Role of marine sediments mineralogy in the study of magnetotactic bacteria

• Main Author: Cornaggia, Flaminia
• Other Authors: Jovane, Luigi
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Biblioteca Digital de Teses e Dissertações da USP 2020
• Subjects: Bactérias magnetotáticas; Sedimentos marinhos; Reconstrução paleoambiental; Paleoceanografia; Mineralogia; Difração de raios-X; Mineralogy; Marine sediment; Paleoceanography; Paleoenvironmental reconstruction; Magnetotactic bacteria; X-ray diffraction; Ocean acidification
• Online Access: https://www.teses.usp.br/teses/disponiveis/21/21136/tde-16052022-094049/; https://doi.org/10.11606/T.21.2020.tde-16052022-094049

Marine sedimentary minerals respond to modifications in the sedimentary environment, and thus can be representative of specific environmental and climatic conditions. The use of sedimentary mineralogical composition to reconstruct past and present environmental conditions has great potential, if used with the appropriate care. In this work, samples of marine sediments were analysed with X-Ray Powder Diffraction (XRPD) to characterize the mineralogical assemblages with focus on paleoceanographic reconstructions and characterization of environments in which magnetotactic bacteria (MTB) live. MTB are a heterogeneous group of gram-negative prokaryotes found in aquatic environments worldwide that internally biomineralize magnetic crystals called magnetosomes. Their presence has been linked to past events of global warming and high primary productivity, thus have a potential use as paleoceanographic proxies. Therefore, understanding the processes that link MTB to their environment is fundamental to constrain their ecology and use them efficiently as paleoenvironmental proxies. In particular, we present three case studies in which mineralogical data are integrated with magnetic properties, geochemical data, and statistical analyses. The first presents an abyssal setting (Tasman Abyssal Plain) with climate induced modifications at the 100ky scale during the Middle Eocene Climatic Optimum (MECO) event; the second addresses a lagoonal-estuarine environment (Cananeia, BR) with anthropic interference at the 100y scale; the third focuses on a recent ría environment (Mamanguá, BR) that can be considered stable at the annual to millennial time scales. In the former two cases, main environmental modification are recognized through the variations of mineralogical assemblages, whereas in the latter MTB thrive and no appreciable variations in the mineralogical composition occur. The study of the mineralogical composition of the sediments on the Tasman Abyssal Plain allowed us to confirm the occurrence of ocean acidification during ...