Magnetotactic bacterial abundance in pelagic marine environments is limited by organic carbon flux and availability of dissolved iron
Magnetotactic bacterial abundance in pelagic marine environments is limited by organic carbon flux and availability of dissolved iron
复制标题
DOI：
10.1016/j.epsl.2011.08.011
复制
发表时间：
2011-10-15
影响因子：
5.3
通讯作者：
Gerald, John D. Fitz
中科院分区：
文献类型：
--
作者：
Roberts, Andrew P.;Florindo, Fabio;Gerald, John D. Fitz
趋磁细菌胞内生物矿化磁铁矿，为记录古地磁信号提供了理想的粒度。然而，细菌磁铁矿只在少数前第四纪记录中被报道过，这是因为在缺氧成岩环境中逐渐埋藏导致其溶解。由于有机碳埋藏率低，孔隙-水氧化还原带扩大，深海碳酸盐岩层序为细菌磁铁矿的保存提供了最佳环境。这样的序列在海底以下几十到几百米的地方通常不会缺氧。然而，在这种环境下控制趋磁细菌种群的生物地球化学因素尚不清楚。我们记录了细菌磁铁矿的保存，它们在南大洋克尔盖伦高原南部始新世的上古碳酸盐岩中主导着古地磁信号。我们提供的证据表明，在始新世晚期，铁施肥与风沙通量增加有关，导致地表水富营养化，通过向海底输出有机碳来控制细菌磁铁矿的丰度。风成带铁相通量的增加也将铁输送到海底，其中一些铁通过铁还原成为生物可利用的。我们的研究结果表明，远洋环境中的趋磁细菌种群在很大程度上取决于颗粒铁和有机碳向海底的输送。(C) 2011 Elsevier B.V.版权所有
Magnetotactic bacteria intracellularly biomineralize magnetite of an ideal grain size for recording palaeomagnetic signals. However, bacterial magnetite has only been reported in a few pre-Quaternary records because progressive burial into anoxic diagenetic environments causes its dissolution. Deep-sea carbonate sequences provide optimal environments for preserving bacterial magnetite due to low rates of organic carbon burial and expanded pore-water redox zonations. Such sequences often do not become anoxic for tens to hundreds of metres below the seafloor. Nevertheless, the biogeochemical factors that control magnetotactic bacterial populations in such settings are not well known. We document the preservation of bacterial magnetite, which dominates the palaeomagnetic signal throughout Eocene pelagic carbonates from the southern Kerguelen Plateau, Southern Ocean. We provide evidence that iron fertilization, associated with increased aeolian dust flux, resulted in surface water eutrophication in the late Eocene that controlled bacterial magnetite abundance via export of organic carbon to the seafloor. Increased flux of aeolian iron-bearing phases also delivered iron to the seafloor, some of which became bioavailable through iron reduction. Our results suggest that magnetotactic bacterial populations in pelagic settings depend crucially on particulate iron and organic carbon delivery to the seafloor. (C) 2011 Elsevier B.V. All rights reserved.