Jessica Royles

Plants and soil microbes respond to recent warming on the Antarctic Peninsula.

Annual temperatures on the Antarctic Peninsula, one of the most rapidly warming regions on Earth, have risen by up to 0.56°C per decade since the 1950s. Terrestrial and marine organisms have shown changes in populations and distributions over this time, suggesting that the ecology of the Antarctic Peninsula is changing rapidly. However, these biological records are shorter in length than the meteorological data, and observed population changes cannot be securely linked to longer-term trends apparent in paleoclimate data. We developed a unique time series of past moss growth and soil microbial activity from a 150-year-old moss bank at the southern limit of significant plant growth based on accumulation rates, cellulose δ(13)C, and fossil testate amoebae. We show that growth rates and microbial productivity have risen rapidly since the 1960s, consistent with temperature changes, although recently they may have stalled. The recent increase in terrestrial plant growth rates and soil microbial activity are unprecedented in the last 150 years and are consistent with climate change. Future changes in terrestrial biota are likely to track projected temperature increases closely and will fundamentally change the ecology and appearance of the Antarctic Peninsula.

Invited review: climate change impacts in polar regions: lessons from Antarctic moss bank archives

Mosses are the dominant plants in polar and boreal regions, areas which are experiencing rapid impacts of regional warming. Long-term monitoring programmes provide some records of the rate of recent climate change, but moss peat banks contain an unrivalled temporal record of past climate change on terrestrial plant Antarctic systems. We summarise the current understanding of climatic proxies and determinants of moss growth for contrasting continental and maritime Antarctic regions, as informed by 13C and 18O signals in organic material. Rates of moss accumulation are more than three times higher in the maritime Antarctic than continental Antarctica with growing season length being a critical determinant of growth rate, and high carbon isotope discrimination values reflecting optimal hydration conditions. Correlation plots of 13C and 18O values show that species (Chorisodontium aciphyllum / Polytrichum strictum) and growth form (hummock / bank) are the major determinants of measured isotope ratios. The interplay between moss growth form, photosynthetic physiology, water status and isotope composition are compared with developments of secondary proxies, such as chlorophyll fluorescence. These approaches provide a framework to consider the potential impact of climate change on terrestrial Antarctic habitats as well as having implications for future studies of temperate, boreal and Arctic peatlands. There are many urgent ecological and environmental problems in the Arctic related to mosses in a changing climate, but the geographical ranges of species and life-forms are difficult to track individually. Our goal was to translate what we have learned from the more simple systems in Antarctica, for application to Arctic habitats.

Establishing lichenometric ages for nineteenth- and twentieth-century glacier fluctuations on South Georgia (South Atlantic).

Abstract. Glaciers in small mountain cirques on South Georgia respond rapidly and sensitively to changes in South Atlantic climate. The timing and rate of their deglaciation can be used to examine the impact that nineteenth‐ and twentieth‐century climate change has had on the glacial dynamics and terrestrial ecosystems of South Georgia. As part of a reconnaissance study in Prince Olav Harbour (POH), South Georgia, we measured the size of lichens (Rhizocarpon Ram. em Th. Fr. subgenus. Rhizocarpon group) on ice‐free moraine ridges around two small mountain cirques. Our aims were twofold: first, to provide age estimates for lichen colonization, and hence, deglaciation of the moraine ridges, and second, to examine the potential of applying lichenometry more widely to provide deglacial age constraints on South Georgia. In the absence of lichen age‐size (dating) curves for South Georgia, we use long‐term Rhizocarpon lichen growth‐rates from recent studies on sub‐Antarctic Islands and the western Antarctic Peninsula to calculate likely age estimates. These data suggest ice retreat from the two outermost moraines occurred between the end of the ‘Little Ice Age’ (post c. 1870) and the early twentieth century on South Georgia. Lichen colonization of the innermost moraines is probably related to glacier retreat during the second half of the twentieth century, which has been linked to a well‐defined warming trend since c. 1950. Patterns of possible nineteenth‐ and twentieth‐century glacial retreat identified in POH need to be tested further by establishing species‐ and site‐specific lichen age‐size (dating) curves for South Georgia, and by applying lichenometry to other mountain cirques across South Georgia.

