The practice of stimulating dense growths of marine phytoplankton in laboratory cultures by the addition of nitrate and phosphate is now well established. Since in the sea the food chain leading ultimately to fish begins with inorganic nutrient salts, and passes through plankton and bottom fauna, it seemed feasible to attempt to stimulate the food cycle by the addition of artificial fertilizers to seawater areas. Nitrate and phosphate alone were considered since these are the nutrients in short supply in the sea.
Raymont, J. E.. 1947. "A fish farming experiment in Scottish sea lochs." Journal of Marine Research 6, (3). https://elischolar.library.yale.edu/journal_of_marine_research/638