Light pollution from illuminated bridges as a potential barrier for migrating fish–Linking measurements with a proposal for a conceptual model

Polarised light pollution on river water surfaces caused by artificial light at night from illuminated bridges and surroundings

“…Studies on polarisation signals have demonstrated that manmade surfaces, including asphalt roads (Kriska et al, 1998), solar panels (Black and Robertson, 2020), black and grey horizontal reflectors (Malik et al, 2008), black and white cloth (Horváth et al, 2011), cars (Wildermuth and Horvéth, 2005;Kriska et al, 2006), and dark glass surfaces (Malik et al, 2008;Kriska et al, 2008) when illuminated with natural light (sunlight), have polarising properties comparable to those of water surfaces when illuminated and have demonstrated reflected horizontally polarised light likely to turn these surfaces into ecological traps for attracted polarotactic organisms. We have recently raised the issue of ALAN from illuminated bridges in inland waters (Pérez Vega et al, 2024) and also mentioned the problem of PLP from ALAN in a review paper (Hölker et al, 2023). However, so far, no studies have considered PLP from ALAN being reflected at the water's surface.…”

“…This suggests that adult aquatic insects may be more susceptible to the effects of light pollution than terrestrial insects. Furthermore, the illumination of bridges and adjacent areas has been shown to induce different types of potential underwater light barriers with unnatural light variations (Pérez Vega et al, 2024). Since aquatic insects spend most of their life cycle as larvae or nymphs in water and then stay near these aquatic systems as adults, the question arises whether ALAN can induce nocturnal polarisation patterns that can lead to disturbance of flying aquatic insects, many of which are polarotactic.…”