Nutrient-limited subarctic caves harbour more diverse and complex bacterial communities than their surface soil

Abstract

Background Subarctic regions are particularly vulnerable to climate change, yet little is known about nutrient availability and biodiversity of their cave ecosystems. Such knowledge is crucial for predicting the vulnerability of these ecosystems to consequences of climate change. Thus, to improve our understanding of life in these habitats, we characterized environmental variables, as well as bacterial and invertebrate communities of six subarctic caves in Northern Norway. Results Only a minuscule diversity of surface-adapted invertebrates were found in these caves. However, the bacterial communities in caves were compositionally different, more diverse and more complex than the nutrient-richer surface soil. Cave soil microbiomes were less variable between caves than between surface communities in the same area, suggesting that the stable cave environments with tougher conditions drive the uniform microbial communities. We also observed only a small proportion of cave bacterial genera originating from the surface, indicating unique cave-adapted microbial communities. Increased diversity within caves may stem from higher niche specialization and levels of interdependencies for nutrient cycling among bacterial taxa in these oligotrophic environments. Conclusions Taken together this suggest that environmental changes, e.g., faster melting of snow as a result of global warming that could alter nutrient influx, can have a detrimental impact on interactions and dependencies of these complex communities. This comparative exploration of cave and surface microbiomes also lays the foundation to further investigate the long-term environmental variables that shape the biodiversity of these vulnerable ecosystems.

Microbiological exploration of the Cueva del Viento lava tube system in Tenerife, Canary Islands

“…The class Gemmatimonadetes was relatively abundant in the yellow and 5E‐red biofilms (3.62–6.48%), but scarce in the 11K‐white biofilm (0.43%). This class appeared frequently in diverse caves although with low abundances (Jurado et al, 2020 ; Paun et al, 2019 ; Reboleira et al, 2022 ).…”

“…The genus wb1 P19 ( Pseudomonadota ) is particularly abundant in 7G‐yellow (6.87%–1.68%) and missing in the 11K‐white biofilm. This lineage is abundantly represented in most studied caves (Frazier, 2020 ; Jurado et al, 2020 ; Reboleira et al, 2022 ), and particularly in yellow biofilms (Bastian et al, 2009 ; Martin‐Pozas et al, 2023 ) but data on its metabolism, other than participation in the nitrogen cycle is unknown.…”

Convergent evolution and horizontal gene transfer in Arctic Ocean microalgae

“…The patterns we see in the Arctic genomes may be exceptional, with the younger age (20 mya (103)) and higher connectivity in the Southern Ocean representing a transitional stage of HGT where bacterial gene acquisition is advantageous during initial colonization of a dynamic environment. However, eukaryote-eukaryote HGT may well manifest itself in other isolated biomes with extreme environments, such as geologically isolated cave systems (104).…”

Thermal acclimation and metabolic scaling of a groundwater asellid in the climate change scenario

“…This study is particularly relevant to understand the thermal acclimation ability of stygobitic crustaceans, and by extension its implications in the ecological integrity of groundwater habitats 24 . Furthermore, the omission of groundwater ecosystems from climate change agendas 65 , 66 marginalizes their ecological importance, leaving stygofauna substantially unprotected. Our findings also aim at stimulating open questions on metabolic adaptations of stygobitic species to thermally-stable, nutrient- and oxygen-poor, groundwater habitats.…”