Extended ozone depletion and reduced snow and ice cover-Consequences for Antarctic biota.

Stratospheric ozone, which has been depleted in recent decades by the release of anthropogenic gases, is critical for shielding the biosphere against ultraviolet-B (UV-B) radiation. Although the ozone layer is expected to recover before the end of the 21st century, a hole over Antarctica continues to appear each year. Ozone depletion usually peaks between September and October, when fortunately, most Antarctic terrestrial vegetation and soil biota is frozen, dormant and protected under snow cover. Similarly, much marine life is protected by sea ice cover. The ozone hole used to close before the onset of Antarctic summer, meaning that most biota were not exposed to severe springtime UV-B fluxes. However, in recent years, ozone depletion has persisted into December, which marks the beginning of austral summer. Early summertime ozone depletion is concerning: high incident UV-B radiation coincident with snowmelt and emergence of vegetation will mean biota is more exposed. The start of summer is also peak breeding season for many animals, thus extreme UV-B exposure (UV index up to 14) may come at a vulnerable time in their life cycle. Climate change, including changing wind patterns and strength, and particularly declining sea ice, are likely to compound UV-B exposure of Antarctic organisms, through earlier ice and snowmelt, heatwaves and droughts. Antarctic field research conducted decades ago tended to study UV impacts in isolation and more research that considers multiple climate impacts, and the true magnitude and timing of current UV increases is needed.

Environmental plastics in the context of UV radiation, climate change, and the Montreal Protocol.

There are close links between solar UV radiation, climate change, and plastic pollution. UV-driven weathering is a key process leading to the degradation of plastics in the environment but also the formation of potentially harmful plastic fragments such as micro- and nanoplastic particles. Estimates of the environmental persistence of plastic pollution, and the formation of fragments, will need to take in account plastic dispersal around the globe, as well as projected UV radiation levels and climate change factors.

Plastics in the environment in the context of UV radiation, climate change and the Montreal Protocol: UNEP Environmental Effects Assessment Panel, Update 2023.

This Assessment Update by the Environmental Effects Assessment Panel (EEAP) of the United Nations Environment Programme (UNEP) considers the interactive effects of solar UV radiation, global warming, and other weathering factors on plastics. The Assessment illustrates the significance of solar UV radiation in decreasing the durability of plastic materials, degradation of plastic debris, formation of micro- and nanoplastic particles and accompanying leaching of potential toxic compounds. Micro- and nanoplastics have been found in all ecosystems, the atmosphere, and in humans. While the potential biological risks are not yet well-established, the widespread and increasing occurrence of plastic pollution is reason for continuing research and monitoring. Plastic debris persists after its intended life in soils, water bodies and the atmosphere as well as in living organisms. To counteract accumulation of plastics in the environment, the lifetime of novel plastics or plastic alternatives should better match the functional life of products, with eventual breakdown releasing harmless substances to the environment.

Monitoring of Antarctica's Fragile Vegetation Using Drone-Based Remote Sensing, Multispectral Imagery and AI.

Vegetation in East Antarctica, such as moss and lichen, vulnerable to the effects of climate change and ozone depletion, requires robust non-invasive methods to monitor its health condition. Despite the increasing use of unmanned aerial vehicles (UAVs) to acquire high-resolution data for vegetation analysis in Antarctic regions through artificial intelligence (AI) techniques, the use of multispectral imagery and deep learning (DL) is quite limited. This study addresses this gap with two pivotal contributions: (1) it underscores the potential of deep learning (DL) in a field with notably limited implementations for these datasets; and (2) it introduces an innovative workflow that compares the performance between two supervised machine learning (ML) classifiers: Extreme Gradient Boosting (XGBoost) and U-Net. The proposed workflow is validated by detecting and mapping moss and lichen using data collected in the highly biodiverse Antarctic Specially Protected Area (ASPA) 135, situated near Casey Station, between January and February 2023. The implemented ML models were trained against five classes: Healthy Moss, Stressed Moss, Moribund Moss, Lichen, and Non-vegetated. In the development of the U-Net model, two methods were applied: Method (1) which utilised the original labelled data as those used for XGBoost; and Method (2) which incorporated XGBoost predictions as additional input to that version of U-Net. Results indicate that XGBoost demonstrated robust performance, exceeding 85% in key metrics such as precision, recall, and F1-score. The workflow suggested enhanced accuracy in the classification outputs for U-Net, as Method 2 demonstrated a substantial increase in precision, recall and F1-score compared to Method 1, with notable improvements such as precision for Healthy Moss (Method 2: 94% vs. Method 1: 74%) and recall for Stressed Moss (Method 2: 86% vs. Method 1: 69%). These findings contribute to advancing non-invasive monitoring techniques for the delicate Antarctic ecosystems, showcasing the potential of UAVs, high-resolution multispectral imagery, and ML models in remote sensing applications.

