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The position of South Georgia relative to the Polar Front (white line), and the Antarctic Circumpolar Current (black dashes). doi:10.1371/journal.pone.0019795.g001
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We attempt to quantify how significant the polar archipelago of South Georgia is as a source of regional and global marine biodiversity. We evaluate numbers of rare, endemic and range-edge species and how the faunal structure of South Georgia may respond to some of the fastest warming waters on the planet.
Biodiversity data was collated from a comp...
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Context 1
... archipelago of South Georgia represents one of the largest, most isolated land masses and continental shelf areas in the Southern Ocean. Once situated adjacent to the Terra del Fuego region of South America [1], it is thought to have migrated to its current position 45–20 Ma [2,3]. The region lies , 1800 km to the east of the South American continental shelf ( figure 1) bisecting the Antarctic Circumpolar Current (ACC). The Polar Front (PF) passes approximately 300 km to the north (mean distance derived from [4]) with the South ACC current, which transports nutrients and organisms (e.g. krill) from the Antarctic Peninsula, to the south [5]. The combination of this early separation from a continental land mass, a large shelf area, its high degree of geographic isolation and the proximity of nutrient rich currents represent important catalysts in the evolution of a biologically rich and distinct island, and identify South Georgia as a potentially important locality for biodiversity. Studies of specific taxa [6–9] and multi-national collaboration in biodiversity databases such as SCARMarBIN [10] suggest South Georgia to be a key source of regional biodiversity, potentially supporting anomalously high levels of endemic and range-edge species (full definitions provided in materials and methods). In addition its waters support commercially important fisheries of Patagonian toothfish ( Dissostichus eleginoides ), mackerel icefish ( Champsocephalus gunnari ) and Antarctic krill ( Euphausia superb ). It may also be the most northern continental shelf with no known non indigenous marine species. Continental shelf biota is currently protected by a 22 km radial no-take zone and a 352 km 2 management zone (figure 1) which restricts bottom fishing activities. Concurrent research is emerging however that identifies the near-surface waters around South Georgia as some of the fastest warming on earth [11]. Furthermore model projections suggest that over the coming decades the South Georgia will experience increased stress from ocean wide acidification [12]. With many species potentially at their thermal tolerance limit (reviewed in [13]), coupled with high levels of endemism, any drastic changes in environmental conditions may have severe impacts across scales to global biodiversity. Compounding this vulnerability is the fact that South Georgia’s biota is generally Antarctic in character [9,14]. As such it is characterised by slow growth, increased longevity and deferred sexual maturity [15] so consequently might find both toleration and adaptation difficult. In 2002 a strategic plan was outlined as part of the Convention on Biological Diversity which, by 2010, aimed to achieve a ‘‘significant reduction’’ in the rate of biodiversity loss at regional, national and global levels (www.cbd.int/2010-target). This target was subsequently adopted by almost every nation as a political commitment central to the improvement of conservation, management and remedial practices [16]. Now in 2010 indications are that it is far from being met at a global level [17–19], with criticism levelled at the targets vagueness, as well as the timescale and baselines adopted [20]. One of the overriding problems identified is that in many key areas biodiversity was, and remains, to a large extent unquantified and consequently its loss cannot be measured let alone reduced. South Georgia is archetypal of this paucity in our knowledge of marine biodiversity and as such exemplifies the key failing of the 2010 CBD target whereby due to a lack of known baseline recordings the effects of environmental change are unquantifiable. In order to redress this situation an understanding of the structure and function of biodiversity, especially in ecologically sensitive areas such as South Georgia, is fundamental [21]. Considerable biodiversity data already exists for South Georgia but the majority of this data is scattered across literary sources (ISI journals and grey), in different institutes and languages. Much of such data may not have been checked taxonomically and most is not georeferenced in databases. In this paper we adopt a macroecological approach to collating, checking and mapping all available existing information onto the South Georgia shelf. As such it is the aim of this paper to create a thorough and accurate baseline measure of South Georgian marine biodiversity and thus provide a framework from which to identify ecologically sensitive areas and species, identify conservation priorities and monitor future biogeographical changes. This paper proposes to address four key questions: 1. How important is South Georgia as a source of regional and global biodiversity? 2. How important is it in terms of rare, endemic and range-edge species? 3. How is South Georgian biodiversity structured spatially and taxonomically? 4. Can we identify priority areas around South Georgia which are anomalously rich, vulnerable, or important to investigate due to paucity of knowledge? Geo-referenced biodiversity data for South Georgia held in open access databases offered a relatively poor representation of known marine life around the island. Only six phyla were represented at the time of access, of which some such as Annelids had very few recorded species or specimens. Our collated data increased the number of records . 5 fold, species 4 fold and sites, for which there is some information on biodiversity, by 90% (figure 2). Marine biodiversity around South Georgia was rich across taxonomic levels; our data included representatives from 22 phyla, 51 classes and 436 families (see appendix S1 for full species list). The total number of individual specimens recorded was ...
