Bennett L. Smith Professor of Business and Natural Resources
Resolving the biological versus geological concepts of limitations on oceanic primary production
Wednesday — March 19, 2014
Pacific Forum — 3:00 p.m.
The basic concepts of key limiting nutrients in the sea are derived from agricultural practices derived from Leibig and Blackman. With the 1934 paper, Alfred Redfield, an animal physiologist, suggested that the ratio of nitrogen to phosphorus in the ocean was set by the stoichiometry of the sinking flux of plankton. He resurrected that concept in 1958, and later in 1963. However, he realized that some of the nitrogen in the sinking flux was missing. He had no explanation, but assumed, based on work on lakes, that phosphorus was the "limiting" nutrient in the oceans. Extensive work in the late 1950's and through the 1970's clearly showed that throughout most of the world's low nutrient, low chlorophyll regions, nitrogen was limiting. The notion that nitrogen fixation in the oceans could be limited by another nutrient was discovered by John Reuter - who suggested iron was limiting nitrogen fluxes into the ocean. I resurrected that argument in a series of papers - and have been thinking about why and how that came to be for the past two decades. In this talk I will discuss the testable hypothesis that iron limits nitrogen fixation throughout most of the oceans over long geological time scales.
Next: April 9 - Ivan Amato