Biogeochemical cycling of silicon (Si) in the Barents Sea is under considerable pressure from physical and chemical changes, including dramatic warming and sea ice retreat, together with a decline in dissolved silicic acid (DSi) concentrations of Atlantic inflow waters since 1990. Associated changes in the community composition of phytoplankton blooms will alter the material comprising the depositional flux, which will subsequently influence recycling processes at and within the seafloor. In this study we assess the predominant controls on the early diagenetic cycling of Si, a key nutrient in marine ecosystems, by combining stable isotopic analysis (${\delta }^{30}$Si) of pore water DSi and of operationally defined reactive pools of the solid phase. We show that low biogenic silica (BSi) contents (0.26-0.52 wt% or 92-185 $\mu$mol g dry wt^-1) drive correspondingly low asymptotic concentrations of pore water DSi of $\sim$100 $\mu$M, relative to biosiliceous sediments ($>$20 wt% BSi) wherein DSi can reach $\sim$900 $\mu$M. While Barents Sea surface sediments appear almost devoid of BSi, we present evidence for the rapid recycling of bloom derived BSi that generates striking transient peaks in sediment pore water [DSi] of up to 300 $\mu$M, which is a feature that is subject to future shifts in phytoplankton community compositions. Using a simple isotopic mass balance calculation we show that at two of three stations the pore water DSi pool at 0.5 cm below the seafloor (+0.96 to +1.36 ‰) is sourced from the mixing of core top waters (+1.46 to +1.69 ‰) with the dissolution of BSi (+0.82 to +1.50 ‰), supplemented with a lithogenic Si source (LSi) (-0.89 $\pm$0.16‰). Further, our sediment pore water ${\delta }^{30}$Si profiles uncover a coupling of the Si cycle with the redox cycling of metal oxides associated with isotopically light Si (-2.88 $\pm$0.17‰). We suggest that a high LSi:BSi ratio and apparent metal oxide influence could lead to a degree of stability in the annual background benthic flux of DSi, despite current pressures on pelagic phytoplankton communities. Coupled with supporting isotopic evidence for the precipitation of authigenic clays in Barents Sea sediment cores, our observations have implications for the regional Si budget.

巴伦支海中硅 (Si) 的生物地球化学循环受到物理和化学变化的巨大压力，包括剧烈变暖和海冰退缩，以及自 1990 年以来大西洋流入水的溶解硅酸 (DSi) 浓度下降。相关变化在浮游植物群落组成中，大量的浮游植物将改变构成沉积通量的物质，这将随后影响海底及其内部的回收过程。在这项研究中，我们通过结合稳定同位素分析评估了对海洋生态系统中的关键营养物质 Si 的早期成岩循环的主要控制。${\delta }^{30}$Si) 的孔隙水 DSi 和操作上定义的固相反应池。我们显示低生物二氧化硅 (BSi) 含量（0.26-0.52 wt% 或 92-185$\mu$mol g dry wt ^-1 ) 相应地驱动孔隙水 DSi 的低渐近浓度$～$100$\mu$M，相对于生物硅质沉积物 ($>$20 wt% BSi) 其中 DSi 可以达到$～$900$\mu$M. 虽然巴伦支海表层沉积物似乎几乎没有 BSi，但我们提供的证据表明，水华衍生的 BSi 的快速再循环在沉积物孔隙水 [DSi] 中产生了高达 300 的惊人瞬态峰值$\mu$M，这是一个受未来浮游植物群落组成变化影响的特征。使用简单的同位素质量平衡计算，我们表明在三个站点中的两个站点中，海底以下 0.5 厘米（+0.96 至 +1.36 ‰）的孔隙水 DSi 池来自核心顶部水的混合（+1.46 至 +1.69 ‰） ) 溶解 BSi (+0.82 至 +1.50 ‰)，辅以成岩硅源 (LSi) (-0.89$\pm$0.16‰)。此外，我们的沉积物孔隙水${\delta }^{30}$Si 剖面揭示了 Si 循环与与同位素轻 Si (-2.88) 相关的金属氧化物的氧化还原循环的耦合$\pm$0.17‰)。我们认为，尽管目前浮游植物群落面临压力，但高 LSi:BSi 比率和明显的金属氧化物影响可能会导致 DSi 的年度背景底栖通量在一定程度上保持稳定。再加上支持在巴伦支海沉积物岩心中沉淀自生粘土的同位素证据，我们的观察结果对区域 Si 预算有影响。