Comments on Brugger and others (2018) ‘A quantitative comparison of microfossil extraction methods from ice cores’

Daniela Festi,Klaus Oeggl,Werner Kofler

doi:10.1017/jog.2019.10

Abstract

ABSTRACTIn our comments, we re-evaluate Brugger and others (2018) Lycopodium/Eucalyptus double marker approach, based on the fact that previous evidence already demonstrated that the batch of Eucalyptus tablets used by Brugger and others (2018) is not suitable for quantitative comparisons as they are characterized by inconsistent pollen concentration. We present clear evidence that the Eucalyptus tablets do feature inaccurate pollen concentrations, and are therefore improper for all quantitative comparisons of microfossil extraction methods. Consequently, the results of the quantitative and qualitative assessment of different pollen extraction methods from ice samples compiled by Brugger and others (2018) are highly questionable due to the use of faulty marker tablets.

Highlights

In their paper ‘A quantitative comparison of microfossil extraction methods from ice cores’, Brugger and others (2018) present a comparative evaluation of six pollen extraction protocols from ice samples, by assessing the effects of three types of water reduction procedures: (i) evaporation (Liu and others, 1998, 2005, 2007; Yang and others, 2008; Brugger and others, 2018), (ii) filtration (Short and Holdsworth, 1985) and (iii) centrifugation (Eichler and others, 2011; Festi and others, 2015)
Contrary to Brugger and others (2018), our analysis revealed that, based on a total pollen sum of 1000 marker grains, the Lycopodium/Eucalyptus ratio varied between 0.52 and 0.81
In 40% of the samples, the Lycopodium/Eucalyptus ratio was outside the expected ratio of 0.66 to 0.78 (Fig. 1)

Summary

Introduction

In their paper ‘A quantitative comparison of microfossil extraction methods from ice cores’, Brugger and others (2018) present a comparative evaluation of six pollen extraction protocols from ice samples, by assessing the effects of three types of water reduction procedures: (i) evaporation (Liu and others, 1998, 2005, 2007; Yang and others, 2008; Brugger and others, 2018), (ii) filtration (Short and Holdsworth, 1985) and (iii) centrifugation (Eichler and others, 2011; Festi and others, 2015). Brugger and others (2018) calculated for each extraction method the coefficient of determination (R2) based on the Lycopodium and Eucalyptus values obtained after sample treatment, and used it as a measure for loss variability. Based upon these Lycopodium–Eucalyptus statistics, i.e. Lycopodium/Eucalyptus ratios and derived Lycopodium loss percentages and R2, a quality ranking of the extraction methods was compiled by the authors

Methods

Results

Conclusion