UVP6: a new low power, low cost and deep ocean rated imaging sensor for automatic quantification of particles and plankton from autonomous platforms

Marc Picheral1, Emna Abidi2, François Berry3, Jerome Coindat4, Denis Brousseau5, Fabio Dias6, Sylvain Fevre7, Lionel Guidi8, Jean Olivier Irisson9, Louis Legendre8, Fabien Lombard9, Antoine Manzanera10, Laurent Mortier11, Laurent Navarro12, Laura Picheral1, Lars Stemmann8, Simon Thibault5 and Thierry Tixier13, (1)Laboratoire d’Océanographie de Villefranche (LOV), UMR 7093, Sorbonne Université, Villefranche-sur-Mer, France, (2)Laboratoire d'Océanographie de Villefranche (LOV), UMR 7093, Sorbonne Université, Villefranche sur mer, France, (3)Institut Pascal - UCA CNRS, Aubiere, France, (4)Hydroptic, L'isle Jourdain, France, (5)Université Laval, Center for Optics, Photonics and Lasers, Laval, QC, Canada, (6)WISIP, Clermont Ferrand, France, (7)HYDROPTIC, L'Isle Jourdain, France, (8)Laboratoire d’Océanographie de Villefranche (LOV), UMR 7093, Sorbonne Université, Villefranche sur mer, France, (9)Laboratoire d'Océanographie de Villefranche (LOV), UMR 7093, Sorbonne Université, Villefranche-sur-Mer, France, (10)ENSTA Paris, Institut Polytechnique de Paris, Palaiseau, France, (11)ENSTA-ParisTech, Palaiseau, France, (12)ALTIDEV, Plaisance du Touch, France, (13)WISIP, Clermont-Ferrand, France
In recent years, autonomous platforms have been improved with the objective of observing the deep ocean. Many prototypes have reached 6,000 m, but only a few are commercially available.

Imaging sensors have been developed to study the numbers, sizes and shapes of particles and plankton. These have been deployed independently or mounted on CTD rosettes (e.g. the UVP5 Underwater Vision Profiler). In some areas, they observed high concentrations of large particles down to the bottom of the ocean, showing intense carbon export. They also documented the presence of fragile organisms, such as rhizarians, whose key ecological roles in the ocean was unknown until then.

The new miniaturized UVP6-LP (Low Power) sensor, developed to be mounted on autonomous platforms, is complementary to the larger sensors deployed on CTD rosettes. It also records and identifies particles and plankton, using imagery. It counts and sizes particles >80 µM ESD and identifies large aggregates and plankton >700µM ESD. This, at low cost and with very low power. Six prototypes of the sensor have been inter-calibrated with the reference UVP5. The instrument can be deployed down to 6,000 m, which corresponds to 97% of the ocean surface.

A UVP6-LP was used to quantify particles released from a deep-sea mining experiment at 4,300 m. Others performed transects on gliders and vertical profiles on a float. A UVP6-LP was moored for one year at 50 m at 82°N. Other UVP6-LP will be deployed on the a cabled observatory in the Mediterranean Sea at 2,200 m, and on the SeaCycler mooring in the Labrador Sea. The very low power required for the operation of the UVP6-LP allows to optimize its use on profiling floats and gliders.

Autonomous platforms cannot transmit images due to the limitation of satellite bandwidth or acoustic telemetry. To overcome this limitation, the UVP6-LP includes an embedded algorithm for the automatic classification of large aggregates and plankton images, which provides data that are accurate enough for monitoring programs and scientific studies.

Because scientists, policy makers and the public require easy access to data, a complete software ecosystem is used to pilot the instrument, record the data, and make them freely available to the scientists and the public. When the instruments are recovered after deployment, their data include classified images.