Publications
Late-Holocene palaeoecological reconstruction of Southern Hemisphere Westerlies variability on Subantarctic Macquarie Island
A detailed reconstruction of Southern Hemisphere Westerlies (SHW) variability over the last 2500 years on Macquarie Island reveals periods of strengthened and weakened westerly winds, linked to changes in sea spray-driven lake conductivity. The study found that stronger SHW occurred around ~2500–2300 cal. yr BP and after ~800 cal. yr BP, while weaker SHW prevailed between ~2300–800 cal. yr BP. These findings were derived from palaeoecological analysis of halophilic and halophobic diatoms preserved in lake sediments, which correlate with water conductivity gradients influenced by westerly winds. The study provides a critical long-term record of SHW behavior, offering insights into past atmospheric CO2 concentrations and Southern Hemisphere climate dynamics.
A Novel Invertebrate Predator on an Oceanic Island: Impacts and Invasion Dynamics of Kontikia andersoni on Macquarie Island
Invasive flatworms Kontikia andersoni significantly reduce invertebrate richness at higher elevations on Macquarie Island, threatening native biodiversity. Researchers analyzed species co-occurrence data and community composition across multiple sites, revealing that slope and wind speed are key factors influencing the flatworm's distribution. Habitat suitability modeling identified high-risk areas for invasion, offering critical targets for biosecurity surveillance. This study provides new insights into the ecological impacts of K. andersoni and supports conservation efforts to protect Macquarie Island's fragile ecosystems.
Seasonal and decadal changes in seabird abundance in inshore waters at subantarctic Macquarie Island
Land-based surveys at Macquarie Island reveal significant inter-annual variation in the diversity and abundance of non-breeding seabirds visiting inshore waters, with notable increases in breeding petrel populations following invasive species eradication. The study, comparing data from 2017–2018 and 2022–2023 against a baseline of 2002–2003, documented 41 out of 43 seabird species observed during the baseline period. Nocturnal spotlight surveys also uncovered the first mainland colonies of Common Diving-petrels on Macquarie Island and provided circumstantial evidence for storm-petrel recolonization. While less reliable for detecting changes in penguin abundance or smaller seabirds like prions, diving-petrels, and storm-petrels, these surveys offer valuable insights for marine spatial planning and regional environmental trend monitoring, complementing established on-island studies.
The ongoing decrease in numbers of breeding female southern elephant seals ( Mirounga leonina L.) at Macquarie Island
Southern elephant seal populations at Macquarie Island are uniquely declining, unlike other global populations that remain stable or grow. A 78-year study reveals a steady annual decrease of ~1.1% in breeding females on the isthmus—representing about 20% of the total population—from approximately 9,400 in 1949 to 2,550 in 2023. Annual data since 1984 confirms a similar trend (~0.8% decline), despite interannual variability likely due to breeding skips rather than counting errors. While summer ocean conditions (proxied by the Southern Annular Mode) show no direct link, winter prey dynamics remain the suspected driver of this ongoing decline. The study leverages long-term monitoring and statistical correlation to assess population trends and conservation status.
Derivation of site-specific environmental quality guideline values for fuel-contaminated soils on sub-Antarctic Macquarie Island
Scientists have established the first environmental quality guideline values (EQGVs) for fuel-contaminated soils on sub-Antarctic Macquarie Island, a critical step in protecting its unique ecosystem. Using a species sensitivity distribution model, researchers derived a protective concentration (PC80) of 97 mg/kg total petroleum hydrocarbons (TPH C9–C40), suitable for the immediate station area, and more conservative values for higher conservation zones. The study synthesized ecotoxicological data from 13 critical effect concentrations, representing diverse biota responses to fuels at various degradation stages and carbon contents. This groundbreaking work provides a framework for managing fuel contamination in sub-Antarctic and Antarctic regions, informing remediation efforts and broader environmental protection strategies.
Seabird Populations and Ecosystem Recovery on Macquarie Island: A Palaeoecological Perspective
Macquarie Island's seabird populations exhibit significant recovery following the eradication of invasive species, as revealed by a palaeoecological study combining peat core analysis and contemporary monitoring. Radiometric dating and geochemical analyses of marine-derived nutrients from guano deposition demonstrated that seabird presence fluctuated dramatically over time, with notable declines during periods of invasive species dominance. The study underscores the effectiveness of invasive species eradication in restoring seabird populations and highlights the importance of integrating palaeoecological data with ongoing monitoring to assess ecosystem recovery. These findings provide critical insights for conservation management in subantarctic environments.
