The use of invertebrates as indicators of environmental change in alpine rivers and lakes

Abstract

1In alpine regions climatic change will alter the balance between water sources (rainfall, ice-2 melt, snowmelt, and groundwater) for aquatic systems, particularly modifying the relative 3 contributions of meltwater, groundwater and rain to both rivers and lakes. Whilst these 4 changes are expected to have implications for alpine aquatic ecosystems, little is known about 5 potential ecological tipping points and associated indicator taxa. Within the EU-FP7 6 ACQWA project we examined changes in biotic communities along a gradient of glacier 7 influence for two study systems; (1) a stream network in the French Pyrénées and (2) a 8 network of lakes in the Italian Alps, with the aim of identifying potential indicator taxa 9 (macroinvertebrates and zooplankton) of glacier retreat in these environments. To assess 10 parallels in biotic responses across streams and lakes, both primary data and findings from 11 other publications were synthesized. Using TITAN (Threshold Indicator Taxa ANalysis) 12 threshold changes in community composition of river taxa were identified at <5.1% glacier 13 cover and <66.6% meltwater contribution. Below this point the loss of cold stenothermic 14 benthic invertebrate taxa, Diamesa spp. and the Pyrenean endemic Rhyacophila angelieri was 15 apparent. Some generalist taxa including Protonemura sp., Perla grandis, Baetis alpinus, 16Rhithrogena loyolaea and Microspectra sp. increased when glacier cover was < 2.7 % and < 17 52 % meltwater. Patterns were not as distinct for the alpine lakes, due to fewer sampling 18 sites; however, Daphnia longispina grp. and the benthic invertebrate groups Plectopera and 19Planaria were identified as potential indictors. While further work is required to assess 20 potential indicator taxa for alpine lake systems findings from alpine river systems were 21 consistent between methods for assessing glacier influence (meltwater contribution/glacier 22 cover). Hence, it is clear that this approach (TITAN) could become a useful a management 23 tool, enabling: (i) the identification of taxa particularly sensitive to glacier retreat; and (ii) 24 conservation efforts/resources to be better directed in alpine aquatic systems. 25

Towards a definition of environmental niches in alpine streams by employing chironomid species preferences

“…Still, our models illustrate the adaptation and environmental tolerance of this species group, being able to withstand harsh conditions, which we found to be their niche in alpine streams. Although we applied a different approach in contrast to other authors (Khamis et al, 2014), we congruently identified several species adapted to a high glacial influence (several Diamesa species). We are aware that the geographic scope of this study, which covered remote parts of the Eastern Alps, is relatively small compared to the geographic distribution of the chironomid species identified (e.g.…”

“…However, instead of comparing niche-based processes with neutral models (Vergnon et al, 2009), we provided modelled requirement-based species preferences in relation to key-environmental variables that mostly affect community structures. While other studies have used coarse indices to quantify glacial influence and selected indicator species for their changes (Khamis et al, 2014), we used reach-scale environmental variables to understand the local stressors provoking different community structures. Nevertheless, we identified similar patterns and indicator taxa.…”

“…The benthic biota is expected to possess a high potential to indicate long-term environmental changes not only due to their high abundance in alpine rivers, and adequate species richness, but also because of the observed sensitivity to environmental change (Ward, 1994;Milner et al 2001;Khamis et al, 2014). Several conceptual models (Milner & Petts, 1994;Milner et al, 2001), distribution and succession concepts Lods-Crozet et al, 2001a) and studies at species level (Lencioni & Rossaro, 2005) are available for alpine stream ecosystems as well as their key species.…”

Small lakes in big landscape: Multi-scale drivers of littoral ecosystem in alpine lakes

“…The two macro-regions are characterised by major climatic differences in water availability and temperature (López-Moreno et al, 2008), with Mediterranean climate being generally warmer, drier and comparatively of larger inter-seasonal variability than the Atlantic climate. This means potential tipping points in alpine lake ecosystems due to climate change effects (particularly through sharp changes in water temperature and dynamics; Khamis et al, 2014) is likely to happen faster across horizontal than vertical gradients in biogeographical boundary regions such as this one, with potentially unexpected effects. The changes could affect ecological processes such as niche retention in benthic biota, but they could also potentially affect longer-term biotic speciation in these regions (Doebeli and Dieckmann, 2003).…”

“…For example the functional diversity of alpine stream benthic invertebrate communities can be particularly affected by climate change-driven glacier retreat (Khamis et al, 2014).…”