Euphausiids play important roles in ecosystems worldwide, transferring energy from primary producers to secondary consumers. Antarctic krill are the most abundant euphausiid on Earth and play important roles as critically important species in Southern Ocean ecosystems. Microplastics have been found throughout the Southern Ocean ecosystem, including krill. Here, we examine where krill and microplastics interact throughout the coastal ocean of the West Antarctic Peninsula. Using a physical ocean model to simulate the transport of vertically migrating krill and drifting microplastics, we identified several hotspots around the Antarctic Peninsula where both are consistently found in higher than average abundances. The extent of the overlap was modulated by both currents in the near-surface (< 50 m) and deep (> 50 m) ocean, and the vertical migration behaviors of Antarctic krill. Therefore, in order to understand the impacts of microplastics, we need to evaluate overlap in the context of euphausiid behavior and oceanographic conditions.

Penguins are emblematic inhabitants of the Antarctic continent and play a significant role in the biogeochemical cycles of the Southern Ocean by transferring essential nutrients to marine ecosystems via guano production. Despite their ecological importance, the contribution of penguin guano to carbon cycling remains largely unexplored. Microplastics (MPs) add complexity to these dynamics. MPs in fecal material can limit carbon export by reducing sinking rates and increasing remineralization. We examined guano from two penguin species, the Chinstrap (P. antarcticus) (n = 25) and Gentoo (P. papua) (n = 7), from the South Shetland Islands. We quantified biogeochemical particulate components (carbon, nitrogen, and biogenic silica) and characterized MP polymeric composition. Both species showed similar values for natural particulate fractions. Microplastics were detected in 91% of samples, dominated by small particles (25-50 μm, 46%). Chinstrap guano contained the highest amount of MPs. Polypropylene was the predominant polymer (34% in Chinstrap, 75% in Gentoo), followed by polyethylene (37% in Chinstrap, not found in Gentoo). This study provides the first survey of the smallest MP fraction (down to 25 μm) in penguin guano, offering new insight into how a shift in the partitioning from natural to MP particles, previously overlooked, may influence guano-mediated carbon pathways.

Abstract Human-induced global climate change and other anthropogenic stressors are fundamentally altering our oceans. Understanding the ecological and societal implications of these changes is critical for developing mitigation strategies and conservation measures. However, major components of the marine pelagic ecosystem remain poorly understood. This is true for euphausiids (“krill”), which are a crucial part of marine food webs and play an important role in elemental cycling, including in the biological carbon pump, but for which we know surprisingly little. In this review, we first provide an overview of the ecological and socio-economic value of krill, highlighting their function in marine food webs and biogeochemical cycling. Next, we describe what is currently known regarding the response of krill to climate change and other anthropogenic stressors, focusing on changes in their biogeography, physiology, life history, as well as the impacts of krill fishing and their association with pathogens and parasites. We identify five key gaps in our current knowledge of krill: (1) the effects of krill on food web dynamics and stability, (2) the effects of changing predator and/or prey communities on krill populations, (3) the identification of important krill habitats, (4) the understanding of vertical and horizontal range shifts, and (5) the combined effects of multiple climate change and other anthropogenic stressors on krill. We also highlight the krill species, regions, and habitats that are understudied. Finally, we propose strategies to improve our understanding of this ecologically important taxonomic group, including the sustained funding for time series; implementation of novel research technologies; expanding research on understudied species and regions; and creating a global community of krill researchers.

The Weddell Sea, Southern Ocean, is a highly productive location of deep-water formation and a globally important site of carbon sequestration. Here, the biological carbon pump is dominated by carbon-rich particulates which are both actively and passively transported to deep water (e.g. zooplankton faecal pellets and phytoplankton detritus). However, climate driven changes in sea ice have the potential to disrupt these processes, highlighting a need for contemporary observations. This study quantified the flux of particulate organic carbon (POC) and nitrogen (PON) across three depths (50, 100, 150 m) at five locations (including shelf, off shelf, ice covered and ice-free environments) in the western Weddell Sea using a drifting sediment trap. POC and PON fluxes were greater on shelf than off-shelf, likely reflecting increased nutrient supply and productivity on shelf. No strong patterns between sea ice and ice-free stations were present, likely because the ice pack was constantly shifting, with most sites influenced by sea ice. The POC flux remained stable or increased with depth at most stations, ranging from 42.5–364.1 mg C m−2 d−1 (mean of 123.2 mg C m−2 d−1). Krill faecal pellets represented 98 % of all pellets, which contributed an estimated 17 %–99 % (median of 48 %) of the POC flux. The faecal pellet flux peaked at 100 m across the shelf, suggesting krill defecating at depth effectively counteracted attenuation in the upper ocean. Our findings emphasise the importance of zooplankton-mediated processes in determining the particle flux and the benefits of resolving the vertical flux at a resolution which incorporates their ecology. It is unclear how changing sea ice dynamics will impact zooplankton, so a process-driven understanding of biogeochemical fluxes is integral for predicting the future of carbon cycling in the Southern Ocean.

