Blood Falls is a unique feature that appears at the snout of the Taylor Glacier in the upper Taylor Valley, East Antarctica. It is an iron-rich brine that occasionally gets expulsed from a subglacial source due to the weight and movement of the overlying glacier. The brine that emanates stains the glacier as it oxidizes at the surface and flows towards the West Lobe of Lake Bonney (WLB). Recent work (Spigel et al. 2018, Lawrence et al. 2020) has shown that, besides the Blood Falls contribution, the brine enters the WLB all along the front of Taylor Glacier, creating cold water anomalies at the depth where this subglacial brine’s density is matched by the surrounding lake water. Mikucki et al. (2015) detected substantial brine at the base of Taylor Glacier using an airborne transient electromagnetic sensor. Badgeley et al. (2017) used radio echo sounding to delineate the brine further and to show that there are subglacial flow pathways that direct the brine to the centre and south side of Taylor Glacier’s snout, in addition to what flows from Blood Falls.

Abstract The Earth’s poles have always aroused great interest and fascination, first for explorers looking for the Northern Pass in the Arctic or for a new continent and natural resources to exploit, and today for scientists due to the significant role that the Arctic and Antarctic oceans play in the dynamics and future of our planet, especially in the current context of global change. To raise awareness of the importance and vulnerability of the polar oceans and to bring scientific advances in marine science to schools and the general public, we have worked from different approaches: 1) the online participation of students in polar oceanographic expeditions (through the ICM Divulga educational website), 2) face-to-face talks and workshops on polar ecosystems involving the observation of samples and/or videos, 3) the coordination and the edition of the book Observando los polos with a global and multidisciplinary vision of the state of scientific knowledge on polar areas, 4) the elaboration of the photographic exhibition ‘Una mirada polar’ and 5) the multi-institutional collaborative project surrounding the XIth Scientific Committee on Antarctic Research (SCAR) International Biology Symposium. These approaches, some of which involved Dr Andrés Barbosa’s collaboration, align with his objective of disseminating the results of research and scientific experience to the public. An evaluation of the strengths and weaknesses of the diverse strategies used to provide education about polar science is presented.

Abstract Many authors have studied the biogeography of the Southern Ocean (SO), defined its limits and proposed their division into biogeographical zones and provinces. In this work we analyse the biogeography of sea slugs in a broad sense (Mollusca, Gastropoda, Heterobranchia) in the different areas and zones of the SO below 41°S. Most of the published scientific publications, databases and technical reports where records of benthic sea slugs appear in the SO have been analysed in addition to our own records, cataloguing a total of 355 different benthic species. The following areas and zones of the SO have been considered: Antarctica (Weddell Sea, West Antarctica, Ross Sea, East Antarctica), the sub-Antarctic zone (Falkland Islands, South Georgia Island, South Orkney Islands, South Sandwich Islands, Bouvet Island, Crozet and Prince Edward islands, Kerguelen Islands, Macquarie Island), southern South America (Patagonia/Magellan), Tasmania and New Zealand (South Island). A presence/absence table for all recorded species in the different zones has been compiled, and the differences and similarities between them have been calculated using the Sorensen index. The best representation has been obtained by classifying the zones into five groups: G1 (the four Antarctic zones, South Georgia Island, South Sandwich Islands, South Orkney Islands), G2 (Kerguelen Islands, Crozet and Prince Edward islands and Macquarie Island), G3 (Falkland Islands and Patagonia/Magellan), G4 (Tasmania and New Zealand’s South Island) and G5 (Bouvet Island). In addition, the concordance between the non-hierarchical classification (K-mean) and the hierarchical classification obtained using the WARD and UPGMA cluster analysis methods has been verified. The representative and distinctive species of each of these groups are indicated. In this work, as regards benthic sea slugs, the biogeographical affinities between the Antarctic zones and some of the sub-Antarctic zones are confirmed, as well as between the fauna of these molluscs in the Patagonian/Magallan zone and the Falkland Islands, while the affinities between the other zones need further confirmation when more species records become available.

Abstract This article explores the evolution of US policy on Antarctica, focusing on its legal, environmental and geopolitical aspects. It aims to identify changing US priorities in this regard. The Antarctic Treaty System (ATS) governs the region, emphasizing peace, scientific cooperation and environmental protection. The USA has issued four major memoranda on Antarctica in 1982, 1994, 2020 and 2024. This article highlights growing geopolitical competition, particularly with China and Russia. China frames Antarctica as essential to its global rise, using dual-purpose technologies that blur the line between science and strategic military interests. Similarly, Russia’s activities in the region raise concerns about potential violations of the ATS’s peaceful purpose mandate. The USA maintains its leadership in Antarctic diplomacy, advocating for environmental preservation and scientific cooperation. This article concludes by emphasizing the need for international collaboration to address climate change, resource exploitation and rising strategic tensions, ensuring Antarctica remains a region dedicated to peace and science.

