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Impact of transparent exopolymer particles on the dynamics of dissolved organic carbon in the Amundsen Sea, Antarctica
Full text linkThe Southern Ocean is an important carbon sink pool and plays a critical role in the global carbon cycling. The Amundsen Sea was reported to be highly productive in inshore area in the Southern Ocean. In order to investigate the influence of transparent exopolymer particles (TEP) on the behavior of dissolved organic carbon (DOC) in this region, a comprehensive study was conducted, encompassing both open water areas and highly productive polynyas. It was found that microbial heterotrophic metabolism is the primary process responsible for the production of humic-like fluorescent components in the open ocean. The relationship between apparent oxygen utilization and the two humic-like components can be accurately described by a power-law function, with a conversion rate consistent with that observed globally. The presence of TEP was found to have little impact on this process. Additionally, the study revealed the accumulation of DOC at the sea surface in the Amundsen Sea Polynya, suggesting that TEP may play a critical role in this phenomenon. These findings contribute to a deeper understanding of the dynamics and surface accumulation of DOC in the Amundsen Sea Polynya, and provide valuable insights into the carbon cycle in this region
2024 Department of Defense Arctic Strategy
Full text linkThis strategy lays out the Department of Defense’s (DoD’s) approach to the Arctic as the region undergoes rapid geophysical and geopolitical change. The strategy aligns with and nests under the 2022 National Security Strategy (NSS), 2022 National Defense Strategy (NDS), and 2022 National Strategy for the Arctic Region (NSAR). It also aligns with and implements the intent of the 2023 DoD Homeland Defense Policy Guidance
Environmental changes affect picoplanktonic composition in Antarctic Peninsula ponds
Full text linkAntarctic Peninsula is experiencing one of the largest global warming events worldwide. Shallow water bodies generated by the melting of snow in summer are numerous, and they might act as sentinels of climate change due to their rapid response and ability to integrate catchment information. Shifts in climate can influence the structure of microbial communities which dominate these freshwaters ecosystems. Here, we characterize three ponds at Cierva Point (Antarctic Peninsula) by examining their physico-chemical and morphological characteristics and we explored how different factors modify the structure of the microbial community. We studied the abundance and biomass of heterotrophic bacteria, picocyanobacteria and picoeukaryote algae during January and February of two consecutive summers (2017 and 2018). We found that ponds had different limnological characteristics, due to their location, geomorphological features and presence of the surrounding flora and fauna. Physico-chemical parameters as well as microbial community differed between ponds, months and years. In 2017, most ponds were oligo to mesotrophic states. The larger accumulated rainfall (as a result of environmental changes on the Antarctic Peninsula) during 2018, particularly in February, causes nutrient runoff into water bodies. This affects those ponds with the highest seabird circulation, such as gentoo penguin, increasing eutrophication. As a result, picoplanktonic abundances were higher, and the community structure shifts to a largely heterotrophic bacteria dominated one. These results suggest that these communities could act as sentinels to environmental changes, anticipating a future with mostly hypertrophic ponds
Microscopic analysis on eukaryotic algae and cyanobacteria in nine seasonal lakes and ponds in Vestfjella, Dronning Maud Land, Antarctica
Full text linkAntarctic continental lakes and ponds are among the most impoverished aquatic environments on earth but many of them support flourishing populations of cyanobacteria, eukaryotic algae, protozoans, and some multicellular animals. In this study, we present results of a microscopic analysis of cyanobacteria and eukaryotic algae from nine diverse types of Antarctic continental water bodies during one austral summer. The results supplement and enlarge our previous studies on the limnological characteristics of the epiglacial and supraglacial lakes and ponds in Dronning Maud Land, an area that has received little attention from limnologists. The taxon with highest frequency among the samples (n=79) was Mesotaenium cf. berggrenii, a eukaryotic Zygnematophyceae, which occurred in 82% of the samples with a maximum cell density of 68 cellsmL–1 . The taxa with second and third highest frequency were the prokaryotes Gloeocapsopsis (60%) and Leptolyngbya (41%), followed by Chlamydomonas (34%) and Cyanothece (29%). The number of taxa varied between 7–21 among the lakes and ponds, being highest in a supraglacial lake, and lowest in an epiglacial lake. The results did not reveal any obvious correlation between the abundance of any taxa and the water chemistry, but water bodies with inorganic sediments had higher cell densities and biomasses than those without sediment. This suggests the importance of sediment in supporting biological diversity in these ultraoligotrophic lakes and ponds
