Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Discussion papers
https://doi.org/10.5194/bg-2019-472
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2019-472
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 22 Jan 2020

Submitted as: research article | 22 Jan 2020

Review status
This preprint is currently under review for the journal BG.

A 15 million-year long record of phenotypic evolution in the heavily calcified coccolithophore Helicosphaera and its biogeochemical implications

Luka Šupraha1,a and Jorijntje Henderiks1,2 Luka Šupraha and Jorijntje Henderiks
  • 1Department of Earth Sciences, Uppsala University, Villavägen 16, 752 36 Uppsala, Sweden
  • 2Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, P.O. Box 1066 Blindern, 0316 Oslo, Norway
  • apresent address: Section for Aquatic Biology and Toxicology (AQUA), Department of Biosciences, University of Oslo, P.O. Box 1066 Blindern, 0316 Oslo, Norway

Abstract. The biogeochemical performance of coccolithophores is defined by their overall abundance in the oceans, but also by a wide range in cell size, degree of calcification and carbon production rates between different species. Species’ sensitivity to environmental forcing has been suggested to relate to their cellular PIC : POC ratio and other physiological constraints. Understanding both the short and longer-term adaptive strategies of different coccolithophore lineages, and how these in turn shape the biogeochemical role of the group, is therefore crucial for modeling the ongoing changes in the global carbon cycle. Here we present data on the phenotypic evolution of a large and heavily-calcified genus Helicosphaera (order Zygodiscales) over the past 15 million years (Ma), at two deep-sea drill sites from the tropical Indian Ocean and temperate South Atlantic. The modern species Helicosphaera carteri, which displays eco-physiological adaptations in modern strains, was used to benchmark the use of its coccolith morphology as a physiological proxy in the fossil record.

Our results show that, on the single-genotype level, coccolith morphology has no correlation with physiological traits in H. carteri. However, significant correlations of coccolith morphometric parameters with cell size and physiological rates do emerge once multiple genotypes or closely related lineages are pooled together. Using this insight, we interpret the phenotypic evolution in Helicosphaera as a global, resource limitation-driven selection for smaller cells, which appears to be a common adaptive trait among different coccolithophore lineages, from the warm and high-CO2 world of the middle Miocene to the cooler and low-CO2 conditions of the Pleistocene. However, despite a significant decrease in mean size, Helicosphaera kept relatively stable PIC : POC (as inferred from the coccolith aspect ratio) and thus highly conservative biogeochemical output on the cellular level. We argue that this supports its status as an obligate calcifier, like other large and heavily-calcified genera such as Calcidiscus and Coccolithus, and that other adaptive strategies, beyond size-adaptation, must support the persistent, albeit less abundant, occurrence of these taxa. This is in stark contrast with the ancestral lineage of Emiliania and Gephyrocapsa, which not only decreased in mean size but also displayed much higher phenotypic plasticity in degree of calcification while becoming globally more dominant in plankton communities.

Luka Šupraha and Jorijntje Henderiks

Interactive discussion

Status: open (until 04 Mar 2020)
Status: open (until 04 Mar 2020)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
[Subscribe to comment alert] Printer-friendly Version - Printer-friendly version Supplement - Supplement
  • RC1: 'Review', Anonymous Referee #1, 14 Feb 2020 Printer-friendly Version

Luka Šupraha and Jorijntje Henderiks

Luka Šupraha and Jorijntje Henderiks

Viewed

Total article views: 174 (including HTML, PDF, and XML)
HTML PDF XML Total Supplement BibTeX EndNote
118 51 5 174 8 1 3
  • HTML: 118
  • PDF: 51
  • XML: 5
  • Total: 174
  • Supplement: 8
  • BibTeX: 1
  • EndNote: 3
Views and downloads (calculated since 22 Jan 2020)
Cumulative views and downloads (calculated since 22 Jan 2020)

Viewed (geographical distribution)

Total article views: 158 (including HTML, PDF, and XML) Thereof 158 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 

Cited

Saved

No saved metrics found.

Discussed

No discussed metrics found.
Latest update: 25 Feb 2020
Publications Copernicus
Download
Short summary
The cell size, degree of calcification and growth rates of coccolithophores impact their role in the carbon cycle and may also influence their adaptation to environmental change. Combining insights from culture experiments and the fossil record, we show that the selection for smaller cells over the past 15 million years was a common adaptive trait among different lineages. However, heavily-calcified species maintained a more stable biogeochemical output than the ancestral lineage of E. huxleyi.
The cell size, degree of calcification and growth rates of coccolithophores impact their role in...
Citation