Paleoceanography of the southern Agulhas Plateau during the last 150 ka: Inferences from benthic foraminiferal assemblages and multispecies epifaunal carbon isotopes

Paula Diz, Ian R. Hall, Rainer Zahn, Elizabeth Molyneux

Research output: Contribution to journalLiterature review

14 Citations (Scopus)

Abstract

Benthic foraminiferal assemblages and the carbon isotope composition of the epifaunal benthic foraminifera Epistominella exigua and Fontbotia wuellerstorfi have been investigated along core MD02-2589 located at the southern Agulhas Plateau ( 41 degrees 26.03'S, 25 degrees 15.30'E, 2660 m water depth). This study aims to evaluate changes in the benthic paleoenvironment and its influence on benthic delta C-13 with a notable focus on E. exigua, a species associated with phytodetritus deposits and poorly studied in isotope paleoceanographic reconstructions. The benthic foraminiferal assemblages (> 63 mu m) show large fluctuations in species composition suggesting significant changes in the pattern of ocean surface productivity conceivably related to migrations of the Subtropical Convergence ( STC) and Subantarctic Front ( SAF). Low to moderate seasonality and relatively higher food supply to the seafloor are indicated during glacial marine isotope stages ( MIS) 6, 4, and 2 and during MIS 3, probably associated with the northward migration of the SAF and confluence with the more stationary STC above the southern flank of the Agulhas Plateau. The lowest organic carbon supply to the seafloor is indicated from late MIS 5b to MIS 4 as a consequence of increased influence of the Agulhas Front ( AF) and/ or weakening of the influence of the STC over the region. Episodic delivery of fresh organic matter, similar to modern conditions at the core location, is indicated during MIS 5c-MIS 5e and at Termination I. Comparison of this paleoenvironmental information with the paired delta C-13 records of E. exigua and F. wuellerstorfi suggests that organic carbon offsets delta C-13 of E. exigua from ambient bottom water delta C-13(DIC), while its delta C-13 amplitude, on glacial-interglacial timescales, does not seem affected by changes of organic carbon supply to the seafloor. This suggests that this species calcifies preferentially during the short time span of the year when productivity peaks and phytodetritus is delivered to the seafloor. Therefore E. exigua, while offset from delta C-13(DIC), potentially more faithfully records the amplitude of ambient bottom water delta C-13(DIC) changes than F. wuellerstorfi, notably in settings such as the Southern Ocean that experienced substantial changes through time in the organic carbon supply to the seafloor.

Original languageEnglish
Article numberPA4218
Number of pages16
JournalPaleoceanography
Volume22
Issue number4
DOIs
Publication statusPublished - 29 Dec 2007

Keywords

  • deep-water circulation
  • phytoplankton pigment distribution
  • surface ocean productivity
  • eastern equatorial pacific
  • convergence zone south
  • Swedish west-coast
  • Atlantic-Ocean
  • Indian-Ocean
  • glacial maximum
  • organic-carbon

Cite this

Paleoceanography of the southern Agulhas Plateau during the last 150 ka: Inferences from benthic foraminiferal assemblages and multispecies epifaunal carbon isotopes. / Diz, Paula; Hall, Ian R.; Zahn, Rainer; Molyneux, Elizabeth.

In: Paleoceanography, Vol. 22, No. 4, PA4218, 29.12.2007.

Research output: Contribution to journalLiterature review

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abstract = "Benthic foraminiferal assemblages and the carbon isotope composition of the epifaunal benthic foraminifera Epistominella exigua and Fontbotia wuellerstorfi have been investigated along core MD02-2589 located at the southern Agulhas Plateau ( 41 degrees 26.03'S, 25 degrees 15.30'E, 2660 m water depth). This study aims to evaluate changes in the benthic paleoenvironment and its influence on benthic delta C-13 with a notable focus on E. exigua, a species associated with phytodetritus deposits and poorly studied in isotope paleoceanographic reconstructions. The benthic foraminiferal assemblages (> 63 mu m) show large fluctuations in species composition suggesting significant changes in the pattern of ocean surface productivity conceivably related to migrations of the Subtropical Convergence ( STC) and Subantarctic Front ( SAF). Low to moderate seasonality and relatively higher food supply to the seafloor are indicated during glacial marine isotope stages ( MIS) 6, 4, and 2 and during MIS 3, probably associated with the northward migration of the SAF and confluence with the more stationary STC above the southern flank of the Agulhas Plateau. The lowest organic carbon supply to the seafloor is indicated from late MIS 5b to MIS 4 as a consequence of increased influence of the Agulhas Front ( AF) and/ or weakening of the influence of the STC over the region. Episodic delivery of fresh organic matter, similar to modern conditions at the core location, is indicated during MIS 5c-MIS 5e and at Termination I. Comparison of this paleoenvironmental information with the paired delta C-13 records of E. exigua and F. wuellerstorfi suggests that organic carbon offsets delta C-13 of E. exigua from ambient bottom water delta C-13(DIC), while its delta C-13 amplitude, on glacial-interglacial timescales, does not seem affected by changes of organic carbon supply to the seafloor. This suggests that this species calcifies preferentially during the short time span of the year when productivity peaks and phytodetritus is delivered to the seafloor. Therefore E. exigua, while offset from delta C-13(DIC), potentially more faithfully records the amplitude of ambient bottom water delta C-13(DIC) changes than F. wuellerstorfi, notably in settings such as the Southern Ocean that experienced substantial changes through time in the organic carbon supply to the seafloor.",
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author = "Paula Diz and Hall, {Ian R.} and Rainer Zahn and Elizabeth Molyneux",
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T1 - Paleoceanography of the southern Agulhas Plateau during the last 150 ka: Inferences from benthic foraminiferal assemblages and multispecies epifaunal carbon isotopes

AU - Diz, Paula

AU - Hall, Ian R.

