Geochemical analysis and porewater analysis of sediment profile at station M57/3_203 from Walvis Ridge

Phosphorite deposits in marine sediments are a long-term sink for an essential nutrient, phosphorus. Here we show that apatite abundance in sediments on the Namibian shelf correlates with the abundance and activity of the giant sulfur bacterium Thiomargarita namibiensis, which suggests that sulfur bacteria drive phosphogenesis. Sediments populated by Thiomargarita showed sharp peaks of pore water phosphate (<=300 micromolar) and massive phosphorite accumulations (>=50 grams of phosphorus per kilogram). Laboratory experiments revealed that under anoxic conditions, Thiomargarita released enough phosphate to account for the precipitation of hydroxyapatite observed in the environment.海洋沉积物中的磷矿床是必需营养元素磷的长期储库。本研究表明，纳米比亚陆架沉积物中的磷灰石丰度与巨型硫细菌纳米比亚嗜硫珠菌（Thiomargarita namibiensis）的丰度及活性呈显著相关，提示硫细菌驱动了磷矿化过程。栖息有该嗜硫珠菌的沉积物中，孔隙水磷酸盐浓度存在尖锐峰值（≤300微摩尔），且伴随大规模磷矿床堆积（每千克沉积物中磷含量≥50克）。实验室实验证实，在厌氧条件下，该嗜硫珠菌释放的磷酸盐足以支撑环境中观测到的羟基磷灰石沉淀。