LEPORI, F. and ORMEROD, S. J. (2005) Effects of spring acid episodes on macroinvertebrates revealed by population data and in situ toxicity tests. Freshwater Biology, 50 (9). pp. 1568-1577. ISSN 0046-5070
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1. While streams in Europe and North America are now recovering chemically from chronic acidification, severe episodic acidification continues to threaten sensitive biota. To appraise further the biological importance of episodic acidification, we surveyed the distribution of the mayfly Baetis alpinus in streams in the Southern Alps (Canton Ticino, Switzerland) in relation to runoff acidity during spring floods. Moreover, to improve mechanistic understanding, in situ toxicity assays were carried out on nymphal B. alpinus during low flows and spring floods, both in streams prone to acid episodes and in well-buffered controls. 2. Streams surveyed for invertebrates represented three groups which contrasted in susceptibility to episodic acidity. Group one included streams that were acid (alkalinity <0) in spring; group two streams were susceptible to acid episodes because of low base-flow alkalinity (<200 μeq L−1); and group three streams were well-buffered and unlikely ever to be acid. The abundance of B. alpinus was similar among groups during stable flows in winter and summer, but was significantly lower in groups one and two following spring snowmelt. 3. During the bioassays, control streams remained circumneutral to alkaline (pH >6.4). By contrast, episodic streams were circumneutral at low flows, but became acid (pH 4.5–5.6 and total dissolved aluminium to 276 μg L−1) during intense spring snowmelt. After 15-day exposures, nymphal B. alpinus survival in the circumneutral control streams exceeded 92% irrespective of flow. In the episodic streams, survival matched the controls during low flows, but declined significantly to 10–20% during acid episodes in spring. Shorter exposure (2–4 days) to pH 5.5–5.7 did not cause significant mortality either during the exposure or over the following 7 days, indicating that B. alpinus might recover from short acid episodes. 4. Our data suggest that the spring distribution of B. alpinus in acid sensitive parts of the Alps directly reflects the toxicity of acid runoff during snowmelt. Our study illustrates that even mild episodic acidification can have significant consequences in Alpine streams for one of the most important invertebrate indicators of acidity.
Item Type: | Scientific journal article, Newspaper article or Magazine article |
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Subjects: | Biological Sciences > Biology > Environmental biology Biological Sciences > Biology > Marine/Freshwater biology Biological Sciences > Biology > Marine/Freshwater biology > Freshwater biology Biological Sciences > Biology > Population biology Biological Sciences > Biology > Ecology Biological Sciences > Biology > Ecology > Ecosystem ecology & land use Biological Sciences > Biology > Ecology > Ecotoxicology Physical sciences > Chemistry > Environmental chemistry Physical sciences > Science of aquatic & terrestrial environments > Science of aquatic & terrestrial environments not elsewhere classified |
Department/unit: | Dipartimento ambiente costruzioni e design > Istituto scienze della Terra |
Depositing User: | Fabio Lepori |
Date Deposited: | 09 Aug 2021 06:27 |
Last Modified: | 09 Aug 2021 06:27 |
URI: | http://repository.supsi.ch/id/eprint/12711 |
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