Saunders Island Research Articles

Volcanic activity and gas emissions along the South Sandwich Arc

The South Sandwich Volcanic Arc is one of the most remote and enigmatic arcs on Earth. Sporadic observations from rare cloud-free satellite images—and even rarer in situ reports—provide glimpses into a dynamic arc system characterised by persistent gas emissions and frequent eruptive activity. Our understanding of the state of volcanic activity along this arc is incomplete compared to arcs globally. To fill this gap, we present here detailed geological and volcanological observations made during an expedition to the South Sandwich Islands in January 2020. We report the first in situ measurements of gas chemistry, emission rate and carbon isotope composition from along the arc. We show that Mt. Michael on Saunders Island is a persistent source of gas emissions, releasing 145 ± 59 t day−1 SO2 in a plume characterised by a CO2/SO2 molar ratio of 1.8 ± 0.2. Combining this CO2/SO2 ratio with our independent SO2 emission rate measured near simultaneously, we derive a CO2 flux of 179 ± 76 t day−1. Outgassing from low temperature (90–100 °C) fumaroles is pervasive at the active centres of Candlemas and Bellingshausen, with measured gas compositions indicative of interaction between magmatic fluids and hydrothermal systems. Carbon isotope measurements of dilute plume and fumarole gases from along the arc indicate a magmatic δ13C of − 4.5 ± 2.0‰. Interpreted most simply, this result suggests a carbon source dominated by mantle-derived carbon. However, based on a carbon mass balance from sediment core ODP 701, we show that mixing between depleted upper mantle and a subduction component composed of sediment and altered crust is also permissible. We conclude that, although remote, the South Sandwich Volcanic Arc is an ideal tectonic setting in which to explore geochemical processes in a young, developing arc.

Rockhopper Penguin–Imperial Cormorant mixed colonies in the Falkland Islands: a stroke of luck for late breeders

AbstractMixed‐species colonies occur frequently, especially among seabirds, and may provide mutual benefits among associated species including antipredator advantages. The “protector” species in such associations may provide early warning signals or by aggressively defending their own nests, may expel predators from the area. We explored costs and benefits to Rockhopper Penguins (Eudyptes chrysocome) in relation to offspring production in both monospecific colonies and those mixed with Imperial Cormorants (Phalacrocorax atriceps) at Saunders Island (Falkland Islands), emphasizing differences in predation pressure. We considered behavioral responses of chicks (in crèches), as well as differences in their nutritional condition, morphometric measurements, and survival compared among different breeding colonies. Our study revealed a paradox: High‐quality adult penguins, those arriving early and occupying lower‐elevation sites closer to the coast, produced better‐nourished chicks earlier in the season. However, they averaged half the number of chicks fledged, compared to breeders that arrived later in the season. Late breeders were forced by unavailability of optimal habitat to nest in more elevated areas, forming mixed colonies with cormorants, which, in turn, provided them with protection from nest predators. This study provides an example of the role of luck in nature, and how it may compensate for differences in individual fitness.

Seasonal activity levels of a farm-island population of striated caracaras (Phalcoboenus australis) in the Falkland Islands

BackgroundAnimals need adaptive strategies to cope with seasonal changes in prey availability to survive and reproduce, which can include migrating, prey-switching, or reducing metabolic needs. Human settlements can disrupt spatiotemporal patterning in resource availability, which can affect animals’ foraging success, particularly for juveniles who are behaviorally developing and learning efficient foraging skills. Here, we investigate behavioral responses of juvenile striated caracaras, a near-threatened scavenging falconid, to seasonally migratory seabird prey and a farm settlement on Saunders Island, Falklands. We deployed accelerometer–GPS dataloggers (n = 27) to measure seasonal differences in daily and hourly vectorial dynamic body acceleration (VeDBA; an activity index measured in gravitational g) and space use, and investigated seasonal variation in body mass of the tagged subset and an additional 65 caracaras.ResultsJuvenile caracaras were overall similarly active in winter and summer. However, during winter, caracaras made the most of limited daylight by increasing average daytime activity (winter males: 0.16 ± 0.03 g, summer males: 0.09 ± 0.01 g, winter females: 0.12 ± 0.02 g, summer females: 0.08 ± 0.01 g). During winter, both sexes increased the percentage of daylight spent in high activity (winter males: 35 ± 5%, summer males: 21 ± 3%, winter females: 25 ± 6%, summer females: 16 ± 3%, p < 0.001) and ranged nearly 4 times farther (95% kernel density estimate winter: 2.36 ± 0.96 km2, summer: 0.61 ± 0.20 km2; p < 0.001). Furthermore, on a daily scale, males were 21% more active than females year-round (24-h average VeDBA: males 0.07 ± 0.01 g, females 0.06 ± 0.01 g; p < 0.01). We did not observe a significant seasonal difference in mass.ConclusionThat caracaras’ daily activity and body mass did not vary between seasons suggests that wintering birds on Saunders are meeting resource requirements despite the absence of seasonally migratory prey. We hypothesize that human subsidies may mitigate the effect of seasonal food limitations. Further research should include studies on seasonal energetics to improve our understanding of baseline body condition, and comparative studies on other islands and including adults to understand the importance of human subsidies.

