Diatoms from the Spring Ecosystems Selected for the Long-Term Monitoring of Climate-Change Effects in the Berchtesgaden National Park (Germany)

Marco Cantonati,Dimitri Bernabè,Abdullah A Saber,Daniel Spitale,Kurt Lichtenwöhrer,Olena Bilous,Stefano Segadelli,Reinhard Gerecke,Nicola Angeli

doi:10.3390/w14030381

Abstract

We studied diatoms from the fifteen springs selected in the Berchtesgaden National Park on behalf of the Bavarian State Ministry for the Environment to be sentinel environments of climate-change effects. For three of these springs, diatom data based on samples taken in 1997 were also available. A total of 162 species belonging to 49 genera were found sampling three microhabitat types (lithic materials, bryophytes, surface sediments). The cumulative percentage of all species included in a threat category including endangered species was 43%, confirming previous findings for comparable environments of the Alps. We could find a statistically significant positive association between the Meinzer variability index for discharge and the cumulative relative abundance of aerial diatom species. This study thus highlighted once again the relevance of discharge (and associated water-level) variability as an environmental determinant of diatom assemblages in spring ecosystems. Increased nitrate concentrations in some springs, likely due to diffuse airborne pollution and, locally, to impacts such as forest management, game, and cattle, led to a relevant occurrence of eutraphentic diatom species. Our results show a segregation of the older data in non-parametric diatom-based ordinations, suggesting a strong potential for the use of spring diatoms in studies aiming at tracking the effects of climate and environmental change.

Highlights

Diatoms are a group of unicellular microalgae characterised by a silica frustule—with a structure often compared to a pillbox—that encloses the cell
The 15 springs considered for this work (Table 1) were: Sommerbichel—source area
(BeNP-459) and source on the right bank of Klausbach (Klaustal-Hintersee) (BeNP-462); Schwarzbrunnen, western source (Klaustal-Hintersee) (BeNP-503); Klausbach, source flowing from N oh Hintersee (Klaustal-Hintersee) (BeNP-519); Eckau, source in the Eckaugraben (Klaustal-Hintersee) (BeNP-536); rheocrene near Bartler, Wimbachklamm S-exit (Wimbach)

Summary

Introduction

Diatoms are a group of unicellular microalgae characterised by a silica frustule—with a structure often compared to a pillbox—that encloses the cell. Diatoms are common in fresh, brackish, and salty waters, and in all terrestrial habitats where some moisture is at least sporadically available. A notable diatom-taxa richness is typically found in oligotrophic freshwater systems (e.g., [4]). Notwithstanding the special role of these systems for biodiversity conservation, revealed, for instance, by high numbers of rare and endangered Red-List taxa [5,6] and the relevant occurrence of endemic diatom taxa in the most isolated ones [7], diatoms in oligotrophic aquatic environments have been less-intensively studied than those in more impacted fresh waters [8]. Oligotrophic aquatic habitats, such as headwaters, if indepth studied, may provide important evidence for the identification of pristine/reference sites to inform conservation and restoration efforts. These kinds of habitats are becoming increasingly rare due to direct and indirect human impacts

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Conclusion