Geochemistry of sediment cores from METEOR cruise M76/1b

Marine sediments are the main sink in the oceanic phosphorus (P) cycle. The activity of benthic microorganisms is decisive for regeneration, reflux, or burial of inorganic phosphate (Pi), which has a strong impact on marine productivity. Recent formation of phosphorites on the continental shelf and a succession of different sedimentary environments make the Benguela upwelling system a prime region for studying the role of microbes in P biogeochemistry. The oxygen isotope signature of pore water phosphate (d18OP) carries characteristic information of microbial P cycling: Intracellular turnover of phosphorylated biomolecules results in isotopic equilibrium with ambient water, while enzymatic regeneration of Pi from organic matter produces distinct offsets from equilibrium. The balance of these two processes is the major control for d18OP. […]

海洋沉积物是海洋磷（P）循环的主要汇。底栖微生物的活性对于无机磷酸盐（Pi）的再生、回流或埋藏起着决定性作用，这对海洋生产力产生重大影响。大陆架上磷矿床的近期形成以及一系列不同的沉积环境，使得本格拉上升流系统成为研究微生物在磷生物地球化学中作用的关键区域。孔隙水磷酸盐（d18OP）的氧同位素特征携带着微生物磷循环的特征信息：磷酸化生物大分子在细胞内的周转导致与周围水的同位素平衡，而从有机物质中酶促再生Pi则产生与平衡状态不同的偏移。这两种过程的平衡是d18OP的主要控制因素。 [...]