AbstractPigment content (chi a and phaeo-pigments) of phytobenthos (mainly mosses and some small algae) were studied in December 1985, after a dry period, and in May 1986, after a period of rain. Chi a increases in submerged plants, carotene/chi a ratios and phaeo-pigment increase following emergence. Seasonal fluctuations in pigments can be related to variations in microclimate caused by changes in river level.