Stable isotope signatures of Holocene syngenetic permafrost trace seabird presence in the Thule District (NW Greenland)

Abstract. Holocene permafrost from ice wedge polygons in the vicinity of large seabird breeding colonies in the Thule District, NW Greenland, was drilled to explore the relation between permafrost aggradation and seabird presence. The latter is reliant on the presence of the North Water Polynya (NOW) in the northern Baffin Bay. The onset of peat accumulation associated with the arrival of little auks (Alle alle) in a breeding colony at Annikitisoq, north of Cape York, is radiocarbon-dated to 4400 cal BP. A thick-billed murre (Uria lomvia) colony on Appat (Saunders Island) in the mouth of the Wolstenholme Fjord started 5650 cal BP. Both species provide marine-derived nutrients (MDNs) that fertilize vegetation and promote peat growth. The geochemical signature of organic matter left by the birds is traceable in the frozen Holocene peat. The peat accumulation rates at both sites are highest after the onset, decrease over time, and were about 2-times faster at the little auk site than at the thick-billed murre site. High accumulation rates induce shorter periods of organic matter (OM) decomposition before it enters the perennially frozen state. This is seen in comparably high C∕N ratios and less depleted δ13C, pointing to a lower degree of OM decomposition at the little auk site, while the opposite pattern can be discerned at the thick-billed murre site. Peat accumulation rates correspond to δ15N trends, where decreasing accumulation led to increasing depletion in δ15N as seen in the little-auk-related data. In contrast, the more decomposed OM of the thick-billed murre site shows almost stable δ15N. Late Holocene wedge ice fed by cold season precipitation was studied at the little auk site and provides the first stable-water isotopic record from Greenland with mean δ18O of -18.0±0.8 ‰, mean δD of -136.2±5.7 ‰, mean d excess of 7.7±0.7 ‰, and a δ18O-δD slope of 7.27, which is close to those of the modern Thule meteoric water line. The syngenetic ice wedge polygon development is mirrored in testacean records of the little auk site and delineates polygon low-center, dry-out, and polygon-high-center stages. The syngenetic permafrost formation directly depending on peat growth (controlled by bird activity) falls within the period of neoglacial cooling and the establishment of the NOW, thus indirectly following the Holocene climate trends.

Evidence for a lava lake on Mt. Michael volcano, Saunders Island (South Sandwich Islands) from Landsat, Sentinel-2 and ASTER satellite imagery

