This report describes laboratory studies with volcanic ash intended to aid the assessment of the possible effects of ash presence on the blue-green algal populations in lakes. Bioassays using leachate from volcanic ash of the May 18, 1980, eruption of Mount St. Helens, Wash., indicate that leachate derived from ash collected at Richland, Washington, is toxic to the blue-green alga Anabaena flos-aquae, whereas leachate from ash collected at Moses Lake, Wash., is not. The difference in the toxicity of the two leachates may be attributable to differences in concentration of cationic-exchangeable, dissolved, organic compounds. Seventeen percent of the dissolved organic carbon from the leachate from ash collected at Richland was retained on a cation-exchange column, whereas only six percent of the dissolved organic carbon from the leachate from ash collected at Moses Lake was retained. Anabaena flos-aquae cultures spiked with dilutions as large as 1 to 250 of leachate derived from volcanic ash collected at Richland showed toxic effects, whereas cultures spiked with a 1 to 25 dilution of leachate derived from ash collected at Moses Lake showed no toxic effects.
The toxic components of the volcanic ash are nonuniformly distributed over the ash fall area. Preliminary data indicate that the toxic components may belong to one or more of the following classes of substances: {1) cationic organic compounds such as amines; (2) highly hydrophobic (sparingly soluble) organic compounds such as phenols that interact with and are retained by the cation-exchange-resin matrix; or (3) metal-organic complexes that are retained by interaction of the metal with the cation-exchange resin.
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