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Symbiont ‘bleaching’ in planktic foraminifera during the Middle Eocene Climatic Optimum

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) pp. 15–18.

DOI (Digital Object Identifier) Link: http://dx.doi.org/10.1130/G33388.1
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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 (δ13C) 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 δ18O values and reduction in test size–δ13C 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.

Item Type: Journal Article
Copyright Holders: 2012 Geological Society of America
ISSN: 0091-7613
Extra Information: First published online: 19 October 2012
Academic Unit/Department: Science > Environment, Earth and Ecosystems
Interdisciplinary Research Centre: Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR)
Item ID: 35137
Depositing User: Philip Sexton
Date Deposited: 01 Nov 2012 11:59
Last Modified: 05 Dec 2013 15:20
URI: http://oro.open.ac.uk/id/eprint/35137
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