Basking in the sun: how mosses photosynthesise and survive in Antarctica.

The Antarctic environment is extremely cold, windy and dry. Ozone depletion has resulted in increasing ultraviolet-B radiation, and increasing greenhouse gases and decreasing stratospheric ozone have altered Antarctica's climate. How do mosses thrive photosynthetically in this harsh environment? Antarctic mosses take advantage of microclimates where the combination of protection from wind, sufficient melt water, nutrients from seabirds and optimal sunlight provides both photosynthetic energy and sufficient warmth for efficient metabolism. The amount of sunlight presents a challenge: more light creates warmer canopies which are optimal for photosynthetic enzymes but can contain excess light energy that could damage the photochemical apparatus. Antarctic mosses thus exhibit strong photoprotective potential in the form of xanthophyll cycle pigments. Conversion to zeaxanthin is high when conditions are most extreme, especially when water content is low. Antarctic mosses also produce UV screening compounds which are maintained in cell walls in some species and appear to protect from DNA damage under elevated UV-B radiation. These plants thus survive in one of the harshest places on Earth by taking advantage of the best real estate to optimise their metabolism. But survival is precarious and it remains to be seen if these strategies will still work as the Antarctic climate changes.

Threat management priorities for conserving Antarctic biodiversity.

Antarctic terrestrial biodiversity faces multiple threats, from invasive species to climate change. Yet no large-scale assessments of threat management strategies exist. Applying a structured participatory approach, we demonstrate that existing conservation efforts are insufficient in a changing world, estimating that 65% (at best 37%, at worst 97%) of native terrestrial taxa and land-associated seabirds are likely to decline by 2100 under current trajectories. Emperor penguins are identified as the most vulnerable taxon, followed by other seabirds and dry soil nematodes. We find that implementing 10 key threat management strategies in parallel, at an estimated present-day equivalent annual cost of US$23 million, could benefit up to 84% of Antarctic taxa. Climate change is identified as the most pervasive threat to Antarctic biodiversity and influencing global policy to effectively limit climate change is the most beneficial conservation strategy. However, minimising impacts of human activities and improved planning and management of new infrastructure projects are cost-effective and will help to minimise regional threats. Simultaneous global and regional efforts are critical to secure Antarctic biodiversity for future generations.

Stable isotope approaches and opportunities for improving plant conservation.

Successful conservation of threatened species and ecosystems in a rapidly changing world requires scientifically sound decision-making tools that are readily accessible to conservation practitioners. Physiological applications that examine how plants and animals interact with their environment are now widely used when planning, implementing and monitoring conservation. Among these tools, stable-isotope physiology is a potentially powerful, yet under-utilized cornerstone of current and future conservation efforts of threatened and endangered plants. We review the underlying concepts and theory of stable-isotope physiology and describe how stable-isotope applications can support plant conservation. We focus on stable isotopes of carbon, hydrogen, oxygen and nitrogen to address plant ecophysiological responses to changing environmental conditions across temporal scales from hours to centuries. We review examples from a broad range of plant taxa, life forms and habitats and provide specific examples where stable-isotope analysis can directly improve conservation, in part by helping identify resilient, locally adapted genotypes or populations. Our review aims to provide a guide for practitioners to easily access and evaluate the information that can be derived from stable-isotope signatures, their limitations and how stable isotopes can improve conservation efforts.

