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EXPERIMENTAL ACIDIFICATION OF A STREAM TRIBUTARY TO HUBBARD BROOK
Citation:
Hall, R. AND G. Likens. EXPERIMENTAL ACIDIFICATION OF A STREAM TRIBUTARY TO HUBBARD BROOK. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/M-85/011 (NTIS PB85222792), 1985.
Description:
Long (5 mo.) and short-term (1 h to 2 days) effects of acidic pH have been measured in a poorly buffered mountain stream within the Hubbard Brook Experimental Forest, New Hampshire. Over a 5-month period aluminum, calcium, magnesium, and potassium were mobilized into the stream water during experimental acidification, and nitrogen was lost via invertebrates and organic matter. Periphyton biomass increased at low pH and fungal densities increased. Emergence of adult mayflies, stoneflies and true flies decreased, whereas immature invertebrates in the drift increased. Short-term pulses of acid also changed the stream ecosystem as indicated by significant net fluxes of organic carbon, nitrogen, and phosphorus in biologically bound forms. Aluminum chloride was added to the stream to simulate increased aluminum concentrations during snowmelt. A significant decrease in pH and dissolved organic carbon (DOC) occurred, as well as an increase in foam accumulation at the stream surface. Foam production is thought to be due to decreased surface tension of the water. A 20% reduction of surface tension of stream water was measured in the laboratory. The cause of the reduction is postulated to be the formation of organo-aluminum complexes in the stream. Increases in aluminum concentration were accompanied by changes in both terrestrial and aquatic drift behavior. Six citations are given for complete publications.