Our understanding of the fate and distribution of micro-and nano-plastics in the marine environment and their impact on the biota compartment is limited by the intrinsic difficulties of conventional analytical techniques (light scattering, FT-IR, Raman, optical and electron microscopies) in the detection, quantification and chemical identification of small particles in liquid samples. Here we propose the use of optical tweezers, a technique awarded in 2018 with the Nobel prize, as an analytical tool for the study of micro-and nano-plastics in sea water. In particular, we exploit the combination of optical tweezers with Raman spectroscopy (Raman Tweezers, RTs) to optically trap plastic particles with sizes from tens of µm down to 90 nm and unambiguously reveal their chemical composition. RTs applications are shown on particles made of the most common plastic pollutants, including polyethylene, polypropylene, nylon and polystyrene, that are artificially fragmented and aged directly in seawater. RTs allow us to assess the size and shapes of microparticles (beads, fragments, fibers) and can be applied to investigate particles covered with organic layers. Furthermore, operating at the single particle level, RTs enable unambiguous distinction of plastic particles from marine microorganisms and seawater minerals, overcoming the capacities of standard Raman spectroscopy in liquid, limited to average measurements. Coupled to suitable extraction and concentration protocols, RTs could have a strong impact in the study of the fate of micro and nanoplastics in marine environment, as well as in the understanding of the fragmentation processes on a multi-scale level.

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Our understanding of the fate and distribution of micro- and nano- plastics in the marine environment and their impact on the biota compartment is limited by the intrinsic difficulties of conventional analytical techniques (light scattering, FT-IR, Raman, optical and electron microscopies) in the detection, quantification and chemical identification of small particles in liquid samples. Here we propose the use of optical tweezers, a technique awarded in 2018 with the Nobel prize, as an analytical tool for the study of micro- and nano- plastics in sea water. In particular, we exploit the combination of optical tweezers with Raman spectroscopy (Raman Tweezers, RTs) to optically trap plastic particles with sizes from tens of µm down to 90 nm and unambiguously reveal their chemical composition. RTs applications are shown on particles made of the most common plastic pollutants, including polyethylene, polypropylene, nylon and polystyrene, that are artificially fragmented and aged directly in seawater. RTs allow us to assess the size and shapes of microparticles (beads, fragments, fibers) and can be applied to investigate particles covered with organic layers. Furthermore, operating at the single particle level, RTs enable unambiguous distinction of plastic particles from marine microorganisms and seawater minerals, overcoming the capacities of standard Raman spectroscopy in liquid, limited to average measurements. Coupled to suitable extraction and concentration protocols, RTs could have a strong impact in the study of the fate of micro and nanoplastics in marine environment, as well as in the understanding of the fragmentation processes on a multi-scale level.

In this paper we present the ZooCAM, a system designed to digitize and analyse on board large volume samples of preserved and living metazooplankton (i.e. multicellular zooplankton) and fish eggs > 300 µm ESD. The ZooCAM has been specifically designed to overcome the difficulties to analyse zooplankton and fish eggs in the framework of the PELGAS survey, and provide high frequency data. The ZooCAM fish eggs counts were comparable to those done with a dissecting microscope. The ZooCAM enabled the accurate prediction and fast on board validation of staged anchovy and sardine eggs in almost real time after collection. A comparison with the ZooScan, on a more complex zooplanktonic community, provided encouraging results on the agreement between the 2 instruments. ZooCAM and ZooScan enabled the identification of similar communities and produced similar total zooplankton abundances, size distributions, and size spectra slopes, when tested on the same samples. However these results need to be further refined due to the small number of samples used to compare the two instruments. The main ZooCAM drawback resides in a slight but sensible underestimation of abundances and sizes, and therefore individual and community biovolumes. The ZooCAM have been successfully deployed over 4 years, on numerous surveys without suffering any major failure. When used in line with the CUFES it provided high resolution maps of staged fish eggs and zooplanktonic functional groups. Hence the ZooCAM is an appropriate tool for the development of on board, high frequency, high spatial coverage zooplanktonic and ecosystemic studies. Highlights ► The ZooCAM is a new inflow imaging system for fast onboard counting, sizing and classification of fish eggs and metazooplankton. ► The ZooCAM has been used on-board for 4 years without suffering any failure and enabled the analysis ∼10,000 samples so far (CUFES, WP2 and other plankton nets). ► The ZooCAM provided staged fish eggs counts that were equivalent to those traditionally done by microscopic examination. These data were used for 2016 and 2017 anchovy and sardine stocks estimations in the Bay of Biscay (DEPM method) ► The ZooCAM enable the real time, on-board, imaging of complex communities zooplankton samples and provide results comparable to on-land, well established counterpart, the ZooScan. ► The ZooCAM is a valuable tool to improve zooplanktonic studies, in term of spatial coverage and temporal frequency, to perform ecosystemic studies.

A power-over-fiber (PoF) and communication system for extending a cabled seafloor observatory is demonstrated in this contribution. The system allows the cabled seafloor observatory to be linked, through a single optical fiber, to a sensor node located 8 km away. The PoF system is based on an optical architecture in which power and data propagate simultaneously on the same single-mode fiber. The Raman scattering effect is exploited to amplify the optical data signals and leads to the minimization of the sensor node power consumption. Versatile low power electronic interfaces have been developed to ensure compatibility with a wide range of marine sensors. A low-consumption fieldprogrammable gate array and an energy-efficient microcontroller are used to develop the electronic interfaces. For an electrical input power of 31 W, up to 190 mW is recovered at the sensor node while a data bitrate of up to 3.6 Mb/s is achieved. The PoF system has been tested and validated for turbidity and acoustic measurement applications. The current study focuses on the electronic development and the validation of the PoF system.