Journal list menu

Volume 67, Issue 3 p. 540-551
Article

Elemental and macromolecular composition of the marine Chloropicophyceae, a major group of oceanic photosynthetic picoeukaryotes

Vinitha Ebenezer

Corresponding Author

Vinitha Ebenezer

Department of Oceanography, Dalhousie University, Halifax, Nova Scotia, Canada

Correspondence: [email protected]

Search for more papers by this author
Yingyu Hu

Yingyu Hu

Department of Oceanography, Dalhousie University, Halifax, Nova Scotia, Canada

Search for more papers by this author
Olga Carnicer

Olga Carnicer

Department of Mathematics and Statistics, Dalhousie University, Halifax, Nova Scotia, Canada

Search for more papers by this author
Andrew J. Irwin

Andrew J. Irwin

Department of Earth, Atmospheric and Planetary Science, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA

Search for more papers by this author
Michael J. FollowsZoe V. Finkel

Zoe V. Finkel

Department of Oceanography, Dalhousie University, Halifax, Nova Scotia, Canada

Search for more papers by this author
First published: 25 January 2022
Citations: 4

Author Contribution Statement: V.E., Y.Y.H., A.I., and Z.F. contributed to the conceptualization and experimental design of the work. V.E. and O.C. contributed to sample collection. V.E. and Y.Y.H. performed all biochemical analyses. V.E. wrote the first manuscript draft. A.I. contributed to data analysis. Z.F., A.I., M.J.F., Y.Y.H., and O.C. contributed to the writing and revisions. All authors read and approved the submitted version.

Editor-in-Chief: K. David Hambright

Abstract

Chloropicophyceae (Prasinophyte Clade VII) are small nonmotile coccoid cells with cell diameters ranging from 1 to 3 μm. Molecular surveys indicate they are relatively high in abundance in moderately oligotrophic oceanic waters and may substantively contribute to biogeochemical cycling in the sea. Here, we quantify the elemental and macromolecular composition of three subtropical Chloropicophyceae strains: Chloropicon mariensis, Chloropicon maureeniae, and Chloropicon roscoffensis under nutrient-sufficient exponential growth and nitrate starvation. Under nutrient-sufficient conditions the Chloropicophyceae are high in C : N and quite low in C : P and N : P relative to the canonical Redfield ratio, reflecting their relatively high nucleic acid composition compared to many other phytoplankton taxa. Nitrate starvation causes increases in C : N and C : P and decreases in N : P, primarily due to increases in carbohydrate and lipid and decreases in protein and RNA. There is genetic evidence that unlike most other green algae, Chloropicophyceae are diploid. The high nucleic acid content in the Chloropicon is consistent with the hypothesis that the nucleus, as a nonscalable component, takes up a larger and substantial proportion of cell mass in diploid picoeukaryotes. The elemental and macromolecular composition of these Chloropicophyceae, and relatively homeostatic response to N-starvation compared to diatoms, provides some insight into their success in the moderately oligotrophic ocean.

Conflict of interest

None declared.