Widespread Biological Response to Rapid Warming on the Antarctic Peninsula

Recent climate change on the Antarctic Peninsula is well documented [1-5], with warming, alongside increases in precipitation, wind strength, and melt season length [1, 6, 7], driving environmental change [8, 9]. However, meteorological records mostly began in the 1950s, and paleoenvironmental datasets that provide a longer-term context to recent climate change are limited in number and often from single sites [7] and/or discontinuous in time [10, 11]. Here we use moss bank cores from a 600-km transect from Green Island (65.3°S) to Elephant Island (61.1°S) as paleoclimate archives sensitive to regional temperature change, moderated by water availability and surface microclimate [12, 13]. Mosses grow slowly, but cold temperatures minimize decomposition, facilitating multi-proxy analysis of preserved peat [14]. Carbon isotope discrimination (Δ13C) in cellulose indicates the favorability of conditions for photosynthesis [15]. Testate amoebae are representative heterotrophs in peatlands [16-18], so their populations are an indicator of microbial productivity [14]. Moss growth and mass accumulation rates represent the balance between growth and decomposition [19]. Analyzing these proxies in five cores at three sites over 150 years reveals increased biological activity over the past ca. 50 years, in response to climate change. We identified significant changepoints in all sites and proxies, suggesting fundamental and widespread changes in the terrestrial biosphere. The regional sensitivity of moss growth to past temperature rises suggests that terrestrial ecosystems will alter rapidly under future warming, leading to major changes in the biology and landscape of this iconic region-an Antarctic greening to parallel well-established observations in the Arctic [20].

Moss stable isotopes (carbon-13, oxygen-18) and testate amoebae reflect environmental inputs and microclimate along a latitudinal gradient on the Antarctic Peninsula.

The stable isotope compositions of moss tissue water (δ2H and δ18O) and cellulose (δ13C and δ18O), and testate amoebae populations were sampled from 61 contemporary surface samples along a 600-km latitudinal gradient of the Antarctic Peninsula (AP) to provide a spatial record of environmental change. The isotopic composition of moss tissue water represented an annually integrated precipitation signal with the expected isotopic depletion with increasing latitude. There was a weak, but significant, relationship between cellulose δ18O and latitude, with predicted source water inputs isotopically enriched compared to measured precipitation. Cellulose δ13C values were dependent on moss species and water content, and may reflect site exposure to strong winds. Testate amoebae assemblages were characterised by low concentrations and taxonomic diversity, with Corythion dubium and Microcorycia radiata types the most cosmopolitan taxa. The similarity between the intra- and inter-site ranges measured in all proxies suggests that microclimate and micro-topographical conditions around the moss surface were important determinants of proxy values. Isotope and testate amoebae analyses have proven value as palaeoclimatic, temporal proxies of climate change, whereas this study demonstrates that variations in isotopic and amoeboid proxies between microsites can be beyond the bounds of the current spatial variability in AP climate.

Bryophyte gas-exchange dynamics along varying hydration status reveal a significant carbonyl sulphide (COS) sink in the dark and COS source in the light

Summary Carbonyl sulphide (COS) is a potential tracer of gross primary productivity (GPP), assuming a unidirectional COS flux into the vegetation that scales with GPP. However, carbonic anhydrase (CA), the enzyme that hydrolyses COS, is expected to be light independent, and thus plants without stomata should continue to take up COS in the dark. We measured net CO 2 (AC) and COS (AS) uptake rates from two astomatous bryophytes at different relative water contents (RWCs), COS concentrations, temperatures and light intensities. We found large AS in the dark, indicating that CA activity continues without photosynthesis. More surprisingly, we found a nonzero COS compensation point in light and dark conditions, indicating a temperature‐driven COS source with a Q 10 (fractional change for a 10°C temperature increase) of 3.7. This resulted in greater AS in the dark than in the light at similar RWC. The processes underlying such COS emissions remain unknown. Our results suggest that ecosystems dominated by bryophytes might be strong atmospheric sinks of COS at night and weaker sinks or even sources of COS during daytime. Biotic COS production in bryophytes could result from symbiotic fungal and bacterial partners that could also be found on vascular plants.

