Comparison of different preparation and analysis techniques for quantitative coccolith studies focusing on biogeographic patterns of species

摘要

The scanning Electron Microscope (SEM) and the Petrographic Microscope (Light Microscope, LM) are devices which both are used in routine analysis of coccolithophore assemblages, but comparisons and/or combinations of quantitative data from both sources are difficult. In this paper a comparison is made between the results obtained with the Flores and Sierro settling technique (1997) for LM and the Andruleit filtration technique (1996) for SEM, considering their advantages and drawbacks. Twenty-six surface sediment samples from the South Atlantic and Southeast Pacific were studied. All the taxa distinguished were reduced to fourteen groups accounting for 100%. The biogeographical patterns of coccolithophorid species and species groups determined using both techniques are highly comparable, although the trends in relative and absolute numbers are not always identical. In particular, the numbers of coccoliths per gram of sediment are higher in the case of the filtration technique/SEM-technique than for the settling technique/LM technique and an approach is introduced to estimate LM values using SEM counts with a linear regression equation. The results obtained allow different methodologies to be compared for the study of current coccolithophore biogeography.