In Cayuga Lake water amended with 30 micro g of glucose or amino acids per ml, an added strain of Pseudomonas fluorescens and indigenous bacteria grew extensively, Pseudomonas sp. B4 and two rhizobia multiplied to a moderate extent, and introduced Escherichia coli and Klebsiella pneumoniae multiplied but to only a slight degree. In nonsterile lake water amended with 30 micro g of Trypticase soy broth per ml, the indigenous bacteria greatly increased in abundance, the pseudomonads, rhizobia, and E. coli developed to a lesser extent, the numbers of K. pneumoniae, A. citreus and M. flavus showed little increase, and B. subtilis did not survive. Based on the behavior of the test species, it is proposed that Ks value, micro max value, length of lag phase, and resistance to stress can be used to predict behavior of bacteria in lake water receiving low levels of organic nutrients. (Copyright (c) 1990 Kluwer Academic Publishers.)