Microbial assemblages reflect environmental heterogeneity in alpine streams.

Area of Science:

• Ecology
• Microbiology
• Environmental Science

Background:

• Alpine streams host significant biodiversity, influenced by varied hydrological sources.
• Climate change threatens alpine stream diversity by reducing meltwater and homogenizing habitats.
• Microbial diversity in alpine streams remains understudied, despite its importance for understanding climate change impacts.

Purpose of the Study:

• To characterize the microbial diversity (Bacteria and Archaea) in diverse alpine streams and microhabitats.
• To investigate how hydrological sources and microhabitats influence microbial community structure and diversity.
• To assess the potential impact of climate change on alpine stream microbial ecosystems.

Main Methods:

• 16S rRNA gene sequencing was used to analyze microbial communities in 13 Rocky Mountain streams.
• Streams represented a range of sources: glaciers, snowfields, subterranean ice, and groundwater.
• Microhabitats sampled included ice, biofilms, and streamwater.

Main Results:

• Regional microbial diversity showed no difference between subranges, but significant variation existed among stream types and microhabitats.
• Within-stream alpha diversity was highest in groundwater-fed springs and lowest in glacier-fed streams.
• Microbial diversity was positively correlated with water temperature in streamwater and biofilm communities.
• Icy seeps, fed by subterranean ice, were identified as a unique habitat with cold temperatures and high conductivity.

Conclusions:

• Declining meltwater sources are predicted to increase local diversity but decrease regional diversity in alpine streams.
• Icy seeps, buffered by insulating debris, may act as crucial refugia for microbial biodiversity.
• These findings highlight the vulnerability of alpine stream ecosystems to climate change and the importance of identifying resilient habitats.