Impact of different colors of artificial light at night on phototaxis in aquatic insects

January 3 – Febuary 28, 2021

Meeting Abstract

S1-7  Mon Jan 4 15:00 – 15:30  Impact of different colors of artificial light at night on phototaxis in aquatic insects Hölker, F*; Kühne, JL; Jechow, A; van Grunsven, RHA; Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin, Germany; IGB, Berlin, Germany; IGB, Berlin, Germany; Dutch Butterfly Conservation, Wageningen, The Netherlands

The use of artificial light at night (ALAN) is increasing exponentially worldwide and there is growing evidence that ALAN contributes to the decline of insect populations. Especially light sources with short wavelength emissions have been shown to attract the highest numbers of flying insects. Furthermore, aquatic flying insects are reported to be more vulnerable to ALAN than terrestrial insects. This is concerning because freshwaters are likely affected by ALAN that originates from human activity centers, which are typically close to freshwater systems. However, the effects on aquatic insects, that spend their larval phase or their whole life cycle in freshwaters, are entirely understudied. Here, we investigated phototaxis of aquatic insects to ALAN at different wavelengths and intensities. We used floating light traps and compared 4 near-monochromatic colors at 2 different light intensities in an ALAN-naïve ditch system. Similar to flying insects, we found a strong positive phototaxis of aquatic insects to ALAN. However, there is no preference for short-waved light. Overall, wavelengths in the center of the visible range (green, yellow) cause the strongest attraction. This is likely an adaption to how light propagates in aquatic systems, where the water itself and optical constituents act as a color filter. Also, insects living in freshwater bodies often live in green-dominated environments and might therefore be especially sensitive to green light. In conclusion, the different spectral sensitivities of both aquatic and terrestrial organisms have thus to be taken into account when planning lighting near fresh water systems.

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