Despite the remoteness of their breeding sites, subantarctic seabirds are susceptible to anthropogenic pollutants (e.g. microplastics) and other chemical stressors (e.g. plastic additives) that are released from ships and research stations, arrive in ocean currents, are transported in the atmosphere, or are ingested when the birds feed north of the Antarctic Polar Front. In this study, we investigated the presence and levels of microplastics and several groups of endocrine-disrupting chemicals (EDCs) in adults or chicks of seven seabird species breeding at the subantarctic islands of South Georgia. A total of 1275 anthropogenic particles were recovered in the gastrointestinal tracts of 76 seabirds, with a frequency of occurrence of 97.4%, a mean value of 16.78 ± 18.79 particles per individual and of 0.03 ± 0.03 particles/g body weight. Ten percent (n = 130 particles) of the particles were identified chemically using microFTIR spectroscopy, of which 59% were synthetic, 18% were natural, 19% were anthropogenic unknown and 4% were anthropogenic cellulosic. Of the EDCs, only polybrominated diphenyl ethers (PBDEs) and methoxylated polybrominated diphenyl ethers (MeO-PBDEs) congeners occurred at levels above the limit of quantification. Liver samples consistently exhibited the highest concentrations of both contaminant groups. The highest concentrations of PBDEs were in adult brown skuas (133.96 ng/g) and of MeO-PBDEs were in wandering albatross chicks (6.50 ng/g). This research provides evidence of plastics and plastic additives in subantarctic seabirds, underscoring the need to strengthen measures aimed at reducing marine pollution.

Theme 5 examines the impacts of human activities in Antarctica, including exploring human impacts such as scientific operations, tourism, shipping, local and global pollution, and krill fisheries. interact with climate change to inform environmental policy within and beyond the Antarctic Treaty System. Local pressures generate chemical and plastic pollution, black carbon, underwater noise, wildlife disturbance, invasive species, and antimicrobial resistance, affecting ecosystem resilience. The theme seeks to quantify and monitor anthropogenic pressures through standardized, internationally coordinated protocols spanning chemical, biological, ecological, and cultural dimensions during InSync. Key topics include pollutants and plastics, underwater soundscapes, tourism impacts, fishery ecosystem effects and management, environmental DNA and antimicrobial resistance, marine pollution impacts and climate feedback, and the cultural legacies of historic expeditions. Approaches combine harmonized sampling, long-term monitoring, remote sensing, in situ observations, and modelling to identify hotspots and cumulative impacts. By integrating open-access data across disciplines, Theme 5 advances predictive risk assessment, science-based mitigation, and conservation strategies to detect anthropogenic signatures and strengthen the protection of Antarctic ecosystems.

Microplastics (MP) are a relevant stressor in Arctic marine ecosystems. Their small size and ubiquity make them readily ingestible by zooplankton, placing copepods at the entry point of MP into high-latitude food webs. Calanus hyperboreus is a key Arctic species characterised by exceptionally large lipid reserves that fuel overwinter survival, support higher trophic levels as energy-rich prey, and facilitate carbon sequestration via the lipid pump. Successful lipid accumulation is therefore critical for individual fitness and ecosystem functioning, and MP-driven disruptions may have cascading effects on food-web dynamics and regional carbon sequestration. To address this, we exposed wild-caught C. hyperboreus copepodite stage V (CV) from southeastern Greenland to pristine and biofouled MP under feeding and food-deprived conditions during late summer (July–August 2024) aboard RRS Sir David Attenborough. Across experiments, control copepods exhibited seasonal shifts consistent with increasing lipid reserves and changes in fatty-acid composition over time. Responses to MP exposure were strongly context dependent. Pristine MP produced modest and variable changes in lipid content and fatty-acid profiles, whereas the most pronounced shifts were observed during late-summer exposure to biofouled MP under food-replete conditions, including reduced lipid mass and altered fatty-acid composition characterised by lower long-chain monounsaturated fatty acids and higher relative contributions of docosahexaenoic acid. Together, these patterns suggest that MP exposure during periods of active lipid accumulation may interfere with normal energy storage and fatty-acid allocation. These findings also identify a potentially crucial late-summer exposure context in which effects of MP on copepod lipid metabolism are most evident, rather than isolating biofouling as a sole causal factor. Overall, this study highlights the importance of seasonal physiological state and particle conditioning in shaping MP impacts on Arctic zooplankton, with potential implications for food-web dynamics and lipid-driven carbon export.

