Table_1_Biogenic silica cycling in the Skagerrak.xlsx

Dissolved silicate (H4SiO4) is essential for the formation of the opaline skeletal structures of diatoms and other siliceous plankton. A fraction of particulate biogenic silica (bSi) formed in surface waters sinks to the seabed, where it either dissolves and returns to the water column or is permanently buried. Global silica budgets are still poorly constrained since data on benthic bSi cycling are lacking, especially on continental margins. This study describes benthic bSi cycling in the Skagerrak, a sedimentary depocenter for particles from the North Sea. Biogenic silica burial fluxes, benthic H4SiO4 fluxes to the water column and bSi burial efficiencies are reported for nine stations by evaluating data from in-situ benthic landers and sediment cores with a diagenetic reaction-transport model. The model simulates bSi contents and H4SiO4 concentrations at all sites using a novel power law to describe bSi dissolution kinetics with a small number of adjustable parameters. Our results show that, on average, 1100 mmol m-2 yr-1 of bSi rains down to the Skagerrak basin seafloor, of which 50% is released back to overlying waters, with the remainder being buried. Biogenic silica cycling in the Skagerrak is generally consistent with previously reported global trends, showing higher Si fluxes and burial efficiencies than deep-sea sites and similar values compared to other continental margins. A significant finding of this work is a molar bSi-to-organic carbon burial ratio of 0.22 in Skagerrak sediments, which is distinctively lower compared to other continental margins. We suggest that the continuous dissolution of bSi in suspended sediments transported over long distances from the North Sea leads to the apparent decoupling between bSi and organic carbon in Skagerrak sediments.

溶解态硅酸盐（Dissolved silicate, H4SiO4）对于硅藻及其他硅质浮游生物的蛋白石质骨骼结构形成至关重要。部分在表层水体中生成的颗粒态生物硅（particulate biogenic silica, bSi）会沉降至海底，在此处要么发生溶解并重新返回水柱，要么被永久埋藏。由于缺乏底栖生物硅循环的相关数据，全球硅收支仍难以得到精准约束，尤其在大陆边缘区域。本研究针对斯卡格拉克海峡——一处接收北海沉积物的沉积中心——的底栖生物硅循环展开探究。通过整合原位底栖着陆器观测数据与沉积物岩芯数据，并运用成岩反应-输运模型，本研究报道了9个站位的生物硅埋藏通量、底栖溶解态硅酸盐向水柱的输送通量以及生物硅埋藏效率。该模型采用一种新型幂律方程描述生物硅溶解动力学，仅需少量可调参数，即可模拟所有站位的生物硅含量与溶解态硅酸盐浓度。研究结果显示，平均每年有1100毫摩尔每平方米的生物硅沉降至斯卡格拉克海峡盆地的海底，其中50%会重新释放至上覆水体，剩余部分则被永久埋藏。斯卡格拉克海峡的生物硅循环整体符合此前报道的全球趋势：其硅通量与埋藏效率均高于深海站位，且与其他大陆边缘区域的数值相近。本研究的一项重要发现是，斯卡格拉克海峡沉积物中生物硅与有机碳的埋藏摩尔比为0.22，显著低于其他大陆边缘区域。我们推测，从北海长途输运而来的悬浮沉积物中持续发生的生物硅溶解作用，导致了斯卡格拉克海峡沉积物中生物硅与有机碳之间出现明显解耦。