Context 2
... archipelago of South Georgia represents one of the largest, most isolated land masses and continental shelf areas in the Southern Ocean. Once situated adjacent to the Terra del Fuego region of South America [1], it is thought to have migrated to its current position 45–20 Ma [2,3]. The region lies , 1800 km to the east of the South American continental shelf ( figure 1) bisecting the Antarctic Circumpolar Current (ACC). The Polar Front (PF) passes approximately 300 km to the north (mean distance derived from [4]) with the South ACC current, which transports nutrients and organisms (e.g. krill) from the Antarctic Peninsula, to the south [5]. The combination of this early separation from a continental land mass, a large shelf area, its high degree of geographic isolation and the proximity of nutrient rich currents represent important catalysts in the evolution of a biologically rich and distinct island, and identify South Georgia as a potentially important locality for biodiversity. Studies of specific taxa [6–9] and multi-national collaboration in biodiversity databases such as SCARMarBIN [10] suggest South Georgia to be a key source of regional biodiversity, potentially supporting anomalously high levels of endemic and range-edge species (full definitions provided in materials and methods). In addition its waters support commercially important fisheries of Patagonian toothfish ( Dissostichus eleginoides ), mackerel icefish ( Champsocephalus gunnari ) and Antarctic krill ( Euphausia superb ). It may also be the most northern continental shelf with no known non indigenous marine species. Continental shelf biota is currently protected by a 22 km radial no-take zone and a 352 km 2 management zone (figure 1) which restricts bottom fishing activities. Concurrent research is emerging however that identifies the near-surface waters around South Georgia as some of the fastest warming on earth [11]. Furthermore model projections suggest that over the coming decades the South Georgia will experience increased stress from ocean wide acidification [12]. With many species potentially at their thermal tolerance limit (reviewed in [13]), coupled with high levels of endemism, any drastic changes in environmental conditions may have severe impacts across scales to global biodiversity. Compounding this vulnerability is the fact that South Georgia’s biota is generally Antarctic in character [9,14]. As such it is characterised by slow growth, increased longevity and deferred sexual maturity [15] so consequently might find both toleration and adaptation difficult. In 2002 a strategic plan was outlined as part of the Convention on Biological Diversity which, by 2010, aimed to achieve a ‘‘significant reduction’’ in the rate of biodiversity loss at regional, national and global levels (www.cbd.int/2010-target). This target was subsequently adopted by almost every nation as a political commitment central to the improvement of conservation, management and remedial practices [16]. Now in 2010 indications are that it is far from being met at a global level [17–19], with criticism levelled at the targets vagueness, as well as the timescale and baselines adopted [20]. One of the overriding problems identified is that in many key areas biodiversity was, and remains, to a large extent unquantified and consequently its loss cannot be measured let alone reduced. South Georgia is archetypal of this paucity in our knowledge of marine biodiversity and as such exemplifies the key failing of the 2010 CBD target whereby due to a lack of known baseline recordings the effects of environmental change are unquantifiable. In order to redress this situation an understanding of the structure and function of biodiversity, especially in ecologically sensitive areas such as South Georgia, is fundamental [21]. Considerable biodiversity data already exists for South Georgia but the majority of this data is scattered across literary sources (ISI journals and grey), in different institutes and languages. Much of such data may not have been checked taxonomically and most is not georeferenced in databases. In this paper we adopt a macroecological approach to collating, checking and mapping all available existing information onto the South Georgia shelf. As such it is the aim of this paper to create a thorough and accurate baseline measure of South Georgian marine biodiversity and thus provide a framework from which to identify ecologically sensitive areas and species, identify conservation priorities and monitor future biogeographical changes. This paper proposes to address four key questions: 1. How important is South Georgia as a source of regional and global biodiversity? 