Coccolithus pelagicus subsp. pelagicus versus Coccolithus pelagicus subsp. braarudii (Coccolithophore, Haptophyta): A proxy for surface subarctic Atlantic waters off Iberia during the last 200 kyr

Aurea Narciso,Mario Cachão,Lucia De Abreu

doi:10.1016/j.marmicro.2005.12.001

Aurea Narciso, Mario Cachão + Show 1 more

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https://doi.org/10.1016/j.marmicro.2005.12.001

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Abstract

A Multivariate Morphon Analysis (MMA) of Coccolithus pelagicus (s. l.) coccoliths was performed on 178 samples from an oceanic core recovered off the Portuguese margin (MD95-2040), in order to define the morphometric boundaries of its morphotypes and their behaviour during the last two glacial cycles. The recurrent occurrence of the smaller morphotype of this taxon, C. pelagicus subsp. pelagicus, was recognized for the first time off the Portuguese coast. Three sections, around Heinrich Layers 1 and 6 and Termination II-Eemian, were selected to establish high resolution comparisons between C. pelagicus subsp. pelagicus and C. pelagicus subsp. braarudii and two independent proxies for cold water masses: the records of the planktonic foraminifera Neogloboquadrina pachyderma (sinistral) and ice-rafted detritus (IRD). There is an overall negative correlation between C. pelagicus subsp. pelagicus and C. pelagicus subsp. braarudii as expressed by MMA Factor 1, the scores of which respond similarly to those of two non-cocolithophore proxies and consequently, is proposed as a calcareous nannoplankton proxy for the influence of subpolar waters in the region. Detailed analysis, however, showed occasional decoupling amongst these three proxies, which are used to highlight significant changes between the cooling–warming sequences of distinct events off Iberia.

Highlights

Coccolith morphometry has already been used to address questions such as taxonomy, biostratigraphy and palaeoecology of several calcareous nannoplankton (e.g. Samtleben, 1980; Backman and Hermelin, 1986; Young, 1990; Wei, 1992; Baumann, 1995; Knappertsbusch, 2000; Colmenero-Hidalgo et al, 2002)
Based on detailed morphometric analysis, Parente et al (2004) confirmed the existence of three morphotypes of C. pelagicus (s. l.): the smaller morphotype related to C. pelagicus subsp. pelagicus, the intermediate size morphotype related to C. pelagicus subsp. braarudii, and a larger new one described as C. pelagicus subsp. azorinus
Factor 1, with a variance of 43%, is strongly influenced by morphons 5 to 9 (5 to 8 with loadings higher than 0.7 and 9 with loadings of 0.63) in negative correlation to morphons 12 and 13, reflecting an opposite behaviour between these two clusters of morphons, the two morphotypes associated to C. pelagicus subsp. pelagicus and C. pelagicus subsp. braarudii, respectively

Summary

Introduction

Samtleben, 1980; Backman and Hermelin, 1986; Young, 1990; Wei, 1992; Baumann, 1995; Knappertsbusch, 2000; Colmenero-Hidalgo et al, 2002) This approach is based on the fact that heterococcoliths (hereafter referred to as coccoliths), being produced intracellularly, are completed formed prior to being extruded from the coccosphere L.) included upwelling regions (Cachao and Moita, 2000) This apparent contradiction started to be resolved when Geisen et al (2002) presented life cycle evidences for the existence of two extant subspecies of C. pelagicus: C. pelagicus subsp.

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