JpGU-AGU Joint Meeting 2017

講演情報

[EE] 口頭発表

セッション記号 B (地球生命科学) » B-PT 古生物学・古生態学

[B-PT03] [EE] バイオミネラリゼーションと環境指標

2017年5月20日(土) 13:45 〜 15:15 201B (国際会議場 2F)

コンビーナ:豊福 高志(独立行政法人海洋研究開発機構)、北里 洋(国立大学法人東京海洋大学大学改革準備室)、Bijma Jelle(アルフレッドウェゲナー極域海洋研究所)、座長:豊福 高志(独立行政法人海洋研究開発機構)

13:45 〜 14:00

[BPT03-01] Cold seeps in the Sea of Marmara: a refuge for “extremophile” foraminifera?

*Christophe Fontanier1Delphine Dissard2Livio Ruffine3Emmanuel Ponzevera3Ewan Pelleter3François Baudin4Angélique Roubi3Sandrine Chéron3Audrey Boissier3Nicolas Gayet5Sylvain Bermell-Fleury3Vivien Guyader3Françoise Lesongeur5Florence Savignac4 (1.EPOC Laboratory (University of Bordeaux, France), Ifremer Géosciences Marines (Plouzané, France), FORAM Study Group (Villevêque, France) & University of Angers (France)、2.IRD-Sorbonne Universités, UPMC, Univ Paris 06-CNRS-MNHN, LOCEAN Laboratory (Paris, France)、3.Ifremer Géosciences Marines (Plouzané, France)、4.ISTeP-Sorbonne Universités, UPMC, Univ Paris 06, UMR 7193 (Paris France)、5.Ifremer Etude des Ecosystèmes Profonds (Plouzané, France))

キーワード:Living (stained) benthic foraminifera, Sea of Marmara, Cold seeps, Extreme ecosystems, Trace elements, Stable isotopes

In this study, we investigate living (stained) deep-sea foraminifera from the Sea of Marmara. We focus on faunal composition and geochemical signatures (trace elements and stable isotopes) in foraminiferal tests at two cold-seep sites, which are located at 329 and ~1240 m depth. Both study areas are bathed by dysoxic water mass (O2 < 20 µmol/L). They present extreme conditions characterized by a remarkable spatial heterogeneity. This variability is expressed through (1) contrasted geochemical process (e.g., free methane gas seepages provoking sulfate reduction, authigenic carbonate precipitation), (2) various sedimentary facies (e.g., coarse facies related to gravity flow, Mn-carbonates-enriched sediments, sapropel layers) and (3) an obvious biozonation of benthic life (e.g. microbial mat observed at 329 m depth). Overall dysoxia prevailing at both study areas restricts foraminiferal diversity to very low values (S < 9, H’< 0.97). Stress-tolerant species Bolivina vadescens and Globobulimina affinis dominate living faunas in both environments, with the highest standing stock recorded in shallower site where bacterial mat spreads. We assume that filamentous bacterial mat consists in a refuge for “extremophile” foraminifera, which can thereby survive and proliferate in dysoxic and sulfidic ecosystems. Moreover, our biogeochemical results show that the interpretation of the foraminiferal Mn/Ca ratio as a reliable proxy for bottom water oxygenation is neither straightforward nor equivoque, and depends strongly on basin physiography, sedimentary process and water column structure in modern and past periods.