| Autor: |
Cassarino, Lucie, Hendry, Katharine R., Henley, Sian F., MacDonald, Ellen, Arndt, Sandra, Freitas, Felipe S., Pike, Jennifer, Firing, Yvonne L. |
| Předmět: |
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| Zdroj: |
Global Biogeochemical Cycles; Dec2020, Vol. 34 Issue 12, p1-17, 17p |
| Abstrakt: |
In this study we evaluate the benthic fluxes of silicic acid along the West Antarctic Peninsula (WAP). Silicic acid (DSi) is one of the macronutrients essential in fuelling biological hot spots of diatom‐dominated primary production along the WAP. Here we measure the concentration and stable silicon isotopic composition of DSi in porewater profiles, biogenic silica content (BSi), and diatom abundance from sediment cores collected along the WAP. We couple these measurements with reaction‐transport modeling, to assess the DSi flux and the processes that release this key nutrient from the sediment into the overlying waters. Our results show that the benthic DSi flux is dominated by the diffusive flux, which is estimated to be equivalent to 26.7 ± 2.7 Gmol yr−1 for the WAP continental shelf. The DSi isotope profiles reveal the important impact of sedimentary processes on porewater DSi and suggest that biogenic silica dissolution is the main source of DSi in porewaters and consequently of the benthic fluxes. Our integrated data‐model assessment highlights the impact of surface productivity on sedimentary processes and the dynamic environment of core‐top sediments where dissolution and reverse weathering reactions control DSi exchanges. Plain Language Summary: The West Antarctic Peninsula (WAP) is a highly productive region dominated by siliceous algae, diatoms. Biomass distribution is patchy along the WAP, and these hot spots are potentially enhanced by essential nutrients, that is, dissolved silicon, released from shallow marine sediments. We use observations of porewater concentrations and isotopes to show that the dissolved silicon flux from the sediments before the major diatom bloom period is low compared to the open Southern Ocean. However, both our observations and modeling reveal a strong link between surface water uptake and sedimentary release of dissolved silicon, such that benthic fluxes will increase during the summer season. We predict a significant variability in benthic silicon flux, tied to diatom productivity, which is highly sensitive to climatically driven changes in sea ice dynamics. Key Points: Dissolved silicon fluxes from marine sediment along the West Antarctic Peninsula continental shelf are reported for the first timeThe silicon isotopic composition of porewater is used to assess diagenetic processes and the silicon budget at the sediment‐water interfaceWe find no clear evidence of a significant source of silicon from marine sediment along the West Antarctic Peninsula continental shelf [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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