2. How important is it in terms of rare, endemic and range-edge species? 3. How is South Georgian biodiversity structured spatially and taxonomically? 4. Can we identify priority areas around South Georgia which are anomalously rich, vulnerable, or important to investigate due to paucity of knowledge? Geo-referenced biodiversity data for South Georgia held in open access databases offered a relatively poor representation of known marine life around the island. Only six phyla were represented at the time of access, of which some such as Annelids had very few recorded species or specimens. Our collated data increased the number of records . 5 fold, species 4 fold and sites, for which there is some information on biodiversity, by 90% (figure 2). Marine biodiversity around South Georgia was rich across taxonomic levels; our data included representatives from 22 phyla, 51 classes and 436 families (see appendix S1 for full species list). The total number of individual specimens recorded was ...
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Citations
... SGSSI's location just south of the Polar Frontal Zone and north of the Antarctic Circumpolar Current Front, means it acts as both a Northern and Southern range limit for many species (Griffiths et al., 2009;Hogg et al., 2011;Queirós et al., 2024). This biogeographic isolation and the increasing number of international vessels frequently crossing the natural barrier of the fronts, makes this area at growing risk of invasion (Hughes et al., 2020;Kennicutt et al., 2019;McCarthy et al., 2019). ...
... Relatively little is known about the full diversity of existing native species found around the SGSSI archipelago and their natural extent (Barnes et al., 2006;Brewin & Brickle, 2010;Convey & Peck, 2019;Glon et al., 2020;Hogg et al., 2011). Baseline data are essential to highlight new non-native species and predict and manage their effect on native systems. ...
The threat from novel marine species introductions is a global issue. When non-native marine species are introduced to novel environments and become invasive, they can affect biodiversity, industry, ecosystem function, and both human and wildlife health. Isolated areas with sensitive or highly specialised endemic species can be particularly impacted. The global increase in the scope of tourism and other human activities, together with a rapidly changing climate, now put these remote ecosystems under threat. In this context, we analyse invasion pathways into South Georgia and the South Sandwich Islands (SGSSI) for marine non-native species via vessel biofouling. The SGSSI archipelago has high biodiversity and endemism, and has historically been highly isolated from the South American mainland. The islands sit just below the Polar Front temperature boundary, affording some protection against introductions. However, the region is now warming and SGSSI increasingly acts as a gateway port for vessel traffic into the wider Antarctic, amplifying invasion likelihood. We use remote Automatic Identification System vessel-tracking data over a 2-year period to map vessel movement and behaviour around South Georgia, and across the ‘Scotia Sea’, ‘Magellanic’ and northern ‘Continental High Antarctic’ ecoregions. We find multiple vessel types from locations across the globe frequently now enter shallow inshore waters and stop for prolonged periods (weeks/months) at anchor. Vessels are active throughout the year and stop at multiple port hubs, frequently crossing international waters and ecoregions. Management recommendations to reduce marine invasion likelihood within SGSSI include initiating benthic and hull monitoring at the identified activity/dispersion hubs of King Edward Point, Bay of Isles, Gold Harbour, St Andrews Bay and Stromness Bay. More broadly, regional collaboration and coordination is necessary at neighbouring international ports. Here vessels need increased pre- and post-arrival biosecurity assessment following set protocols, and improved monitoring of hulls for biofouling to pre-emptively mitigate this threat.