Giant Antarctic iceberg calving is projected to increase with climate change, affecting ocean circulation, nutrient supply, and carbon cycling. These icebergs can stimulate primary production and influence Southern Ocean carbon fluxes through modification of upper ocean physics and biogeochemistry, yet the underlying mechanisms remain poorly constrained. We investigate the coupled effects of meltwater input and nutrient dynamics around two of the largest known icebergs, A-76A and A-23A, using silicon isotopes alongside hydrographic, meltwater, and macronutrient observations to examine nutrient cycling. Around A-76A, enhanced glacial meltwater input coincides with macronutrient variability and strong silicon isotope fractionation, indicating diatom utilisation sustained by continued macronutrient supply. In contrast, waters around A-23A show minimal glacial meltwater enhancement and remain macronutrient-rich, with no silicon isotope fractionation, indicating limited biological uptake despite favourable background conditions. These contrasting regimes reveal that iceberg influence on ocean biogeochemistry is highly heterogeneous, reflecting the combined effects of micronutrient fertilisation, macronutrient resupply, and environmental context. Our findings demonstrate that giant icebergs exert dual controls on productivity by initiating blooms through micronutrient delivery and sustaining biomass accumulation through resupply from depth. This mechanistic understanding is critical for assessing the role of increasing iceberg discharge in future Southern Ocean productivity and carbon cycling.

Climate change is reshaping contaminant pathways in Antarctica by mobilizing rare earth elements (REEs) and heavy metals from the cryosphere into marine ecosystems. Thaw-driven changes in salinity, pH, stratification, and primary productivity modify contaminant behaviour and bioavailability. The ice-algae interface is hypothesized to concentrate these elements; for heavy metals this pathway is empirically supported, while for REEs it remains to be directly measured in krill Krill are the fundamental species of the food web in the Southern Ocean. Krill are well established as biovectors for metals and may represent an important pathway for future transfer of emerging contaminants, including REEs, although direct empirical evidence in Antarctic krill remains absent. Krill are established biovectors for metals and may represent a plausible exposure pathway for emerging contaminants, including REEs, although direct field measurements of REEs in Antarctic krill remain unavailable. Current evidence reveals substantial knowledge gaps in Antarctic contaminant research, particularly because mercury remains the only contaminant with comparatively coherent Southern Ocean datasets, whereas REEspecific field measurements in Antarctic krill remain entirely absent. This evidence gap continues to limit quantitative assessment of climate-driven contaminant mobilisation, ecological exposure pathways, and foodweb transfer in Antarctic marine ecosystems. The lack of baseline data and long-term datasets necessitates advanced ultra-trace analytical approaches and sustained monitoring frameworks to enable comprehensive quantitative risk assessment and the detection of climate-driven trends in contaminant dynamics. Antarctica's protected status under the Antarctic Treaty System highlights the critical need for enhanced international cooperation and integrated governance frameworks to address REE and metal concerns in a rapidly warming Southern Ocean.

The increase in shipping in the Canadian Arctic has significant impacts on Inuit coastal communities and their traditional way of life. Examples include the risk of chemical spills, underwater noise and ships’ hulls acting as vectors for non-indigenous species, all of which impact ecosystems and wildlife which Inuit rely on for health, food security and cultural sustainability. However, the number and types of ships travelling near communities and the associated risks remain poorly quantified, limiting effective management strategies. We use ship tracklines generated from Automatic Identification System (AIS) ship positions between 2013 and 2022 to calculate voyages within 20 km of 43 communities distributed throughout Northern Canada (north of 60° N and Hudson Bay). Over 10 years, voyages increased significantly by a factor of 1.7 (from 116 in 2013 to 317 in 2022), with the largest increases due to dry bulk, cargo and government/research vessels. This varies between communities, with 15 (35

The cycling of calcium carbonate (CaCO3) in the ocean is closely linked to seawater alkalinity and the regulation of atmospheric CO2. In the modern pelagic ocean, almost all CaCO3 is produced by three groups of calcifying planktonic organisms: coccolithophores, foraminifers, and shelled pteropods. In this Review, we examine the differences in functional traits that define each group's distinctive role in the global carbon cycle and their sensitivity to climate change and ocean acidification. This synthesis reveals that a single representation of CaCO3 in climate models is unlikely to accurately reflect system dynamics or their impacts on biogeochemical cycling under climate change. We argue that understanding past and future CaCO3 cycle requires a better delineation of the traits that make up the diversity of calcifying plankton groups.

