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Factors influencing test porosity in planktonic foraminifera

Factors influencing test porosity in planktonic foraminifera
Factors influencing test porosity in planktonic foraminifera

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.

1726-4170
6607-6619
Burke, Janet E.
826d61d1-4a1d-4ad0-afa5-f646edd9e3c7
Renema, Willem
735cca3b-96d5-47e6-8411-d607520afa78
Henehan, Michael J.
1dae087e-6389-4f29-b966-26929951881d
Elder, Leanne E.
98ac4665-b68a-4fc0-896b-6fd2beca8f40
Davis, Catherine V.
705fa2d9-d903-4025-9222-0681025f43b6
Maas, Amy E.
1b4c7577-2234-4d03-83b4-db53d82bc686
Foster, Gavin L.
fbaa7255-7267-4443-a55e-e2a791213022
Schiebel, Ralf
eb56bd42-3b0a-44bd-8d21-d50786263986
Hull, Pincelli M.
071e549a-6172-448b-b339-9359c495c03c
Burke, Janet E.
826d61d1-4a1d-4ad0-afa5-f646edd9e3c7
Renema, Willem
735cca3b-96d5-47e6-8411-d607520afa78
Henehan, Michael J.
1dae087e-6389-4f29-b966-26929951881d
Elder, Leanne E.
98ac4665-b68a-4fc0-896b-6fd2beca8f40
Davis, Catherine V.
705fa2d9-d903-4025-9222-0681025f43b6
Maas, Amy E.
1b4c7577-2234-4d03-83b4-db53d82bc686
Foster, Gavin L.
fbaa7255-7267-4443-a55e-e2a791213022
Schiebel, Ralf
eb56bd42-3b0a-44bd-8d21-d50786263986
Hull, Pincelli M.
071e549a-6172-448b-b339-9359c495c03c

Burke, Janet E., Renema, Willem, Henehan, Michael J., Elder, Leanne E., Davis, Catherine V., Maas, Amy E., Foster, Gavin L., Schiebel, Ralf and Hull, Pincelli M. (2018) Factors influencing test porosity in planktonic foraminifera. Biogeosciences, 15 (21), 6607-6619. (doi:10.5194/bg-15-6607-2018).

Record type: Article

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.

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Accepted/In Press date: 10 October 2018
e-pub ahead of print date: 7 November 2018
Published date: 7 November 2018

Identifiers

Local EPrints ID: 426504
URI: https://eprints.soton.ac.uk/id/eprint/426504
ISSN: 1726-4170
PURE UUID: 81f38950-0070-47d7-8e59-daeaf5407d4a

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Date deposited: 29 Nov 2018 17:30
Last modified: 13 Mar 2019 17:46

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