... Benthic ecosystems of sub-Antarctic islands host a unique and diverse biodiversity, characterized by high-level endemism (Branch et al., 1993;Chown et al., 2001;Barnes et al., 2006;Freeman et al., 2011;Hogg et al., 2011;Clark et al., 2019). While marine ecosystems of these isolated territories are of high conservation value (Chown et al., 2001), they remain understudied and vulnerable to multiple anthropogenic threats, including climate change (Hogg et al., 2011), biological invasion (Smith, 2002;Hogg et al., 2011;McCarthy et al., 2019), and increasing maritime traffic (i.e., fisheries, tourism activities and scientific research). ...
... Benthic ecosystems of sub-Antarctic islands host a unique and diverse biodiversity, characterized by high-level endemism (Branch et al., 1993;Chown et al., 2001;Barnes et al., 2006;Freeman et al., 2011;Hogg et al., 2011;Clark et al., 2019). While marine ecosystems of these isolated territories are of high conservation value (Chown et al., 2001), they remain understudied and vulnerable to multiple anthropogenic threats, including climate change (Hogg et al., 2011), biological invasion (Smith, 2002;Hogg et al., 2011;McCarthy et al., 2019), and increasing maritime traffic (i.e., fisheries, tourism activities and scientific research). These synergistic threats can lead to a shift in benthic communities caused by: (i) the loss of a wide range of habitats and associated diversity (including species subject to conservation measures) (Saucède et al., 2017); (ii) altered food web structure (Ehrenfeld, 2010;Kortsch et al., 2015); (iii) modified biotic interactions (Montoya and Raffaelli, 2010); and (iv) formation of a new range of habitats available for benthic and potentially alien species (McCarthy et al., 2019). ...
... Benthic ecosystems of sub-Antarctic islands host a unique and diverse biodiversity, characterized by high-level endemism (Branch et al., 1993;Chown et al., 2001;Barnes et al., 2006;Freeman et al., 2011;Hogg et al., 2011;Clark et al., 2019). While marine ecosystems of these isolated territories are of high conservation value (Chown et al., 2001), they remain understudied and vulnerable to multiple anthropogenic threats, including climate change (Hogg et al., 2011), biological invasion (Smith, 2002;Hogg et al., 2011;McCarthy et al., 2019), and increasing maritime traffic (i.e., fisheries, tourism activities and scientific research). These synergistic threats can lead to a shift in benthic communities caused by: (i) the loss of a wide range of habitats and associated diversity (including species subject to conservation measures) (Saucède et al., 2017); (ii) altered food web structure (Ehrenfeld, 2010;Kortsch et al., 2015); (iii) modified biotic interactions (Montoya and Raffaelli, 2010); and (iv) formation of a new range of habitats available for benthic and potentially alien species (McCarthy et al., 2019). ...
Sub-Antarctic coastal marine ecosystems harbor rich and diverse benthic communities. Despite their ecological uniqueness and vulnerability to global changes, studies on benthic communities remain limited. Using underwater video-imagery, we investigated the taxonomic and functional diversity of benthic communities associated with hard substrates at Baie du Marin (Ile de la Possession, Crozet archipelago). The Baie du Marin species richness and diversity were additively partitioned to evaluate spatial patterns of species through the following spatial scales: within images, among images within transects, and among transects. We analyzed imagery data from seven transects located at different sites inside Baie du Marin and covering contrasting natural rocky habitats and underwater artificial cable substrates. A total of 50 faunal (mainly represented by Echinodermata and Porifera phyla) and 14 algae (mainly represented by Rhodophyta phylum) taxa were identified. Rocky substrates were dominated by high densities of the polychaetes Parasabella sp. and Lanice marionensis, whereas submarine cables were dominated by high densities of the bivalve Kidderia sp. attached to macroalgae. Our results show contrasted distribution patterns in the faunal and algal assemblages within the Baie du Marin, with significant ecological differences between submarine cables and natural rocky substrates. Larger spatial scale (i.e., among transects) accounted for most of the bay richness and diversity, highlighting a high-level of habitat heterogeneity within the bay. Through a trait-based approach, our findings revealed that Crozet benthic communities are characterized by low functional richness, evenness, and redundancy, highlighting a potential vulnerability to current and future natural and anthropogenic changes. This study provides a novel bentho-ecological baseline for future assessments of natural and anthropogenic impacts on the marine environment of the Crozet archipelago; and for the conservation management of these remote habitats that make part of the French Southern Territories Marine Protected Area, recently inscribed on the UNESCO World Heritage list.
