Effect of Euxinic Conditions on Planktic Foraminifers: Culture Experiments and Implications for Past and Future Environments. Issue 1 (24th January 2019)

• Record Type: Journal Article
• Authors: Kuroyanagi, Azumi; Toyofuku, Takashi; Nagai, Yukiko; Kimoto, Katsunori; Nishi, Hiroshi; Takashima, Reishi; Kawahata, Hodaka
• Is Part Of: Paleoceanography and paleoclimatology. Volume 34:Issue 1(2019)
• Page Start: 54
• Page End: 62
• Publication Date: 2019-01-24
• Subjects: planktic foraminifer (planktonic foraminifer) -- euxinic condition -- hydrogen sulfide -- oceanic anoxic events; Paleoceanography -- Periodicals; Paleoclimatology -- Periodicals; 551.46
• DOI: 10.1029/2018PA003539
• Languages: English
• ISSNs: 2572-4517

Abstract

Abstract: The oceanic redox state is an essential determinant for life on Earth, and "anoxic events, " periods when large parts of the oceans were anoxic or euxinic (free hydrogen sulfide (H2 S) present), may have substantially affected the oceanic biosphere. We present the first culture data showing the effects of euxinic conditions on planktic foraminifers. We cultured six species of planktic foraminifers ( n = 31) in three treatments: ~2 mg H2 S/L, ~9 mg H2 S/L, and a control, without H2 S. Under the H2 S treatments, planktic foraminifers did not survive for more than 48 hr, and gametogenesis percentages were very low (8% and 17%), while the time to gametogenesis was short (less than 1 day). However, some species (e.g., Neogloboquadrina dutertrei ) survived episodic or temporary exposure to H2 S for a relatively short time (i.e., <24 hr, such as a tidal cycle), indicating species‐specific tolerance levels for H2 S. The biological response of foraminifers to euxinia thus is fundamentally different from that of dysoxia (i.e., low dissolved oxygen; ~0.7 mg O2 /L or ~22 μmol O2 /L), when they survive, add chambers, feed, and undergo gametogenesis. The presence/absence of planktic foraminifers in sediments thus may help to elucidate the redox state of the euphotic zone in the oceans of the past, with planktic foraminifers absent in sediments deposited when euphotic waters became euxinic. Key Points: Planktic foraminifers were cultured in the presence of free hydrogen sulfide (euxinic conditions) at different levels Under euxinic conditions, planktic foraminifers did not survive more than 48 hr, and gametogenesis was low, although they survive well under dysoxic conditions Planktic foraminifers may be absent in sediments deposited below a euxinic euphotic zone