Distributions of dissolved oxygen and apparent oxygen utilization in the Cosmonaut Sea and Amundsen Sea in austral summer 2022
Full text linkDissolved oxygen (DO) and apparent oxygen utilization (AOU) are essential parameters for evaluating the impact of climate change on marine ecosystems. In this study, we utilized data on DO and AOU collected from the Amundsen Sea (western Antarctic) and the Cosmonaut Sea (eastern Antarctic) during the 38th Chinese National Antarctic Research Expedition, along with chlorophyll a (Chl a) data, to analyze the impact of primary production and the spatial distribution and structural features of water masses in these regions. The findings show that the standard deviation range of parallel DO samples is between 0.1 and 3.9 μmol·L−1, meeting the precision criteria of the survey method. AOU values lower than 0.0 μmol·L−1 were commonly observed in the surface waters of both regions, with the highest incidence in the polynya of Amundsen Sea, indicating a strong influence of high primary production. The Cosmonaut Sea exhibited the highest AOU values (higher than 160.0 μmol·L−1) in the 75–500 m layer, while AOU value in the Amundsen Sea did not exceed 160.0 μmol·L−1, suggesting potential upwelling of Circumpolar Deep Water to 100 m in the Cosmonaut Sea with minimal changes in its properties, whereas significant changes were noted in the properties of upwelling modified Circumpolar Deep Water in the Amundsen Sea. AOU values lower than 125.0 μmol·L−1 were detected in the near-bottom waters of the Cosmonaut Sea, indicating the presence of Antarctic Bottom Water
Diversity and interactions of lichen mycobionts and photobionts in the Fildes Region, King George Island, maritime Antarctica
Full text linkLichens, as dual organisms comprising a major mycobiont and a major photobiont, exhibit remarkable survival capabilities in extreme conditions, such as those found in Antarctica. Despite their adaptability, the diversity and distribution of lichen photobionts in the ice-free areas of maritime Antarctica remain less understood compared to their mycobiont counterparts. In our study, we investigated the diversity of both lichen mycobionts and photobionts in 56 samples collected from the Fildes Region on King George Island, maritime Antarctica. Through sequencing of the nuclear ribosomal internal transcribed spacer regions and subsequent phylogenetic analysis, we examined the relationships and association patterns between mycobionts and photobionts. Our findings revealed 19 taxa of lichen mycobionts across 13 families and seven orders, along with nine photobiont species within the class Trebouxiophyceae. These photobionts encompassed six Trebouxia species, one Asterochloris species, one Chloroidium species, and one Stichococcus species. In particular, a new Trebouxia lineage (Trebouxia sp. OTU D08) and a new Chloroidium lineage were found. The analysis indicated that many mycobionts could be associated with multiple photobiont species, a pattern also observed among the photobionts. These results contribute significantly to our understanding of the complex diversity of lichen mycobionts and photobionts in the ice-free areas of maritime Antarctica
A new look at the first dinosaur discovered in Antarctica: reappraisal of Antarctopelta oliveroi (Ankylosauria: Parankylosauria)
Full text linkThe first dinosaur discovered in the Antarctic continent was the ankylosaur Antarctopelta oliveroi in the 1980s. Nevertheless, since then several hypotheses of phylogenetical relationships have been proposed because these have been depended on how the skeletal remains have been interpreted. The main obstacle for clarifying its phylogenetic position is that many portions of the skeleton remain unknown, in addition to the presence of unknown characters in typical ankylosaurs. Considered an ankylosaurid, nodosaurid, or even a chimaera, a recent proposal based on mostly complete material of a new ankylosaur from Chilean Patagonia provided support for a novel phylogenetic hypothesis: Antarctopelta and other southern ankylosaurs are an early branching clade, the Parankylosauria, whose origin probably dates to the Late Jurassic. In the light of this new view, a redescription of the available skeletal remains is provided together with a new reconstruction of the first Antarctic dinosaur known to the science community