Anthropogenic petroleum signatures and biodegradation in subantarctic Macquarie Island soils
A study on Macquarie Island reveals complex petroleum contamination patterns, with evidence of multiple spills and variable biodegradation rates. Soil samples from contaminated sites, including a fuel farm and powerhouse, showed higher concentrations and diversity of hydrocarbons, indicative of repeated SAB diesel spills. However, some locations exhibited signatures suggestive of heavier fuels or crude oil, hinting at diverse contamination sources. Reference sites, though less contaminated, also displayed signs of fuel oil presence. The findings highlight the environmental impact of anthropogenic petroleum in subantarctic soils and underscore the need for robust monitoring and remediation strategies.
Assessing the cloud radiative bias at Macquarie Island in the ACCESS-AM2 model
A significant overestimation of downwelling surface shortwave radiation (+9.5±33.5 W m −2) and underestimation of longwave radiation (-2.3±13.5 W m −2) in the ACCESS-AM2 climate model was identified at Macquarie Island, with biases more pronounced during summer (+25.0±48.0 W m −2). The study utilized surface-based observations and lidar simulations to reveal that these radiation biases are linked to underestimated cloud fraction and low-level cloud occurrence, suggesting modeled cloud phase may also play a role. Additionally, the CERES product showed similar biases, indicating both require further development to improve accuracy in simulating Southern Ocean radiation. This long-term, seasonal evaluation highlights critical gaps in climate modeling that impact sea surface temperature and atmospheric circulation.
Earth-system-model evaluation of cloud and precipitation occurrence for supercooled and warm clouds over the Southern Ocean's Macquarie Island
A year-long study at Macquarie Island, part of the UNESCO-listed Southern Ocean, reveals that liquid-phase clouds precipitate approximately 70% of the time, with deeper and colder clouds showing higher precipitation frequency and intensity. Supercooled cloud layers also precipitate more readily than warmer ones, regardless of thickness. The research utilized ground-based profiling instruments during the Macquarie Island Cloud and Radiation Experiment (MICRE) to evaluate a 9-year Earth-system-model simulation using the GISS-ModelE3. The model, processed through the Earth Model Column Collaboratory (EMC 2), showed deficiencies in cloud occurrence and precipitation frequency but accurately reproduced observed tendencies for deeper clouds to precipitate more frequently. This study demonstrates a valuable framework for evaluating cloud radiative feedbacks in Earth-system models.
Slow recovery of stream invertebrates on subantarctic Macquarie Island after eradication of introduced rabbits and regrowth of vegetation
Stream invertebrate communities on subantarctic Macquarie Island showed slow recovery following the eradication of invasive rabbits and subsequent vegetation regrowth, with taxon richness and composition remaining largely unchanged a decade after rabbit removal. Initial sampling in 1992 recorded an average of 11.6 taxa per site, but this declined to 7.4–8.4 taxa during peak rabbit grazing (2000–2011). Despite substantial vegetation recovery by 2016, resampling revealed minimal improvement in invertebrate diversity and structure, suggesting limited refuges hindered rebound. The study, which resampled 13 of the original 15 sites using kick sampling, found that climate and water quality changes did not significantly influence recovery. These findings imply that stream ecosystems may require decades to recover from severe anthropogenic disturbances.
Southern Ocean Low Cloud and Precipitation Phase Observed During the Macquarie Island Cloud and Radiation Experiment (MICRE)
A significant portion of low clouds over Macquarie Island, particularly those with cold tops (≤0°C), exhibit predominantly liquid-phase characteristics at cloud base, despite the potential for mixed or ice-phase precipitation below. This study, conducted during the Macquarie Island Cloud and Radiation Experiment (MICRE) from April 2016 to March 2017, found that around two-thirds of low clouds were cold-topped, with these clouds being thicker and having higher bases compared to warm-topped clouds. The research utilized ground-based ceilometer, depolarization lidar, and W-band radar measurements to characterize cloud macrophysics and precipitation phase. Notably, 83–88% of cold-topped clouds were liquid at the base, while small-particle (low-radar-reflectivity) precipitation was mostly liquid below-cloud, contrasting with large-particle precipitation that was predominantly mixed or ice-phase. This insight is crucial for understanding the radiative properties and climate impacts of Southern Ocean low clouds.
Terrace types and vegetation dynamics on Macquarie Island
Macquarie Island's terraced landscapes reveal dynamic interactions between vegetation and terrain under current climatic conditions. A study of 38 non-windward terraced sites demonstrated that wind, moisture, slope stability, and vegetation collectively shape terrace forms, indicating an active process rather than a static one. This challenges the assumption that such features are relics of past environmental conditions, suggesting instead that they evolve in response to ongoing ecological and geological factors.
