Suttle, C.A. and P.J. Harrison. 1988. Rapid ammonium uptake by freshwater phytoplankton. Journal of Phycology 24:13-16.

A natural assemblage of freshwater phytoplankton was removed from an oligotrophic lake and grown at N:P supply ratios of 5:1, 15:1, and 45:1 (by atoms) in semicontinuous culture. After a minimum of 31 days at an average daily growth rate of 0.5 /d, experiments were conducted examining the time-course of saturated ammonium uptake rates. Cultures grown under the two lowest N:P supply ratios demonstrated greatly elevated initial, specific uptake rates for ammonium and were able to sequester between 7 and 21% of their daily N requirement in less than 5 min. The initial rates declined rapidly but were followed by a subsequent increase and decrease over a 120 min period.