Islands in the ice: Potential impacts of habitat transformation on Antarctic biodiversity.

Antarctic biodiversity faces an unknown future with a changing climate. Most terrestrial biota is restricted to limited patches of ice-free land in a sea of ice, where they are adapted to the continent's extreme cold and wind and exploit microhabitats of suitable conditions. As temperatures rise, ice-free areas are predicted to expand, more rapidly in some areas than others. There is high uncertainty as to how species' distributions, physiology, abundance, and survivorship will be affected as their habitats transform. Here we use current knowledge to propose hypotheses that ice-free area expansion (i) will increase habitat availability, though the quality of habitat will vary; (ii) will increase structural connectivity, although not necessarily increase opportunities for species establishment; (iii) combined with milder climates will increase likelihood of non-native species establishment, but may also lengthen activity windows for all species; and (iv) will benefit some species and not others, possibly resulting in increased homogeneity of biodiversity. We anticipate considerable spatial, temporal, and taxonomic variation in species responses, and a heightened need for interdisciplinary research to understand the factors associated with ecosystem resilience under future scenarios. Such research will help identify at-risk species or vulnerable localities and is crucial for informing environmental management and policymaking into the future.

Emerging biological archives can reveal ecological and climatic change in Antarctica.

Anthropogenic climate change is causing observable changes in Antarctica and the Southern Ocean including increased air and ocean temperatures, glacial melt leading to sea-level rise and a reduction in salinity, and changes to freshwater water availability on land. These changes impact local Antarctic ecosystems and the Earth's climate system. The Antarctic has experienced significant past environmental change, including cycles of glaciation over the Quaternary Period (the past ~2.6 million years). Understanding Antarctica's paleoecosystems, and the corresponding paleoenvironments and climates that have shaped them, provides insight into present day ecosystem change, and importantly, helps constrain model projections of future change. Biological archives such as extant moss beds and peat profiles, biological proxies in lake and marine sediments, vertebrate animal colonies, and extant terrestrial and benthic marine invertebrates, complement other Antarctic paleoclimate archives by recording the nature and rate of past ecological change, the paleoenvironmental drivers of that change, and constrain current ecosystem and climate models. These archives provide invaluable information about terrestrial ice-free areas, a key location for Antarctic biodiversity, and the continental margin which is important for understanding ice sheet dynamics. Recent significant advances in analytical techniques (e.g., genomics, biogeochemical analyses) have led to new applications and greater power in elucidating the environmental records contained within biological archives. Paleoecological and paleoclimate discoveries derived from biological archives, and integration with existing data from other paleoclimate data sources, will significantly expand our understanding of past, present, and future ecological change, alongside climate change, in a unique, globally significant region.

Climate change and extreme events are changing the biology of Polar Regions.

Polar landscapes and their unique biodiversity are threatened by climate change. Wild reindeer are cultural and ecological keystone species, traversing across the northern Eurasian Arctic throughout the year (Wild reindeer in the sub-Arctic in Kuhmo, Finland. Photo: Antti Leinonen, Snowchange Cooperative. Used with permission). In contrast, Antarctic terrestrial biodiversity is found on islands in the ice (or ocean) which support unique assemblages of plants and animals (King George Island, South Shetlands; photo Andrew Netherwood. Used with permission). This VSI examines how the changing climate threatens these diverse marine and terrestrial habitats and the biodiversity that they support.

Limitations to photosynthesis in bryophytes: certainties and uncertainties regarding methodology.

