The Antarctic ozone layer is recovering, a major environmental success following the Montreal Protocol. As the ozone layer heals, less ultraviolet radiation reaches the Antarctic surface—a change usually viewed as beneficial for living organisms.
But a new field study suggests that the ecological story may be more complicated. Researchers from the Institute of Atmospheric Physics, Chinese Academy of Sciences, China together with collaborators from the University of Science and Technology of China and other institutions, found that reduced ultraviolet radiation can substantially weaken the ability of Antarctic tundra to absorb carbon dioxide. These results were recently published in Atmospheric and Oceanic Science Letters .
The team carried out in situ field experiments on Ardley Island in West Antarctica, where mosses and lichens form fragile tundra communities. Using transparent filters, the researchers simulated two levels of ultraviolet reduction—about 20% and 50%—while measuring carbon dioxide exchange, photosynthesis, and ecosystem respiration.
The results were striking. A 20% reduction in ultraviolet radiation weakened the tundra carbon sink by about half. A 50% reduction weakened it by about 80%, and in some observation periods the tundra even showed signs of shifting from a carbon sink to a carbon source.
"We might expect lower ultraviolet radiation to be simply beneficial, but Antarctic tundra does not respond in such a straightforward way," says Prof. Xiyan Xu, a corresponding author of the study. "In this sensitive ecosystem, changes in ultraviolet radiation can affect plant photosynthesis, microbial decomposition, and the overall carbon balance at the same time."
The study also found that different tundra environments respond through different pathways. In western lowland tundra, where penguin and other marine animal activity is limited, the weakened carbon sink was mainly linked to reduced photosynthesis. Antarctic mosses and lichens have adapted to high-ultraviolet environments, and lower ultraviolet exposure may alter their protective pigments, light-use processes, and carbon fixation capacity.
In eastern lowland tundra, where penguin activity is strong, the main driver was increased ecosystem respiration. Penguin colonies add large amounts of organic carbon and nitrogen to the soil, creating nutrient-rich conditions for microbes. When ultraviolet stress is reduced, microbial activity may increase, accelerating decomposition and releasing more carbon dioxide.
"Penguin-derived nutrients make these tundra soils biologically active," says Dr. Tao Bao, the first author of the study. "Under lower ultraviolet radiation, this nutrient-rich environment may amplify respiratory carbon loss from the ecosystem."
The findings suggest that ozone-layer recovery should not be viewed only through the lens of reduced ultraviolet damage. For Antarctic tundra communities that have long adapted to strong ultraviolet exposure, declining ultraviolet radiation may reshape plant–microbe interactions and carbon cycling. The researchers plan to combine longer-term field observations with ecosystem modeling to better understand how ultraviolet change, penguin activity, and climate warming together influence the future carbon balance of Antarctic tundra.
