Prokaryotic diversity and biogeochemical characteristics of benthic microbial ecosystems from James Ross Archipelago (West Antarctica)

The James Ross archipelago houses numerous lakes and ponds. In this region, a vast diatom and cyanobacterial variety has been reported; however, the prokaryotic diversity in microbial mats from these lakes remains poorly explored. Here, a high-throughput sequencing of 16S rRNA gene in microbial mats from Lake Bart-Roja in James Ross Island and lakes Pan Negro and North Pan Negro located in Vega Island was performed. Combined with mineralogical and environmental characteristics, we analyzed the diversity and structure of the microbial communities. Sequences assigned to Archaea were extremely low, while Bacteria domain prevailed with the abundance of Proteobacteria (mostly Betaproteobacteriales) followed by Bacteroidetes, Verrucomicrobia, Firmicutes, and Cyanobacteria. Local environmental conditions, such as conductivity and Eh, provided differential microbial assemblages that might have implications in the oligotrophic status of the lakes. Consequently, a clear segregation at the family level was observed. In this sense, the assigned diversity was related to taxa recognized as denitrifiers and sulfur oxidizers. Particularly, in Lake Pan Negro sulfur-reducing and methanogenic representatives were also found and positively correlate with alkalinity and water depth. Moreover, Deinococcus-Thermus was observed in Lake Bart-Roja, while Melainabacteria (Cyanobacteria)—poorly reported in Antarctic mats—was detected in Lake Pan Negro. Epsilonbacteraeota was exclusively found in this lake, suggesting new potential phylotypes. This study contributes to the understanding of the diversity, composition, and structure of Antarctic benthic microbial ecosystems and provides highly valuable information, which can be used as a proxy to evaluate environmental changes affecting Antarctic microbiota.Fil: Fernández, Guillermo César. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Lecomte, Karina Leticia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Vignoni, Paula. German Research Centre for Geosciences; AlemaniaFil: Soto Rueda, Eliana Marcela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Coria, Silvia Herminda. Ministerio de Relaciones Exteriores y Culto. Direccion Nacional del Antartico. Instituto Antartico Argentino. Departamento de Microbiologia Ambiental.; ArgentinaFil: Lirio, Juan Manuel. Ministerio de Relaciones Exteriores y Culto. Direccion Nacional del Antartico. Instituto Antartico Argentino. Coordinacion Ciencias de la Tierra.; ArgentinaFil: Mlewski, Estela Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentin

Habitat controls on limno-terrestrial diatom communities of Clearwater Mesa, James Ross Island, Maritime Antarctica

Diatoms are important ecological indicators in Antarctica, and paleolimnologists routinely apply transfer functions to fossil diatoms recovered from lake sediments to reconstruct past environments. However, living diatom communities may differ among the possible habitat types represented in sediment cores (both within lakes and their immediate proximity), hindering the full and accurate interpretation of fossil records. Therefore, an improved understanding of Antarctic diatom habitat preferences would substantially aid in interpreting regional paleo-material. To gain insights into habitat differences, we sampled epipelon, epilithon, Nostoc mats, lake-adjacent moss, and wet soil from > 30 lakes and ponds from Clearwater Mesa, James Ross Island, spanning a broad gradient in conductivity (a common basis for transfer functions). We found that diatom communities significantly differed between habitat types (although abundances were too low in Nostoc mats to characterize communities), with the clearest distinctions being between submerged (epipelon and epilithon) and exposed (moss and wet soil) groups. Submerged habitat types had greater abundances of attached aquatic taxa (i.e. Gomphonema spp.), while exposed habitats harboured more abundant aerophilic genera (e.g. Hantzschia, Luticola, and Pinnularia). Furthermore, only epilithon communities were significantly related to conductivity, and both epipelon and epilithon habitats showed conspicuous increases in Denticula jamesrossensis at greater conductivity values. Collectively, these results improve our knowledge of limno-terrestrial diatoms from the Maritime Antarctic Region, and further highlight the utility of incorporating knowledge of habitat preferences into (paleo)ecological research.Fil: Kopalová, K.. Charles University; Faculty of Science; Department of Ecology; República ChecaFil: Soukup, J.. Charles University; Faculty of Science; Department of Ecology; República ChecaFil: Kohler, T.J.. Charles University; Faculty of Science; Department of Ecology; República ChecaFil: Roman, M.. Masaryk University; República ChecaFil: Coria, Silvia Herminda. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; ArgentinaFil: Vignoni, P. A.. Universidad Nacional de Córdoba; Argentina. German Research Centre for Geosciences; AlemaniaFil: Lecomte, Karina Leticia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Nedbalová, L.. Charles University; Faculty of Science; Department of Ecology; República ChecaFil: Nývlt, D.. Masaryk University; República ChecaFil: Lirio, Juan Manuel. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; Argentin

