Antarctic mosses reveal high resolution records of local microclimates

Full text: Life in Antarctica is living in the extreme. To survive there, life must be resilient to sub-zero temperatures, high levels of damaging ultraviolet and solar radiation, strong winds and waterlimiting environments. In this harsh continent where water is locked up as snow and ice for most of the year, mosses are the dominant plant form. Like many living things, these small plants rely on liquid water to survive. The amount of potential water that is available to drive growth, distribution and survival of Antarctic flora is strongly influenced by the changing climate, especially temperature, precipitation and winds. However, meteorological climate records in most of the biologically diverse regions in Antarctica are sparse and limited to a few decades or less. In these areas, there is an increasing need for local climate proxies. We show that Antarctic moss species can be used as living proxies for local water availability through preserved stable carbon isotopes captured in cellulose. Using accelerator and isotope ratio mass spectrometry techniques, we obtained radiocarbon ages and δ¹³C signatures along 26 cores of long shoots of moss collected from the Windmill Islands, East Antarctica and South Shetland Islands in the Maritime Antarctic. AMS radiocarbon results showed that these once living cores are up to 500 years old. The five moss species studied grew at different rates; the slowest species grew at less than 1 mm/year while the fastest achieved 8 mm/year. These moss cores provide a high-resolution record, at annual to decadal scales, of their microclimate. Our results also reveal that growth patterns of these Antarctic plants are dependent on local moisture environments. Trends in δ¹³C signatures indicate microclimates in these regions are drying. This work suggests that mosses have considerable potential as climate proxies by providing a temporal and spatial history of microclimate in Antarctica. Applying these measures will allow us to determine which terrestrial sites are at risk of the negative impacts of climate change in order to inform critical conservation efforts in a rapidly changing environment.