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

Abstract

Abstract. Two branches forming the headwaters of a stream in the Czech Republic were studied. Both streams have similar catchment characteristics and historical deposition; however one is rain-fed and strongly affected by acid atmospheric deposition, the other spring-fed and only moderately acidified. The MAGIC model was used to reconstruct past stream water and soil chemistry of the rain-fed branch, and predict future recovery up to 2050 under current proposed emissions levels. A future increase in air temperature calculated by a regional climate model was then used to derive climate-related scenarios to test possible factors affecting chemical recovery up to 2100. Macroinvertebrates were sampled from both branches, and differences in stream chemistry were reflected in the community structures. According to modelled forecasts, recovery of the rain-fed branch will be gradual and limited, and continued high levels of sulphate release from the soils will continue to dominate stream water chemistry, while scenarios related to a predicted increase in temperature will have little impact. The likelihood of colonization of species from the spring-fed branch was evaluated considering the predicted extent of chemical recovery. The results suggest that the possibility of colonization of species from the spring-fed branch to the rain-fed will be limited to only the acid-tolerant stonefly, caddisfly and dipteran taxa in the modelled period.

Differences in benthic macroinvertebrate structure of headwater streams with extreme hydrochemistry

“…A gradual return of acid-sensitive species is expected with changes in water chemistry, particularly pH increases and R-Al concentration decreases, as reported, e.g., by Tipping et al (2002) and Raddum & Fjellheim (2003 Braukmann (2001) as acid-sensitive and only few species considered partially acid-tolerant (third class acid) were found in the strongly acidified sites during the studied period. A comparison of the benthic community structure found at LIR with the results of previous studies (Horecký et al 2006;Hardekopf et al 2008) also does not show any significant difference. The newly found taxa at the site LIR [e.g., Notonecta glauca L., 1758, Hybomitra sp.…”

“…Based on these and previously published results (Horecký et al 2002(Horecký et al , 2006Hardekopf et al 2008), a return of some species that are less tolerant to stream acidity to the strongly acidified sites may be expected, if pH increases at least over 4.5. In poorly mineralized mountain streams these could be e.g.…”

“…The basic catchment characteristics are shown in the Table 1, for further details see Hardekopf et al (2008), Krám et al (1997), and Křeček et al (2006).…”

“…Moreover, Lysina is in two international networks of the International Cooperative Programme -ICP Integrated Monitoring and ICP Waters, both organized under the Economic Commission for Europe of the United Nations. Litavka -right branch (referred to as the Litavka rain-fed branch by Hardekopf et al 2008) belongs to the Czech GEOMON network of small forested catchments.…”

“…Nowadays, this reserve is gradually leaching (Alewell et al 2000), resulting in only slight increases of pH and decreases of ionic concentrations forms of aluminium (so called hysteresis; Kopáček et al 2002). Results of dynamic hydrochemical modelling of small catchments (Hruška et al 2002;Hardekopf et al 2008) show that acidification, despite decreasing trends in atmospheric deposition, will still affect freshwater ecosystems for a significant period of time.…”