THE RELATIONSHIP BETWEEN NUTRIENTS AND TROPHIC-LEVEL BIOMASS IN TURBID TROPICAL PONDS

1. The total phosphoms-algal biomass relationship from a set of turbid tropical ponds in Kenya was compared with predictions derived from su rveys of temperate and subtropical lakes. Despite high concentrations of total phosphorus (TP) (up to 797 mu g L-1) and inorganic turbidity (up to 800 mg L-1), the log-log relationship between algal biomass and TP was steeper than expected. 2. No evidence of nitrogen limitation w as found at high TP, and total nitrogen (TN):TP ratios were higher tha n in lakes with similar TP levels studied previously. High TN:TP ratio s may be a consequence of excretion by cattle into the ponds, a nutrie nt source characterized by a high ratio of available N to available P. 3. Despite extremely high turbidity, the ratio of mixed layer depth t o euphotic depth was generally low because these ponds are shallow (le ss than or equal to 2 m), and was not related to algal yield. A positi ve relationship was also found between TP and zooplankton biomass, and between TP and the density of the zooplanktivorous bug, Anisops. In c ontrast, no relationship was found between fish biomass and TP, algal biomass or zooplankton biomass.