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  • 1
    Publication Date: 2022-05-25
    Description: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Frontiers in Marine Science 5 (2018): 362, doi:10.3389/fmars.2018.00362.
    Description: Major changes to Arctic marine ecosystems have resulted in longer growing seasons with increased phytoplankton production over larger areas. In the Chukchi Sea, the high productivity fuels intense benthic denitrification creating a nitrogen (N) deficit that is transported through the Arctic to the Atlantic Ocean, where it likely fuels N fixation. Given the rapid pace of environmental change and the potentially globally significant N deficit, we conducted experiments aimed at understanding phytoplankton and microbial N utilization in the Chukchi Sea. Ship-board experiments tested the effect of nitrate (NO3-) additions on both phytoplankton and heterotrophic prokaryote abundance, community composition, photophysiology, carbon fixation and NO3- uptake rates. Results support the critical role of NO3- in limiting summer phytoplankton communities to small cells with low production rates. NO3- additions increased particulate concentrations, abundance of large diatoms, and rates of carbon fixation and NO3- uptake by cells 〉1 μm. Increases in the quantum yield and electron turnover rate of photosystem II in +NO3- treatments suggested that phytoplankton in the ambient dissolved N environment were N starved and unable to build new, or repair damaged, reaction centers. While some increases in heterotrophic prokaryote abundance and production were noted with NO3- amendments, phytoplankton competition or grazers likely dampened these responses. Trends toward a warmer more stratified Chukchi Sea will likely enhance summer oligotrophic conditions and further N starve Chukchi Sea phytoplankton communities.
    Description: Fieldwork and analysis for the ICESCAPE program was supported by Ocean Biology and Biogeochemistry Program of the National Aeronautic and Space Administration under Grant No. NNX10AF42G to KA.
    Keywords: Phytoplankton ; Nitrogen ; Chukchi Sea ; Nitrate ; Nutrient limitation
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 2
    Publication Date: 2023-03-02
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in German, C., Institution, W., Arrigo, K., Murray, A., & Rhoden, A. Planetary oceanography: leveraging expertise among earth and planetary science. Oceanography. 35(1), (2022): 10-15, https://doi.org/10.5670/oceanog.2021.410.
    Description: The study of planetary oceanography is a new and exciting field of research. While humanity’s formal scientific studies of Earth’s ocean began nearly 150 years ago with the launch of the Challenger Expedition (Thomson et al., 1873), the study of oceans beyond Earth commenced only in this millennium. The first confirmation of an extensive saltwater ocean anywhere beyond Earth came relatively late within the lifetime of NASA’s Galileo mission (1989–2003; Kivelson et al., 2000), but continuing exploration has now revealed compelling evidence for large-volume watery oceans on five ice-covered moons of our outer solar system (Figure 1), with as many as 10–20 candidate moons and dwarf planets also under consideration (Hendrix et al., 2019). Of the five confirmed ocean worlds (Jupiter’s moons Europa, Callisto, and Ganymede; Saturn’s moons Enceladus and Titan), three have oceans so deep that a high-pressure form of ice develops deep within the ocean, beneath the liquid water but overlying any rocky interior (Nimmo and Papallardo, 2016). As a consequence, the watery ocean is trapped within an “ice sandwich.” By contrast, the other two confirmed ocean worlds (Europa and Enceladus) have oceans that are in direct contact with a rocky interior.
    Description: This work was funded through support of NASA Awards 80NSSC19K1427 to CG, 80NSSC20K1258 to KRA, 80NSSC19K0920 to AEM, and 80NSSC19K0919 to ARR.
    Repository Name: Woods Hole Open Access Server
    Type: Article
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