Lacustrine systems of Clearwater Mesa (James Ross Island, north-eastern Antarctic Peninsula): Geomorphological setting and limnological characterization

Lentic freshwater habitats are important centres of biodiversity within the infrequent ice-free oases across Antarctica. Given imminent climate changes, it is crucial to catalogue these habitats in order to provide baseline data for future monitoring and biological surveys. The lacustrine systems of Clearwater Mesa, a previously unexplored part of James Ross Island, north-eastern Antarctic Peninsula, are described here. We conducted basic geomorphological and limnological surveys over three Antarctic summers (2009-16) to characterize landscape evolution, infer the origin of lake basins and assess the variability in their water chemistry. Stable shallow lakes, formed in depressions between lava tumuli following the last deglaciation, were found to dominate the volcanic mesa, although several peripheral lakes in ice-proximal settings appear to have formed recently as a result of post-Neoglacial ice recession. We found large heterogeneity in conductivity (~10-7000 μS cm-1), despite the lithologically uniform substrate. This variability was shown to be related to lake type, basin type (open vs closed), meltwater source and proximity to the coast. Inter-annual differences were attributed to changes in sea spray influx and snow accumulation driven by variable weather conditions. Overall, the ion composition of lakes suggested that sea spray was the dominant source of ions, followed by the weathering of bedrock.Fil: Roman, Matej. Charles University; República Checa. Masaryk University; República ChecaFil: Nedbalová, Linda. Charles University; República ChecaFil: Kohler, Tyler J.. Charles University; República ChecaFil: Lirio, Juan Manuel. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; ArgentinaFil: Coria, Silvia Herminda. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; ArgentinaFil: Kopácek, Jirí. Institute Of Hydrobiology, Biology Centre Of The Academy Of Sciences Of The Czech Republic; República ChecaFil: Vignoni, Paula A.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Kopalová, Katerina. Charles University; República ChecaFil: Lecomte, Karina Leticia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Elster, Josef. University of South Bohemia; República ChecaFil: Nývlt, Daniel. Masaryk University; República Chec

Late-Holocene palaeoenvironmental changes at Lake Esmeralda (Vega Island, Antarctic Peninsula) based on a multi-proxy analysis of laminated lake sediment

We have studied laminated sediments from Lake Esmeralda, Vega Island, in order to reconstruct its history. We describe both inorganic and organic components of the sediment using a combination of the following analytical methods: x-ray fluorescence (XRF), x-ray diffraction (XRD), magnetic susceptibility measurement, chemical analysis for determination of cation exchange capacity, grain size determination, geochemical analyses (total inorganic carbon (TIC), total organic carbon (TOC), total sulphur (TS)), spectrophotometry, high-pressure liquid chromatography, and diatom assemblage and faunal remains characterization. The geochronology of the core was based on modelling optically stimulated luminescence ages and supported by laminae counting. The dating results imply a maximum age of ~400 years for the 177-cm long core and a period covered of ~200 years, suggesting (quasi-)annual laminae formation. Such a young age contradicts previous findings based on radiocarbon dating. Geomorphological evidence indicates that river capture isolated the lake catchment from upslope sediment delivery, effectively terminating accumulation ~230 years ago. Conversely, our short-term palaeoenvironmental record yields a subdecadal temporal resolution, which is unparalleled in comparison with other Antarctic palaeolimnological studies. Our interpretations of the geochemical and mineralogical proxy data give us insight into the past lake catchment and waterbody evolution, and lead us to recognize periods of enhanced weathering, bottom anoxia and to distinguish major lake level changes