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Modulation and daily banding of Mg/Ca Orbulina universa tests by symbiont photosynthesis and respiration: a complication for seawater thermometry?

Eggins, Stephen; Sadekov, Aleksey; De Deckker, Patrick

Description

The Mg/Ca composition of calcium carbonate tests (shells) secreted by planktonic foraminifera is increasingly being employed to estimate past seawater temperatures and reconstruct paleocean and climate records spanning hundreds of thousands of years. We show, using two high-resolution microanalysis techniques, that the final chamber of the planktonic foraminifera Orbulina universa typically comprises between three and six paired, low and high Mg, growth bands. The number and spacing of these...[Show more]

dc.contributor.authorEggins, Stephen
dc.contributor.authorSadekov, Aleksey
dc.contributor.authorDe Deckker, Patrick
dc.date.accessioned2015-12-13T23:08:56Z
dc.identifier.issn0012-821X
dc.identifier.urihttp://hdl.handle.net/1885/86793
dc.description.abstractThe Mg/Ca composition of calcium carbonate tests (shells) secreted by planktonic foraminifera is increasingly being employed to estimate past seawater temperatures and reconstruct paleocean and climate records spanning hundreds of thousands of years. We show, using two high-resolution microanalysis techniques, that the final chamber of the planktonic foraminifera Orbulina universa typically comprises between three and six paired, low and high Mg, growth bands. The number and spacing of these bands is consistent with a diurnal origin, modulated by changing pH within the foraminiferal microenvironment due to the day-night, photosynthesis-respiration cycle of algal symbionts. The amplitude of Mg/Ca variation within individual tests and across many daily growth bands cannot be accounted for by seawater temperature in the shallow, euphotic zone habitat of O. universa. Our results indicate the Mg/Ca composition of calcite precipitated by O. universa in nature is strongly influenced by diurnal changes in the biological activity of algal symbionts and the host foraminifer. This brings into question the fundamental premise often made in applying Mg/Ca palaeoseawater thermometry, that the Mg/Ca composition of foraminiferal calcite is determined by seawater temperature, and whether the Mg/Ca composition of other planktonic species that are more widely used for palaeoseawater thermometry are subject to similar influences.
dc.publisherElsevier
dc.sourceEarth and Planetary Science Letters
dc.subjectKeywords: Microanalysis techniques; Paleoseawater; Planktonic foraminifera; Thermometry; Calcium; Composition; Magnesium printing plates; Parameter estimation; pH effects; Photosynthesis; Plants (botany); Ocean habitats; accuracy assessment; calcium; calcium carbon Foraminifera; Laser ablation ICPMS; Mg/Ca; Palaeoceanography; Seawater thermometry
dc.titleModulation and daily banding of Mg/Ca Orbulina universa tests by symbiont photosynthesis and respiration: a complication for seawater thermometry?
dc.typeJournal article
local.description.notesImported from ARIES
local.description.refereedYes
local.identifier.citationvolume225
dc.date.issued2004
local.identifier.absfor040299 - Geochemistry not elsewhere classified
local.identifier.absfor040399 - Geology not elsewhere classified
local.identifier.ariespublicationMigratedxPub15786
local.type.statusPublished Version
local.contributor.affiliationEggins, Stephen, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationSadekov, Aleksey, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationDe Deckker, Patrick, College of Physical and Mathematical Sciences, ANU
local.description.embargo2037-12-31
local.bibliographicCitation.startpage411
local.bibliographicCitation.lastpage419
local.identifier.doi10.1016/j.epsl.2004.06.019
local.identifier.absseo970104 - Expanding Knowledge in the Earth Sciences
dc.date.updated2015-12-12T08:16:47Z
local.identifier.scopusID2-s2.0-10044226108
CollectionsANU Research Publications

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