Factors influencing test porosity in planktonic foraminifera

Janet E. Burke*, Willem Renema, Michael J. Henehan, Leanne E. Elder, Catherine V. Davis, Amy E. Maas, Gavin L. Foster, Ralf Schiebel, Pincelli M. Hull

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

15 Citations (Scopus)

Abstract

The clustering of mitochondria near pores in the test walls of foraminifera suggests that these perforations play a critical role in metabolic gas exchange. As such, pore measurements could provide a novel means of tracking changes in metabolic rate in the fossil record. However, in planktonic foraminifera, variation in average pore area, density, and porosity (the total percentage of a test wall that is open pore space) have been variously attributed to environmental, biological, and taxonomic drivers, complicating such an interpretation. Here we examine the environmental, biological, and evolutionary determinants of pore characteristics in 718 individuals, representing 17 morphospecies of planktonic foraminifera from 6 core tops in the North Atlantic. Using random forest models, we find that porosity is primarily correlated to test surface area, test volume, and habitat temperature, key factors in determining metabolic rates. In order to test if this correlation arose spuriously through the association of cryptic species with distinct biomes, we cultured Globigerinoides ruber in three different temperature conditions, and found that porosity increased with temperature. Crucially, these results show that porosity can be plastic: changing in response to environmental drivers within the lifetime of an individual foraminifer. This demonstrates the potential of porosity as a proxy for foraminiferal metabolic rates, with significance for interpreting geochemical data and the physiology of foraminifera in non-analog environments. It also highlights the importance of phenotypic plasticity (i.e., ecophenotypy) in accounting for some aspects of morphological variation in the modern and fossil record.

Original languageEnglish
Pages (from-to)6607-6619
Number of pages13
JournalBiogeosciences
Volume15
Issue number21
DOIs
Publication statusPublished - 7 Nov 2018

Bibliographical note

Funding Information:
Acknowledgements. The authors of this manuscript would like to thank the following people for help in completing this work: Jessica Utrup of the Yale Peabody Museum for assistance in cataloging specimen images; Jessie Maisano at the University of Texas and Dirk van der Marel at the Naturalis Biodiversity Center for help obtaining CT scans; Leocadio Blanco-Bercial, Samantha de Putron, and the staff at BIOS for use of laboratory space and equipment; Kaylea Nelson at the Yale Center for Research Computing for assistance with the image analyses; Bruce Corliss from the University of Rhode Island and Richard Norris from the Scripps Institution of Oceanography for providing the core-top materials; and Ellen Thomas and the members of the Hull Lab at Yale for feedback and comments on the manuscript. Janet E. Burke was supported by the National Science Foundation Graduate Research Fellowship under grant no. DGE-1122492 and Pincelli M. Hull by a Sloan Research Fellowship. Additional financial support for this work was provided by the Cushman Foundation for Foraminiferal Research, the Naturalis Biodiversity Center Martin Fellowship, the Bermuda Institute of Ocean Sciences Grants-in-Aid of Research program, and the Yale Peabody Museum.

Publisher Copyright:
© Author(s) 2018.

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