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Symbiont 'bleaching' in planktic foraminifera during the Middle Eocene Climatic Optimum

Symbiont 'bleaching' in planktic foraminifera during the Middle Eocene Climatic Optimum
Symbiont 'bleaching' in planktic foraminifera during the Middle Eocene Climatic Optimum
Many genera of modern planktic foraminifera are adapted to nutrient-poor (oligotrophic) surface waters by hosting photosynthetic symbionts, but it is unknown how they will respond to future changes in ocean temperature and acidity. Here we show that ca. 40 Ma, some fossil photosymbiont-bearing planktic foraminifera were temporarily ‘bleached’ of their symbionts coincident with transient global warming during the Middle Eocene Climatic Optimum (MECO). At Ocean Drilling Program (ODP) Sites 748 and 1051 (Southern Ocean and mid-latitude North Atlantic, respectively), the typically positive relationship between the size of photosymbiont-bearing planktic foraminifer tests and their carbon isotope ratios (?13C) was temporarily reduced for ?100 k.y. during the peak of the MECO. At the same time, the typically photosymbiont-bearing planktic foraminifera Acarinina suffered transient reductions in test size and relative abundance, indicating ecological stress. The coincidence of minimum ?18O values and reduction in test size–?13C gradients suggests a link between increased sea-surface temperatures and bleaching during the MECO, although changes in pH and nutrient availability may also have played a role. Our findings show that host-photosymbiont interactions are not constant through geological time, with implications for both the evolution of trophic strategies in marine plankton and the reliability of geochemical proxy records generated from symbiont-bearing planktic foraminifera.
0091-7613
15-18
Edgar, K.M.
64ceab33-7d48-49d2-aac8-c6f1366576b1
Bohaty, S.M.
af9dbe78-8b9f-44f2-ba1d-20795837d2d1
Gibbs, S.J.
82dfbcbc-3a8a-40da-8a80-fe7ad83f3110
Sexton, P.F.
8f381c3d-6181-4027-bc35-258780a1f383
Norris, R.D.
81ac4a17-2a84-4c7c-9c02-c9f14bb2695e
Wilson, P.A.
f940a9f0-fa5a-4a64-9061-f0794bfbf7c6
Edgar, K.M.
64ceab33-7d48-49d2-aac8-c6f1366576b1
Bohaty, S.M.
af9dbe78-8b9f-44f2-ba1d-20795837d2d1
Gibbs, S.J.
82dfbcbc-3a8a-40da-8a80-fe7ad83f3110
Sexton, P.F.
8f381c3d-6181-4027-bc35-258780a1f383
Norris, R.D.
81ac4a17-2a84-4c7c-9c02-c9f14bb2695e
Wilson, P.A.
f940a9f0-fa5a-4a64-9061-f0794bfbf7c6

Edgar, K.M., Bohaty, S.M., Gibbs, S.J., Sexton, P.F., Norris, R.D. and Wilson, P.A. (2013) Symbiont 'bleaching' in planktic foraminifera during the Middle Eocene Climatic Optimum. Geology, 41 (1), 15-18. (doi:10.1130/G33388.1).

Record type: Article

Abstract

Many genera of modern planktic foraminifera are adapted to nutrient-poor (oligotrophic) surface waters by hosting photosynthetic symbionts, but it is unknown how they will respond to future changes in ocean temperature and acidity. Here we show that ca. 40 Ma, some fossil photosymbiont-bearing planktic foraminifera were temporarily ‘bleached’ of their symbionts coincident with transient global warming during the Middle Eocene Climatic Optimum (MECO). At Ocean Drilling Program (ODP) Sites 748 and 1051 (Southern Ocean and mid-latitude North Atlantic, respectively), the typically positive relationship between the size of photosymbiont-bearing planktic foraminifer tests and their carbon isotope ratios (?13C) was temporarily reduced for ?100 k.y. during the peak of the MECO. At the same time, the typically photosymbiont-bearing planktic foraminifera Acarinina suffered transient reductions in test size and relative abundance, indicating ecological stress. The coincidence of minimum ?18O values and reduction in test size–?13C gradients suggests a link between increased sea-surface temperatures and bleaching during the MECO, although changes in pH and nutrient availability may also have played a role. Our findings show that host-photosymbiont interactions are not constant through geological time, with implications for both the evolution of trophic strategies in marine plankton and the reliability of geochemical proxy records generated from symbiont-bearing planktic foraminifera.

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More information

Published date: 2013
Organisations: Paleooceanography & Palaeoclimate

Identifiers

Local EPrints ID: 347064
URI: https://eprints.soton.ac.uk/id/eprint/347064
ISSN: 0091-7613
PURE UUID: d21dde1f-21d2-43f8-91a4-38df67c18bd3
ORCID for S.M. Bohaty: ORCID iD orcid.org/0000-0002-1193-7398

Catalogue record

Date deposited: 15 Jan 2013 16:50
Last modified: 06 Jun 2018 12:39

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