Abstract
We present a fluorosensor for the detection of laser-induced autofluorescence of zooplankton in marine environments. The sensor uses an inexpensive 410 nm laser diode as excitation source and simultaneously measures two fluorescence bands, 500-550 nm and 675-725 nm, using two identical 16-bit linear array detectors. We show continuous measurements at 200 Hz of zooplankton swimming through a water volume illuminated by the 410 nm laser. The sensor can distinguish salmon lice (Lepeophtheirus salmonis) larvae from an algae-eating reference species (Acartia tonsa) with a sensitivity of up to 99%. The system successfully differentiates the two species using mixed-species cultures at different ratios. This work shows the potential of fluorescent pest monitoring in the salmon farming industry and paves the way for single-ended aquatic lidars.
Highlights
In the past decade, we have seen a growing interest in the use of photonics technologies to monitor and survey fauna in both air and water [1]
Its gut is empty for the majority of the measurements, since A. tonsa clears its gut within 30-60 minutes of being in filtered seawater [14]. This suggests that the red fluorescence does not stem exclusively from the ingested chlorophyll in the gut, as there is no large variation in the cyan over red fluorescence ratio over time
We have presented a dual-wavelength-band fluorosensor for the detection of zooplankton and demonstrated its ability to detect individual animals of 0.7-1 mm body lengths
Summary
We have seen a growing interest in the use of photonics technologies to monitor and survey fauna in both air and water [1]. A number of optical systems have been developed based on different optical properties of target species. These systems have been dominated by camerabased approaches such as the video plankton recorder and the optical plankton counter [2] and holographic based techniques [3]. Laser-induced fluorescence (LIF) based systems have been used for in situ monitoring and classification of chlorophyll-rich phytoplankton [4,5], and remote sensing of water quality [6] but have yet to be applied to underwater sensing of zooplankton
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