Differences in benthic macroinvertebrate structure of headwater streams with extreme hydrochemistry

Abstract

A synoptic study of acidified mountain streams covering six Czech sites was performed. The aim was to provide biological data from small mountain streams in catchments with historically high acid atmospheric deposition, which have so far been subject of intensive long-term monitoring of hydrology and hydrochemistry only, in order to follow the development of the structure of benthic macroinvertebrates in the course of recovery from acidification. We focused on small headwater streams with minimum human influence in the catchment and relatively low concentrations of dissolved organic matter. The sites were classified according to their water pH status: three of them were strongly acidified (pH 4.07-4.57, concentration of reactive aluminium R-Al 448-1913 µg L −1 ), two were moderately acidified (pH 5.08-6.38, R-Al 52-261 µg L −1 ) and one non-acidified (pH 7.63-7.89, R-Al 12-59 µg L −1 ). The largest biotic difference detected by PCA was in the presence of the caddisflies Drusus, Rhyacophila, and Chaetopteryx villosa and stoneflies Leuctra pseudocingulata and Diura bicaudata. The results indicate that at the most acidified sites (the Lysina and the right branch of the Litavka), the process of biological recovery has not started yet due to an insufficient increase in stream pH. Indeed, MAGIC modelling published earlier shows that significant increases cannot be expected in the following decades. An average pH of at least 4.5 is needed for return of less acid-tolerant taxa such as Diura bicaudata, Leuctra major, L. pseudocingulata, L. pseudosignifera, Drusus or Rhyacophila. However, at the Sklářský potok -Jizerka site, both the clear-cut of mature spruce plantations in [1984][1985][1986][1987][1988][1989][1990] and the regional drop in SO2 emissions in the 1990s resulted in a decline of acid deposition and rising streamwater pH. Mean annual pH at the Sklářský potok -Jizerka outlet increased from 4.0 (1982-1985) to 5.3 (1990-1994), but episodic acidification has still resulted in a delay in recovery of the biota, particularly acid-sensitive species, which may be expected within a couple decades.

Impacts of an extreme flood on the ecosystem of a headwater stream

“…Continuing recovery from acidification during the two years after the flood brought a further improvement in water chemistry (Fig. 5), and the abundance of both dominant and less acid-tolerant species increased, as reported also from other acidified headwater catchments in the Czech Republic (Horecký et al 2013;Beneš et al, 2017) and abroad (Edwards, 1998;Garmo et al, 2014;Stockdale et al, 2014).…”

“…6), being similar to other first-order headwater streams of the European Black Triangle as well as other mountain streams affected by anthropogenic acidification (Horecký et al, 2013;Stockdale et al, 2014). While such streams are very susceptible to hydrological extremes (floods and droughts), the most dominant species, such as the omnivorous stoneflies Leuctra nigra and Nemurella pictetii and the predatory caddisfly Plectrocnemia conspersa, are well adapted to such conditions (Horecký et al, 2006(Horecký et al, , 2013 and so survived the flood of 2010 (Appendix 1).…”

“…In Central Europe, the biota in many mountain streams has been affected by acid atmospheric deposition and its consequences (Horecký et al, 2013). Anthropogenic emissions of acidic precursors (sulphur and nitrogen oxides, and ammonia) increased from the industrial revolution of the 19th century and culminated in the late 1980s (Schöpp et al, 2003).…”

Assess hydrological responses to a warming climate at the Lysina Critical Zone Observatory in Central Europe

“…The catchment has been monitored since 1988 for the purpose of understanding long‐term hydrobiogeochemical patterns in the base‐poor and acid‐sensitive catchment. Hydrologic and geochemical observations within Lysina have helped us understand water yield mechanism of a forested catchment (Buzek et al, 1995; Yu et al, 2015), biogeochemical response to high loadings of acidic deposition (Hrus̆ka et al, 2002; Krám et al, 2017; Oulehle et al, 2012), hydrobiological status (Horecký et al, 2013), chemical weathering processes (Hayes et al, 2020), and climate change impacts on hydrological and biogeochemical processes (Benčoková, Hruška, et al, 2011; Benčoková, Krám, et al, 2011).…”

Benthic Communities of Low-Order Streams Affected by Acid Mine Drainages: A Case Study from Central Europe

“…Here, mayflies were totally absent, and stonefly and caddisfly assemblages consisted of just a few tolerant taxa. As stated above, mayflies have been recognized as being particularly sensitive to metal pollution in streams and quickly disappear with decreasing pH [63]. Nevertheless, some EPT taxa may be largely tolerant and even dominate at AMD-polluted sites [12,22,59,64].…”