Coccolithophore export production in response to monsoonal upwelling off Somalia (northwestern Indian Ocean)

Broerse, Alexandra T.C.; Brummer, Geert-Jan A; Hinte, J.E. van

doi:10.1016/s0967-0645(00)00021-7

Cited by 98 publications

(55 citation statements)

References 38 publications

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“…Moreover, total alkenone concentrations and alkenone accumulation rates (calculated using dry bulk density) in JPC32, indicators of total coccolithophorid production, are consistently higher during the last glacial period compared to the Holocene (Figure 8). That is, if the general association of G. oceanica with high productivity [Broerse et al, 2000;Giraudeau, 1992;Martínez et al, 2006;Ziveri et al, 1995] holds true in the Panama Basin, high glacial alkenone concentrations would suggest higher G. oceanica abundances and therefore lower dD alk values [Schouten et al, 2006], opposite to what is observed. This suggests that the last glacial D enrichment cannot be due to higher E. huxleyi relative to G. oceanica abundances, and that the observed glacial-to-interglacial dD alk decline must be considered a minimum change.…”

Section: Age Model For Jpc32mentioning

confidence: 88%

Eastern tropical Pacific hydrologic changes during the past 27,000 years from D/H ratios in alkenones

et al. 2007

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[1] The tropical Pacific plays a central role in the climate system by providing large diabatic heating that drives the global atmospheric circulation. Quantifying the role of the tropics in late Pleistocene climate change has been hampered by the paucity of paleoclimate records from this region and the lack of realistic transient climate model simulations covering this period. Here we present records of hydrogen isotope ratios (dD) of alkenones from the Panama Basin off the Colombian coast that document hydrologic changes in equatorial South America and the eastern tropical Pacific over the past 27,000 years (a) and the past 3 centuries in detail. Comparison of alkenone dD values with instrumental records of precipitation over the past $100 a suggests that dD can be used as a hydrologic proxy. On long timescales our records indicate reduced rainfall during the last glacial period that can be explained by a southward shift of the mean position of the Intertropical Convergence Zone and an associated reduction of Pacific moisture transport into Colombia. Precipitation increases at $17 ka in concert with sea surface temperature (SST) cooling in the North Atlantic and the eastern tropical Pacific. A regional coupled model, forced by negative SST anomalies in the Caribbean, simulates an intensification of northeasterly trade winds across Central America, increased evaporative cooling, and a band of increased rainfall in the northeastern tropical Pacific. These results are consistent with the alkenone SST and dD reconstructions that suggest increasing precipitation and SST cooling at the time of Heinrich event 1.

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Section: Age Model For Jpc32mentioning

confidence: 88%

Eastern tropical Pacific hydrologic changes during the past 27,000 years from D/H ratios in alkenones

et al. 2007

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“…In modern coccolithophore assemblages, variations in the Shannon measure of ecological diversity (H) are correlated to changes in the nutrient content of surface waters, with r-selected, opportunist, usually placolith-bearing species, dominant in eutrophic conditions (low H diversity) while a more diverse flora of k-selected species develops under nutrient-limited conditions (high H diversity) [Broerse et al, 2000;Jordan, 2002]. The most rapid transition in the coccolithophore assemblages in this study is immediately after the EOB and is marked by a major and rapid decline in H diversity from late Eocene assemblages with a mean value of 2.67 to those of the earliest Oligocene with a mean of 2.41 (Figure 3b).…”

Section: Nannofossil Assemblages and Paleoproductivitymentioning

confidence: 99%

“…In the modern oceans there is a general correlation between high-productivity environments and low-diversity coccolithophore assemblages, dominated by bloom-forming species such as Emiliania huxleyi, while oligotrophic environments are associated with diverse assemblages, often with a clear depth zonation and a distinct lower photic zone (LPZ) flora [Broerse et al, 2000;Kinkel et al, 2000;McIntyre and Bé, 1967;Okada and Honjo, 1973]. The response of the calcareous phytoplankton to global change through the Eocene-Oligocene boundary is poorly known when compared to other critical intervals such as the Paleocene-Eocene boundary [e.g., Bralower, 2002;Gibbs et al, 2006aGibbs et al, , 2006bRaffi et al, 2005].…”

