A New Method to Speed Up Nannofossil Picking for Monospecific Geochemical Analyses

Abstract

Investigating the trace elements contained in the coccoliths, i.e., the carbonate exoskeleton, of unicellular marine phytoplankton called coccolithophores, is fundamental for calibrating environmental climate proxies, which are key tools for studying past and future climate changes. To date, lab-cultivated coccolithophores have been mainly used for measuring the elements retained within the coccoliths, whereas geochemical studies in fossil records have been limited by the difficulty in isolating monospecific samples from sediments containing highly diversified fossil assemblages. Since a comparison of the geochemical data collected from both fossil and living species is fundamental for calibrating the environmental proxies, an improvement of coccolith-picking methodology should be envisaged. Here, we present a significant advancement in the isolation of fossil species-specific coccolith achieved using a hydraulic micromanipulation system together with wet samples, never applied before on coccoliths. Our technique allows the picking of around 100 monospecific coccoliths per h, a number never achieved before with other isolation methodologies. This method opens up new possibilities in applying monospecific geochemical analyses to the fossil record not attainable before (e.g., the use of the mass spectrometer), leading to an increase in knowledge of environmental proxy calibration and coccolithophore element incorporation strategies.