The first record of dermochelyid turtles in the Eocene of Tierra del Fuego: new insights on the evolution of the Weddellian faunas
Full text linkThe Antarctic Paleogene marine fossil record has been the key to reconstructing the evolution of the Weddellian Sea and final dismemberment of Southern Gondwana. In this context, Eocene marine vertebrates from Seymour (Marambio) Island have provided valuable information. We present the first Eocene record of marine reptiles from the southern Atlantic Coast of South America. This corresponds to several postcranial turtle remains represented by a proximal end of the right humerus, three caudal and one thoracic vertebrae, a fragment of the left pubis, and ten ossicles of the dorsal carapace, coming from the Leticia Formation (late-mid Eocene) at Cabo Tiburones, Tierra del Fuego, Argentina. These materials show several features such as the size and general morphology of the humerus and vertebrae, and the presence of relatively small, irregular, smooth, and unkeeled ossicles, which allow us to assign them to Dermochelyidae indet. Dermochelyids are a cosmopolitan group of cryptodiran turtles, registered from the late Cretaceous up to the recent, with some physiological-biological peculiarities (e.g., endothermy and an exclusive jellyfish-based diet) and characterized by the presence of an osseous carapace formed by ossicles. The new finding from the Leticia Formation is an addition to the scarce and extremely fragmentary record of Eocene dermochelyids from the southern seas like those from the La Meseta and Submeseta formations (Antarctica) and the Waihao and Burnside formations (New Zealand). This new information allows us to discuss the presence of these turtles in such high latitudes in the past and its implication in the evolution of the Weddellian fauna
The enhanced synoptic variation in sea ice over Pacific sector of Arctic Ocean during summer half year
Full text linkThis study investigates the synoptic Arctic sea ice variation during the summer half year based on a regional daily sea ice concentration (SIC) tendency index during 1979–2021. Results indicate an enhancement in synoptic SIC variation over the Pacific sector of Arctic Ocean, with the maximum amplitude concentrating along the sea ice edge to covering a larger domain. Most synoptic severe sea ice variations occur for a single day or 2–3 d, typically starting after mid-June and ending in mid-November over Beaufort–Chukchi seas. However, there is a clear shift in ending time over the East Siberian–Laptev seas from early October to early November. Further analysis suggests that wind-driven sea ice drift may significantly contribute to the amplification of synoptic sea ice variation. This result contributes to our understanding of regional Arctic sea ice predictability, particularly in relation to the Arctic northeast shipping passage
Atmospheric gaseous elemental mercury in the Arctic: role of long-range transport and sea ice
Full text linkThe potential sources of atmospheric mercury in the Arctic are still not well understood. Here, we analyzed the round-year observations of atmospheric gaseous elemental mercury (GEM) concentrations in 2010 at two sites in the Arctic: Zeppelin Observatory (78.90°N, 11.88°E) and Alert Observatory (82.47°N, 62.50°W). The results showed clearly different characteristics at these two sites. During the winter of 2010, the long-range transport of anthropogenic emissions was the dominant factor for elevated GEM at Zeppelin Observatory while which had little contribution to GEM at Alert Observatory. The change in GEM at Zeppelin Observatory during January, February and October was dominated by long-range transported anthropogenic emissions. The emission inventory combined with backward trajectory analysis suggested that the main sources were unintentional industrial sources, stationary combustion sources, and intentional use and product waste-associated sectors, which contributed 49%, 33%, and 18%, respectively. Potential source contribution function analysis was then conducted and found that Europe was the important source region. During the summer of 2010, sea ice concentration was an important factor affecting GEM at Alert Observatory while which had little effect on GEM at Zeppelin Observatory. These results further indicated the role of anthropogenic sources and climate warming on the spatial variation in GEM over the Arctic