Porovnání paleo a recentních společenstev sladkovodních rozsivek z ostrova Vega, Antarktida.

Rozsivky v Antarktické oblasti obývají různorodé limno-terestrické habitaty, z nichž každý má svůj jedinečný ekologický význam v biomonitoringu, paleoekologii a v biogeografii, avšak naše znalosti se stále zaměřují převážně na obsáhnutí a zaznamenávání diversity u daných habitatů v různých částech Antarktidy. Abychom získali větší vhled do toho, co ovlivňuje strukturu společenstev antarktických rozsivek z prostorového a habitatového hlediska, popisuji jejich rozmanitost a ekologii. Zaměřuji se na čtyři různé habitaty (jezera, mechy, potoky a mělké mokřady) na dvou protilehlých stranách ostrova Vega, který se nachází v souostroví Jamese Rosse ve Weddellově moři. Nalezla jsem různorodou flóru 136 taxonů patřících do 31 rodů, kterým dominoval rod Nitzschia. Dále naznačuje, že flóra ostrova Vega je biogeograficky ovlivněna jak kontinentálními, tak Maritimními antarktickými bioregiony. Bylo zjištěno, že typ stanoviště je rozhodujícím faktorem pro složení společenstva rozsivek, a že tento vliv je silnější, než vliv rozmístění v rámci ostrova. V ordinační analýze byly separovány vzorky mechů primárně druhem Chamaepinnularia krookiformis, zatímco vzorky jezer byly odděleny hlavně druhem Nitzschia paleacea. Potoky určuje především Fistulifera pelliculosa. Tato recentní společenstva byla následně porovnána s...In Antarctica, diatoms inhabit multiple limno-terrestrial habitat types, which may each individually offer unique ecological information for use in biomonitoring, paleoecology, and biogeography. However, we are still at the initial exploration stage of documenting the diversity among habitat types from different Antarctic regions, which is necessary to serve as baseline data for the aforementioned scientific disciplines, and ultimately inform conservation decisions. To gain insight into the spatial and habitat controls on Antarctic diatom communities, the importance of habitat type and island aspect was investigated by studying diatoms living in ponds, mosses, streams, and seepage areas on two opposite sides Vega Island, Antarctic Peninsula. A diverse flora of 136 taxa belonging to 31 genera was revealed, which was dominated by the genus Nitzschia, and suggests that the flora of Vega Island is biogeographically influenced by both continental and Maritime Antarctic bioregions. Habitat type was found to be a crucial factor for diatom community composition, and was stronger than the influence of island aspect. In ordination analyses, moss samples were separated primarily by their abundances of the diatom Chamaepinnularia krookiformis, while pond samples were separated by Nitzschia paleacea and stream...Katedra ekologieDepartment of EcologyPřírodovědecká fakultaFaculty of Scienc

Catchment characteristics and seasonality control the composition of microbial assemblages exported from three outlet glaciers of the Greenland Ice Sheet

