Problem: “The amount of nitrogen leaving the ocean exceed estimates of the amount of nitrogen coming in by several hundred teragrams (that’s one billion kilograms) per year.”
Observation: “Nitrogen can make it into the ocean in one of three ways: it can be deposited as particles from the atmosphere, it can come from the land via rivers or groundwater, or it can be taken directly from the atmosphere by specialized microscopic organisms that break the very strong chemical bond between two nitrogen atoms. It is this last pathway, called nitrogen fixation, that will be the focus of the cruise.” — ALYSON SANTORO
Source: http://scientistatwork.blogs.nytimes.com/2011/03/23/where-has-all-the-nitrogen-gone/?ref=science