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In-situ holography microscopy of plankton and particles over the continental shelf of Senegal


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Hermand, J.-P., Randall, J., Dubois, F., Queeckers, P., Yourassowsky, C., Roubaud, F., Grelet, J., Roudaut, G., Sarre, A. and Brehmer, P. 2013 , 'In-situ holography microscopy of plankton and particles over the continental shelf of Senegal', paper presented at the International Symposium on Ocean Electronics (SYMPOL), 2013, 23-25 October, 2013, Kochi, India.

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We present the first results obtained by a newly developed submersible
digital holography microscope (DHM), Holoflow@Sea, to enable continuous in-situ
monitoring of ocean or fresh water bodies in a less intrusive manner. The
microscope features an off-axis configuration with reduced-coherence illumination.
The optics is designed to image plankton and particles in the size range
2 μm�200 μm within a water volume of 1 mm x 1 mm x 2 mm. The prototype was
successfully deployed for the first time over the continental shelf of Senegal during a
fisheries survey carried out in March 2013. The objective was to combine several
laboratory techniques used for plankton and particle identification (highperformance
liquid chromatography, flow cytometry and optical microscopy) on
discrete collected samples with DHM images taken in situ at locations with different
environmental conditions. Hologram data were acquired inside an upwelling cell,
i.e., new water, and along the coast, i.e., old water, as well as off the upwelling cell
at the continental shelf border. Preliminary results of holographic reconstruction are
encouraging, with the distinctive morphology of some phytoplankton species
allowing easy identification to genera level. Challenges are recognised with the
identification of small spheroid organisms. Analyses are underway to allow
comparison with traditional methods of plankton identification and evaluate the
benefit of additional in-situ observations obtained by holography microscopy. The
preliminary results already demonstrate the potential of DHM for in-situ studies of
plankton and particles.

Item Type: Conference or Workshop Item (Paper)
Authors/Creators:Hermand, J.-P. and Randall, J. and Dubois, F. and Queeckers, P. and Yourassowsky, C. and Roubaud, F. and Grelet, J. and Roudaut, G. and Sarre, A. and Brehmer, P.
Keywords: Behaviour, Dynamics, Diatom chain, Dinoflagellate, Fisheries acoustics, Holoflow@Sea, Identification, Marine snow, Off-axis digital holography, Phytoplankton, Submersible microscope, Zooplankton
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