Periphyton diversity in two different Antarctic lakes assessed using metabarcoding

Antarctic lakes have generally simple periphyton communities when compared with those of lower latitudes. To date, assessment of microbial diversity in Antarctica has relied heavily on traditional direct observation and cultivation methods. In this study, sterilized cotton baits were left submerged for two years in two lakes on King George Island and Deception Island, South Shetland Islands (Maritime Antarctic), followed by assessment of diversity by metabarcoding using high-throughput sequencing. DNA sequences of 44 taxa belonging to four kingdoms and seven phyla were found. Thirty-six taxa were detected in Hennequin Lake on King George Island and 20 taxa were detected in Soto Lake on Deception Island. However, no significant difference in species composition was detected between the two assemblages (Shannon index). Our data suggest that metabarcoding provides a suitable method for the assessment of periphyton biodiversity in oligotrophic Antarctic lakes.

Microbial Communities Present in Hydrothermal Sediments from Deception Island, Antarctica

Deception Island is a geothermal location in Antarctica that presents active fumaroles, which confers unique characteristics to this habitat. Several studies about microbial communities in Antarctica have been carried out, nevertheless, Antarctic microbiota is still partially unknown. Here we present a multidisciplinary study about sediments obtained by deposition during 4 years in which several approaches have been considered for their characterization. First, a physicochemical characterization, using ionic chromatography and mass spectrometry for the determination of most abundant ions (chloride and sulphate) and elements (mainly silicon), was conducted. In addition, the total microbial community was studied using a metataxonomical approach, revealing a bacterial community dominated by Proteobacteria and Thaumarchaeota as the main archaeal genera and a fungal community mainly composed by Aspergillaceae. Culture-dependent studies showed low microbial diversity, only achieving the isolation of Bacillus-related species, some of them thermophilic, and the isolation of common fungi of Aspergillus or Penicillium spp. Furthermore, diatoms were detected in the sediment and characterized attending to their morphological characteristics using scanning electron microscopy. The study reveals a high influence of the physicochemical conditions in the microbial populations and their distribution, offering valuable data on the interaction between the island and water microbiota.

Exploring the plant environmental DNA diversity in soil from two sites on Deception Island (Antarctica, South Shetland Islands) using metabarcoding

The few Antarctic studies to date to have applied metabarcoding in Antarctica have primarily focused on microorganisms. In this study, for the first time, we apply high-throughput sequencing of environmental DNA to investigate the diversity of Embryophyta (Viridiplantae) DNA present in soil samples from two contrasting locations on Deception Island. The first was a relatively undisturbed site within an Antarctic Specially Protected Area at Crater Lake, and the second was a heavily human-impacted site in Whalers Bay. In samples obtained at Crater Lake, 84% of DNA reads represented fungi, 14% represented Chlorophyta and 2% represented Streptophyta, while at Whalers Bay, 79% of reads represented fungi, 20% represented Chlorophyta and < 1% represented Streptophyta, with ~1% of reads being unassigned. Among the Embryophyta we found 16 plant operational taxonomic units from three Divisions, including one Marchantiophyta, eight Bryophyta and seven Magnoliophyta. Sequences of six taxa were detected at both sampling sites, eight only at Whalers Bay and two only at Crater Lake. All of the Magnoliophyta sequences (flowering plants) represent species that are exotic to Antarctica, with most being plausibly linked to human food sources originating from local national research operator and tourism facilities.

Spatial distribution of microzooplankton in different areas of the northern Antarctic Peninsula region, with an emphasis on tintinnids

The Western Antarctic Peninsula (WAP) is experiencing rapid climate warming, resulting in affecting the marine food web. To investigate the microzooplankton spatial distribution and to assess how climate change could affect the tintinnids community, sea water samples were collected during late summer 2018 at 19 stations in three different areas: Deception Island, Elephant Island and Antarctic Sound. The microzooplankton community comprised mainly tintinnids, aloricate ciliates, heterotrophic dinoflagellates and micrometazoans. Microzooplankton abundance varied between 3 and 109 ind. L−1 and biomass ranged from 0.009 to 2.55 µg C L−1. Significant differences in terms of abundance and taxonomic composition of microzooplankton were found among the three sampling areas. Deception Island area showed 44% of tintinnids and the rest were heterotrophic dinoflagellate, aloricate ciliates and micrometazoans. In Elephant Island and Antarctic Sound areas, tintinnids reached, respectively, 73% and 83% of the microzooplankton composition, with all the other groups varying between 20 and 30%. Tintinnids were the most representative group in the area, with the species Codonellopsis balechi, Codonellopsis glacialis, Cymatocylis convallaria and Cymatocylis drygalskii. The highest amounts of tintinnids were found at the surface and 100 m depth. The above mentioned species may be considered key species for the WAP and therefore they can be used to track environmental and hydrographical changes in the area. In late summer, microzooplankton presented low abundances and biomass, nevertheless they represented an important fraction of the planktonic community in the area.

APPLICATION OF IMPROVED ACCURACY SFM-MVS FOR PHOTOGRAMMETRIC RESTITUTION AND COMPARISON OF PRE- AND POST-ERUPTION ARCHIVAL AERIAL IMAGERY ON DECEPTION ISLAND (SOUTH SHETLAND, ANTARCTICA)

Despite today's extensive remote sensing imagery with all kinds of sensors, the use of old aerial imagery is still importantin the study of slowly evolving land processes to reconstruct past landscape forms. Numerous organisations sharephotogrammetric data in public repositories, offering opportunities to exploit them to identify historical, natural andanthropogenic topographic changes, which is particularly interesting if they are difficult to access areas, possibly affectedsince historic times by climate change and other geodynamic processes. This work proposes and applies a workflow basedon the SfM-MVS photogrammetric technique to 22 and 33 historical aerial photographs of the English FIDASE (1956/57)and Argentinean Navy (1968) flights, scanned at 1016dpi and 96dpi, black and white, of Deception Island (South Shetland,Antarctica). The photogrammetric processing controls the threshold values of the reconstruction uncertainties andprojection accuracy. The 3D point clouds obtained are geroreferenced with 37 ground control points (GCP) geographicallypositioned in a QuickBird2 satellite image over island areas not affected by volcanism. The quality of the DTM is controlledby comparison with the 1960 topographic map 1:25000 of the island, which allows the volumes of material emitted in thevolcanic eruption of 1967 to be evaluated. The results obtained improve considerably and extend the set of resultscompared to those obtained by classical contour line digitizing. The applied method, the DTM and orthomosaic of 1956and 1968 presented will allow us to evaluate, together with the analysis applied to later historical flights, English 1979 andChilean 1986, the recent changes produced by the recent volcanism, the local external geodynamics, the possible climaticdeterioration and the scope of current human activity from 1956 to the present day.