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Foto credits Antonio Cascella (INGV PI)
A sample every 4 cm has been prepared following the filtration technique, in order to have an even distribution of coccolithophore specimens on a filter membrane to calculate the numerical abundance of nannofossils, an useful tool for palaeoceanographic analysis.
Some information about the preparation:
A portion of sample weighing between 0.1 and 0.2 g was placed in a graded 25 ml test-tube and 20 ml of tap water was added. The sample suspension was agitated till it was homogeneous. A fraction of sample suspension was extracted with a micropipette (between 70 to 200 microliter, depending upon the richness of nannofossils) and poured into a small beaker containing 20 ml of tap water. The contents of the beaker were mixed and filtered through a plain white, 47 mm diameter, 0.22 micrometer pore-size, cellulose mixed-ester membrane filter. For the analysis of assemblages under a polarising light microscope, at x640 to x1250 magnification, an approximately 1.2cm x 1.2cm portion of the dried filter is cut out and placed on a glass slide. The piece of filter is rendered transparent with a drop of immersion oil and covered with a coverslip. The four corners of the coverslip are fixed to the slide using nail polish.