Abstract Primary production is fundamental to ecosystems, and in many extreme environments production is facilitated by microbial mats. Microbial mats are complex assemblages of photo- and heterotrophic microorganisms colonizing sediment and soil surfaces. These communities are the dominant producers of the McMurdo Dry Valleys, Antarctica, where they occupy lentic and lotic environments as well as intermittently wet soils. While the influence of microbial mats on stream nutrient dynamics and lake organic matter cycling is well documented, the influence of microbial mats on underlying soil is less well understood, particularly the effects of microbial mat nitrogen and carbon fixation. Taylor Valley soils occur across variable levels of inorganic phosphorus availability, with the Ross Sea drift containing four times that of the Taylor drifts, providing opportunities to examine how soil geochemistry influences microbial mats and the ecological functions they regulate. We found that inorganic phosphorus availability is positively correlated with microbial mat biomass, pigment concentration and nitrogen fixation potential. Additionally, our results demonstrate that dense microbial mats influence the ecological functioning of underlying soils by enriching organic carbon and total nitrogen stocks (two times higher). This work contributes to ongoing questions regarding the sources of energy fuelling soil food webs and the regional carbon balance in the McMurdo Dry Valleys.

Abstract In the sub-Antarctic, where food webs are relatively simple and species richness is low, the introduction of predators can be devastating, as native prey may lack sufficient defences and native predators may be less competitive. Merizodus soledadinus Guerin-Meneville, 1930 is a predatory carabid beetle that has been introduced to two sub-Antarctic islands. This ground beetle is known to threaten native insect populations; however, the full extent of its impacts in its introduced ranges is unknown because of its poorly described dietary breadth. As invasive predator impacts depend strongly on their dietary preferences and behaviour, we performed experiments to study the responses of this beetle to olfactory cues and sub-Antarctic diet. We studied the responses of M. soledadinus to olfactory cues to understand whether this species relies on odour to locate prey or different habitats, but we found no significantly different responses to different stimuli. We found that M. soledadinus attacked and consumed mostly juvenile forms of invertebrates from diverse phylogenetic lineages, indicating that many native species may be at risk from this predator and that attack by multiple individuals increased their success with hunting difficult prey. Our findings reveal that M. soledadinus has a wide dietary breadth, which has probably contributed to its successful establishment in multiple novel communities. We discuss the implications of our results for the ecology and conservation of terrestrial macroinvertebrate communities in its colonized range, where limited options exist to prevent further spread of this invader.

Abstract Antarctica is populated by a diverse array of terrestrial fauna that have successfully adapted to its extreme environmental conditions. The origins and diversity of the taxa have been of continuous interest to ecologists since their discovery. Early theory considered contemporary populations as descendants of recent arrivals; however, mounting molecular evidence points to firmly established indigenous taxa far earlier than the Last Glacial Maximum, thus indicating more ancient origins. Here we present insights into Antarctica's terrestrial invertebrates by synthesizing available phylogeographic studies. Molecular dating supports ancient origins for most indigenous taxa, including Acari (up to 100 million years ago; Ma), Collembola (21–11 Ma), Nematoda (~30 Ma), Tardigrada (> 1 Ma) and Chironomidae (> 49 Ma), while Rotifera appear to be more recent colonizers (~130 Ka). Subsequent population bottlenecks and rapid speciation have occurred with limited gene transfer between Continental and Maritime Antarctica, while repeated wind- or water-borne dispersal and colonization of contiguous regions during interglacial periods shaped current distributions. Greater knowledge of Antarctica's fauna will focus conservation efforts to ensure their persistence.

Abstract Marambio (Seymour) Island is located in the James Ross Archipelago east of the Antarctic Peninsula. Although several research groups have carried out studies on the biodiversity on the island for decades, surveys of bryophytes have not been developed. That is why there are currently only six species of mosses recorded in the northern part of the island. During the 2021–2022 summer Antarctic field trip, 15 mosses species were surveyed in Marambio Island. Of the total number of collected species, nine are reported for the first time for Marambio Island. For the remaining four species, their distributions are now expanded to Marambio Island.

Abstract Globally, the grey-headed albatross Thalassarche chrysostoma is listed as Endangered due to decreasing populations at its major breeding colonies. We analysed the population trend at Marion Island using annual counts of incubating pairs and fledglings from 1984 to 2021 and three methods: TRends and Indices for Monitoring data (TRIM), a generalized additive model and a state-space model. In contrast to rapid decreases at most other colonies, all three methods indicated a local population increase at an average annual rate of 1.3%. The latter two models indicated a decreasing trend from 1997 to 2002, presumably related to mortality on longlines set for Patagonian toothfish Dissostichus eleginoides around the island, which peaked from 1996 to 1998. Grey-headed albatrosses exhibit greater variation in annual counts than other seabird species at Marion Island, possibly linked to interannual variation in breeding success because they are biennial breeders. However, breeding success alone was not significant in any of the models, presumably because it cannot capture the complexities of both population processes and environmental variation. Although all three models predicted the overall trends well, integrated population models, which can account for demographic processes, might be more appropriate to model long-term population trends.