Pelagic organisms avoid white, blue, and red artificial light from scientific instruments

Jørgen Berge,Pierre Priou,Malin Daase,Geir Johnsen,Arnault Le Bris,David McKee,Jonathan Cohen,Øystein Varpe,Tom Langbehn,Jonathan A. D. Fisher,Maxime Geoffroy

doi:10.1038/s41598-021-94355-6

Abstract

In situ observations of pelagic fish and zooplankton with optical instruments usually rely on external light sources. However, artificial light may attract or repulse marine organisms, which results in biased measurements. It is often assumed that most pelagic organisms do not perceive the red part of the visible spectrum and that red light can be used for underwater optical measurements of biological processes. Using hull-mounted echosounders above an acoustic probe or a baited video camera, each equipped with light sources of different colours (white, blue and red), we demonstrate that pelagic organisms in Arctic and temperate regions strongly avoid artificial light, including visible red light (575–700 nm), from instruments lowered in the water column. The density of organisms decreased by up to 99% when exposed to artificial light and the distance of avoidance varied from 23 to 94 m from the light source, depending on colours, irradiance levels and, possibly, species communities. We conclude that observations from optical and acoustic instruments, including baited cameras, using light sources with broad spectral composition in the 400–700 nm wavelengths do not capture the real state of the ecosystem and that they cannot be used alone for reliable abundance estimates or behavioural studies.

Highlights

In situ observations of pelagic fish and zooplankton with optical instruments usually rely on external light sources
Despite a growing body of literature reporting behavioural disturbance of marine organisms exposed to artificial light, external light sources remain widely used in oceanography and marine ecology studies
Station, we deployed an acoustic probe composed of a Wideband Acoustic Transceiver (WBAT; Kongsberg Maritime AS) mounted on a CTD-rosette and connected to a sideward-looking 38 kHz split beam transducer operated in broadband mode (Model ES38-18DK split-beam wideband (35–45 kHz); see Supplementary Table S1 online for details of the settings)

Summary

Introduction

In situ observations of pelagic fish and zooplankton with optical instruments usually rely on external light sources. Recent advances in optical technology, combined with the increased desire to use non-lethal observation approaches, have driven the development of new sensors and instruments to document marine e cosystems[14], but these instruments generally require an external light source. The use of red light has been suggested for marine surveys requiring external light sources because it is assumed that most species do not react as much to red light as to shorter wavelengths, such as blue or green[22,28,32] In support of this hypothesis, Peña et al.[12] and Underwood et al.[11] deployed oceanographic probes equipped with different light colours and showed that mesopelagic (200–1000 m) fish avoid white, blue and green, but not red light. Behavioural responses to in situ light sources of different colours and irradiance levels on instruments lowered in the upper pelagic layers (< 200 m) remain poorly documented

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Conclusion