Importance of size measurements for coccolith carbonate flux estimates

摘要

Reliable estimates of coccolilh masses of the different species are an important prerequisite in determining coccolith carbonate fluxes. This paper presents data from sediment trap samples that were analysed in order to determine the contribution of coccolithophores to the flux through the water column and to compare relative flux contribution based on different size estimates. Biometrical analyses of distinct coccolith species were therefore performed on samples from four additional time-series stations. Besides analysing the numerically dominant taxa Emiliania huxleyi and Florisphaera profunda, measurements have been made on Calcidiscus leptoporus, Gephyrocapsa oceanica, Helicosphaera carteri and Syracosphaera pulchra. This study strongly reinforces the previous conclusion that size calibrations are essential for reliable results, i.e. that the superficially attractive alternative of adopting "standard" size estimates for species is an invalid approach. The most extreme example of variable volume calculation is given for C. leptoporus. Mean size plots differ significantly from different regions, either with large, intermediate or small coccoliths dominating. The variability in size is likely to result in an approximately three-fold variability in carbonate mass contribution.