CORRELATIONS BETWEEN PREDOMINANT HETEROTROPHIC BACTERIA AND PHYSICOCHEMICAL WATER-QUALITY PARAMETERS IN 2 CANADIAN RIVERS

The heterotrophic bacterial populations in 2 contrasting rivers (the Meduxmekeag and the Dunbar) were examined over a period of 1 year. The populations were analyzed as total heterotrophic counts; as species numbers, using numerical taxonomy; by diversity indices; and by factor analysis. Isolates were obtained by plating directly from water samples and by chemostat enrichment. Four factors emerged which profiled the bacterial community and were common to both rivers. They were, in order of decreasing importance, fermentative metabolism, inorganic N metabolism, fluorescence-oxidative metabolism and lack of starch hydrolysis. Several factors produced significant correlations with a range of physicochemical parameters, which were also measured. The correlations suggested an intricate algal-bacterial interaction. The oxidative metabolism factor correlated with rainfall in 1 river, suggesting that the oxidative bacteria may be washed in from the surrounding land. In the other river, the oxidative-fermentative factor correlated negatively with sunshine. Factor analysis was the most effective method for revealing correlations between bacterial characteristics and the environmental parameters; however, the use of a variety of methods provided more insight into the ecological aspects.