Effects of episodic acidification on macroinvertebrate assemblages in Swiss Alpine streams

Abstract

Summary 1. Despite long‐standing ecotoxicological evidence that episodes of acidification in streams are important biologically, there is still uncertainty about their effects on invertebrate communities. We surveyed 20 streams in an acid sensitive Alpine area (Canton Ticino, Switzerland), where episodes are driven by snowmelt in spring and by rainstorms at other times of the year. Samples of water and macroinvertebrates were collected in pre‐event conditions (winter and summer) and during periods of high flow (spring and autumn). 2. Using pH, [Ca2+] and [Aln+], streams were clustered into six acid–base groups that were either well buffered (groups 4–6), soft‐water with stable pH (group 3), or poorly buffered with low pH at high flow (groups 1 and 2). 3. Severe episodes occurred during snowmelt, when the group 1 streams became acidic with pH down to 5.0 and [Aln+] up to 140 μg L−1. pH declined to 6.2 in streams of group 2, but remained > 6.6 in groups 3–6. 4. Detrended canonical correspondence analysis showed that the streams sensitive to episodes (groups 1 and 2) had different invertebrate assemblages from well‐buffered sites (groups 4 and 5) or soft‐water stable streams (group 3), with faunal differences largest following spring snowmelt. Empididae, Isoperla rivulorum, Rhithrogena spp. and Baetis spp. were scarce in streams sensitive to episodes (groups 1 and 2). By contrast, Amphinemura sulcicollis was scarcer in hard‐water streams (groups 4–6). Taxonomic richness was lower in the episodic streams of group 1 than in other streams. 5. Together, these results indicate clear biological differences between acid‐sensitive streams with similar low‐flow chemistry but contrasting episode chemistry. Severe episodes of acidification appear to affect macroinvertebrate assemblages in streams in the southern Swiss Alps.

Phytoplankton of a mountain lake (L’adové pleso, the Tatra Mountains, Slovakia): Seasonal development and first indications of a response to decreased acid deposition

“…Snowmelt-induced episodic acidification associated with changes in water chemistry is commonly reported from mountain streams, and has frequently profound effects on their biota (e.g., Lepori et al, 2003). Studies reporting this phenomenon from mountain lakes are scarcer (Stoddard, 1995).…”

The impact of a catastrophic storm event on benthic macroinvertebrate communities in upland headwater streams and potential implications for ecological diversity and assessment of ecological status

“…The frequency, amount and intensity of rainfall, together with antecedent climatic conditions have been shown to influence the magnitude, duration and nature of episodic stream acidification occurring during such highflow conditions (Ormerod et al 1989;Kelly-Quinn et al 1996;Kowalik et al 2007). This in turn has been shown to affect benthic macroinvertebrate survival in such streams (Tierney et al, 1998;Lepori et al, 2003;Kowalik and Ormerod 2006;Tixier et al, 2009;Feeley et al, 2011). Furthermore, the increased discharges and velocities, and the resultant disturbance and movement of the streambed substrates during high-flow events alter macroinvertebrate community composition and structure within streams, especially during the peaks of high-flow periods (Robinson and Minshall, 1986;Brittain and Eikland, 1988;Resh et al, 1988;Death, 2003).…”

Predicting long-term recovery of a strongly acidified stream using MAGIC and climate models (Litavka, Czech Republic)

“…Historical deposition curves of ions were taken from those used by Kopáček et al (2001) for the nearby Bohemian Forest. These deposition sequences have been successfully used to apply the MAGIC model to three lakes in the region (Majer et al, 2003), and well represent the large changes in deposition of S and N that have occurred in central Europe in the past few decades. 2.…”

“…Large reductions in S and N inputs in the 1980s and 1990s have resulted in significant reversal of acidification in some of these fresh waters . Dynamic models have been successfully applied to many catchments in the region (Majer et al, 2003;Hruška and Krám, 2003;Kopáček et al, 2004a) and have proven to be robust in predicting changes in soil and water chemistry in response to the decreased deposition. Future predictions based on expected atmospheric emission reductions required under European Union agreements (Gothenburg Protocol -UN-ECE, 1999), however, show that recovery of these ecosystems is complicated by continued leaching of sulphate (SO 4 ), and in some cases nitrate (NO 3 ), from soils exposed to long-term deposition of these compounds (Kopáček et al, 2002;Hruška et al, 2002).…”