title: Lamp-lit bridges as dual light-traps for the night-swarming mayfly, Ephoron virgo: interaction of polarized and unpolarized light pollution.
abstract: Ecological photopollution created by artificial night lighting can alter animal behavior and lead to population declines and biodiversity loss. Polarized light pollution is a second type of photopollution that triggers water-seeking insects to ovisposit on smooth and dark man-made objects, because they simulate the polarization signatures of natural water bodies. We document a case study of the interaction of these two forms of photopollution by conducting observations and experiments near a lamp-lit bridge over the river Danube that attracts mass swarms of the mayfly Ephoron virgo away from the river to oviposit on the asphalt road of the bridge. Millions of mayflies swarmed near bridge-lights for two weeks. We found these swarms to be composed of 99% adult females performing their upstream compensatory flight and were attracted upward toward unpolarized bridge-lamp light, and away from the horizontally polarized light trail of the river. Imaging polarimetry confirmed that the asphalt surface of the bridge was strongly and horizontally polarized, providing a supernormal ovipositional cue to Ephoron virgo, while other parts of the bridge were poor polarizers of lamplight. Collectively, we confirm that Ephoron virgo is independently attracted to both unpolarized and polarized light sources, that both types of photopollution are being produced at the bridge, and that spatial patterns of swarming and oviposition are consistent with evolved behaviors being triggered maladaptively by these two types of light pollution. We suggest solutions to bridge and lighting design that should prevent or mitigate the impacts of such scenarios in the future. The detrimental impacts of such scenarios may extend beyond Ephoron virgo.
authors: Environmental Optics Laboratory, Department of Biological Physics, Physical Institute, Eötvös University, Budapest, Hungary.
authors: Denes
authors: D
authors: Szaz
authors: Environmental Optics Laboratory, Department of Biological Physics, Physical Institute, Eötvös University, Budapest, Hungary.
authors: Gabor
authors: G
authors: Horvath
authors: Environmental Optics Laboratory, Department of Biological Physics, Physical Institute, Eötvös University, Budapest, Hungary.
authors: Andras
authors: A
authors: Barta
authors: Division of Science, Mathematics and Computing, Bard College, Annandale-on-Hudson, New York, United States of America.
authors: Bruce A
authors: BA
authors: Robertson
authors: Environmental Optics Laboratory, Department of Biological Physics, Physical Institute, Eötvös University, Budapest, Hungary; Danube Research Institute, Centre for Ecological Research, Hungarian Academy of Sciences, Budapest, Hungary.
authors: Alexandra
authors: A
authors: Farkas
authors: Environmental Optics Laboratory, Department of Biological Physics, Physical Institute, Eötvös University, Budapest, Hungary; Danube Research Institute, Centre for Ecological Research, Hungarian Academy of Sciences, Budapest, Hungary.
authors: Adam
authors: A
authors: Egri
authors: Danube Research Institute, Centre for Ecological Research, Hungarian Academy of Sciences, Budapest, Hungary.
authors: Nikolett
authors: N
authors: Tarjanyi
authors: Environmental Optics Laboratory, Department of Biological Physics, Physical Institute, Eötvös University, Budapest, Hungary.
authors: Gergely
authors: G
authors: Racz
authors: Danube Research Institute, Centre for Ecological Research, Hungarian Academy of Sciences, Budapest, Hungary; Group for Methodology in Biology Teaching, Biological Institute, Eötvös University, Budapest, Hungary.
authors: Gyorgy
authors: G
authors: Kriska
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000502:physiology* / Q000528:radiation effects; D004787:Environmental Pollution; D065133:Ephemeroptera / Q000502:physiology / Q000528:radiation effects; D005260:Female; D008027:Light; D008297:Male; D010058:Oviposition / Q000502:physiology* / Q000528:radiation effects