East Antarctica has shown little evidence of warming to date 1-3 with no coherent picture of how climate change is affecting vegetation 4-6 . In stark contrast, the Antarctic Peninsula experienced some of the most rapid warming on the planet at the end of the last century 2,3,7,8 causing changes to growth and distribution of plants 9-11 . Here we show that vegetation in the Windmill Islands, East Antarctica is changing rapidly in response to a drying climate. This drying trend is evident across the region, demonstrated by changes in isotopic signatures measured along moss shoots 12,13 , moss community composition and declining health, as well as long-term observations of lake salinity 14 and weather. The regional drying is possibly due to the more positive Southern Annular Mode (SAM) in recent decades. The more positive SAM is a consequence of Antarctic ozone depletion and increased greenhouse gases, and causes strong westerly winds to circulate closer to the continent, maintaining colder temperatures in East Antarctica despite the increasing global average 15-18 . Colder summers in this region likely result in reduced snow melt and increased aridity. We demonstrate that rapid vegetation change is occurring in East Antarctica and that its mosses provide potentially important proxies for monitoring coastal climate change.Climate change is causing many species to shift poleward in response to increasing global temperatures 19 . Antarctic continental vegetation, however, is unlikely to exhibit such simple and predictable responses, as warming is inconsistent over the continent 1,3 , and species distributions are largely determined by local availability of ice-free habitats and water, rather than temperature per se 6,[20][21][22] . Small changes in microclimate (temperature, precipitation, wind or humidity) can impact the water balance or freeze-thaw cycles 23 and thus impact vegetation, even in the absence of regional warming.

Ceratodon purpureus is a cosmopolitan moss that survives some of the harshest places on Earth: from frozen Antarctica to hot South Australian deserts. In a study on the survival mechanisms of the species, nine compounds were isolated from Australian and Antarctic C. purpureus. This included five biflavonoids, with complete structural elucidation of 1 and 2 reported here for the first time, as well as an additional four known phenolic compounds. Dispersion-corrected DFT calculations suggested a rotational barrier, leading to atropisomerism, resulting in the presence of diastereomers for compound 2. All isolates absorbed strongly in the ultraviolet (UV) spectrum, e.g., biflavone 1 (UV-A, 315-400 nm), which displayed the strongest radical-scavenging activity, 13% more efficient than the standard rutin; p-coumaric acid and trans-ferulic acid showed the highest UV-B (280-315 nm) absorption. The more complex and abundant 1 and 2 presumably have dual roles as both UV-screening and antioxidant compounds. They are strongly bound to Antarctic moss cell walls as well as located inside the cells of moss from both locations. The combined high stability and photoprotective abilities of these isolates may account for the known resilience of this species to UV-B radiation and its survival in some of the toughest locations in the world.

The terrestrial flora of Antarctica's frozen continent is restricted to sparse ice-free areas and dominated by lichens and bryophytes. These plants frequently battle sub-zero temperatures, extreme winds and reduced water availability; all influencing their ability to survive and grow. Antarctic mosses, however, can have canopy temperatures well above air temperature. At midday, canopy temperatures can exceed 15°C, depending on moss turf water content. In this study, the optimum temperature of photosynthesis was determined for six Antarctic moss species: Bryum pseudotriquetrum, Ceratodon purpureus, Chorisodontium aciphyllum, Polytrichastrum alpinum, Sanionia uncinata, and Schistidium antarctici collected from King George Island (maritime Antarctica) and/ or the Windmill Islands, East Antarctica. Both chlorophyll fluorescence and gas exchange showed maximum values of electron transport rate occurred at canopy temperatures higher than 20°C. The optimum temperature for both net assimilation of CO 2 and photoprotective heat dissipation of three East Antarctic species was 20-30°C and at temperatures below 10°C, mesophyll conductance did not significantly differ from 0. Maximum mitochondrial respiration rates occurred at temperatures higher than 35°C and were lower by around 80% at 5°C. Despite the extreme cold conditions that Antarctic mosses face over winter, the photosynthetic apparatus appears optimised to warm temperatures. Our estimation of the total carbon balance suggests that survival in this cold environment may rely on a capacity to maximize photosynthesis for brief periods during summer and minimize respiratory carbon losses in cold conditions.

BackgroundAntarctic bryophytes (mosses and liverworts) are resilient to physiologically extreme environmental conditions including elevated levels of ultraviolet (UV) radiation due to depletion of stratospheric ozone. Many Antarctic bryophytes synthesise UV-B-absorbing compounds (UVAC) that are localised in their cells and cell walls, a location that is rarely investigated for UVAC in plants. This study compares the concentrations and localisation of intracellular and cell wall UVAC in Antarctic Ceratodon purpureus, Bryum pseudotriquetrum and Schistidium antarctici from the Windmill Islands, East Antarctica.ResultsMultiple stresses, including desiccation and naturally high UV and visible light, seemed to enhance the incorporation of total UVAC including red pigments in the cell walls of all three Antarctic species analysed. The red growth form of C. purpureus had significantly higher levels of cell wall bound and lower intracellular UVAC concentrations than its nearby green form. Microscopic and spectroscopic analyses showed that the red colouration in this species was associated with the cell wall and that these red cell walls contained less pectin and phenolic esters than the green form. All three moss species showed a natural increase in cell wall UVAC content during the growing season and a decline in these compounds in new tissue grown under less stressful conditions in the laboratory.ConclusionsUVAC and red pigments are tightly bound to the cell wall and likely have a long-term protective role in Antarctic bryophytes. Although the identity of these red pigments remains unknown, our study demonstrates the importance of investigating cell wall UVAC in plants and contributes to our current understanding of UV-protective strategies employed by particular Antarctic bryophytes. Studies such as these provide clues to how these plants survive in such extreme habitats and are helpful in predicting future survival of the species studied.Electronic supplementary materialThe online version of this article (10.1186/s40659-018-0196-1) contains supplementary material, which is available to authorized users.