Patterns and Drivers of Extracellular Enzyme Activity in New Zealand Glacier-Fed Streams

In glacier-fed streams, ecological windows of opportunity allow complex microbial biofilms to develop and transiently form the basis of the food web, thereby controlling key ecosystem processes. Using metagenome-assembled genomes, we unravel strategies that allow biofilms to seize this opportunity in an ecosystem otherwise characterized by harsh environmental conditions. We observe a diverse microbiome spanning the entire tree of life including a rich virome. Various co-existing energy acquisition pathways point to diverse niches and the exploitation of available resources, likely fostering the establishment of complex biofilms during windows of opportunity. The wide occurrence of rhodopsins, besides chlorophyll, highlights the role of solar energy capture in these biofilms while internal carbon and nutrient cycling between photoautotrophs and heterotrophs may help overcome constraints imposed by oligotrophy in these habitats. Mechanisms potentially protecting bacteria against low temperatures and high UV-radiation are also revealed and the selective pressure of this environment is further highlighted by a phylogenomic analysis differentiating important components of the glacier-fed stream microbiome from other ecosystems. Our findings reveal key genomic underpinnings of adaptive traits contributing to the success of complex biofilms to exploit environmental opportunities in glacier-fed streams, which are now rapidly changing owing to global warming.

show abstract

Section: Resultssupporting

confidence: 62%

Genomic and metabolic adaptations of biofilms to ecological windows of opportunity in glacier-fed streams

et al. 2022

Self Cite

View full text Add to dashboard Cite

show abstract

“…DNRA, if not conducive to N2O production, would enhance nitrogen recycling within epilithic biofilms through ammonia assimilation by algae and cyanobacteria, for instance. Our genomic evidence for nitrogen recycling that potentially overwhelms nitrogen losses through denitrification is corroborated by flux measurements from microbial mats in Antarctic GFSs 50 , and highlights recycling as a strategy to cope with nutrient limitation in glacier ecosystems [50][51][52] . Strikingly, we found only few MAGs, mostly belonging to Deinococcota, Gammaproteobacteria, Beijerinckiaceae and Crenarchaeota, involved in the oxidation of ammonia and nitrite potentially leading to the accumulation of nitrate.…”

Section: Further Genomic Insights Into the Nitrogen Cycle Revealed The Dissimilatory Nitratesupporting

confidence: 55%

Genomic and metabolic adaptations of biofilms to ecological windows of opportunities in glacier-fed streams

Busi

Bourquin

Fodelianakis

et al. 2021

Preprint

Self Cite

View full text Add to dashboard Cite

Microorganisms dominate life in cryospheric ecosystems. In glacier-fed streams (GFSs), ecological windows of opportunities allow complex microbial biofilms to develop and transiently form the basis of the food web, thereby controlling key ecosystem processes. Here, using high-resolution metagenomics, we unravel strategies that allow biofilms to seize this opportunity in an ecosystem otherwise characterized by harsh environmental conditions. We found a diverse microbiome spanning the entire tree of life and including a rich virome. Various and co-existing energy acquisition pathways point to diverse niches and the simultaneous exploitation of available resources, likely fostering the establishment of complex biofilms in GFSs during windows of opportunity. The wide occurrence of rhodopsins across metagenome-assembled genomes (MAGs), besides chlorophyll, highlights the role of solar energy capture in these biofilms. Concomitantly, internal carbon and nutrient cycling between photoautotrophs and heterotrophs may help overcome constraints imposed by the high oligotrophy in GFSs. MAGs also revealed mechanisms potentially protecting bacteria against low temperatures and high UV-radiation. The selective pressure of the GFS environment is further highlighted by the phylogenomic analysis, differentiating the representatives of the genus Polaromonas, an important component of the GFS microbiome, from those found in other ecosystems. Our findings reveal key genomic underpinnings of adaptive traits that contribute to the success of complex biofilms to exploit environmental opportunities in GFSs, now rapidly changing owing to global warming.

show abstract

“…The sampled GFSs spanned a gradient in latitude, elevation, glacier size, and catchment geology (Data S1). Sampling was conducted as previously described (Fodelianakis et al, 2021; Kohler et al, 2020). Briefly, samples were collected from two reaches of each GFS, with one near the glacier snout and the other located downstream (median: 434 m) before the confluence with another tributary.…”

Section: Methodsmentioning

confidence: 99%

Glacier shrinkage will accelerate downstream decomposition of organic matter and alters microbiome structure and function

Kohler

Fodelianakis

Michoud

et al. 2022

Global Change Biology

Self Cite

View full text Add to dashboard Cite

The shrinking of glaciers is among the most iconic consequences of climate change. Despite this, the downstream consequences for ecosystem processes and related microbiome structure and function remain poorly understood. Here, using a space‐for‐time substitution approach across 101 glacier‐fed streams (GFSs) from six major regions worldwide, we investigated how glacier shrinkage is likely to impact the organic matter (OM) decomposition rates of benthic biofilms. To do this, we measured the activities of five common extracellular enzymes and estimated decomposition rates by using enzyme allocation equations based on stoichiometry. We found decomposition rates to average 0.0129 (% d−1), and that decreases in glacier influence (estimated by percent glacier catchment coverage, turbidity, and a glacier index) accelerates decomposition rates. To explore mechanisms behind these relationships, we further compared decomposition rates with biofilm and stream water characteristics. We found that chlorophyll‐a, temperature, and stream water N:P together explained 61% of the variability in decomposition. Algal biomass, which is also increasing with glacier shrinkage, showed a particularly strong relationship with decomposition, likely indicating their importance in contributing labile organic compounds to these carbon‐poor habitats. We also found high relative abundances of chytrid fungi in GFS sediments, which putatively parasitize these algae, promoting decomposition through a fungal shunt. Exploring the biofilm microbiome, we then sought to identify bacterial phylogenetic clades significantly associated with decomposition, and found numerous positively (e.g., Saprospiraceae) and negatively (e.g., Nitrospira) related clades. Lastly, using metagenomics, we found evidence of different bacterial classes possessing different proportions of EEA‐encoding genes, potentially informing some of the microbial associations with decomposition rates. Our results, therefore, present new mechanistic insights into OM decomposition in GFSs by demonstrating that an algal‐based “green food web” is likely to increase in importance in the future and will promote important biogeochemical shifts in these streams as glaciers vanish.

show abstract

Patterns and Drivers of Extracellular Enzyme Activity in New Zealand Glacier-Fed Streams

Cited by 19 publications

References 69 publications

Genomic and metabolic adaptations of biofilms to ecological windows of opportunity in glacier-fed streams

Genomic and metabolic adaptations of biofilms to ecological windows of opportunity in glacier-fed streams

Genomic and metabolic adaptations of biofilms to ecological windows of opportunities in glacier-fed streams

Glacier shrinkage will accelerate downstream decomposition of organic matter and alters microbiome structure and function

Contact Info

Product

Resources

About