Microplastic pollution in remote inland Antarctica is largely unknown. This study explored the plastic footprint of snow from remote Antarctic camps; Union Glacier, Schanz Glacier and the South Pole. Refined automated FTIR techniques enabled interrogation of <25 µm microplastics and fibres in Antarctic snow for the first time. Microplastics were pervasive (73 - 3,099 MP L-1). The majority (95%) measured <50 µm, indicating that previous microplastic reports in Antarctica may be underestimated, due to analytical restrictions. Polymer composition and concentration did not vary significantly between sites, with dominant polymers being polyamide (PA), polyethylene terephthalate (PET), polyethylene (PE) and synthetic rubbers, likely from both local (clothing, ropes, flags) and long-range (aerially deposited) sources. Results indicate that even in the most remote regions of earth, humans are leaving a plastic legacy in the snow, and illustrate the importance of remote, cryospheric regions as critical study sites for determining temporal fluxes in microplastic pollution.

The Southern Ocean is a globally significant site of carbon sequestration with the copepod community exerting a strong influence on the carbon flux. Currently, a holistic understanding of Southern Ocean copepod ecology is limited by a lack of data, particularly during winter. This study analyzed the composition and abundance of copepods caught in a sediment trap (400 m depth) in the Northeast Scotia Sea, providing a view of year-round copepod community dynamics. We found strong seasonal trends in abundance and composition of copepod taxa, with Calanus simillimus and Metridia spp dominating throughout. The capture of Metridinidae copepods likely occurred as they carried out their pronounced diel vertical migrations (DVM). The disproportionate abundance of male specimens of Metridia spp., as well as another member of the Metridinidae, Pleuromamma robusta, indicates sex-specific differences in their DVM ranges, with males remaining deeper. The C5 developmental stage of C. simillimus showed a distinct seasonal pattern, characterized by high abundances in autumn followed by low numbers in winter. We propose that this reflects an autumnal seasonal descent beyond which their fate could be one of three scenarios. Firstly, that these individuals seasonally migrate deeper than the sediment trap depth but remain active and feed on deep particulate matter. Secondly, that they become dormant whilst at this depth and respire their fat reserves. Thirdly, that they become dormant but at shallower depths, at and around the depth of the sediment trap, where they remain static and are not captured. Each of these scenarios has different implications for the seasonal carbon flux generated by C. simillimus. This study highlights the importance of understanding species-specific copepod ecology and emphasizes the need to collect ecological data over full annual cycles.

Microplastic release in Antarctica is an issue of increasing concern, despite the limited human presence in the region. This study estimates the annual release of microplastics from the wastewaters of scientific facilities through the use of personal care products and laundering. Furthermore, it analyses the most cost-efficient policy interventions to target this pollution. The study has estimated a potential release of 238 kg per year, which is negligible on a continental scale but could have substantial local environmental impacts. A comprehensive cost-efficiency analysis demonstrates that microplastic release can be effectively mitigated through low-cost preventative measures, such as installing washing machine filters and banning hygiene products containing microbeads. Furthermore, the implementation of wastewater treatment systems is suggested as a crucial and long-term cost-effective solution for treating wastewater effluent and removing other pollutants from the Antarctic region. These results provide a framework to inform policy decisions on microplastic release in Antarctica and lay the foundation for improved environmental protection strategies in this sensitive region.

Monitoring the movement of plastic into marine food webs is central to understanding and mitigating the plastic pollution crisis.

The Southern Ocean plays a crucial role in absorbing carbon dioxide from the atmosphere, accounting for 20% of the ocean's carbon sink despite covering only 10% of the global ocean area. Antarctic Krill (Euphausia superba) are central to this process, as their faeces help remove carbon from the upper ocean by sinking to deeper layers. However, microplastics are increasingly polluting the Southern Ocean, and have been found in zooplankton, especially krill. These buoyant microplastics may slow the sinking of krill faeces, potentially reducing the amount of carbon that is trapped in the deep ocean. Whether, and to what extent, microplastics impact faeces sinking is still an open question. To address this gap, we developed a theoretical model to study how microplastics affect the density and fragmentation of krill FP which in turn will impact their vertical sinking to the oceanic depths. Our findings suggest that in environmentally relevant concentrations, microplastics could slow down the sinking of these pellets. Larger microplastics have the most impact, causing greater fragmentation of the faeces as they settle in the water column. While the buoyancy effect of microplastics is currently marginal due to the density change, under a business-as-usual scenario. Our results highlight that future increases in microplastics will likely have a significant negative impact on the ability of krill to promote the storage of carbon in the deep ocean.