Refractive index and volume fractions of various cellular components of plankton

The refractive index (RI) of plankton, especially of live cells, has seldom been measured despite its critical role in determining the optical properties of phytoplankton and their effect on underwater light propagation. Here we present measurements of the RI of live cells representing several phyto...

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Bibliographic Details
Published in:Optics express 2023-10, Vol.31 (22), p.35892-35907
Main Authors: Kamowski, Michael, Mojica, Kristina, Lange, Kacey, Zhang, Xiaodong
Format: Article
Language:English
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Summary:The refractive index (RI) of plankton, especially of live cells, has seldom been measured despite its critical role in determining the optical properties of phytoplankton and their effect on underwater light propagation. Here we present measurements of the RI of live cells representing several phytoplankton groups and ciliates collected from field and lab samples using a high precision holo-tomographic microscope, 3D Cell Explorer. The instrument was able to clearly differentiate three separate cellular structures according to their refractive index: membrane, chloroplast for phytoplankton (or cytoplasm for ciliate), and cytosol. RI values for membranes were distinct according to composition; for chloroplasts, were relatively conserved across phytoplankton taxa; and for cytosol, were close to that of seawater. The volumetric fractions of the membrane and chloroplast scale inversely with cell size whereas the volume of cytosol increased logistically. These results provide a more accurate measurement of RI and volume fractions of various cellular structures that can be used to improve optical modeling of marine plankton.
ISSN:1094-4087
1094-4087
DOI:10.1364/OE.502465