... obs.), although its shallow subtidal ecosystems remain poorly studied (Barnes et al. 2006;Rogers et al. 2015), particularly with regard to seaweeds (Clubbe et al. 2020). Existing seaweed species lists for South Georgia are based on morphological identification and outdated species concepts, making it difficult to make biogeographical comparisons; however, given the dominance of endemic and range-edge species in South Georgia's benthic invertebrate fauna (Hogg et al. 2011), its seaweed flora may be expected to have similar characteristics. The unique inshore marine biodiversity of South Georgia faces threats predominantly from climate change and invasive species (Hogg et al. 2011;Rogers et al. 2015), including seaweeds, which could be introduced to the island via international shipping (Dawson et al. 2022) involving tourist, research and fishing vessels. ...
... Existing seaweed species lists for South Georgia are based on morphological identification and outdated species concepts, making it difficult to make biogeographical comparisons; however, given the dominance of endemic and range-edge species in South Georgia's benthic invertebrate fauna (Hogg et al. 2011), its seaweed flora may be expected to have similar characteristics. The unique inshore marine biodiversity of South Georgia faces threats predominantly from climate change and invasive species (Hogg et al. 2011;Rogers et al. 2015), including seaweeds, which could be introduced to the island via international shipping (Dawson et al. 2022) involving tourist, research and fishing vessels. Many of these vessels arrive from the Falkland Islands, located approximately 1450 km west of South Georgia, which, therefore, represent a potential source of marine non-natives. ...
Detecting non-native species can be challenging, particularly in the case of taxa such as seaweeds, which can be difficult to distinguish based on morphology and often require molecular-assisted taxonomy for reliable identification. The sub-Antarctic island of South Georgia supports unique and important marine biodiversity, including a rich seaweed flora, but despite its isolation, its inshore ecosystems are susceptible to the introduction of potentially invasive non-native species. Here, we provide the first report of a non-native seaweed in South Georgia, Ulva fenestrata Postels & Ruprecht (Ulvophyceae, Chlorophyta), and confirm its widespread presence in the Falkland Islands via molecular-assisted taxonomy. Phylogenetic analyses of tufA and rbcL-3P genetic markers enabled the identification of a specimen collected from Grytviken, South Georgia in November 2021 as U. fenestrata. In terms of tufA sequence, this sample was identical to specimens collected from four sites spanning West and East Falkland in 2013 and 2018. This study represents the second Southern Hemisphere record of U. fenestrata, which is generally regarded as a Northern Hemisphere species. Our findings provide a foundation for monitoring this potentially invasive species in South Georgia, and for determining its likely source and mode of arrival, while emphasising the importance of robust biosecurity measures.
... Terrestrial ecosystems of sub-Antarctic islands, including SG, have attracted considerable scientific attention, focusing on the impacts of climate change and the dispersal of invasive species (Bergstrom and Chown, 1999). However, because of its remoteness, marine ecosystems of SG remain largely understudied (Barnes, 2005), despite their important contribution to global and regional biodiversity (Hogg et al., 2011). ...
... Moreover, there is a disparity between FAs dominant in inner-fjord settings, which are found only in SG, and the more biogeographically widespread assemblages inhabiting outer fjords and shelf sites (Earland, 1933). This is consistent with the contrast between shallow-water SG macrofaunal communities, which show clear Antarctic characteristics, and the more geographically widespread macrofauna in surrounding deep waters which do not (Barnes et al., 2006), further emphasizing the exceptional character of the SG biota (Hogg et al., 2011). ...
