Coastal urban lighting has ecological consequences for multiple trophic levels under the sea

D Bolton; M Mayer-Pinto; G F Clark; K A Dafforn; W A Brassil; A Becker; E L Johnston

doi:10.1016/j.scitotenv.2016.10.037

Coastal urban lighting has ecological consequences for multiple trophic levels under the sea

Sci Total Environ. 2017 Jan 15:576:1-9. doi: 10.1016/j.scitotenv.2016.10.037. Epub 2016 Oct 22.

Authors

D Bolton¹, M Mayer-Pinto², G F Clark¹, K A Dafforn³, W A Brassil¹, A Becker⁴, E L Johnston³

Affiliations

¹ Evolution and Ecology Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, Australia.
² Evolution and Ecology Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, Australia; Sydney Institute of Marine Sciences, Mosman, NSW 2088, Australia. Electronic address: m.mayerpinto@unsw.edu.au.
³ Evolution and Ecology Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, Australia; Sydney Institute of Marine Sciences, Mosman, NSW 2088, Australia.
⁴ NSW Department of Primary Industries, Port Stephens Fisheries Institute, Taylors Beach, NSW, Australia.

PMID: 27780095
DOI: 10.1016/j.scitotenv.2016.10.037

Abstract

Urban land and seascapes are increasingly exposed to artificial lighting at night (ALAN), which is a significant source of light pollution. A broad range of ecological effects are associated with ALAN, but the changes to ecological processes remain largely unstudied. Predation is a key ecological process that structures assemblages and responds to natural cycles of light and dark. We investigated the effect of ALAN on fish predatory behaviour, and sessile invertebrate prey assemblages. Over 21days fish and sessile assemblages were exposed to 3 light treatments (Day, Night and ALAN). An array of LED spotlights was installed under a wharf to create the ALAN treatments. We used GoPro cameras to film during the day and ALAN treatments, and a Dual frequency IDentification SONar (DIDSON) to film during the night treatments. Fish were most abundant during unlit nights, but were also relatively sedentary. Predatory behaviour was greatest during the day and under ALAN than at night, suggesting that fish are using structures for non-feeding purposes (e.g. shelter) at night, but artificial light dramatically increases their predatory behaviour. Altered predator behaviour corresponded with structural changes to sessile prey assemblages among the experimental lighting treatments. We demonstrate the direct effects of artificial lighting on fish behaviour and the concomitant indirect effects on sessile assemblage structure. Current and future projected use of artificial lights has the potential to significantly affect predator-prey interactions in marine systems by altering habitat use for both predators and prey. However, developments in lighting technology are a promising avenue for mitigation. This is among the first empirical evidence from the marine system on how ALAN can directly alter predation, a fundamental ecosystem process, and have indirect trophic consequences.

Keywords: Artificial light; Artificial structures; Fish; Fouling communities; Marine systems; Predation; Urban ecology.