JpGU-AGU Joint Meeting 2017

Presentation information

[JJ] Oral

M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS23] [JJ] Paleoclimatology and paleoceanography

Tue. May 23, 2017 10:45 AM - 12:15 PM IC (International Conference Hall 2F)

convener:Tomohisa Irino(Faculty of Environmental Earth Science, Hokkaido University), Akira Oka(Atmosphere and Ocean Research Institute, The University of Tokyo), Ikuko Kitaba(Research Centre for Palaleoclimatology, Ritsumeikan University), Masaki Sano(Research Institute for Humanity and Nature), Chairperson:Minoru Ikehara(Center for Advanced Marine Core Research, Kochi University)

11:45 AM - 12:00 PM

[MIS23-29] Implications for paleo-oceanographic oxygen conditions during the Cretaceous OAEs: Results from laboratory culture experiments

*Azumi Kuroyanagi1,4, Takashi Toyofuku2, Yukiko Nagai2,3, Katsunori Kimoto2, Hiroshi Nishi1, Reishi Takashima1, Hodaka Kawahata4 (1.Tohoku University Museum, The Center for Academic Resources and Archives, Tohoku University, 2.Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 3.Yokohama National University, 4.Atmosphere and Ocean Research Institute, The university of Tokyo)

Keywords:oceanic anoxic events, hydrogen sulfide, Planktonic foraminifera

The oceanic redox state is a critical determinant of the evolutionary history of life on Earth, and “anoxic events” have been proposed as one of the causal mechanisms for mass extinctions. During the mid-Cretaceous, oceanic anoxic events (OAEs) occurred several times with substantial turnover of planktonic foraminiferal species. However, the direct effects of the anoxic condition on planktonic foraminifera remain obscure. In this study, we cultured 6 species (n = 31) in all at three treatments: ~2 mg hydrogen sulfide (H2S) L-1 (H1 treatments), ~9 mg H2S L-1 (H2 treatments), and control (without H2S). All planktonic foraminifera could not survive more than 48 hours. Furthermore, gametogenesis ratio of each H2S treatments showed considerable low value (8% and 17%), and time to gametogenesis was also very short (less than one day) under H2S occurrence. It revealed that foraminiferal biological response of anoxic with the presence of H2S should be fundamentally different from that of the dysoxic (i.e., low dissolved oxygen; ~0.7 mg O2 L-1 or ~22 µmol O2 L-1). Our results also proposed the species-specific tolerance for H2S and that if harmful influence of H2S restricted in relatively short time (i.e., less than 24 hours) such as tidal cycle, some foraminifera (e.g., Neogloboquadrina dutertrei) might have the potential to survive even under the episodic/temporary occurrence of H2S. Complete disappearance of planktonic foraminifera at Cretaceous OAE2 could result from the photic-zone euxinia (free H2S), and presence/absence record of planktonic foraminifera could contribute to examine the detailed oceanic redox state in the photic zone around anoxic events.