Sub-Antarctic fjords are among the environments most affected by the recent climate change. In our dynamically changing world, it is essential to monitor changes in these vulnerable settings. Here, we present a baseline study of "living" (rose-bengal-stained) benthic foraminifera from fjords of South Georgia, including fjords with and without tidewater glaciers. Their distribution is analyzed in the light of new fjord water and sediment property data, including grain size and sorting, total organic carbon, total sulfur, and δ 13 C of bulk organic matter. Four well-defined foraminiferal assemblages are recognized. Miliammina earlandi dominates in the most restricted, near-shore and glacier-proximal habitats, Cassidulinoides aff. parkerianus in mid-fjord areas, and Globocassidulina aff. rossensis and an assemblage dominated by Ammobaculites rostratus, Reophax subfusiformis, and Astrononion echolsi are in the outer parts of the fjords. Miliammina earlandi can tolerate strong glacial influence, including high sedimentation rates in fjord heads and sediment anoxia, as inferred from sediment color and total organic carbon / sulfur ratios. This versatile species thrives both in the food-poor inner reaches of fjords that receive mainly refractory petrogenic organic matter from glacial meltwater and in shallow-water coves, where it benefits from an abundant supply of fresh, terrestrial, and marine organic matter. A smooth-walled variant of C. aff. parkerianus, apparently endemic to South Georgia, is the calcareous rotaliid best adapted to inner-fjord conditions characterized by moderate glacial influence and sedimentation rates and showing no preference for particular sedimentary redox conditions. The outer parts of fjords with clear, well-oxygenated bottom water are inhabited by G. aff. rossensis. Ammobaculites rostratus, R. subfusiformis, and A. echolsi dominate in the deepest-water settings, with water salinities ≥ 33.9 PSU and temperatures 0.2-1.4 • C, characteristic of winter water and Upper Circumpolar Deep Water. The inner-and mid-fjord foraminiferal assemblages seem specific to South Georgia, although with continued warming and deglaciation, they may become more widespread in the Southern Ocean.
... Thus, experimental studies addressing responses to environmental changes should be performed using organisms from different habitats as they can be adapted to local conditions and this may explain why some ecosystems are more sensitive to warming than others. For example, a small increase in temperature can be enough to drive significant consequences in ecosystems characterised by extremely stable temperature, such as in the Southern Ocean (Hogg et al., 2011). Benthic organisms, such as those forming Marine Animal Forests (MAFs; sensu Rossi et al., 2017), may also be particularly threatened by ocean warming due to their inability to move away from adverse environmental conditions. ...
... The United Kingdom Overseas Territories (OTs) are mostly islands and are widely distributed around the world, spanning the Atlantic, Indian, Pacific, and Southern Oceans and the Caribbean Sea (Figure 1), spanning a wide range of climates that largely reflect the diversity of small islands globally (Loft, 2021). Over 32,000 native species have been documented in the OTs, including 1500 endemic species (Churchyard et al., 2016), and are often rare (Hogg et al., 2011) and globally threatened (Churchyard et al., 2016). People living in the OTs are highly dependent on the natural environment for their economic and social wellbeing (Smith, 2019), but those natural environments are and will continue to be at risk from biological invasions (Key & Moore, 2019). ...
Invasive non‐native species (INNS) are recognized as a major threat to island biodiversity, ecosystems, and economies globally. Preventing high‐risk INNS from being introduced is the most cost‐effective way to avoid their adverse impacts. We applied a horizon scanning approach to identify potentially INNS in the United Kingdom Overseas Territories (OTs), ranging from Antarctica to the Caribbean, and from the Pacific to the Atlantic. High‐risk species were identified according to their potential for arrival, establishment, and likely impacts on biodiversity and ecosystem function, economies, and human health. Across OTs, 231 taxa were included on high‐risk lists. The highest ranking species were the Asian green mussel (Perna viridis), little fire ant (Wasmannia auropunctata), brown rat (Rattus norvegicus), and mesquite tree (Prosopis juliflora). Shipping containers were identified as the introduction pathway associated with the most species. The shared high‐risk species and pathways identified provide a guide for other remote islands and archipelagos to focus ongoing biosecurity and surveillance aimed at preventing future incursions.
