An empirical method for absolute calibration of coccolith thickness ...

• Main Authors: González-Lemos, Saúl, Guitián, José, Fuertes, Miguel-Ángel, Flores, José-Abel, Stoll, Heather M.
• Format: Article in Journal/Newspaper
• Language: English
• Published: ETH Zurich 2018
• Subjects: Ocean acidification
• Online Access: https://dx.doi.org/10.3929/ethz-b-000248940; http://hdl.handle.net/20.500.11850/248940

As major calcifiers in the open ocean, coccolithophores play a key role in the marine carbon cycle. Because they may be sensitive to changing CO2 and ocean acidification, there is significant interest in quantifying past and present variations in their cellular calcification by quantifying the thickness of the coccoliths or calcite plates that cover their cells. Polarized light microscopy has emerged as a key tool for quantifying the thickness of these calcite plates, but the reproducibility and accuracy of such determinations has been limited by the absence of suitable calibration materials in the thickness range of coccoliths (0–4 µm). Here, we describe the fabrication of a calcite wedge with a constant slope over this thickness range, and the independent determination of calcite thickness along the wedge profile. We show how the calcite wedge provides more robust calibrations in the 0 to 1.55 µm range than previous approaches using rhabdoliths. We show the particular advantages of the calcite wedge ... : Biogeosciences, 15 (4) ...