Abstract
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.
Highlights
The West Antarctic Peninsula (WAP) is characterized by high algal production during the austral summer months, which supplies organic matter to support a rich ecosystem that contributes to a substantial sequestration of carbon (Barnes, 2018)
In this study we evaluate the benthic fluxes of silicic acid along the West Antarctic Peninsula (WAP)
This study presents seawater and porewater profiles of DSi and δ30SiDSi to evaluate for the first time the Si benthic fluxes along the WAP continental shelf
Summary
The West Antarctic Peninsula (WAP) is characterized by high algal production during the austral summer months, which supplies organic matter to support a rich ecosystem that contributes to a substantial sequestration of carbon (Barnes, 2018). The highly dynamic sea ice cycle along the WAP causes oceanographic conditions—and so light, nutrient, and grazing conditions—to vary over fine spatial and temporal scales resulting in highly heterogeneous production concentrated in biological hot spots (Kohut et al, 2018; Schofield et al, 2013; Venables et al, 2013). The specific mechanisms behind the location and extent of these hot spots, and so the productivity and storage of organic carbon, are not fully understood.
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