PS 43-65 - CANCELLED - High β-diversity among sites, but limited direct effects of artificial light at night, characterizes urban stream macroinvertebrate assemblages

Background/Question/Methods

Artificial light at night (ALAN) is growing ecological issue that is pervasive in urban environments, yet its potential effects on biotic communities of urban streams are not fully understood. In 20 lit-unlit paired stream reaches in Columbus, Ohio, USA, we investigated the effects of ALAN on benthic macroinvertebrate assemblages.

Results/Conclusions

Our results show that light trespass into urban streams is approximately twice as great during leaf-off in winter months (1.97 lux ± 0.28) compared to leaf-on in summer months (1.00 lux ± 0.19), indicating an important interceptive effect of canopy coverage in headwater systems. We found no differences in macroinvertebrate assemblages between lit and unlit reaches, but our sites were characterized by high β-diversity. Our results suggest that the relatively low-levels of ALAN observed in canopied streams may exert only subtle effects on small stream macroinvertebrate assemblages, which are difficult to detect amongst the multiple, confounded stressors impacting these systems. Finely tuned experimental approaches or large-scale manipulative studies may be necessary to isolate the effects of ALAN in complex urban environments.