Soils under seal carcasses with varying degrees of decomposition: oasis of nutrients and vegetation in Antarctica.

Areas of high concentration of seal carcasses have been observed in localized areas of James Ross Island, Antarctica. Such carcasses show an unusual vegetation development, in a semi-arid area with bare soils under intense winds, high salinity and sandy texture. We investigated carcasses of seals around a lake in James Ross Island, with four different stages of decomposition, with three replicates: Seal (S01), with recently mummified carcasses; S02, with partially degraded carcasses; S03, with broken carcasses with partially degraded exposed bones, and S04, with completely broken, scattered skeletons. The vegetation showed a maximum degree of development in carcasses at stages S02 and S03, with the environment between the skin and the skeleton as the preferred place for vegetation establishment. The chemical alteration was greater with increasing carcass decomposition but reduced with the spreading and final decomposition of the bones, with anomalous values observed only in the vicinity of the carcasses. It is concluded that the presence of carcasses of seals, concentrated in wet places, even in a semi-desert climate, represent important oases of nutrients, with a combination of physical and chemical effects throughout the decomposition process that favor plant establishment and succession.

Ornithogenesis and soil-landscape interplays at northern Harmony Point, Nelson Island, Maritime Antarctica.

Understanding the influence of soil-forming factors and processes in ornithogenic soils is important to predict impacts of climate change on Antarctic ecosystems. Herein, we analyzed the soil-landscape interplays and development of ornithogenic soils at Harmony Point (HP), Nelson Island. We collected, described, and classified 24 soil profiles, combined with vegetation and landforms descriptions. Geoprocessing techniques were employed for mapping. Soil physical, chemical, geochemical, and mineralogical analyses were applied. Patterned ground, "Ornithogenic"/Typic Gelorthent, and moss carpets were the dominant landform, soil and vegetation classes, respectively. Soils from rocky outcrops were more structured, acidic, with higher organic carbon, organometallic complexes, and secondary phosphate minerals, due to former bird influence. Soils from cryoplanated platforms presented higher water pH, base saturation, clay content, and secondary silicate minerals. Soils from marine terraces presented high exchangeable bases, phosphorous, and amorphous phosphate minerals. Soil chemical weathering is enhanced by ornithogenesis and widespread in HP. Besides ornithogenesis, organic matter accumulation, cryoturbation, and cryoclastic processes are also important to pedogenesis of ornithogenic soils. The soils of the cryoplanated platforms exhibited a gradient of pedogenetic development corresponding to increasing biota influence and distance from glacier. In contrast, soils of rocky outcrops were more developed even close to the glacier, due to ornithogenesis.

Thermal monitoring of a Cryosol in a high marine terrace (Half Moon Island, Maritime Antarctica).

Active layer and permafrost are important indicators of climate changes in periglacial areas of Antarctica, and the soil thermal regime of Maritime Antarctica is sensitive to the current warming trend. This research aimed to characterize the active layer thermal regime of a patterned ground located at an upper marine terrace in Half Moon Island, during 2015-2018. Temperature and moisture sensors were installed at different soil depths, combined with air temperature, collecting hourly data. Statistical analysis was applied to describe the soil thermal regime and estimate active layer thickness. The thermal regime of the studied soil was typical of periglacial environment, with high variability in temperature and water content in the summer, resulting in frequent freeze-thaw cycles. We detected dominant freezing conditions, whereas soil temperatures increased, and the period of high soil moisture content lasted longer over the years. Active layer thickness varied between the years, reaching a maximum depth in 2018. Permafrost degradation affects soil drainage and triggers erosion in the upper marine terrace, where permafrost occurrence is unlikely. Longer monitoring periods are necessary for a detailed understanding on how current climatic and geomorphic conditions affect the unstable permafrost of low-lying areas of Antarctica (marine terraces).

Soil-landform-vegetation interplays at Stinker Point, Elephant Island, Antarctica.

The geomorphic dynamics on ice-free areas are crucial for understanding soil formation, vegetation and landscape stability in maritime Antarctic. We aimed to describe the soil formation on different landforms, following the Holocene glacial retreat at Stinker Point. Twenty profiles were sampled and classified, grouped into three landforms units: middle platforms and scarps, till/glacial deposits and present/Holocene raised beaches. Soil chemical and physical attributes were determined, and the vegetation type identified and quantified. Soils from till and glacial deposits can be separated by the age of exposure: older soils are stony, skeletic; and recently exposed till has soils with moderate depth, alkaline reaction and very high base saturation. Soils at the middle platforms are shallow, coarse-grained, skeletic, with abundant vegetation. Soils from the present-day beaches are alkaline, very coarse with no horizon differentiation, whereas soils on Holocene beaches are acid and nutrient-rich due to past or present-day influence of fauna. Soils from Stinker Point are generally shallow, skeletic and strongly related to the landforms and biogenic influences. Compared with other islands of the South Shetlands, in Elephant Island soil development is less pronounced, being this mainly attributed to the metamorphic nature of parent material, with greater resistance to weathering.

Changes in plant communities and soil attributes in the "Cousteau's whale bone skeleton" tourist attraction area in Keller Peninsula after 48 years.

Ice-free areas of Antarctica represent an important study region that helps us understand how human activity affects plant communities and soil properties. The goal of this study was to determine the changes in plant composition and soil properties around a whale bone skeleton (WB) near Ferraz Station, King George Island, Antarctica from 1972 to 2020 (48 years). The WB was assembled in 1972 by Jacques-Yves Cousteau and his team. It is located in a large moss field and visited by many tourists. We studied the plant composition and development based on historical and recent photographs and phytosociological studies from 1986 to 2020. The soil was sampled in February 2009 to determine general properties. The results showed that human activity surrounding the WB directly affected the plant community composition and soil properties. The Syntrichia cushions were positively affected by the calcium deposits from bone dissolution. The principal component analysis revealed that mineralization of the bones increased soil nutrient assembly. A strong phosphatization process was observed in the WB area, similar to that in ornithogenic soils. The WB on the marine terrace enhanced soil fertility and changed the plant community.

