Impact of mild experimental acidification on short term invertebrate drift in a sensitive British Columbia stream

Abstract

We report daytime drift behavior of lotic macroinvertebrates following short term (12 h) additions of HCl or HCl plus AlCl, to a circumneutral softwater (alkalinity ca. 100 peq l-') mountain stream in British Columbia, Canada. Addition of HCl (pH reduced from 7.0 to 5.9) resulted in an overall tripling of invertebrate drift density with rapid (< 1 h) increases in chironomid Diptera and Trichoptera. Small Ephemeroptera also entered the drift at high densities, but were delayed about 6 h. Addition of AlCl, (0.7 1 to 0.95 mg l-l total Al3 + ) in HCl (stream pH reduced to 5.9) resulted in an overall 6-fold increase in invertebrate drift, with rapid increases by Ephemeroptera and delayed responses by chironomids and Trichoptera. These results suggest that the behavior of several macroinvertebrates from low alkalinity, unacidified streams can be altered by simulations of short-term, mild acidic deposition events. Further, the magnitude and timing of entry into the drift varies among taxonomic groups with the presence or absence of low concentrations of aluminum ions.

Experimental acidification of two biogeochemically-distinct neotropical streams: Buffering mechanisms and macroinvertebrate drift

“…This study provides an initial "worst-case" scenario of how two tropical streams respond to short-term pH declines. Our results are in line with previous studies that have shown that acidification experiments can provide valuable insights into the ecological (Bernard et al, 1990;Hall et al, 1980) and biogeochemical (Hedin et al, 1990;Hruska et al, 1999;Goss and Norton, 2008) responses to pH drops (Table 5).…”

“…Entrance into drift is a well-known macroinvertebrate response to disturbances and increases in drift have been reported following episodic acidification (Bernard et al, 1990;Hall et al, 1980;Ormerod et al, 1987). Previous studies have shown that macroinvertebrates might show delayed responses to environmental stressors.…”

“…Contrasting with previous studies, cladocerans and copepods were dominant in drift during acid addition. Although those two groups were not dominant in either benthic or drift samples at La Selva, they are known to occur in drift after acidification in temperate streams (Bernard et al, 1990).…”

“…Episodic acidification can be caused by base cation dilution from high discharge (due to snow melt or precipitation), flushing organic acids or oxidized nitrogen and sulfur from soils, and inputs of marine aerosols (Wigington et al, 1996). These low pH events can have detrimental effects on fish and macroinvertebrates (Bernard et al, 1990). While much research has been conducted in North American and European streams on the causes and consequences of episodic acidification, tropical streams have received little attention (Kuylenstierna et al, 2001).…”

Performance of selected macroinvertebrate-based biotic indices for rivers draining the Merendon Mountains region of Honduras

“…The Costa Rican ASPT system was quite effective, this is not surprising as this was calibrated in Central America and had the lowest number of non-scoring families at nine. Three of these were tricopteran families (Apataniidae, Brachycentridae and Rhyacophilidae) taxa which generally tend to be sensitive to various pressures (Bernard, Neil & Rowe, 1990;Vuori, 1996;Maret et al, 2003;Menetrey et al, 2008). However, none of these taxa left scoreless by the Costa Rican BMWP was either widespread or present in large numbers and so would not be considered important as indicators.…”