THE EFFECTS OF DIURON ON BACTERIAL POPULATIONS IN AQUATIC ENVIRONMENTS¹

Abstract

The naturally occurring, aerobic, heterotrophic bacterial populations of two impounded ecosystems were studied in a laboratory tank system. One reservoir received runoff from a rural drainage basin only, while the second received treated municipal sewage, industrial waste and heavy recreational use. Water from each reservoir was treated with 1.4 ppm final concentration of diuron and studied for total bacterial counts and nutritional source types. Control tanks were studied concurrently. Total counts increased shortly after diuron addition; however, this was followed by a decrease to a level below the control. Reduction in diversity was significantly greater in water from the polluted reservoir, but chromagenic bacteria were significantly reduced in the non‐polluted reservoir. The effects on isolation of specific nutrient types from the two systems following herbicide addition revealed that starch utilizers were the most affected group. Bacteria growing on protein or glucose salts were essentially unaffected. (KEY TERMS: Diuron; Bacteria; Herbicides in Aquatic Environments; Chromagenic Bacteria: Natural Aquatic Bacteria.)

EFFECTS OF SELECTED HERBICIDES ON BACTERIAL POPULATIONS IN NONTREATED AND TREATED WATER1

“…They also observed an increase in bacterial counts as the result of paraquat (a member of the same chemical family as diquat) addition. Guthrie, Cherry, and Ferebee (1974) reported that diuron (1.4 mg/l) changed the natural bacterial population balance in lake aquatic systems. Some members of the population were inhibited and others possibly were stimulated by diuron.…”

“…Future studies should attempt to identify the types of bacteria that survive and/or undergo selective enrichment. Although Guthrie, Cherry, and Ferebee (1974) observed that diuron persisted during a test period of 28 days, the possible degradation of it and other herbicides used in aquatic weed control should be established.…”

“…Little information about the fate of diuron in an aquatic system is available. Diuron applied at 0.7 mgll and 1.4 mg/l to a laboratory culture battely caused a. reduction in the total bacterial counts and selective enrichment (Guthrie, Cherry, and Ferebee, 1974).…”