The importance of ammonia as a sourc:e of available nitrogen for phytoplanktonic populations off New England has been evaluated for August and January 1962. During August, when only trace amounts of nitrate persist in the photic layer, ammonia appears to be the major source of available nitrogen. Therefore, meaningful estimates of the relative amounts of nitrogen and phosphorus being assimilated at such times require consideration of the nitrogen occurring as ammonia....
Vaccaro, Ralph F.. 1963. "Available nitrogen and phosphorus and the biochemical cycle in the Atlantic off New England." Journal of Marine Research 21, (3). https://elischolar.library.yale.edu/journal_of_marine_research/1012