AU - Zahn, Rainer

AU - Molyneux, Elizabeth

PY - 2007/12/29

Y1 - 2007/12/29

N2 - Benthic foraminiferal assemblages and the carbon isotope composition of the epifaunal benthic foraminifera Epistominella exigua and Fontbotia wuellerstorfi have been investigated along core MD02-2589 located at the southern Agulhas Plateau ( 41 degrees 26.03'S, 25 degrees 15.30'E, 2660 m water depth). This study aims to evaluate changes in the benthic paleoenvironment and its influence on benthic delta C-13 with a notable focus on E. exigua, a species associated with phytodetritus deposits and poorly studied in isotope paleoceanographic reconstructions. The benthic foraminiferal assemblages (> 63 mu m) show large fluctuations in species composition suggesting significant changes in the pattern of ocean surface productivity conceivably related to migrations of the Subtropical Convergence ( STC) and Subantarctic Front ( SAF). Low to moderate seasonality and relatively higher food supply to the seafloor are indicated during glacial marine isotope stages ( MIS) 6, 4, and 2 and during MIS 3, probably associated with the northward migration of the SAF and confluence with the more stationary STC above the southern flank of the Agulhas Plateau. The lowest organic carbon supply to the seafloor is indicated from late MIS 5b to MIS 4 as a consequence of increased influence of the Agulhas Front ( AF) and/ or weakening of the influence of the STC over the region. Episodic delivery of fresh organic matter, similar to modern conditions at the core location, is indicated during MIS 5c-MIS 5e and at Termination I. Comparison of this paleoenvironmental information with the paired delta C-13 records of E. exigua and F. wuellerstorfi suggests that organic carbon offsets delta C-13 of E. exigua from ambient bottom water delta C-13(DIC), while its delta C-13 amplitude, on glacial-interglacial timescales, does not seem affected by changes of organic carbon supply to the seafloor. This suggests that this species calcifies preferentially during the short time span of the year when productivity peaks and phytodetritus is delivered to the seafloor. Therefore E. exigua, while offset from delta C-13(DIC), potentially more faithfully records the amplitude of ambient bottom water delta C-13(DIC) changes than F. wuellerstorfi, notably in settings such as the Southern Ocean that experienced substantial changes through time in the organic carbon supply to the seafloor.

AB - Benthic foraminiferal assemblages and the carbon isotope composition of the epifaunal benthic foraminifera Epistominella exigua and Fontbotia wuellerstorfi have been investigated along core MD02-2589 located at the southern Agulhas Plateau ( 41 degrees 26.03'S, 25 degrees 15.30'E, 2660 m water depth). This study aims to evaluate changes in the benthic paleoenvironment and its influence on benthic delta C-13 with a notable focus on E. exigua, a species associated with phytodetritus deposits and poorly studied in isotope paleoceanographic reconstructions. The benthic foraminiferal assemblages (> 63 mu m) show large fluctuations in species composition suggesting significant changes in the pattern of ocean surface productivity conceivably related to migrations of the Subtropical Convergence ( STC) and Subantarctic Front ( SAF). Low to moderate seasonality and relatively higher food supply to the seafloor are indicated during glacial marine isotope stages ( MIS) 6, 4, and 2 and during MIS 3, probably associated with the northward migration of the SAF and confluence with the more stationary STC above the southern flank of the Agulhas Plateau. The lowest organic carbon supply to the seafloor is indicated from late MIS 5b to MIS 4 as a consequence of increased influence of the Agulhas Front ( AF) and/ or weakening of the influence of the STC over the region. Episodic delivery of fresh organic matter, similar to modern conditions at the core location, is indicated during MIS 5c-MIS 5e and at Termination I. Comparison of this paleoenvironmental information with the paired delta C-13 records of E. exigua and F. wuellerstorfi suggests that organic carbon offsets delta C-13 of E. exigua from ambient bottom water delta C-13(DIC), while its delta C-13 amplitude, on glacial-interglacial timescales, does not seem affected by changes of organic carbon supply to the seafloor. This suggests that this species calcifies preferentially during the short time span of the year when productivity peaks and phytodetritus is delivered to the seafloor. Therefore E. exigua, while offset from delta C-13(DIC), potentially more faithfully records the amplitude of ambient bottom water delta C-13(DIC) changes than F. wuellerstorfi, notably in settings such as the Southern Ocean that experienced substantial changes through time in the organic carbon supply to the seafloor.

KW - deep-water circulation

KW - phytoplankton pigment distribution

KW - surface ocean productivity

KW - eastern equatorial pacific

KW - convergence zone south

KW - Swedish west-coast

KW - Atlantic-Ocean

KW - Indian-Ocean

KW - glacial maximum

KW - organic-carbon

U2 - 10.1029/2007PA001511

DO - 10.1029/2007PA001511

M3 - Literature review

VL - 22

JO - Paleoceanography and Paleoclimatology

JF - Paleoceanography and Paleoclimatology

SN - 0883-8305

IS - 4

M1 - PA4218

ER -