The unique marine ecosystem surrounding Macquarie Island
Macquarie Island's marine ecosystem, spanning approximately 478,000 km² within Australia’s Exclusive Economic Zone (EEZ), is a thriving biodiversity hotspot despite its harsh Sub-Antarctic environment. This study highlights the unique properties of the waters surrounding the island, emphasizing its role as one of the world's recovering wild places. The research underscores the significance of Macquarie Island's geoheritage and undersea features, which support a multitude of marine life. While Australia holds sovereign rights over this area, it also carries the responsibility to conserve and manage it for humanity. The study contributes to understanding the ecological dynamics and resilience of this unique marine ecosystem.
Tracking the origins of the introduced terrestrial amphipod, Puhuruhuru patersoni , on sub‐Antarctic Macquarie Island
A genetic analysis of the introduced amphipod Puhuruhuru patersoni on Macquarie Island reveals that the species likely originated from the southern region of New Zealand's South Island. The study, which compared mitochondrial DNA (mtDNA) data across the known range of P. patersoni, found significantly lower genetic diversity on Macquarie Island than in its native range. Phylogenetic reconstructions further supported this conclusion, suggesting that the introduction to the sub-Antarctic island was probably linked to historical activities between New Zealand and Macquarie Island. This finding sheds light on the origins of invasive species and their potential impact on fragile ecosystems like those found at UNESCO World Heritage Sites.
Ecology and management of invasive plants in the sub-Antarctic and Antarctic regions: evidence and synthesis from Macquarie Island
Invasive plant species, particularly those adapted to extreme cold conditions, pose significant threats to sub-Antarctic and Antarctic ecosystems. Research on Macquarie Island reveals that these species, such as Poa annua and Stellaria media, persist through large, long-lived soil seed banks and are facilitated by human introductions, animal disturbances, and climate change. While no single biological trait predicts invasiveness in the sub-Antarctic, ecological drivers like accidental human movement and soil disturbance enable their spread. The study emphasizes the need for proactive measures to prevent further invasion, develop low-impact control methods, and protect these fragile ecosystems from potential threats extending into Antarctica due to warming climates.
Hydrochemical and isotopic baselines for understanding hydrological processes across Macquarie Island
A comprehensive island-wide survey of Macquarie Island reveals that groundwater significantly influences lake hydrochemistry and hydrology, a factor previously overlooked. This study used stable isotope ratios (δ13C, δ18O, δ2H) and strontium isotopic ratios (87Sr/86Sr) to analyze 40 lakes, identifying distinct geochemical drivers such as sea spray aerosols on the western side and water–rock interactions in lower elevation catchments. Lakes at higher elevations were found to be more dilute, while those at lower elevations contained terrestrial-sourced ions, likely from groundwater. These findings provide critical baseline data for understanding nutrient cycling and ecosystem health, with implications for predicting shifts due to climate change.
So Close Yet So Far: Age and Growth of Blue Antimora Antimora rostrata (Moridae, Gadiformes, Teleostei) off New Zealand and Macquarie Island (Southwestern Pacific Ocean)
Blue antimora (Antimora rostrata) populations off Macquarie Island exhibit growth rates comparable to those in other Southern Ocean regions, including the Ross, Lazarev, and Weddell Seas, as well as near Kerguelen and Crozet Islands. However, individuals from New Zealand waters demonstrate significantly slower growth, akin to those found in the Flemish Cap area. This study analyzed age and growth patterns using samples collected from bycatch in the Patagonian toothfish longline fishery (Macquarie Island) and bottom trawl catches (New Zealand). Age estimates ranged from 11 to 44 years, with total lengths varying between 22.5–71.1 cm. The most abundant age classes differed between regions, suggesting potential stock structure variations. Further research is needed to clarify population distinctions across the species' broad range.
Southern Ocean Precipitation Characteristics Observed From CloudSat and Ground Instrumentation During the Macquarie Island Cloud & Radiation Experiment (MICRE): April 2016 to March 2017
A year-long study on Macquarie Island revealed that precipitation, primarily composed of small particles, occurred 44% of the time between April 2016 and March 2017. The research combined surface measurements from disdrometers, radars, and tipping buckets with CloudSat satellite data to analyze precipitation types and their characteristics. Key findings included the identification of distinct patterns in ice, mixed-phase, and rain precipitation, linked to the island's position relative to cyclonic low-pressure systems. Ice and mixed-phase precipitation were more common when Macquarie Island was northwest of these systems, while rain was frequent when southeast of them. Additionally, a weak diurnal cycle was observed, with higher frequencies between 03:00 and 06:00 local time. The study also noted that CloudSat overestimated total liquid precipitation and mixed-phase occurrences but accurately captured rain rates above 0.5 mm/hr.
