Whole-lake experiments were conducted on three ponds in interior Alaska to test the effects of calcium magnesium acetate (CMA), an experimental road deicer, on aquatic organisms. The CMA added to the test ponds equalled approximately one chemical application applied to 0.4 km of a typical section of road (one lane) draining entirely to a small pond. Calcium elevation did not persist into the next summer; it may have been flushed out by snowmelt. Acetate from the CMA mixture was apparently rapidly taken up by aquatic organisms and cycled for several months, depleting dissolved oxygen in the water. Dissolved oxygen became extremely low in a small pond of about 2,600 m3treated with 55 mg/L calcium acetate (calculated from calcium elevation). Bacteria and algae both appeared to be stimulated by CMA additions, as indicated by higher standing crops in treated ponds. The algae were probably stimulated by bacterial metabolism products of the acetate, or by phosphorus in the CMA used. Cladocerans were more dense in treated ponds than in control ponds, probably because more food (bacteria and algae) was available. Salmonid fishes, not present in the test ponds, might be stressed by low dissolved oxygen caused by CMA.