Section: Introductionmentioning

confidence: 99%

Major shifts in calcareous phytoplankton assemblages through the Eocene‐Oligocene transition of Tanzania and their implications for low‐latitude primary production

et al. 2008

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A high‐resolution record of exceptionally well preserved calcareous nannofossil assemblages from Tanzania is marked by two key transitions closely related to the climatic events of the Eocene‐Oligocene transition (EOT). The first transition, at ∼34.0 Ma, precedes the first positive shift in δ18O and coincides with a distinct interval of very low nannofossil abundance and a cooling in sea surface temperatures (SST). The second, at ∼33.63 Ma, is immediately above the Eocene‐Oligocene boundary (EOB) and is associated with a significant drop in nannofossil diversity. Both transitions involve significant reductions in the abundance of holococcoliths and other oligotrophic taxa. These changes in calcareous phytoplankton assemblages indicate (1) a widespread and significant perturbation to the low‐latitude surface ocean closely tied to the EOB, (2) a potential role for reduced carbonate primary production at the onset of global cooling, and (3) a significant increase in nutrient availability in the low‐latitude surface ocean through the EOT.

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“…This species is known to preferentially thrive in high-nutrient environments, such as upwelling areas or continental shelves (MitchellInnes & Winter 1987;Houghton & Guptha 1991;Giraudeau 1992;Young 1994). It was suggested by Broerse et al (2000) that this species indicates maximum upwelling conditions and that it positively responds to the input of nutrients (Andruleit et al 2000). Although nutrient data are lacking, maximum abundances in the near shore samples support the impression of it being a r-selected species.…”

Section: G G G G Geol Eol Eolmentioning

confidence: 90%

Distribution of coccolithophores as a potential proxy in paleoceanography: The case of the Oman Sea monsoonal pattern

Mojtahedin¹,

Hadavi²,

Lak³

2015

Geologica Carpathica

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High abundances of coccoliths have been observed in surface sediment samples from near the coasts of the Oman Sea in February 2011. At the end of the NE monsoon, the locally observed high Gephyrocapsa oceanica production is hypothesized to respond to local injections of nutrient-rich deep water into the surface water due to sea-surface cooling leading to convection. The most abundant coccolithophore species are G. oceanica followed by Emiliania huxleyi, Helicosphaera carteri, Calcidiscus leptoporus. Some species, such as Gephyrocapsa muellerae, Gephyrocapsa ericsonii, Umbilicosphaera sibogae, Umbellosphaera tenuis and Florisphaera profunda, are rare. The G. oceanica suggested a prevalence of upwelling conditions or high supply of nutrients in the Oman Sea (especially West Jask) at the end of the NE monsoon. E. huxleyi showed low relative abundances at the end of the NE monsoon. Due to the location of the Oman Sea in low latitudes with high temperatures, we have observed low abundances of G. muellerae in the study area. Additionally, we have identified low abundances of G. ericsonii at the end of the NE monsoon. Helicosphaera carteri showed a clear negative response with decreasing amounts (relative abundances) at the end of the NE monsoon. C. leptoporus, U. sibogae and U. tenuis have very low relative abundances in the NE monsoon and declined extremely at the end of the NE monsoon. F. profunda, which is known to inhabit the lower photic zone ( < 100 m depht) was rarely observed in the samples.

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Coccolithophore export production in response to monsoonal upwelling off Somalia (northwestern Indian Ocean)

Cited by 98 publications

References 38 publications

Eastern tropical Pacific hydrologic changes during the past 27,000 years from D/H ratios in alkenones

Eastern tropical Pacific hydrologic changes during the past 27,000 years from D/H ratios in alkenones

Major shifts in calcareous phytoplankton assemblages through the Eocene‐Oligocene transition of Tanzania and their implications for low‐latitude primary production

Distribution of coccolithophores as a potential proxy in paleoceanography: The case of the Oman Sea monsoonal pattern

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