Effect of Euxinic Conditions on Planktic Foraminifers: Culture Experiments and Implications for Past and Future Environments

Azumi Kuroyanagi, Takashi Toyofuku, Yukiko Nagai, Katsunori Kimoto, Hiroshi Nishi, Reishi Takashima, Hodaka Kawahata

Research output: Contribution to journalArticle

4 Citations (Scopus)

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 (H 2 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 H 2 S/L, ~9 mg H 2 S/L, and a control, without H 2 S. Under the H 2 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 H 2 S for a relatively short time (i.e., <24 hr, such as a tidal cycle), indicating species-specific tolerance levels for H 2 S. The biological response of foraminifers to euxinia thus is fundamentally different from that of dysoxia (i.e., low dissolved oxygen; ~0.7 mg O 2 /L or ~22 μmol O 2 /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.

Original languageEnglish
Pages (from-to)54-62
Number of pages9
JournalPaleoceanography and Paleoclimatology
Volume34
Issue number1
DOIs
Publication statusPublished - 2019 Jan

Keywords

  • euxinic condition
  • hydrogen sulfide
  • oceanic anoxic events
  • planktic foraminifer (planktonic foraminifer)

ASJC Scopus subject areas

  • Oceanography
  • Atmospheric Science
  • Palaeontology

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