Mt. Michael is an active stratovolcano on Saunders Island in the South Sandwich Islands; a remote, oceanic island arc in the southern Atlantic Ocean, bordering the Southern Ocean. The arc contains the only active volcanoes in the South Georgia and South Sandwich Islands British Overseas Territory, yet little is known of their activity. Despite lava lakes being extremely rare with only a few global examples, previous analyses of satellite AVHRR imagery of Mt. Michael in the 1990s showed persistent thermal anomalies not associated with magma overflowing the crater. This suggested the existence of a lava lake inside Mt. Michael's crater. However, their study relied on 1 km resolution imagery, and there have been no long-term investigations to determine if this is a persistent feature.In-situ observations of Mt. Michael are extremely difficult given the location. We used Landsat, Sentinel-2 and ASTER satellite data to monitor activity and detect thermal anomalies within the crater. Persistent volcanic plumes and eruptions were identified throughout the thirty-year period studied. On all 15 occasions that a suitable satellite image was available a thermal anomaly within the crater was detected in the high transmissivity shortwave infrared bands (SWIR) centred on 1.65 μm and 2.2 μm. Pixel-integrated surface temperatures over the crater floor yield temperatures of 284–419 °C; comparable to lava lakes elsewhere. Unmixing these temperatures using the dual-band method reveals a molten lava component at basaltic temperatures (989–1279 °C) among a cooler crust. This is the first evidence for a lava lake within Mt. Michael from data that can resolve the crater floor, and the first evidence for magmatic temperatures. As thermal anomalies were detected in all images showing the crater, we suggest that the lava lake is a common and persistent feature.

Nutritional condition determines behavioral response of nestling Black-browed albatrosses to a shy-bold continuum test

We used biochemical analyses of blood to quantify nutritional status and a standardized test to measure the response to a novel object (bold-shy test). Our aim was to examine the relationship between nutritional status and behavioral responses in nestlings of Black-browed albatrosses (Thalassarche melanophrys). A total of 66 nestlings from Saunders Island (Falkland) were analyzed. Around 41% of the differences in the intensity of responses (number of peaks per 1 min) were explained by the age and physiological conditions of the individual. Blood urea levels alone explained more than 28% of differences in number of pecks per minute. Nutritional condition can be a confounding factor when we study behavioral responses using a typical bold-shy test. Our results encourage other authors to be more cautious when designing experiments and to take into account the potential effect of nutritional level and age as potential partial explanations of individual behavioral responses.

The fungal ecology of seabird nesting sites in the Falkland Islands indicates a niche for mycoparasites

Abstract Soil fungal communities are complex and heterogeneous, possessing important functions in most terrestrial ecological systems. Their study has been advanced due to the development of high-throughput sequencing, which allow for complex fungal communities to be described with techniques such as metabarcoding. The Falkland Islands contain large populations of breeding seabirds; one such internationally recognised area is Saunders Island, located off the coast of the West Falkland. It contains breeding populations of gentoo penguins ( Pygoscelis papua ), Magellanic penguins ( Spheniscus magellanicus ), black-browed albatross ( Thalassarche melanophris ), king penguins ( Aptenodytes patagonicus ) and western rockhopper penguins ( Eudyptes chrysocome chrysocome ). The fungal communities of these sites were investigated using a fungal metabarcode approach. We found these sites contain a large spatial heterogeneity, with communities that are dominated by saprotrophic fungi. However, we noticed that the most abundant species tended to be known mycoparasites. We hypothesise the fungal communities in system undergo a ‘boom-bust’ cycle of varying alpha diversity which is dependent upon the breeding populations, and driven by highly competitive mycoparasitic fungi.

The genus Eunotia (Bacillariophyta) in the Falkland Islands and species-area relationships in sub-Antarctic islands

We document the morphology of 15 species of Eunotia from freshwater habitats in the Falkland Islands using light and electron microscopy, and describe four new species, Eunotia australovalida, Eunotia inconspicua, Eunotia floweriana and Eunotia latecapitata. Diatom assemblages were studied from a range of habitats on East Falkland, West Falkland, Saunders Island and Pebble Island, which differed in water chemistry and hydrological conditions including streams, ponds, lakes, springs and damp terrestrial habitats. Significant site and species groups obtained by cluster analysis are related to environmental conditions. Island species-area relationships for Eunotia from the sub-Antarctic region, and the wider geographic distributions of seven Eunotia species from the Falkland Islands are shown.