... Thus, experimental studies addressing responses to environmental changes should be performed using organisms from different habitats as they can be adapted to local conditions and this may explain why some ecosystems are more sensitive to warming than others. For example, a small increase in temperature can be enough to drive significant consequences in ecosystems characterised by extremely stable temperature, such as in the Southern Ocean (Hogg et al., 2011). Benthic organisms, such as those forming Marine Animal Forests (MAFs; sensu Rossi et al., 2017), may also be particularly threatened by ocean warming due to their inability to move away from adverse environmental conditions. ...
Antipatharians (black corals) are major components of mesophotic ecosystems in the Mediterranean Sea. The arborescent species Antipathella subpinnata has received particular attention as it is the most abundant and forms dense forests harbouring high levels of biodiversity. This species is currently categorized as "Near Threatened" in the IUCN Red List, due to increasing fishing pressure and bottom-trawling activities. Yet, the effects of ocean warming have never been investigated for this species, nor for any other antipatharians from temperate regions. Our study aimed at evaluating the effects of increasing seawater temperatures on A. subpinnata, by combining predictive distribution modelling with a physiological tolerance experiment. During the latter, we exposed A. subpinnata for 15 days to different temperature conditions spanning the current seasonal range to forecasted temperatures for 2100, while measuring biological endpoints such as oxygen consumption rates and different signs of stress (tissue necrosis, total antioxidant capacity). Unexpectedly, no stress was found at organism nor cellular level (wide thermal breadth) suggesting low susceptibility of this species to mid-term temperature increase. If the response to the 15-days heat stress is representative of the response to longer-term warming, ocean warming is unlikely to affect A. subpinnata. The species distribution model predicted the presence of A. subpinnata at depths that correspond to temperatures colder than its maximum thermal tolerance (as determined by the physiology experiment). This suggests that the presence of A. subpinnata at shallower depths is not limited by physiological constraints but by other ecological factors including interspecific competition.
... Moreover, there is a disparity between FAs dominant in inner fjord settings, which are found only in SG, and the more biogeographically widespread assemblages inhabiting outer-fjords and shelf sites (Earland, 1933). This is consistent with the contrast between shallow-water SG macrofaunal communities, which show clear Antarctic characteristics, and the more geographically 570 widespread macrofauna in surrounding deep waters which do not (Barnes et al., 2006), further emphasizing the exceptional character of the SG biota (Hogg et al., 2011). ...
Sub-Antarctic fjords are among the environments most affected by the recent climate change. In our dynamically changing world, it is essential to monitor changes in these vulnerable settings. Here, we present a baseline study of “living” (rose Bengal stained) benthic foraminifera from fjords of South Georgia, including fjords with and without tidewater glaciers. Their distribution is analyzed in the light of new fjord water and sediment property data, including grain size and sorting, total organic carbon, total sulfur, and δ13C of bulk organic matter. Four well-defined foraminiferal assemblages are recognized. Miliammina earlandi dominates in the most restricted, near-shore and glacier-proximal habitats, Cassidulinoides aff. parkerianus in mid-fjord areas, and Globocassidulina aff. rossensis and Reophax subfusiformis in the outer parts of fjords. Miliammina earlandi can tolerate strong glacial influence, including high sedimentation rates in fjord heads and sediment anoxia, as inferred from sediment color and total organic carbon/sulfur ratios. This versatile species thrives both in the food-poor inner reaches of fjords that receive mainly refractory petrogenic organic matter from glacial meltwater, and in shallow-water coves where it benefits from an abundant supply of fresh, terrestrial and marine organic matter. A smooth-walled variant of C. aff. parkerianus, apparently endemic to South Georgia, is the calcareous rotaliid best adapted to inner fjord conditions characterized by moderate glacial influence and sedimentation rates and showing no preference for particular sedimentary redox conditions. The outer parts of fjords with clear, slightly warmer bottom water, are inhabited by G. aff. rossensis. Reophax subfusiformis dominates in the deepest-water settings with water salinities ≥ 33.9 PSU and temperatures 0.2–1.4 °C, characteristic for Winter Water and Upper Circumpolar Deep Water. The inner- and mid-fjord foraminiferal assemblages seem specific to South Georgia, although with continued warming and deglaciation they may become more widespread in the Southern Ocean.
