Radiocarbon bomb spike reveals climate change is stunting growth of century old Antarctic moss shoots

Background/Question/Methods

The Antarctic has experienced major changes in temperature, wind speed and stratospheric ozone levels over the last 50 years. However until recently continental Antarctica appeared to be little impacted by climate warming, thus biological changes were predicted to be relatively slow. Detecting the biological effects of Antarctic climate change has been hindered by the paucity of long-term data sets, particularly for organisms that have been exposed to these changes throughout their lives. We have shown that radiocarbon signals preserved along shoots of the dominant Antarctic moss flora can be used to determine accurate growth rates over a period of several decades, allowing us to explore the influence of environmental variables on growth and providing a dramatic demonstration of the effects of climate change.

Results/Conclusions

Detailed 60-year growth records have been generated for Ceratodon purpureus and three other East Antarctic moss species (Bryum pseudotriquetrum, Schistidium antarctici and Bryoerythrophyllum recurvirostre) using the 1960s radiocarbon bomb spike. Growth rate and stable carbon isotope (d¹³C) data show that C. purpureus’ growth rates are correlated with key climatic variables, and furthermore that the observed effects of climate variation on growth are mediated through changes in water availability. Many of the sites investigated showed evidence of drying over recent decades and this was associated with reductions in moss growth rate. The most likely cause of this drying is increased wind speeds around the coast of Antarctica linked to depletion of the ozone layer. The finding that stable isotope signals laid down as the mosses grow can be used to determine changes in microhabitat water availability over recent decades means that in future, Antarctic mosses could be used as proxies for past coastal climate. Changes in water availability during the growing season may determine the fate of these mosses and the associated communities that form oases of Antarctic biodiversity.

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