Glacial meltwater drains into proglacial rivers where it interacts with the surrounding landscape, collecting microbial cells as it travels downstream. Characterizing the composition of the resulting microbial assemblages in transport can inform us about intra-annual changes in meltwater flowpaths beneath the glacier as well as hydrological connectivity with proglacial areas. Here, we investigated how the structure of suspended microbial assemblages evolves over the course of a melt season for three proglacial catchments of the Greenland Ice Sheet (GrIS), reasoning that differences in glacier size and the proportion of glacierized versus non-glacierized catchment areas will influence both the identity and relative abundance of microbial taxa in transport. Streamwater samples were taken at the same time each day over a period of 3 weeks (summer 2018) to identify temporal patterns in microbial assemblages for three outlet glaciers of the GrIS, which differed in glacier size (smallest to largest; Russell, Leverett, and Isunnguata Sermia [IS]) and their glacierized: proglacial catchment area ratio (Leverett, 76; Isunnguata Sermia, 25; Russell, 2). DNA was extracted from samples, and 16S rRNA gene amplicons sequenced to characterize the structure of assemblages. We found that microbial diversity was significantly greater in Isunnguata Sermia and Russell Glacier rivers compared to Leverett Glacier, the latter of which having the smallest relative proglacial catchment area. Furthermore, the microbial diversity of the former two catchments continued to increase over monitored period, presumably due to increasing hydrologic connectivity with proglacial habitats. Meanwhile, diversity decreased over the monitored period in Leverett, which may have resulted from the evolution of an efficient subglacial drainage system. Linear discriminant analysis further revealed that bacteria characteristic to soils were disproportionately represented in the Isunnguata Sermia river, while putative methylotrophs were disproportionately abundant in Russell Glacier. Meanwhile, taxa typical for glacierized habitats (i.e., Rhodoferax and Polaromonas) dominated in the Leverett Glacier river. Our findings suggest that the proportion of deglaciated catchment area is more influential to suspended microbial assemblage structure than absolute glacier size, and improve our understanding of hydrological flowpaths, particulate entrainment, and transport

Large subglacial source of mercury from the southwestern margin of the Greenland Ice Sheet

The Greenland Ice Sheet is currently not accounted for in Arctic mercury budgets, despite large and increasing annual runoff to the ocean and the socio-economic concerns of high mercury levels in Arctic organisms. Here we present concentrations of mercury in meltwaters from three glacial catchments on the southwestern margin of the Greenland Ice Sheet and evaluate the export of mercury to downstream fjords based on samples collected during summer ablation seasons. We show that concentrations of dissolved mercury are among the highest recorded in natural waters and mercury yields from these glacial catchments (521–3,300 mmol km−2 year−1) are two orders of magnitude higher than from Arctic rivers (4–20 mmol km−2 year−1). Fluxes of dissolved mercury from the southwestern region of Greenland are estimated to be globally significant (15.4–212 kmol year−1), accounting for about 10% of the estimated global riverine flux, and include export of bioaccumulating methylmercury (0.31–1.97 kmol year−1). High dissolved mercury concentrations (~20 pM inorganic mercury and ~2 pM methylmercury) were found to persist across salinity gradients of fjords. Mean particulate mercury concentrations were among the highest recorded in the literature (~51,000 pM), and dissolved mercury concentrations in runoff exceed reported surface snow and ice values. These results suggest a geological source of mercury at the ice sheet bed. The high concentrations of mercury and its large export to the downstream fjords have important implications for Arctic ecosystems, highlighting an urgent need to better understand mercury dynamics in ice sheet runoff under global warming

Can anatomy and morphology of seagrass root systems predict their colonization by symbiotic fungi?

Seagrasses are narrow ecological and taxonomic group of plants which evolved from terrestrial ancestors some 100 million years ago. Unlike most terrestrial plants they are traditionally considered as a group not forming mycorrhizal symbioses or specific root endophytic associations. However, this opinion is likely biased by a very low number of studies targeting this group of vascular plants. For example, an anatomically and morphologically unique endophytic fungal symbiosis was recently discovered in the roots of the Mediterranean endemic species Posidonia oceanica, a species that is considered to be one of the best studied. It thus seems that more specialized research can yield similar results, i.e. discoveries of new fungal association in seagrasses. This could have a big impact on our opinions regarding not only mineral nutrition of these fascinating plants. The aims of this thesis therefore are 1) to summarize published information about fungal associations in the roots of seagrasses, 2) to summarize basic knowledge of anatomy and morphology of the roots of individual groups of seagrasses and 3) an attempt to predict seagrass groups where we may more likely assume presence of fungal associations. Special emphasis will be placed on the genus Posidonia which has an evolutionary origin in the..

A comparison between paleo and recent freshwater diatom communities from Vega Island, Antarctica.

