Green synthesis of silver nanoparticles using psychrotolerant strains of Tulasnella albida from South Orkney Islands (Antarctica)

Nanoparticles are widely studied due to their possible uses in biological and technological systems. Four psychrotolerant strains of Tulasnella albida isolated from Antarctica were tested and compared in their ability to synthesize silver nanoparticles. The four strains were capable of synthesizing silver nanoparticles with the addition of AgNO3 (final concentration of 0.5 mM), showing similar results under the same conditions: 28°C, 200 rpm, pH 9. Additionally, we registered the synthesis of nanoparticles at 6°C using biomass generated at the same temperature. For the characterization of synthesized nanoparticles, TEM and SEM microscopy analyses were performed. The images obtained showed the existence of spherically shaped silver nanoparticles with a log-normal size distribution centered at 2 nm diameter for 28°C. The largest ones showed a capping shell around them, appearing associated with the formation of small silver nanoparticles. Theoretical calculations of optical absorption based on core-shell Ag-Ag2O nanoparticles were used to characterize the experimental absorption spectra of silver nanoparticles colloids. This work contributes to expanding the studies and possible technological applications of psychrotolerant organisms in the industry, particularly in the green synthesis of nanoparticles at suboptimal conditions.

Foraging conditions for breeding penguins improve with distance from colony and progression of the breeding season at the South Orkney Islands

Background According to central place foraging theory, animals will only increase the distance of their foraging trips if more distant prey patches offer better foraging opportunities. Thus, theory predicts that breeding seabirds in large colonies could create a zone of food depletion around the colony, known as “Ashmole’s halo”. However, seabirds’ decisions to forage at a particular distance are likely also complicated by their breeding stage. After chicks hatch, parents must return frequently to feed their offspring, so may be less likely to visit distant foraging patches, even if their quality is higher. However, the interaction between prey availability, intra-specific competition, and breeding stage on the foraging decisions of seabirds is not well understood. The aim of this study was to address this question in chinstrap penguins Pygoscelis antarcticus breeding at a large colony. In particular, we aimed to investigate how breeding stage affects foraging strategy; whether birds foraging far from the colony visit higher quality patches than available locally; and whether there is evidence for intraspecific competition, indicated by prey depletions near the colony increasing over time, and longer foraging trips. Methods We used GPS and temperature-depth recorders to track the foraging movements of 221 chinstrap penguins from 4 sites at the South Orkney Islands during incubation and brood. We identified foraging dives and calculated the index of patch quality based on time allocation during the dive to assess the quality of the foraging patch. Results We found that chinstrap penguin foraging distance varied between stages, and that trips became shorter as incubation progressed. Although patch quality was lower near the colony than at more distant foraging patches, patch quality near the colony improved over the breeding season. Conclusions These results suggest chinstrap penguin foraging strategies are influenced by both breeding stage and prey distribution, and the low patch quality near the colony may be due to a combination of depletion by intraspecific competition but compensated by natural variation in prey. Reduced trip durations towards the end of the incubation period may be due to an increase in food availability, as seabirds time their reproduction so that the period of maximum energy demand in late chick-rearing coincides with maximum resource availability in the environment. This may also explain why patch quality around the colony improved over the breeding season. Overall, our study sheds light on drivers of foraging decisions in colonial seabirds, an important question in foraging ecology.

Discussion on ‘The geological collection from the Scottish National Antarctic Expedition (1902–04) in the Museo de La Plata, Argentina’ by Carrasquero 2021 (Scottish Journal of Geology, 57, 60– 66)

The informative paper by Carrasquero (2021) reveals the personal contribution made by Francisco Moreno to the success of the 1902-04 Scottish National Antarctic Expedition (SNAE) during the time it spent in Buenos Aires, Argentina. It was a crucial intervention, and for the hospitality and generous assistance that Moreno arranged for the expedition's leader, William Speirs Bruce (Fig. 1), the presentation of a few rock specimens might seem scant reward, although as an additional mark of respect Bruce named Point Moreno on the expedition's published map of Laurie Island (Brown et al. 1906, p. 145): the name is still valid – 60° 44’ S, 44° 41’ W. Bruce would have been deeply satisfied by the knowledge that his donation of specimens from the South Orkney Islands had initiated the development of an Antarctic collection at the Museo de La Plata. His scientific outlook was always international and collaborative.

The geological collection from the Scottish National Antarctic Expedition (1902–04) in the Museo de La Plata, Argentina

In December 1903, Williams Speirs Bruce, leader of the Scottish National Antarctic Expedition, arrived in Buenos Aires and contacted Francisco Moreno, director of the Museo de La Plata to request his assistance. Bruce asked Moreno to be an intermediary with the Argentine government and to facilitate Bruce's wish for Argentina to take over the meteorological station that the Scottish expedition had established on Laurie Island (South Orkney Islands). Moreno was please to provide the necessary assistance and was instrumental in Bruce achieving his ambition. As a gesture of appreciation, before leaving Buenos Aires Bruce presented a small collection of Laurie Island rock specimens to Moreno as a donation to the Museo de La Plata. This donation initiated the museum's Antarctic collection.

