W. Stolte et R. Riegman, THE RELATIVE PREFERENCE INDEX (RPI) FOR PHYTOPLANKTON NITROGEN USE ISONLY WEAKLY RELATED TO PHYSIOLOGICAL PREFERENCE, Journal of plankton research, 18(6), 1996, pp. 1041-1045
In field studies where the uptake of different nitrogen compounds in p
hytoplankton is studied, a relative preference index (RPI) is often us
ed which describes uptake relative to the abundance of a particular ni
trogen compound, usually ammonium. This index can easily be misused wh
en it is applied as a physiological preference indicator. In this stud
y, it is shown that the index may be more dependent on nutrient concen
trations than on the algal preference for ammonium under certain circu
mstances.