Blood chemistry values in nestlings of Rockhopper Penguins (Eudyptes chrysocome): the effect of sex and body condition

Hematological studies concerned with the determination of normal values of blood parameters in animals have been increasing. However, studies on normal concentration of blood constituents of free-living birds still are not very common, and less than 5% of the species of birds have been analyzed, mostly in captivity. Avian hematology has been used in ornithological studies, because it provides biological data about these animals, their biology, and can be very important in the understanding of ecological and behavioral issues. The main purpose of the study was to investigate the concentrations of certain plasma biochemical parameters in nestlings of Rockhopper Penguins (Eudyptes chrysocome) at the creche phase and the potential influence of some factors such as sex. We captured 95 nestling Rockhopper during the period 24–31 January 2017. All nestlings were randomly selected from colonies in Saunders Island (Falkland Islands). All the sampled birds were between 25 and 45 days of age, with mean weight of 1.778 ± 0.314 kg and mean bill length of 36.0 ± 2.8 mm. No differences in blood parameters or body condition between sexes were found. No parameters but total protein and urea were related to body index. Body index showed a negative significant relationship with urea levels in blood, with penguins in worse condition (those relatively lighter) showing higher levels of urea in blood than those that were relatively heavier. Same trend was observed for total proteins. Urea concentration in blood would be used as a tool in future studies, particularly in young Rockhoppers when they are in creche phase, a period of high level of mortality mainly by predation. Plasma urea was the single variable that reflects the best body index and also has a rationale background explaining this relationship.

Seasonal micro-migration in a farm-island population of striated caracaras (Phalcoboenus australis) in the Falkland Islands

BackgroundThe extent to which seasonal changes in food availability affect small-scale movements in free-ranging populations of birds of prey is relatively little studied. Here we describe a seasonal “micro-migration” of a farm-island population of striated caracaras (Phalcoboenus australis) in the Falkland Islands in response to seasonal changes in the availability of seabird carcasses. We banded more than 450 individuals on Saunders Island, deployed archival and satellite GPS data loggers on 17 individuals, and monitored movements within and between two feeding areas on Saunders Island, a “marine-subsidized” site near seabird colonies and an anthropogenic “human-subsidized” farm site 16 km to the southeast.ResultsDuring 67 observation days between 2010 and 2015, resightings of 312 banded caracaras were greater at the marine-subsidized site during austral summer than winter, and the total daily resightings varied significantly between spring versus summer, summer versus winter, autumn versus spring, and autumn versus winter. Resightings were higher at the human-subsidized site in austral winter than summer and the total daily resightings varied significantly across all bi-seasonal comparisons. Resightings indicated that at least 12 of 197 birds (6.1%) moved between the human- and marine-subsidized sites at least once during the same winter, 15 of 335 birds (4.5%) did so in spring, none of 164 birds did so in summer, and 16 of 297 birds (5.4%) did so in autumn. Individuals fitted with archival GPS data loggers at the marine-subsidized site in summer maintained highly localized 95% kernel core areas (0.55 ± 0.12 km2 [mean ± SD]), whereas those at the human-subsidized site in winter maintained larger 95% kernel core areas (3.8 ± 4.6 km2). Two of 6 satellite-tagged individuals that summered at known caracara breeding colonies 80 km WNW of Saunders Island were subsequently resighted in winter at the human-subsidized site.ConclusionOur results suggest that seasonal shifts in food resource availability drive seasonal micro-migrations in a farm-island population of striated caracaras, and that farm sites can be critical in providing nutritional resources for caracaras when naturally occurring marine-subsidized resources become less available. Our results have important implications for striated caracara spatial ecology and conservation, as increased winter survival could improve the status of this globally Near-Threatened population.

Foraging flights

Black-browed albatross (Diomedea melanophris) flying near Saunders Island, Falkland Islands. ©iStockphoto.com/GentooMultimediaLimited.

Winter diet of striated caracara Phalcoboenus australis (Aves, Polyborinae) at a farm settlement on the Falkland Islands

Striated caracaras occur only on the Falkland Islands and the outer islands of southern Chile and Argentina. In summer, the species associates with seabirds and seals and depends heavily upon them for food. The winter diet is less well understood. We studied the diet of 90–130 mainly juvenile and sub-adult striated caracaras overwintering at a farm on Saunders Island, Falkland Islands, in mid-winter (July–August) 2011. Direct observations of feeding and regurgitation pellets collected at a roost indicate that the winter diet of the striated caracaras at the site is mainly native geese, beetles and other invertebrates, and the carcasses of domestic sheep. This study illustrates seasonal shifts in the diet of this near-threatened South Atlantic endemic and suggests an important nutritional link between juvenile and subadult caracara survival in winter and traditional human activities at sheep farms.

