Nitrate concentrations in the upwelling source waters observed near Cabo Corbeiro during the JOINT-I experiment were more than twice as high as dissolved silicon concentrations, but dissolved silicon concentrations in the surface layers fell below 0.5 µg-atoms...
Friederich, G. E., and L. A. Codispoti. 1979. "On some factors influencing dissolved silicon distribution over the northwest African shelf." Journal of Marine Research 37, (2). https://elischolar.library.yale.edu/journal_of_marine_research/1472