The current trajectory of king penguin ( Aptenodytes patagonicus ) chick numbers on Macquarie Island in relation to environmental conditions
King penguin chick numbers on Macquarie Island have been declining at a rate of 1.06 ± 0.03% annually since 2007, marking the end of a rapid population increase observed from 1930 to 1980. Annual fluctuations in chick numbers, ranging from 33,513 to 78,714, were negatively correlated with environmental factors such as heavy rainfall, total rainfall, and maximum east coast wave height during incubation, as well as warmer sea surface temperatures in the penguins' foraging region. While causality remains uncertain due to interannual variability and the long generation time of king penguins, this study highlights a potential shift from population growth to stabilization or decline. Ongoing monitoring is crucial to determine the trajectory of this UNESCO-listed site's breeding population.
Rephotography, permanent plots and remote sensing data provide varying insights on vegetation change on subantarctic Macquarie Island, 1980–2015
A comprehensive analysis of vegetation change on Macquarie Island from 1980 to 2015 reveals that rephotography provides the most effective method for detecting spatial and temporal patterns of overall vegetation change, particularly in response to rabbit population dynamics. The study found stability in Acaena herbfield despite reduced disturbance, an increase in Pleurophyllum hookeri cover, and a rise in short grassland vegetation, while Azorella macquariensis cover remained constant. Although long-term plot data were less consistent with rephotography findings and more resource-intensive, sporadically available remote sensing data effectively monitored ground revegetation/devegetation but failed to detect other changes. The research highlights the importance of combining multiple monitoring approaches to accurately assess vegetation dynamics in subantarctic ecosystems.
Assemblages of myxomycetes on subantarctic Macquarie Island and tropical Christmas Island
A comparative study of myxomycete assemblages on subantarctic Macquarie Island and tropical Christmas Island reveals stark differences despite their similar sizes. Only nine species are shared between the two locations, highlighting distinct biogeographical patterns driven by extreme environmental contrasts. Surveys conducted in 1995 (Macquarie) and 2017 (Christmas) identified 85 species in total, including three new to science—two from Macquarie Island and one from Christmas Island. The research underscores the unique ecological niches occupied by myxomycetes in these isolated environments, with subantarctic conditions fostering a far less diverse but equally significant assemblage compared to tropical counterparts.
Evaluation of CERES and CloudSat Surface Radiative Fluxes Over Macquarie Island, the Southern Ocean
A recent evaluation of satellite-derived radiative fluxes over Macquarie Island, a UNESCO World Heritage Site in the Southern Ocean, reveals significant biases in global climate models. The study found that the Clouds and Earth's Radiant Energy System (CERES) and CloudSat retrievals underestimated shortwave radiation reflected back to space while overestimating surface-reaching longwave radiation, with annual mean biases of +10 W/m² for shortwave and -10 W/m² for longwave. These discrepancies, particularly pronounced at night due to poor cloud base representation, suggest that climate models may underestimate the Southern Ocean's radiative effects more than previously thought. The findings, based on surface observations from the Macquarie Island Cloud and Radiation Experiment (MICRE), highlight critical gaps in satellite data validation over this remote region.
Evidence of a Diurnal Cycle in Precipitation over the Southern Ocean as Observed at Macquarie Island
A diurnal cycle in precipitation over the Southern Ocean has been identified, with maximum rainfall occurring during night and early morning, and minimum in the afternoon. This pattern, observed at Macquarie Island from 1998 to 2016, is most pronounced in summer and suggests a significant contribution of marine boundary layer clouds to total precipitation. The study analyzed surface hourly precipitation data and twice-daily upper air soundings (1995–2011), revealing stronger lower tropospheric inversions at night, consistent with the observed diurnal cycle. These findings challenge the assumption that ERA-Interim precipitation products accurately represent natural variability, as they are dominated by a 12-hourly cycle likely due to twice-daily initialization. The implications for satellite-derived precipitation products, such as those from the A-Train constellation, are also discussed.
