Some effects of smelter pollution upon aquatic vegetation near Sudbury, Ontario

The numbers of submerged and floating macrophyte species present in 29 ponds and lakes are inversely related to dissolved sulphates, concentrations of which rise sharply within about 4 to 5 miles of the smelters. Although pollution often leads to strong acidification, numbers of species are low even where sulphuric acid is almost wholly neutralized, and waters are above pH 6. Because sulphate ions are unlikely to be toxic at the levels encountered, and since pollution also increases the concentration of heavy metals in the waters, it is suggested that these may reach toxic levels near the smelters. Leptodlctyum riparium and Eleocharis acicularis v. submersa seem to be most tolerant of smelter pollution, while Utricularia vulgaris and Potamogeton epihydrus v. nuttallii appear rather sensitive to it.