Bryophytes are the group of land plants with the lowest photosynthetic rates, which was considered to be a consequence of their higher anatomical CO2 diffusional limitation compared with tracheophytes. However, the most recent studies assessing limitations due to biochemistry and mesophyll conductance in bryophytes reveal discrepancies based on the methodology used. In this study, we compared data calculated from two different methodologies for estimating mesophyll conductance: variable J and the curve-fitting method. Although correlated, mesophyll conductance estimated by the curve-fitting method was on average 4-fold higher than the conductance obtained by the variable J method; a large enough difference to account for the scale of differences previously shown between the biochemical and diffusional limitations to photosynthesis. Biochemical limitations were predominant when the curve-fitting method was used. We also demonstrated that variations in bryophyte relative water content during measurements can also introduce errors in the estimation of mesophyll conductance, especially for samples which are overly desiccated. Furthermore, total chlorophyll concentration and soluble proteins were significantly lower in bryophytes than in tracheophytes, and the percentage of proteins quantified as Rubisco was also significantly lower in bryophytes (<6.3% in all studied species) than in angiosperms (>16% in all non-stressed cases). Photosynthetic rates normalized by Rubisco were not significantly different between bryophytes and angiosperms. Our data suggest that the biochemical limitation to photosynthesis in bryophytes is more relevant than so far assumed.

Inhibition of non-photochemical quenching increases functional absorption cross-section of photosystem II as excitation from closed reaction centres is transferred to open centres, facilitating earlier light saturation of photosynthetic electron transport.

Induction of non-photochemical quenching (NPQ) of chlorophyll fluorescence in leaves affords photoprotection to the photosynthetic apparatus when, for whatever reason, photon capture in the antennae of photosystems exceeds their capacity to utilise this excitation in photochemistry and ultimately in CO2 assimilation. Here we augment traditional monitoring of NPQ using the fast time resolution, remote and relatively non-intrusive light induced fluorescence transient (LIFT) technique (Kolber et al . 2005 ; Osmond et al . 2017 ) that allows direct measurement of functional (σ'PSII ) and optical cross-sections (a 'PSII ) of PSII in situ , and calculates the half saturation light intensity for ETR (E k ). These parameters are obtained from the saturation and relaxation phases of fluorescence transients elicited by a sequence of 270, high intensity 1 µs flashlets at controlled time intervals over a period of 30 ms in the QA flash at intervals of a few seconds. We report that although σ'PSII undergoes large transient increases after transfer from dark to strong white light (WL) it declines little in steady-state as NPQ is induced in shade- and sun-grown spinach and Arabidopsis genotypes Col , OEpsbs , pgr 5bkg , stn 7 and stn 7/8. In contrast, σ'PSII increases by ~30% when induction of NPQ in spinach is inhibited by dithiothreitol and by inhibition of NPQ in Arabidopsis npq 1, npq 4 and pgr 5. We propose this increase in σ'PSII arises as some excitation from closed PSII reaction centres is transferred to open centres when excitation partitioning to photochemistry (Y II ) and NPQ (Y NP ) declines, and is indicated by an increased excitation dissipation from closed PSII centres (Y NO , including fluorescence emission). Although E k increases following dissipation of excitation as heat when NPQ is engaged, it declines when NPQ is inhibited. Evidently photochemistry becomes more easily light saturated when excitation is transferred from closed RCIIs to open centres with larger σ'PSII . The NPQ mutant pgr 5 is an exception; E k increases markedly in strong light as electron transport QA → PQ and PQ → PSI accelerate and the PQ pool becomes strongly reduced. These novel in situ observations are discussed in the context of contemporary evidence for functional and structural changes in the photosynthetic apparatus during induction of NPQ.

The success of the Montreal Protocol in mitigating interactive effects of stratospheric ozone depletion and climate change on the environment.

The Montreal Protocol and its Amendments have been highly effective in protecting the stratospheric ozone layer, preventing global increases in solar ultraviolet-B radiation (UV-B; 280-315 nm) at Earth's surface, and reducing global warming. While ongoing and projected changes in UV-B radiation and climate still pose a threat to human health, food security, air and water quality, terrestrial and aquatic ecosystems, and construction materials and fabrics, the Montreal Protocol continues to play a critical role in protecting Earth's inhabitants and ecosystems by addressing many of the United Nations Sustainable Development Goals.