Macquarie Island Cloud and Radiation Experiment (MICRE) Field Campaign Report
A collaborative field campaign on Macquarie Island revealed critical insights into the behavior of clouds and radiation over the Southern Ocean. The Macquarie Island Cloud and Radiation Experiment (MICRE), conducted from March 2016 to March 2018, deployed advanced ground instrumentation to collect comprehensive data on surface radiation, cloud properties, precipitation, and aerosols. This study, led by the U.S. Department of Energy's Atmospheric Radiation Measurement (ARM) user facility in partnership with the Australian Antarctic Division (AAD) and the Australian Bureau of Meteorology (BOM), aimed to deepen our understanding of these atmospheric phenomena. The campaign highlighted key data quality issues and developed value-added products to facilitate scientific analysis, providing a robust dataset for future research on climate dynamics in this pristine and ecologically significant region.
Southern Ocean sentinels: demographic insights into the declining population of Southern elephant seals at Macquarie Island
A long-term decline in the Southern elephant seal population at Macquarie Island, unique among stable or growing populations globally, is driven by extreme reproductive costs that significantly reduce survival rates for both first-time and experienced breeders. This study, using an 18-year capture-recapture dataset of over 6,000 individually marked females, revealed that environmental conditions during the post-moult foraging trip—critical to pregnancy initiation—play a pivotal role in whether seals skip reproduction. Incorporating this finding into matrix population models confirmed and re-evaluated the population's decline, offering potential clues to its causes. The research highlights how evolutionary and ecological processes shape life histories in long-lived species, contributing to broader understanding of predator dynamics in the Southern Ocean.
Using an expert judgment response matrix to assess the risk of groundwater discharges from remediated fuel spill sites to the marine environment at sub-Antarctic Macquarie Island, Australia
Residual contamination from remediated fuel spill sites at Macquarie Island poses minimal risk to adjacent marine communities, according to a comprehensive toxicity assessment. The study, using an expert judgment response matrix, found that even under worst-case exposure conditions—undiluted and continuous—native marine invertebrates showed variable and slow responses, with some species exhibiting no adverse effects. Natural site dynamics, such as rapid dilution due to high rainfall and energetic receiving environments, further mitigate potential risks. While toxicity was observed in certain species over extended periods (up to 21 days), no consistent patterns linked to hydrocarbon concentrations were identified. This research provides robust evidence that residual groundwater contamination at remediated sites is unlikely to harm marine ecosystems, offering critical insights for environmental risk assessment in sub-Antarctic regions.
Vegetation change on subantarctic Macquarie Island
Macquarie Island has undergone rapid vegetation change following the successful eradication of feral rabbits, rats, and mice in 2011. This large-scale project revealed that the absence of grazing pressure allows plant species distribution and vegetation structure to be primarily influenced by abiotic factors like climate. Research using repeat photographs over 34 years and satellite imagery demonstrated geographic variation in vegetation trends post-eradication. Spatial analysis showed that south-westerly winds were more damaging to plants than prevailing westerlies, while steep air temperature lapse rates limited diurnal and seasonal variation. Tussock grass and megaherbs, which declined by 2009, rebounded by 2014 without grazing pressure. However, high-elevation feldmark vegetation showed no consistent trends linked to rabbit impacts or climate change. Species distribution models indicated that generalist plant species have a smaller 'core range' where they dominate. The study highlights the ongoing ecosystem recovery and the interplay between climate change and the absence of grazing in shaping Macquarie Island's lowland vegetation.
Warmer and less variable temperatures favour an accelerated plant phenology of two invasive weeds across sub‐Antarctic Macquarie Island
Climate change is enhancing the invasive capabilities of two weed species, Poa annua and Cerastium fontanum, on sub-Antarctic Macquarie Island. The study found that warmer, less variable temperatures accelerate plant growth and phenological development in P. annua, while temperature variability negatively impacts both species. Despite their distinct reproductive strategies, both species successfully produce seeds across all studied sites, demonstrating remarkable acclimation to extreme conditions. This suggests that climatic warming could significantly boost the invasiveness of alien plants even in remote sub-polar regions, underscoring the urgent need for proactive management to prevent further spread.
Qualitative modelling of invasive species eradication on subantarctic Macquarie Island
Simultaneous eradication of rabbits, rats, and mice from Macquarie Island is strongly supported by qualitative modelling due to the high likelihood of continued ecological impacts if only one or two species are targeted. The study predicts positive outcomes for native tall tussock vegetation and burrow- and surface-nesting seabirds but also highlights risks, such as potential failure in eradicating mice and unintended consequences from redpolls and starlings. This approach demonstrates that qualitative modelling can provide consistent insights even with significant ecosystem uncertainty, aiding strategic conservation planning.
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