Engineering challenges in the development of an in situ microorganism imaging system in sea ice.

Béatrice Lessard-Hamel
Laval University
Biochemistry, Microbiology and Bioinformatics

Sea ice is composed of super-salty liquid channels, air, salt crystal, microbial organisms and small invertebrates. Inspired by medical endoscopes, we want to develop a miniature platform for measuring important sea ice in situ variables like salt concentration, nitrate concentration and optical properties. A microscope will be added to this endoscope to observe in-situ living microorganisms in air bubbles and brine pockets inside the sea ice as well as the ice microstructures. Without disturbing the environment, the endoscope will be used to determine how these organisms thrive inside the sea ice. The engineering challenges of developing an in situ micro-organism imaging system are the high biological heterogeneity, the transparency and the dynamic of these organisms. Another challenge is to achieve a taxonomic resolution allowing the identification of the organisms. Considering all these engineering challenges the best imaging system chosen to be tested is an oblique back-scatter microscope probe. This phase contrast technique developed in Jerome Mertz group provides en face gradient images of thick scattering samples. Quantitative phase reconstruction is achieved via deconvolution by modelling the transfer function of the system. Detail on the hardware conception of this probe and the computational phase reconstruction algorithm will be presented.

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