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Publications in Glacier-fed streams by NOMIS researchers

NOMIS Researcher(s)

Published in

April 8, 2025

Glacier-fed streams (GFSs) are harsh environments hosting unique, highly specialized communities. Interestingly, glaciers and their GFSs are also present in Earth’s tropical regions, where environmental characteristics contrast with GFS conditions elsewhere. Yet, despite the unique and isolated nature of tropical GFSs, little is known about their inhabitants, even though they may disappear later this century with ongoing climate change. Here, we examined diatom communities from one of the last tropical African GFSs in the Rwenzori Mountains, Uganda, to characterize the composition and diversity of this unique system. Six sediment-associated biofilm samples were collected from two reaches of a stream draining the Mt. Stanley Glacier, and the resident diatom communities were studied morphologically using light and scanning electron microscopy, as well as through the sequencing of amplicons from extracted DNA (18S and rbcL). In general, morphological results agree well with barcoding results, but each individually provides irreplaceable insights. In total, we identify 24 morphotypes utilizing light microscopy, 101 diatom Amplicon Sequence Variants (ASVs) using 18S sequences, and 65 ASVs with rbcL. Across approaches, common genera include Achnanthidium, Psammothidium, Neidium, Cymbopleura, Eunotia, and Pinnularia. However, only about half of the diversity could be assigned to the species level across methodologies, including several of the most common taxa, indicating a high level of uniqueness. Accordingly, one of the most common taxa encountered is described here as a new species, Neidium rwenzoriense sp. nov. Our results emphasize the Rwenzori Mountains as a global hotspot for endemism, and the novelty of disappearing tropical GFSs as diatom habitats.

Research field(s)
Conservation Biology, Ecology, Environmental Sciences

NOMIS Researcher(s)

Published in

March 24, 2025

As glaciers begin to disappear, technological fixes to slow or halt ice melt are emerging. But regulations are urgently required before these fixes are used widely.

Research field(s)
Conservation Biology, Environmental Sciences

NOMIS Researcher(s)

Published in

February 1, 2025

The shrinkage of glaciers and the vanishing of glacier-fed streams (GFSs) are emblematic of climate change. However, forecasts of how GFS microbiome structure and function will change under projected climate change scenarios are lacking. Combining 2,333 prokaryotic metagenome-assembled genomes with climatic, glaciological, and environmental data collected by the Vanishing Glaciers project from 164 GFSs draining Earth’s major mountain ranges, we here predict the future of the GFS microbiome until the end of the century under various climate change scenarios. Our model framework is rooted in a space-for-time substitution design and leverages statistical learning approaches. We predict that declining environmental selection promotes primary production in GFSs, stimulating both bacterial biomass and biodiversity. Concomitantly, predictions suggest that the phylogenetic structure of the GFS microbiome will change and entire bacterial clades are at risk. Furthermore, genomic projections reveal that microbiome functions will shift, with intensified solar energy acquisition pathways, heterotrophy and algal-bacterial interactions. Altogether, we project a ‘greener’ future of the world’s GFSs accompanied by a loss of clades that have adapted to environmental harshness, with consequences for ecosystem functioning.

Research field(s)
Conservation Biology, Ecology, Environmental Sciences

NOMIS Researcher(s)

Published in

January 2, 2025

Glacier-fed streams (GFS) feature among Earth’s most extreme aquatic ecosystems marked by pronounced oligotrophy and environmental fluctuations. Microorganisms mainly organize in biofilms within them, but how they cope with such conditions is unknown. Here, leveraging 156 metagenomes from the Vanishing Glaciers project obtained from sediment samples in GFS from 9 mountains ranges, we report thousands of metagenome-assembled genomes (MAGs) encompassing prokaryotes, algae, fungi and viruses, that shed light on biotic interactions within glacier-fed stream biofilms. A total of 2,855 bacterial MAGs were characterized by diverse strategies to exploit inorganic and organic energy sources, in part via functional redundancy and mixotrophy. We show that biofilms probably become more complex and switch from chemoautotrophy to heterotrophy as algal biomass increases in GFS owing to glacier shrinkage. Our MAG compendium sheds light on the success of microbial life in GFS and provides a resource for future research on a microbiome potentially impacted by climate change.

Research field(s)
Biology, Evolutionary Biology

NOMIS Researcher(s)

Published in

January 1, 2025

The rapid melting of mountain glaciers and the vanishing of their streams is emblematic of climate change1,2. Glacier-fed streams (GFSs) are cold, oligotrophic and unstable ecosystems in which life is dominated by microbial biofilms2,3. However, current knowledge on the GFS microbiome is scarce4,5, precluding an understanding of its response to glacier shrinkage. Here, by leveraging metabarcoding and metagenomics, we provide a comprehensive survey of bacteria in the benthic microbiome across 152 GFSs draining the Earth’s major mountain ranges. We find that the GFS bacterial microbiome is taxonomically and functionally distinct from other cryospheric microbiomes. GFS bacteria are diverse, with more than half being specific to a given mountain range, some unique to single GFSs and a few cosmopolitan and abundant. We show how geographic isolation and environmental selection shape their biogeography, which is characterized by distinct compositional patterns between mountain ranges and hemispheres. Phylogenetic analyses furthermore uncovered microdiverse clades resulting from environmental selection, probably promoting functional resilience and contributing to GFS bacterial biodiversity and biogeography. Climate-induced glacier shrinkage puts this unique microbiome at risk. Our study provides a global reference for future climate-change microbiology studies on the vanishing GFS ecosystem.

Research field(s)
Biology, Evolutionary Biology