Un-crewed aerial vehicle population survey of three sympatrically breeding seabird species at Signy Island, South Orkney Islands

Surveying seabirds in polar latitudes can be challenging due to sparse human populations, lack of infrastructure and the risk of disturbance to wildlife or damage to habitats. Counting populations using un-crewed aerial vehicles (UAVs) is a promising approach to overcoming these difficulties. However, a careful validation of the approach is needed to ensure comparability with counts collected using conventional methods. Here, we report on surveys of three Antarctic bird species breeding on Signy Island, South Orkney Islands; Chinstrap (Pygoscelis antarctica) and Gentoo (Pygoscelis papua) Penguins, and the South Georgia Shag (Leucocarbo atriceps georgianus). We show that images from low-altitude UAV surveys have sufficient resolution to allow separation of Chinstrap Penguins from contiguously breeding Adélie Penguins (Pygoscelis adéliae), which are very similar in appearance when viewed from overhead. We compare data from ground counts with manual counts of nesting birds on images collected simultaneously by low-altitude aerial photography from multi-rotor UAVs at the same colonies. Results at this long-term monitoring site confirmed a continued population decline for Chinstrap Penguins and increasing Gentoo Penguin population. Although both methods provided breeding pair counts that were generally within ~ 5%, there were significant differences at some locations. We examine these differences in order to highlight potential biases or methodological constraints that should be considered when analysing similar aerial census surveys and comparing them with ground counts.

Ocean currents as a potential dispersal pathway for Antarctica’s most persistent non-native terrestrial insect

The non-native midge Eretmoptera murphyi is Antarctica’s most persistent non-native insect and is known to impact the terrestrial ecosystems. It inhabits by considerably increasing litter turnover and availability of soil nutrients. The midge was introduced to Signy Island, South Orkney Islands, from its native South Georgia, and routes of dispersal to date have been aided by human activities, with little known about non-human-assisted methods of dispersal. This study is the first to determine the potential for dispersal of a terrestrial invertebrate species in Antarctica by combining physiological sea water tolerance data with quantitative assessments of ocean current journey times. Fourth instar larvae tolerated sea water submergence for up to 21 days, but submerged egg sacs had significantly reduced hatching success. Using near-surface drifter data, we conclude that ocean current dispersal from Signy Island would not present a risk of species transfer beyond the South Orkney Islands on the tested timescales. However, if E. murphyi were to be introduced to the South Shetlands Islands or Adelaide Island, which are located offshore of the Antarctic Peninsula, there would be a risk of successful oceanic dispersal to neighbouring islands and the Antarctic Peninsula mainland. This study emphasises the need for effective biosecurity measures and demonstrates the role that currently undocumented pathways may have in dispersing non-native species.

Spatial Structure and Intra-Annual Variability of Weddell Sea Front based on the Data of NOAA OISST Reanalysis

Based on the NOAA OISST reanalysis data, the spatial structure of the Weddell Sea Front in the climatic field of the sea surface temperature was analyzed and the seasonal variability of front’s characteristics was estimated. The spatial position of the frontal zone in the Weddell Sea was analyzed using distributions of the total horizontal temperature gradient. The characteristics of the front (the position of the gradients' extrema corresponding to the front, their magnitude and temperature on the front axis) were determined for each month on the profiles of meridional and zonal temperature gradients along meridians and parallels with a discreteness of 2.5° of longitude and 0.25° of latitude. It is shown that the interaction of Weddell Sea cold waters, which are transported by currents northward along the Antarctic Peninsula coasts, with the warmer waters of the eastern shelf of the Antarctic Peninsula and the Bransfield Strait surface water causes formation of two branches of the Weddell Sea Front. These branches round from a vast shelf at the Antarctic Peninsula tip and the Joinville archipelago the south and north and are traced further east along the boundaries of the bottom rise located approximately between 62.5S and 64.5S. To the south of the South Orkney Islands shelf, the two branches merge into one front, which follows to the east along the depth dump of the relative shallow between the South Orkney and South Sandwich Islands. In the seasonal cycle of the Weddell Sea Front intensity, a time lag was revealed of the front intensification period in the direction from west to east. In Bransfield Strait the front is most intense in February, between the Antarctic Peninsula tip and the South Orkney Islands – in March, east of the South Orkney Islands – in April. The branch of the Weddell Sea Front off the northeastern of the Antarctic Peninsula coasts intensifies in November – January, in the western part of the water area east of the James Ross and Snow Hill Islands – in January – February.