Artificial light at night as a possible driver of E. virgo (Ephemeroptera) decline in a section of the Ebro River

Abstract We studied the evolution of the dusk emerging insect, Ephoron virgo , in a section of the Ebro River (Spain), to estimate the impact of artificial light at night (ALAN) on its population. We analyzed the spatiotemporal patterns of benthic larval densities of E. virgo in 85 km of the river and estimated the number of adults attracted annually during emergence to a bridge with street illumination considered to induce light pollution. E. virgo benthic larvae density decreased with time and proximity to the bridge despite improved water quality. Emergence magnitude at the Tudela Bridge was also declining. We calculated through very conservative estimations that the streetlamps system in the bridge could retain the entire population of this species from up to 20 km of the river benthos. Our findings suggest that ALAN is a potential driver in the reduction of the E. virgo population and could affect its viability.