Ecological interactions in glacier environments: a review of studies on a model Alpine glacier

Abstract

Glaciers host a variety of cold-adapted taxa, many of which have not yet been described. Interactions among glacier organisms are even less clear. Understanding ecological interactions is crucial to unravelling the functioning of glacier ecosystems, particularly in light of current glacier retreat. Through a review of the existing literature, we aim to provide a first overview of the biodiversity, primary production, trophic networks, and matter flow of a glacier ecosystem. We use the Forni Glacier (Central Italian Alps) - one of the best studied alpine glaciers in the world - as a model system for our literature review and integrate additional original data. We reveal the importance of allochthonous organic matter inputs, of Cyanobacteria and eukaryotic green algae in primary production, and the key role of springtails (Vertagopus glacialis) on the glacier surface in sustaining populations of two apex terrestrial predators: Nebria castanea (Coleoptera: Carabidae) and Pardosa saturatior (Araneae: Lycosidae). The cryophilic tardigrade Cryobiotus klebelsbergi is the apex consumer in cryoconite holes. This short food web highlights the fragility of nodes represented by invertebrates, contrasting with structured microbial communities in all glacier habitats. Although further research is necessary to quantify the ecological interactions of glacier organisms, this review summarises and integrates existing knowledge about the ecological processes on alpine glaciers and supports the importance of glacier-adapted organisms in providing ecosystem services.

Keywords: cryophiles; ecological interactions; glacial ecosystems; glacier ecology; supraglacial ecosystem; trophic webs.

Fig. 1

(A) Geographical location of the Forni Glacier. (B) Aerial view of the glacier. CIB, Central Ice Body, EB, Eastern Basin; WB, Western Basin.

Fig. 2

Trophic web for the supraglacial habitat of the Forni reconstructed using published information for this specific site, together with dietary studies on the same species in similar areas on other mountain ranges. Dashed lines indicate trophic interactions not described in the literature that are suggested by the authors. N. castanea, Nebria castanea; P. saturatior, Pardosa saturatior; C. klebelsbergi, Cryobiotus klebelsbergi. Abundance data are from Buda et al. (2020a ) [1], Zawierucha et al. (2019a ) [2], and Turchetti et al. (2008) [3]. Other abundance data are from our own calculations (see Section III.1.e).

Fig. 3

Fluxes of metabolic substrates on the glacier and the metabolic pathways that exploit them. Organisms performing each of the pathways are represented using the same icons as in Fig. 2. AOM, allochtonous organic matter; DOM, dissolved organic matter; MM, mineral matter; supragl. sed, supraglacial sediment; subgl. sed., subglacial sediment; TOC, total organic carbon; TON, total organic nitrogen; TOP, total organic phosphorus. * = debris coverage rate from Azzoni et al. (2016); # = average colony forming units (CFU) g⁻¹ dry mass for sediments, CFU ml⁻¹ for ice, and chemical properties of DOM (as TOC, TON, TOP) from Turchetti et al. (2008); + = estimated deposition rate of allochthonous aeroplankton, estimated from air traps data from Zawierucha et al. (2019a ).