Ref ID : 6092
Sharon G. Berk and John A. Botts; Indirect Effects of Chlorinated Wastewater on Bacteriovorous Protozoa. Environ.Pollut.A 34:237-249, 1984
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Comparisons were made among ciliate population growth on chlorinated Escherichia coli, irradiated E. coli, live Pseudomonas sp. and irradiated Pseudomonas sp. No differences were observed in protozoan population growth when chlorinated E. coli, irradiated E. coli and irradiated Pseudomonas sp. were used, whereas significant differences resulted between live and irradiated Pseudomonas sp. as food. Food selectivity, determined by feeding experiments with chlorinated 14C-labelled E. coli and live Pseudomonas sp., showed that significant consumption of chlorinated coliforms occurred in the presence of live bacteria. To assess the extent to which dead bacterial cells may be available to bacteria-feeders in water receiving chlorinated effluents, percentages of living (respiring) bacteria to total bacteria were determined for several sites downstream of an effluent and in a chlorine contact basin of the treatment plant. Populations upstream had a significantly higher percentage of respiring bacteria than those at the contact basin and a site 20 m downstream, but not those at a site 60 m downstream. Toxicity tests on upstream bacteria revealed significant decreases in the percentage of respiring bacteria after 24 hours' exposure to water from both downstream sites, as well as water from the contact basin. These data indicate that dead bacterial cells can serve as food for ciliates, resulting in decreased ciliate production compared with growth direct discharge of cells to the stream and via lethal toxicity to native stream bacteria.