Arctic microorganisms respond more to elevated UV-B radiation than CO2

Area of Science:

• Ecology
• Environmental Science
• Microbiology

Background:

• Rising surface ultraviolet-B (UV-B) radiation due to ozone depletion and increased atmospheric carbon dioxide (CO2) from fossil fuel burning impact sensitive polar ecosystems.
• Polar plant communities rely on soil microorganisms for nutrient cycling, which are crucial for soil carbon (C) and nitrogen (N).
• Previous assumptions suggested limited effects of UV-B on soil microbial biomass, with stronger impacts expected from elevated CO2 due to increased below-ground carbon allocation.

Purpose of the Study:

• To investigate the effects of enhanced UV-B radiation and elevated CO2 on soil microbial biomass and community structure in a subarctic heath.
• To assess the combined impacts of UV-B and CO2 on the carbon-to-nitrogen (C:N) ratio and bacterial community composition.

Main Methods:

• Experimental exposure of a subarctic heath ecosystem to enhanced UV-B radiation and elevated CO2 for five years.
• Analysis of soil samples to determine changes in the C:N ratio and bacterial community structure.

Main Results:

• Five years of exposure to enhanced UV-B radiation, both alone and in combination with elevated CO2, caused significant alterations in the soil microbial biomass.
• Key changes observed include significant shifts in the soil C:N ratio and the structure of the bacterial community.

Conclusions:

• Enhanced UV-B radiation significantly impacts soil microbial biomass and bacterial community structure, contrary to prior beliefs of minor environmental concern.
• The findings highlight the substantial ecological consequences of ozone depletion and increased UV-B, particularly in vulnerable polar regions.
• Elevated CO2 may interact with UV-B effects, underscoring the complex responses of soil ecosystems to global change drivers.