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Basal monothalamous and pseudochambered benthic foraminifera associated with planktonic foraminiferal shells and mineral grains from the Porcupine Abyssal Plain, NE Atlantic

Basal monothalamous and pseudochambered benthic foraminifera associated with planktonic foraminiferal shells and mineral grains from the Porcupine Abyssal Plain, NE Atlantic
Basal monothalamous and pseudochambered benthic foraminifera associated with planktonic foraminiferal shells and mineral grains from the Porcupine Abyssal Plain, NE Atlantic
We present a survey of ‘live’ (stained) and dead monothalamous (single-chambered, mainly spherical) and pseudochambered (chain-like) foraminifera associated with planktonic foraminiferal shells and mineral grains, based on two samples from one abyssal plain site (F2, 4,880 m water depth) and one abyssal hill site (H4, 4,330 m water depth) on the Porcupine Abyssal Plain (PAP), northeast Atlantic. Our study is the first to focus on this poorly known component of abyssal foraminiferal faunas and highlight their abundances and diversity at the PAP. In both samples these monothalamids and pseudochambered forms represented 27–35 % and 18–23 %, respectively, of the entire ‘live’ and dead foraminiferal assemblage (>150 ?m, 0–1 cm sediment layer). Among 1,078 stained and dead specimens we recognise a total of 18 distinct morphotypes on the basis of test characteristics. Another 144 specimens could not be assigned to any morphotype and are regarded as indeterminate. Most of the monothalamids are small (<150 ?m), although some incorporate planktonic foraminiferal shells to create larger structures. In absolute terms, stained and dead individuals of these morphotypes were more abundant at the abyssal hill site, although data from additional samples are needed to confirm if this is representative of differences between abyssal hills and the surrounding abyssal plain at the PAP. Agglutinated spheres and domes similar to some of our abyssal forms have been reported from shelf and slope settings, but they are generally much larger. Small agglutinated spheres are very common in the abyssal Pacific, at depths close to or below the carbonate compensation depth (CCD). However, they are composed largely of siliceous particles, including mineral grains, radiolarians and diatom fragments. In contrast, carbonate oozes at the PAP, situated above the CCD, are rich in coccoliths and planktonic foraminiferal shells, which are used in the construction of agglutinated spheres and domes. Our results underline the important contribution made by largely underestimated foraminiferal taxa to abyssal communities.
Single-chambered monothalamids, Pseudochambered foraminifera, Diversity, Deep-sea benthos, Abyssal faunas
1867-1616
357-369
Stefanoudis, Paris V.
2cbf86e8-b292-4f14-8b03-c37469df1d96
Gooday, Andrew J.
d9331d67-d518-4cfb-baed-9df3333b05b9
Stefanoudis, Paris V.
2cbf86e8-b292-4f14-8b03-c37469df1d96
Gooday, Andrew J.
d9331d67-d518-4cfb-baed-9df3333b05b9

Stefanoudis, Paris V. and Gooday, Andrew J. (2015) Basal monothalamous and pseudochambered benthic foraminifera associated with planktonic foraminiferal shells and mineral grains from the Porcupine Abyssal Plain, NE Atlantic. Marine Biodiversity, 45 (3), 357-369. (doi:10.1007/s12526-014-0277-5).

Record type: Article

Abstract

We present a survey of ‘live’ (stained) and dead monothalamous (single-chambered, mainly spherical) and pseudochambered (chain-like) foraminifera associated with planktonic foraminiferal shells and mineral grains, based on two samples from one abyssal plain site (F2, 4,880 m water depth) and one abyssal hill site (H4, 4,330 m water depth) on the Porcupine Abyssal Plain (PAP), northeast Atlantic. Our study is the first to focus on this poorly known component of abyssal foraminiferal faunas and highlight their abundances and diversity at the PAP. In both samples these monothalamids and pseudochambered forms represented 27–35 % and 18–23 %, respectively, of the entire ‘live’ and dead foraminiferal assemblage (>150 ?m, 0–1 cm sediment layer). Among 1,078 stained and dead specimens we recognise a total of 18 distinct morphotypes on the basis of test characteristics. Another 144 specimens could not be assigned to any morphotype and are regarded as indeterminate. Most of the monothalamids are small (<150 ?m), although some incorporate planktonic foraminiferal shells to create larger structures. In absolute terms, stained and dead individuals of these morphotypes were more abundant at the abyssal hill site, although data from additional samples are needed to confirm if this is representative of differences between abyssal hills and the surrounding abyssal plain at the PAP. Agglutinated spheres and domes similar to some of our abyssal forms have been reported from shelf and slope settings, but they are generally much larger. Small agglutinated spheres are very common in the abyssal Pacific, at depths close to or below the carbonate compensation depth (CCD). However, they are composed largely of siliceous particles, including mineral grains, radiolarians and diatom fragments. In contrast, carbonate oozes at the PAP, situated above the CCD, are rich in coccoliths and planktonic foraminiferal shells, which are used in the construction of agglutinated spheres and domes. Our results underline the important contribution made by largely underestimated foraminiferal taxa to abyssal communities.

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Stefanoudis & Gooday, 2014 (accepted version).pdf - Accepted Manuscript
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More information

e-pub ahead of print date: October 2014
Published date: September 2015
Keywords: Single-chambered monothalamids, Pseudochambered foraminifera, Diversity, Deep-sea benthos, Abyssal faunas
Organisations: Ocean and Earth Science, Marine Biogeochemistry

Identifiers

Local EPrints ID: 370539
URI: http://eprints.soton.ac.uk/id/eprint/370539
ISSN: 1867-1616
PURE UUID: 2b8167da-3fde-41b5-9837-8c71a0ff957b

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Date deposited: 28 Oct 2014 11:57
Last modified: 08 Jan 2022 15:19

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Contributors

Author: Paris V. Stefanoudis
Author: Andrew J. Gooday

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