean color to compare patterns of upwelling and
biological responses in the four EBCS. The biomass sustained by available nutrients
in the Atlantic EBCS was twice as large as that of the Pacific EBCS, presumably due
to availability of iron, to biomass retention, or to differences in community structure.
Messié et al. (2009) expanded this comparison using surface wind data from satellites
and vertical distributions of nutrients to estimate nitrate supply from coastal Ekman
transport relative to offshore Ekman pumping. Their estimates were that the
Peru/Humboldt, Canary, and Benguela EBCS have similar levels of nitrate supply and
new production, while California has only 60% of the other three. While estimates of
primary production in these areas vary, coastal upwelling systems overall comprise
only 0.3% of the ocean’s surface area but contribute 2% of global ocean primary
production.
(^) Phytoplankton communities can be diverse in EBCS, but blooms are typically