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Biogeosciences An interactive open-access journal of the European Geosciences Union
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© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 26 Apr 2019

Research article | 26 Apr 2019

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Biogeosciences (BG).

Characterizing photosymbiosis in modern planktonic foraminifera

Haruka Takagi1,2, Katsunori Kimoto3, Tetsuichi Fujiki3, Hiroaki Saito1, Christiane Schmidt4, Michal Kucera4, and Kazuyoshi Moriya5 Haruka Takagi et al.
  • 1Atmosphere and Ocean Research Institute, The University of Tokyo, Japan
  • 2Graduate School of Creative Science and Engineering, Waseda University, Japan
  • 3Japan Agency for Earth-Marine Science and Technology, Japan
  • 4MARUM - Center for Marine Environmental Sciences and Faculty of Geosciences, University of Bremen, Germany
  • 5Department of Earth Sciences, School of Education, Waseda University, Japan

Abstract. Photosymbiosis has played a key role in the diversification of foraminifera and their carbonate production through geologic history. However, identification of photosymbiosis in extinct taxa remains challenging and even among the extant species the occurrence and functional relevance of photosymbiosis remains poorly constrained. Here, we investigate photosymbiosis in living planktonic foraminifera by measuring active chlorophyll fluorescence with fast repetition rate fluorometry. This method provides unequivocal evidence for the presence of photosynthetic capacity in individual foraminifera and it allows us to characterize multiple features of symbiont photosynthesis including chlorophyll a (Chl a) content, potential photosynthetic activity (Fv / Fm), and light absorption efficiency (σPSII). To obtain robust evidence for the occurrence and importance of photosymbiosis in modern planktonic foraminifera, we conducted measurements on 1266 individuals from 30 species of the families Globigerinidae, Hastigerinidae, Globorotaliidae, and Candeinidae. Among the studied species, 19 were recognized as symbiotic and 11 as non-symbiotic. Of these, six species were newly confirmed as symbiotic and five as non-symbiotic. Photosymbiotic species have been identified in all families except the Hastigerinidae. A significant positive correlation between test size and Chl a content, found in 16 species, is interpreted as symbiont growth scaled to the growth of the host, consistent with persistent possession of symbionts through the lifetime of the foraminifera. The remaining three symbiont-bearing species did not show such a relationship, and their Fv / Fm values were comparatively low, indicating that their symbionts do not grow once acquired from the environment. The objectively quantified photosymbiotic characteristics have been used to design a metric of photosymbiosis, which allows the studied species to be classified along a gradient of photosynthetic activity, providing a framework for future ecological and physiological investigations of planktonic foraminifera.

Haruka Takagi et al.
Interactive discussion
Status: final response (author comments only)
Status: final response (author comments only)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Haruka Takagi et al.
Haruka Takagi et al.
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Short summary
Photosymbiosis (endosymbiosis with algae) is an evolutionary important ecology for many marine organisms, but has poorly been identified among planktonic foraminifera. In this study, we identified and characterized photosymbiosis of various species of planktonic foraminifera by focusing their photosynthetic activity. We finally proposed a new framework showing a potential strength of photosymbiosis, which will serve as a basis for future ecological studies of planktonic foraminifera.
Photosymbiosis (endosymbiosis with algae) is an evolutionary important ecology for many marine...