Abstract
A unique protocol using a gelatin-based embedding technique allows long-term preservation of sea ice microalgae and phytoplankton cells. The high quality preservation of the cells and their optical properties for over two decades was confirmed after a re-examination of samples collected and prepared during 1987 at McMurdo Station, Antarctica and during 1990 at the California Bight near Los Angeles. Samples stored frozen until 2011 demonstrated the long-term preservation of the cellular structure, as well as their spectral absorption and fluorescence properties. This protocol makes it possible to assemble archives of sea ice microalgae and phytoplankton cells for environmental studies.
Highlights
The proper cell preservation protocol is essential to maintain the cell structure and optical properties that existed at the time of sampling
A visual comparison of the magnitude and shape of the absorption efficiency factor Qa (λ) and fluorescence excitation spectra of the cells before and after two decades of storage indicates that the variability within the spectra does not deviate beyond the range of the natural variability commonly observed in field samples [9,12,13]
The strength and validity of our observations focused on the cell absorption efficiency factor Qa (λ) for chlorophyll a, with peaks at 435-440 nm and 675 nm
Summary
The proper cell preservation protocol is essential to maintain the cell structure and optical properties that existed at the time of sampling. Microphotometric analyses are highly accurate for the determination of the spectral absorption, fluorescence (excitationemission) and reflectance of individual phytoplankton cells and detrital particulates They provide microalgae taxonomic identification, chlorophyll concentration per cell, photo-adaptive state and particle geometrical cross-sectional area [9,10,11,12]. These determinations are time intensive and difficult to perform in the field, a technique capable of preserving cells without altering their optical properties during analysis and storage was developed. In all the revisited samples no changes were observed in the spectral absorption efficiency and the fluorescence excitation spectra of these internal markers
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