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Endospore-forming bacteria as new proxies to assess impact of eutrophication in Lake Geneva (Switzerland-France)

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Publication date 2013
Author Wunderlin Tina, Corella Juan Pablo, Junier Thomas, Bueche Matthieu, Loizeau Jean Luc, Girardclos Stéphanie, Junier Pilar,
Project Quantifying human impact and recent climate change using clastic sediments from lacustrine records in Western Switzerland (Phase 2)
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Original article (peer-reviewed)

Journal Aquatic Sciences
Volume (Issue) 76(S1)
Page(s) 103 - 116
Title of proceedings Aquatic Sciences
DOI 10.1007/s00027-013-0329-0

Open Access

URL http://archive-ouverte.unige.ch/unige:37221
Type of Open Access Repository (Green Open Access)

Abstract

Measurements of chemical composition and biological parameters of sediment cores are used as proxies for changes in past environmental conditions and more recently the human impact on ecosystem health. In this study, endospore-forming bacteria are proposed as a new biological proxy for such paleoecological reconstructions. A sediment core providing a record for the past 90 years (137Cs and magnetic susceptibility dating) was retrieved from the Rhone Delta of Lake Geneva. X-ray fluorescence was analyzed at a 0.2-cm resolution, while DNA extracts, elemental geochemistry and grain size were obtained at 4-cm intervals. The total number of bacteria and endospore-forming bacteria were quantified by qPCR using the 16S rRNA gene and the endosporulation-specific spo0A gene. Furthermore, a spo0A fragment was subjected to amplicon sequencing to define OTUs (operational taxonomic units) and the phylogenetic affiliation of the endospore formers. The results showed that despite the fact that the quantity of extracted DNA decreased with the age of the sediment, the abundance of endospore-forming bacteria remained constant. However, the diversity of this group of bacteria changed significantly, reflecting the eutrophication of the lake from 1960 to 1990. The shift in community composition was linked to the dominance of anaerobic clostridia-like endospore formers. This trend has reversed in the last 10 years of the record, suggesting a recovery after perturbation. This study shows that the abundance and diversity of endospore-forming bacteria can be used as proxies to reconstruct lake history. We hereby successfully introduce a new strategy for paleoecology that could also be applied to ocean sediments and long sediment cores. © 2013 Springer Basel.
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