Temporal separation between CO2 assimilation and growth? Experimental and theoretical evidence from the desiccation‐tolerant moss Syntrichia ruralis

The extent of an external water layer around moss tissue influences CO(2) assimilation. Experiments on the desiccation-tolerant moss Syntrichia ruralis assessed the real-time dependence of the carbon and oxygen isotopic compositions of CO(2) and H(2)O in terms of moss water status and integrated isotope signals in cellulose. As external (capillary) water, and then mesophyll water, evaporated from moss tissue, assimilation rate, relative water content and the stable isotope composition of tissue water (δ(18)O(TW)), and the CO(2) and H(2)O fluxes, were analysed. After drying, carbon (δ(13)C(C)) and oxygen (δ(18)O(C)) cellulose compositions were determined. During desiccation, assimilation and (13)CO(2) discrimination increased to a maximum and then declined; δ(18)O(TW) increased progressively by 8‰, indicative of evaporative isotopic enrichment. Experimental and meteorological data were combined to predict tissue hydration dynamics over one growing season. Nonsteady-state model predictions of δ(18)O(TW) were consistent with instantaneous measurements. δ(13)C(C) values suggest that net assimilation occurs at 25% of maximum relative water content, while δ(18)O(C) data suggests that cellulose is synthesized during much higher relative water content conditions. This implies that carbon assimilation and cellulose synthesis (growth) may be temporally separated, with carbon reserves possibly contributing to desiccation tolerance and resumption of metabolism upon rehydration.

Electrical output of bryophyte microbial fuel cell systems is sufficient to power a radio or an environmental sensor

Plant microbial fuel cells are a recently developed technology that exploits photosynthesis in vascular plants by harnessing solar energy and generating electrical power. In this study, the model moss species Physcomitrella patens, and other environmental samples of mosses, have been used to develop a non-vascular bryophyte microbial fuel cell (bryoMFC). A novel three-dimensional anodic matrix was successfully created and characterized and was further tested in a bryoMFC to determine the capacity of mosses to generate electrical power. The importance of anodophilic microorganisms in the bryoMFC was also determined. It was found that the non-sterile bryoMFCs operated with P. patens delivered over an order of magnitude higher peak power output (2.6 ± 0.6 µW m−2) than bryoMFCs kept in near-sterile conditions (0.2 ± 0.1 µW m−2). These results confirm the importance of the microbial populations for delivering electrons to the anode in a bryoMFC. When the bryoMFCs were operated with environmental samples of moss (non-sterile) the peak power output reached 6.7 ± 0.6 mW m−2. The bryoMFCs operated with environmental samples of moss were able to power a commercial radio receiver or an environmental sensor (LCD desktop weather station).

Taxonomic Implications of Morphological Complexity Within the Testate Amoeba Genus Corythion from the Antarctic Peninsula

Precise and sufficiently detailed morphological taxonomy is vital in biology, for example in the accurate interpretation of ecological and palaeoecological datasets, especially in polar regions, where biodiversity is poor. Testate amoebae on the Antarctic Peninsula (AP) are well-documented and variations in their population size have recently been interpreted as a proxy for microbial productivity changes in response to recent regional climate change. AP testate amoeba assemblages are dominated by a small number of globally ubiquitous taxa. We examine morphological variation in Corythion spp. across the AP, finding clear evidence supporting the presence of two morphospecies. Corythion constricta (Certes 1889) was identified on the AP for the first time and has potentially been previously misidentified. Furthermore, a southerly trend of decreasing average test size in Corythion dubium (Taránek 1881) along the AP suggests adaptive polymorphism, although the precise drivers of this remain unclear, with analysis hindered by limited environmental data. Further work into morphological variation in Corythion is needed elsewhere, alongside molecular analyses, to evaluate the potential for (pseudo)cryptic diversity within the genus. We advocate a parsimonious taxonomical approach that recognises genetic diversity but also examines and develops accurate morphological divisions and descriptions suitable for light microscopy-based ecological and palaeoecological studies.