One hundred research questions in conservation physiology for generating actionable evidence to inform conservation policy and practice.

Environmental change and biodiversity loss are but two of the complex challenges facing conservation practitioners and policy makers. Relevant and robust scientific knowledge is critical for providing decision-makers with the actionable evidence needed to inform conservation decisions. In the Anthropocene, science that leads to meaningful improvements in biodiversity conservation, restoration and management is desperately needed. Conservation Physiology has emerged as a discipline that is well-positioned to identify the mechanisms underpinning population declines, predict responses to environmental change and test different in situ and ex situ conservation interventions for diverse taxa and ecosystems. Here we present a consensus list of 10 priority research themes. Within each theme we identify specific research questions (100 in total), answers to which will address conservation problems and should improve the management of biological resources. The themes frame a set of research questions related to the following: (i) adaptation and phenotypic plasticity; (ii) human-induced environmental change; (iii) human-wildlife interactions; (iv) invasive species; (v) methods, biomarkers and monitoring; (vi) policy, engagement and communication; (vii) pollution; (viii) restoration actions; (ix) threatened species; and (x) urban systems. The themes and questions will hopefully guide and inspire researchers while also helping to demonstrate to practitioners and policy makers the many ways in which physiology can help to support their decisions.

Combating ecosystem collapse from the tropics to the Antarctic.

Globally, collapse of ecosystems-potentially irreversible change to ecosystem structure, composition and function-imperils biodiversity, human health and well-being. We examine the current state and recent trajectories of 19 ecosystems, spanning 58° of latitude across 7.7 M km2 , from Australia's coral reefs to terrestrial Antarctica. Pressures from global climate change and regional human impacts, occurring as chronic 'presses' and/or acute 'pulses', drive ecosystem collapse. Ecosystem responses to 5-17 pressures were categorised as four collapse profiles-abrupt, smooth, stepped and fluctuating. The manifestation of widespread ecosystem collapse is a stark warning of the necessity to take action. We present a three-step assessment and management framework (3As Pathway Awareness, Anticipation and Action) to aid strategic and effective mitigation to alleviate further degradation to help secure our future.

UV-B and Drought Stress Influenced Growth and Cellular Compounds of Two Cultivars of Phaseolus vulgaris L. (Fabaceae).

Combined enhanced UV-B radiation and drought may induce different morphological and physiological alterations in plants than either abiotic stress alone. We evaluated morphology, biomass, and primary and secondary metabolism changes in seedlings of two common bean cultivars, IAC Imperador (drought-resistant) and IAC Milênio. To test the hypothesis that cultivars responded differently to combined stresses in a controlled environment, seedlings of the examined been cultivars were exposed to UV-B and/or drought treatments for three weeks. The cultivars behaved differently, especially to the drought treatment, suggesting that they use different mechanisms to cope with unfavorable environmental conditions. IAC Imperador showed a stronger protective response, modifying wax composition and primary metabolism, and improving its resistance to UV-B radiation. For IAC Imperador, the accumulation of cuticular wax and alkane was higher under combined stress but production of primary alcohols was reduced, suggesting a possible fatty acyl switch. Root/shoot length and biomass ratios increased in both cultivars, particularly for the combined stress, indicating a common plant response. We show that these two bean cultivars responded more strongly to UV-B and combined stress than drought alone as evident in changes to their chemistry and biology. This shows the importance of investigating plant morphological and physiological responses to combined stress.

Latitudinal Biogeographic Structuring in the Globally Distributed Moss Ceratodon purpureus.