First recorded eruption of Mount Belinda volcano (Montagu Island), South Sandwich Islands

The MODVOLC satellite monitoring system has revealed the first recorded eruption of Mount Belinda volcano, on Montagu Island in the remote South Sandwich Islands. Here we present some initial qualitative observations gleaned from a collection of satellite imagery covering the eruption, including MODIS, Landsat 7 ETM+, ASTER, and RADARSAT-1 data. MODVOLC thermal alerts indicate that the eruption started sometime between 12 September and 20 October 2001, with low-intensity subaerial explosive activity from the island’s summit peak, Mount Belinda. By January 2002 a small lava flow had been emplaced near the summit, and activity subsequently increased to some of the highest observed levels in August 2002. Observations from passing ships in February and March 2003 provided the first visual confirmation of the eruption. ASTER images obtained in August 2003 show that the eruption at Mount Belinda entered a new phase around this time, with fresh lava effusion into the surrounding icefield. MODIS radiance trends also suggest that the overall activity level increased significantly after July 2003. Thermal anomalies continued to be observed in MODIS imagery in early 2004, indicating a prolonged low-intensity eruption and the likely establishment of a persistent summit lava lake, similar to that observed on neighboring Saunders Island in 2001. Our new observations also indicate that lava lake activity continues on Saunders Island.

Campylonotus arntzianus, a new species of the Campylonotidae (Crustacea: Decapoda: Caridea) from the Scotia Sea (Antarctica)

Two specimens of Campylonotus arntzianus sp. nov. were caught in the Antarctic Scotia Sea off Saunders Island (5740.31'S, 2627.81'W) using an A- gassiz trawl at one station (depth: 475-589 m). The new species described here is the fifth representative of the monogeneric family Campylonotidae, and the first of the family south of the Antarctic Convergence. Campylon- otus arntzianus sp. nov. is a shrimp of about 5 cm in total length. Due to similarities in adult morphology, C. arntzianus sp. nov. seems to be closely related to C. capensis, a deep-sea species from the Southern Atlantic Ocean. A simple key for the species identifica- tion of the Campylonotidae is provided.

Discovery of a recurrent lava lake on Saunders Island (South Sandwich Islands) using AVHRR imagery

Monitoring of the remote South Sandwich Islands volcanic arc, using advanced very high resolution radiometer (AVHRR) data, has identified a radiant pixel on channels 3 (3.55–3.93μm) and (rarely) 4 (10.3–11.3μm). The position of the pixel is coincident with Mount Michael, Saunders Island, the active summit crater of a snow-covered basaltic stratovolcano with a persistent steam plume. The radiant pixel was continuously present in successive AVHRR images acquired during intervals of several months in the period examined (March 1995–February 1998), although apparently disappearing for similar time intervals. More than 5000 images were examined during this study. The radiant pixel is interpreted to indicate that the crater has contained a lava lake, the first to be recorded in the South Sandwich Islands. The lake appears to persist in the crater for several months at a time, at least. It may have drained completely at times and was probably absent when the crater was viewed briefly during an overflight in January 1997. Persistent or recurring lava lakes are very uncommon world-wide and that at Mount Michael is one of only two recorded in the Antarctic region.

V. An account of Falkland Islands

Falkland's Islands, or, as the Spaniards and French call them, the Maloine Islands, are situated between the latitude of 52° 26' and 51° 6' S. and longitude from London 56° to 60° 30' W. They are numberless, forming a mass of broken high lands, or very low sedgy keys and sunken rocks. The largest is the Easternmost island, and on the Eastern side the Spaniards had a settlement, which the crown of Spain purchased of M. Bougainville, who, on his private account, had formed a settlement in the year 1764, at the time that Commodore Byron had first discovered Port Egmont. The next large island is of a very considerable extent, and hath many excellent harbours on it. Between these two runs Falkland's Sound, which is navigable through; but the South entrance is pretty full of low sandy keys. Adjoining to the second large island, to the Westward, lies Saunders's Island, on which the English settlement was made, a blockhouse erected, several spots inclosed for gardens and three storehouses, and five dwelling-houses or huts, built at different times by the ships crews who were stationed there.