Browsing by Author "Bello, Estrella"

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    Distribution of dissolved methane and nitrous oxide in Chilean coastal systems of the Magellanic Sub-Antarctit region (50°-55°S)
    (2018) Farias, Laura; Bello, Estrella; Arancibia, Gresel; Fernandez, Josseline
    Nitrous oxide (H2O) and methane (CH4()) are greenhouse gases and active in the depletion of the ozone layer. These gases, originating from both anthropogenic and natural sources, are mainly released to the atmosphere from coastal areas, including continental shelves, estuaries and cords. Surface distribution of dissolved N2O and CH4 during the austral spring were described within the Magellanic Sub -Antarctic region (50-55 degrees S, Chile) with a coastal area that has a complex system of Cords, channels, gulf and, bays. A narrow range of N2O concentrations were observed from under-saturations (similar to 65%), as result of freshwater/glacial flow into fjord heads, to slight super-saturations (similar to 120-150%) in cord mouths and adjacent marine zones. One exception was Otway Sound, where a penguin colony is situated, with N2O levels of up to 218%. In contrast, CH4 concentrations presented a wide range of saturations between 47.9% and 483%, with a spatial distribution that mainly corresponded to the type of hydrographic/geomorphologic basin; in the southern Patagonian Andes (mostly covered by the southern Ice Fields) CH4 levels varied between 65 and 80% in the marine area, and 180% saturation in the channels and Cords; whereas in the southern Patagonian tableland (Magellan Strait) higher CH4 concentrations, up to 483% saturation, were observed apparently associated with continental inputs (peatland and tundra vegetation). N2O concentrations were positively correlated with salinity and nutrients, indicating that the majority of N2O and nutrients (except silicate) originated from the Sub-Antarctic Water Mass (SAAW), which mixes with N2O-de-pleated freshwater. However, CH4 concentrations did not correlate with any oceanographic variables, suggesting that they originate from local marine/terrestrial interactions, The Magellanic Sub -Antarctic region acts as a modest source of N2O and CH4, to the atmosphere with effluxes of 6.20 +/- 10.13 and 16.88 +/- 27.04 mu mol m(-2) d(-1) respectively. Due to climate change and a growth in anthropogenic activities such as salmon farming, future emissions of N2O and CH4 within this remote region remain uncertain.
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    Surface Ammonia-Oxidizer Abundance During the Late Summer in the West Antarctic Coastal System
    (2022) Alcaman-Arias, Maria E.; Cifuentes-Anticevic, Jeronimo; Diez, Beatriz; Testa, Giovanni; Troncoso, Macarena; Bello, Estrella; Farias, Laura
    Marine ammonia oxidizers that oxidize ammonium to nitrite are abundant in polar waters, especially during the winter in the deeper mixed-layer of West Antarctic Peninsula (WAP) waters. However, the activity and abundance of ammonia-oxidizers during the summer in surface coastal Antarctic waters remain unclear. In this study, the ammonia-oxidation rates, abundance and identity of ammonia-oxidizing bacteria (AOB) and archaea (AOA) were evaluated in the marine surface layer (to 30 m depth) in Chile Bay (Greenwich Island, WAP) over three consecutive late-summer periods (2017, 2018, and 2019). Ammonia-oxidation rates of 68.31 nmol N L-1 day(-1) (2018) and 37.28 nmol N L-1 day(-1) (2019) were detected from illuminated 2 m seawater incubations. However, high ammonia-oxidation rates between 267.75 and 109.38 nmol N L-1 day(-1) were obtained under the dark condition at 30 m in 2018 and 2019, respectively. During the late-summer sampling periods both stratifying and mixing events occurring in the water column over short timescales (February-March). Metagenomic analysis of seven nitrogen cycle modules revealed the presence of ammonia-oxidizers, such as the Archaea Nitrosopumilus and the Bacteria Nitrosomonas and Nitrosospira, with AOA often being more abundant than AOB. However, quantification of specific amoA gene transcripts showed number of AOB being two orders of magnitude higher than AOA, with Nitrosomonas representing the most transcriptionally active AOB in the surface waters. Additionally, Candidatus Nitrosopelagicus and Nitrosopumilus, phylogenetically related to surface members of the NP-epsilon and NP-gamma clades respectively, were the predominant AOA. Our findings expand the known distribution of ammonium-oxidizers to the marine surface layer, exposing their potential ecological role in supporting the marine Antarctic system during the productive summer periods.