The status of glaciers is alarming globally with still unknown effects on freshwater ecosystems. Thegeneral aim of this study was to investigate the structural and functional changes in the macroinvertebrate communityin stream networks fed by shrinking glaciers in relation to environmental variables. Feeding glaciers haddifferent surface areas and retreating rates. We selected 10 study sites in the Italian Alps, spanning five kryal, twoglacio-rhithral, two krenal and one proglacial pond, sampled twice in summer 2018. Eight of these sites weresampled previously between 1996 and 2014. In all, in 2018, > 15,000 individuals (73 taxa) were collected, of which82 % were chironomids (Diptera Chironomidae) (33 taxa). Diamesa zernyi gr. (Chironomidae Diamesinae) wasthe most frequent and abundant taxon, followed by Oligochaeta and Chironomidae Orthocladiinae. Taxonomical(Shannon index) and functional (based on functional feeding groups) diversity both increased with decreasingglacial influence (estimated as glacial index, GI, based on distance from the glacier snout of each site and glacierarea), from kryal to glacio-rhithral and krenal habitats. Taxa distribution was explained mainly by GI, maximumwater temperature, substrate stability, silica, epilithic chlorophyll-a, and benthic particulate organic matter. Thesame variables explained temporal differences in the community structure for the eight sites re-sampled in the lasttwo decades. Among the taxa best associated with high GI was the chironomid Diamesa steinboecki, that in 2018was exclusive of the kryal sites with GCC (% glacier cover in the catchment, expressed in a range from 0 %–100 %)> 50 % and maximum temperature < 5 °C. This species was absent only in the kryal site C0 (GCC = 33 %), whereit was dominant in 1996 –1997. This site was still fed by ice melt in 2018, but resembled a glacio-rhithral site inhabitat features (e.g. maximum temperature > 6 °C) and biota (e.g. % Diamesa spp. < 30 %). In C0, it was evidentthat in the last 22 years, the macroinvertebrate community changed remarkably. This change was due to upstreammigration of generalist insect species to sites once exclusive for kryal species with consequent changes in food webstructure and loss of strictly kryal species, first D. steinboecki that we propose as the “flagship” species of the kryalin the Alps. The site C0 represents a “tipping point”, showing us the effects of climate change on alpine biodiversityin a relatively short period; unfortunately, there are many such sites in the Italian Alps.
How do macroinvertebrate communities respond to declining glacial influence in the Southern Alps?In the summer of 2018, we compared the macroinvertebrate communities of four streams fed by retreating glaciers and of one pro-glacial pond in the Italian Alps. The general aim was to determine if habitats fed by glaciers with different surface areas host different communities along a longitudinal gradient and to identify which environmental variables can predict these differences. Eight sampling sites were selected with different glacial influences given by the Glacial Index (GI, range 0-1). This index takes into consideration the distance from the snout and glacier surface area. Five were classified as kryal, fed mainly by ice melt and lay within 1 km of the snout; two as glacio-rhithral, with mixed contributions and > 1 km from the snout; and one as a pro-glacial pond, which lays within 50 m from the snout and was fed by ice melt. Chironomids were the most frequent (100 %) and abundant taxa (80 %), followed by EPT (Ephemeroptera, Plecoptera, Trichoptera) which represented 9 % of total abundance. All kryal sites (MA1, CR0, CR1, AG1) were dominated by chironomids (> 98 %), except for C0, which hosts a community resembling that of glacio-rhithral sites (C2, CR2), which are more diversified and have approximately 60 % of their communities composed of chironomids. While C0 is fed mainly by ice-melt, its GI was lower (0.3) than that of the other kryal sites (0.5-1.0) because of the small size of the feeding glacier (0.14 ha). These results emphasise that the glacier surface area affects the benthic fauna and that the GI should be considered when classifying different types of sites. GI was also selected as one of the best predictors of faunal changes by distance-based redundancy analysis (dbRDA), which was performed to investigate the relationships between taxa distribution and environmental conditions, along with the values of maximum water temperature and chlorophyll a concentration. Overall, this study provides new insights into how different glacial influences affect the macroinvertebrate communities of freshwater habitats.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.