Apparent thermal diffusivity of soil in ice-free areas of Keller peninsula in maritime Antarctica.

Heat transfer process in the soil active layer is important for the knowledge of its thermal properties linked with climate issues. The objective of this work was to analyze the energy flux in different soil profiles by estimating the apparent soil thermal diffusivity ($ATD$). The study was carried out in Keller Peninsula, located at King George Island in four different sites differing by soil characteristics, as well as vegetation coverage and landscape setting. The $ATD$ was estimated in function of the long-term hourly temperature records at different soil depths. In addition, we estimated the seasonal mean of the $ATD$ and the freezing $N$-factor. Results showed that $ATD$ values were smaller at shallow depths and increased with depth. The diffusivity values presented lower variability in colder conditions, especially at deeper soil layers. Water content was the main factor affecting soil thermal diffusivity at sites $1$ and $3$ (more than $70$ and $63\%$ of probability). At sites $3$ and $4$ lower $N$-factors were observed, suggesting higher snow pack and permafrost closer to the soil surface. Hence, positive $ATD$ appears in the summer due to thawing increases soil moisture, while negative $ATD$ appears during the freeze of the snow pack and precipitation.

Influence of different seabird species on trace metals content in Antarctic soils.

The behavior and feeding habits of different species of seabirds can influence the enrichment of trace metals in Antarctic soils. This study aimed to evaluate the influence of different species of seabirds on the concentrations of potentially toxic metals in Antarctic soils. For this, we collected soil samples in areas influenced by penguins, kelp gulls, and giant petrels. We analyzed the concentration of total organic carbon (TOC), total nitrogen (TN), available phosphorus (P) and metals by three different methods of extraction: USEPA 3051A, Mehlich-1, and distilled water. The concentrations of Cr and Hg presented positive correlations with P, TOC, and TN by the USEPA 3051A method, indicating the biotransport of these metals by seabirds. Soils influenced by penguins showed higher levels of P, TOC, TN, Cr, and Hg. Comparing the results from the different extractors, we found that Hg had the highest relative levels in the exchangeable fraction and the soil solution. Therefore, the soils with the influence of penguins present higher levels of biotransported trace metals, but this does not necessarily mean that these birds have a higher biotransport potential, since the concentration of trace metals in these soils may be related to their degree of ornithogenesis.

Seabirds enrich Antarctic soil with trace metals in organic fractions.

Coastal areas of Antarctica are subjected to anthropic contamination from around the world by trace metals biotransported and accumulated by seabird excrements. To explore this hypothesis, this study investigated the influence of seabirds on the contents of trace metals in soil organic fractions from Antarctica under different climatic conditions and from different parent materials. For this, soil profiles from the Maritime Antarctica region were selected based on the criteria of ornithogenesis, parent material, and climate. The contents of C, N, and selected metals (Ba, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sr, and Zn) were analysed in the organic matter associated with minerals (MAOM), the particulate fraction (POM), and in the total soil (MAOM + POM). The ornithogenic soils presented the highest amounts of C and N in the soil, MAOM, and POM as compared to nonornithogenic soils. Seabird activity resulted in an enrichment of Pb, Zn, and Cu. Among these biotransported metals, Cu and Zn seem to originate from natural biogenic processes in marine food chains, unlike Pb, which seems to come from anthropogenic sources. The soils developed from igneous rocks presented higher amounts of Ba, Co, Cu, Fe, Mn, and Sr in the soil, MAOM, and POM than soils from sedimentary rocks. The climate had no clear effect on most metals. Hence, seabirds enrich soils, MAOM, and POM with Cu, Zn, and Pb, whereas the amounts of Ba, Co, Cr, Fe, Mn, Ni, and Sr are mainly lithogenic, associated with the parent material. Monitoring biotransported trace metals in ornithogenic soils is of great importance, since they can create environmental toxicity to terrestrial plants and animals and can influence the food chain in the coastal areas of Antarctica.

High-resolution topography for Digital Terrain Model (DTM) in Keller Peninsula, Maritime Antarctica.

High resolution topography (HRT) surveys is an important tool to model landscapes, especially in zones subjected to strong environmental changes, such as Antarctica, where landform is highly influenced by cryoclasty and permafrost melting. The aim of this work was to obtain a high accurate DTM for Keller Peninsula, Maritime Antarctica. The survey study was assessed in the 2014/2015 and 2015/2016 during the austral summer, by using Terrestrial Laser Scanner (TLS). In order to cover 8 km² of the Peninsula, the TLS equipment was installed in 81 different points. Results of the DTM generated by TLS (hereafter, HRT-DTM), and the terrain variables Aspect, Slope and Hillshade obtained were compared with previous models generated by aerophotographic survey (hereafter, APG-DTM). RMSE for the HRT and APG-DTM were 0.726 and 2.397 m, respectively. Spatial resolution of the DTMs was 0.20 m. Morphometric variables obtained from the two methods presented visual differences on the thematic maps, especially related to the Aspect. Generalization was the main process, whereas interpolation occurred for the HRT survey, being the process of choice for the APG method. A large number of points are obtained by the TLS, providing a dense cloud of points, spatially well-distributed, enabling the generalization process to obtain surface models with high performance.