In Antarctica, diatoms inhabit multiple limno-terrestrial habitat types, which may each individually offer unique ecological information for use in biomonitoring, paleoecology, and biogeography. However, we are still at the initial exploration stage of documenting the diversity among habitat types from different Antarctic regions, which is necessary to serve as baseline data for the aforementioned scientific disciplines, and ultimately inform conservation decisions. To gain insight into the spatial and habitat controls on Antarctic diatom communities, the importance of habitat type and island aspect was investigated by studying diatoms living in ponds, mosses, streams, and seepage areas on two opposite sides Vega Island, Antarctic Peninsula. A diverse flora of 136 taxa belonging to 31 genera was revealed, which was dominated by the genus Nitzschia, and suggests that the flora of Vega Island is biogeographically influenced by both continental and Maritime Antarctic bioregions. Habitat type was found to be a crucial factor for diatom community composition, and was stronger than the influence of island aspect. In ordination analyses, moss samples were separated primarily by their abundances of the diatom Chamaepinnularia krookiformis, while pond samples were separated by Nitzschia paleacea and stream..

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

Particulate organic carbon (POC) concentration in meltwater runoff of Leverett Glacier, Russell Glacier, and Isunnguata Sermia, southwest Greenland (2009-2018), Version 1

This dataset describes particulate organic carbon (POC) and particulate carbon (PC) concentrations of suspended sediments in the proglacial rivers of 3 land-terminating glaciers in the Kangerlussuaq area, Southwest Greenland: Leverett Glacier (LG), Leverett River; Russell Glacier (RG), Akuliarusiarsuup Kuua; and Isunnguata Sermia (IS), Isortoq River. Both the Leverett River and Akuliarusiarsuup Kuua are tributaries of the Qinnguata Kuussua (also known as Watson River). The data have already been part of 3 different publications (Lawson et al. 2014, Kohler et al. 2017, and Vrbická et al. 2022) but are archived here for the first time. POC data was collected for LG during the 2009 and 2010 melt seasons (Lawson et al. 2014) as well as 2015 (Kohler et al. 2017). For the 2018 melt season, only total carbon concentrations of suspended sediments (PC) is archived as opposed to POC (see Vrbická et al. 2022)

Datasets for "Large subglacial source of mercury from the southwestern margin of the Greenland Ice Sheet", Version 3

Geochemical measurements and hydrochemical datasets linked to the publication "Large subglacial source of mercury from the southwestern margin of the Greenland Ice Sheet" in Nature Geoscience. Presented are (1) data for mercury concentrations in glacial meltwater outflows from the Greenland Ice Sheet taken in 2012, 2015 and 2018, (2) data for mercury concentrations in fjord waters from Nuup Kangerlua, Ameralik Fjord and Søndre Strømfjord, and (3) all associated hydrochemical data presented in the manuscript. For additional details (analytical techniques, precision, accuracy and limits of detection) please refer to the methodology in the publication. This third version has additional riverine data added the the 2012 dataset

Particulate organic carbon (POC) concentration in meltwater runoff of Leverett Glacier, Russell Glacier, and Isunnguata Sermia, southwest Greenland (2009-2018), Version 2

This dataset describes particulate organic carbon (POC) and particulate carbon (PC) concentrations of suspended sediments in the proglacial rivers of 3 land-terminating glaciers in the Kangerlussuaq area, Southwest Greenland: Leverett Glacier (LG), Leverett River; Russell Glacier (RG), Akuliarusiarsuup Kuua; and Isunnguata Sermia (IS), Isortoq River. Both the Leverett River and Akuliarusiarsuup Kuua are tributaries of the Qinnguata Kuussua (also known as Watson River). The data have already been part of 3 different publications (Lawson et al. 2014, Kohler et al. 2017, and Vrbická et al. 2022) but are archived here for the first time. POC data was collected for LG during the 2009 and 2010 melt seasons (Lawson et al. 2014) as well as 2015 (Kohler et al. 2017). For the 2018 melt season, only total carbon concentrations of suspended sediments (PC) is archived as opposed to POC (see Vrbická et al. 2022)