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Presented at the NABS Annual meeting, Pittsburgh, Pennsylvania, 2002
in Disturbance Ecology I
EPISODIC ACIDIFICATION IN SWISS ALPINE STREAMS: CHEMICAL CAUSES AND CONSEQUENCES TO BENTHIC COMMUNITIES.
F. Lepori1, A. Barbieri2, and S.J. Ormerod1. 1Catchment Research Group, School of Biosciences, Cardiff University, PO Box 915, Cardiff CF10 3 TL, U.K., 2Laboratorio Studi Ambientali, riva Paradiso 15, 6900 Paradiso, C.H.
The most important mountain landscape in Europe, the Alps have been affected by airborne pollution. Deposition of sulfur and nitrogen has led to the acidification of surface waters with low buffer capacity. While the acid-base status of remote alpine lakes has been investigated since the 1980’s, running waters have received surprisingly little attention so far. However, in view of their possible sensitivity, we hypothesized that alpine streams might be affected by acidification, with potential for biological damage. We surveyed streams in one of the regions most at risk from deposition (Canton Ticino, southern Switzerland) for water quality and macroinvertebrates, and we carried out in situ bioassays using sensitive invertebrate taxa. Severe episodes of acidification occurred in most streams, particularly during snowmelt, when some experienced low pH and high aluminum concentrations. Biological data indicated that such conditions were toxic to sensitive invertebrates and affected the community structure. A pulse of nitrate contributed considerably to snowmelt episodes. Considered symptomatic of nitrogen saturation, this phenomenon notably affects areas in northeastern U.S., but is reported here among the first times for Europe.
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