Biogeographic patterns of globally widespread species are expected to reflect regional structure, as well as connectivity caused by occasional long-distance dispersal. We assessed the level and drivers of population structure, connectivity, and timescales of population isolation in one of the most widespread and ruderal plants in the world - the common moss Ceratodon purpureus. We applied phylogenetic, population genetic, and molecular dating analyses to a global (n = 147) sampling data set, using three chloroplast loci and one nuclear locus. The plastid data revealed several distinct and geographically structured lineages, with connectivity patterns associated with worldwide, latitudinal "bands." These imply that connectivity is strongly influenced by global atmospheric circulation patterns, with dispersal and establishment beyond these latitudinal bands less common. Biogeographic patterns were less clear within the nuclear marker, with gene duplication likely hindering the detection of these. Divergence time analyses indicated that the current matrilineal population structure in C. purpureus has developed over the past six million years, with lineages diverging during the late Miocene, Pliocene, and Quaternary. Several colonization events in the Antarctic were apparent, as well as one old and distinct Antarctic clade, possibly isolated on the continent since the Pliocene. As C. purpureus is considered a model organism, the matrilineal biogeographic structure identified here provides a useful framework for future genetic and developmental studies on bryophytes. Our general findings may also be relevant to understanding global environmental influences on the biogeography of other organisms with microscopic propagules (e.g., spores) dispersed by wind.

It Is Hot in the Sun: Antarctic Mosses Have High Temperature Optima for Photosynthesis Despite Cold Climate.

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 CO2 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.

Semi-Automated Analysis of Digital Photographs for Monitoring East Antarctic Vegetation.

Climate change is affecting Antarctica and minimally destructive long-term monitoring of its unique ecosystems is vital to detect biodiversity trends, and to understand how change is affecting these communities. The use of automated or semi-automated methods is especially valuable in harsh polar environments, as access is limited and conditions extreme. We assessed moss health and cover at six time points between 2003 and 2014 at two East Antarctic sites. Semi-automatic object-based image analysis (OBIA) was used to classify digital photographs using a set of rules based on digital red, green, blue (RGB) and hue-saturation-intensity (HSI) value thresholds, assigning vegetation to categories of healthy, stressed or moribund moss and lichens. Comparison with traditional visual estimates showed that estimates of percent cover using semi-automated OBIA classification fell within the range of variation determined by visual methods. Overall moss health, as assessed using the mean percentages of healthy, stressed and moribund mosses within quadrats, changed over the 11 years at both sites. A marked increase in stress and decline in health was observed across both sites in 2008, followed by recovery to baseline levels of health by 2014 at one site, but with significantly more stressed or moribund moss remaining within the two communities at the other site. Our results confirm that vegetation cover can be reliably estimated using semi-automated OBIA, providing similar accuracy to visual estimation by experts. The resulting vegetation cover estimates provide a sensitive measure to assess change in vegetation health over time and have informed a conceptual framework for the changing condition of Antarctic mosses. In demonstrating that this method can be used to monitor ground cover vegetation at small scales, we suggest it may also be suitable for other extreme environments where repeat monitoring via images is required.

Reframing conservation physiology to be more inclusive, integrative, relevant and forward-looking: reflections and a horizon scan.

Applying physiological tools, knowledge and concepts to understand conservation problems (i.e. conservation physiology) has become commonplace and confers an ability to understand mechanistic processes, develop predictive models and identify cause-and-effect relationships. Conservation physiology is making contributions to conservation solutions; the number of 'success stories' is growing, but there remain unexplored opportunities for which conservation physiology shows immense promise and has the potential to contribute to major advances in protecting and restoring biodiversity. Here, we consider how conservation physiology has evolved with a focus on reframing the discipline to be more inclusive and integrative. Using a 'horizon scan', we further explore ways in which conservation physiology can be more relevant to pressing conservation issues of today (e.g. addressing the Sustainable Development Goals; delivering science to support the UN Decade on Ecosystem Restoration), as well as more forward-looking to inform emerging issues and policies for tomorrow. Our horizon scan provides evidence that, as the discipline of conservation physiology continues to mature, it provides a wealth of opportunities to promote integration, inclusivity and forward-thinking goals that contribute to achieving conservation gains. To advance environmental management and ecosystem restoration, we need to ensure that the underlying science (such as that generated by conservation physiology) is relevant with accompanying messaging that is straightforward and accessible to end users.