... Many knowledge gaps (in terms of spatial and/or temporal coverage) regarding biodiversity in the SO remain (e.g. Hogg et al. 2011, Schiaparelli et al. 2013. Various meta-analyses have revealed that published Antarctic biodiversity data are highly heterogeneous, with many sampling hotspots but also vastly under-sampled areas and life-forms (Barry & Elith 2006, Guillaumot et al. 2018a. ...
The western Antarctic Peninsula is facing rapid environmental changes and many recent publications stress the need to gain new knowledge regarding ecosystems responses to these changes. In the framework of the Belgica 121 expedition, we tested the use of a nimble vessel with a moderate environmental footprint as an approach to tackle the urgent needs of the Southern Ocean research community in terms of knowledge regarding the levels of marine biodiversity in shallow areas and the potential impacts of retreating glaciers on this biodiversity in combination with increasing tourism pressure. We discuss the strengths and drawbacks of using a 75' (23 m) sailboat in this research framework, as well as its sampling and environmental efficiency. We propose that the scientific community considers this approach to 1) fill specific knowledge gaps and 2) improve the general coherence of the research objectives of the Antarctic scientific community in terms of biodiversity conservation and the image that such conservation conveys to the general public.
... The island chain represents the visible portions of a series of largely submarine volcanoes formed by subduction of the small South Sandwich Plate under the Scotia Plate. This region has a diverse and distinct biodiversity (Hogg et al. 2011(Hogg et al. , 2021, and comprises part of the South Georgia and South Sandwich Islands Marine Protected Area (SGSSI MPA), within which several levels of protection are enacted to meet the diverse objectives of the MPA. Around 3.6% of the SSI region within the SGSSI MPA is open to a highly regulated and selective benthic longline fishery targeting toothfish species (see also Belchier et al., 2022). ...
... Though little research has focused on specific climate impacts at the SSI, sea surface temperatures at neighbouring SG and south along the Western Antarctic Peninsula are amongst the fastest warming in the Southern Hemisphere (Whitehouse et al., 2008;Schmidtko et al., 2014;Meredith et al., 2019;Siegert et al., 2019) with the potential for future intense warming of subsurface (200-700 m) waters (Spence et al., 2014). In response to environmental change, to avoid local extinction, many organisms must migrate latitudinally, go deeper, or both (Barnes et al., 2009;Hogg et al., 2011;Griffiths et al., 2017). This will likely see a poleward shift with some species ranges contracting towards Antarctic continent (Constable et al., 2014). ...
The South Sandwich Islands (SSI), a chain of volcanic islands in the Atlantic sector of the Southern Ocean, are home to two large notothenoid species: The Patagonian toothfish Dissostichus eleginoides and the Antarctic toothfish Dissostichus mawsoni. Both species support valuable fisheries throughout the Southern Ocean under management of the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). The SSI region, which is located south of the Southern Antarctic Circumpolar Current Front, has a diverse and distinct biodiversity and it represents a range edge for the distribution of both toothfish species. In this paper we have updated and expanded previous biological analyses with recent data, explored the stock hypotheses and links of these species to other regions, and investigated the role of the SSI archipelago in the life cycles of both toothfish species, where they overlap in their distribution. We conclude that Patagonian toothfish around the SSI are linked to the adjacent South Georgia population, but have some unique characteristics, including faster growth and better somatic condition, possibly reflecting ‘Bergmann's rule’ which states that body size increases with decreasing temperature and increasing latitude. By comparison, the Antarctic toothfish at the SSI appear to be the northern extent of a larger stock connecting further south towards the Antarctic continent. Finally, we consider the relative importance of the SSI in the life cycle of both species, including in the context of climatic changes to this region.
