Artificial Light at Night Affects Organism Flux across Ecosystem Boundaries and Drives Community Structure in the Recipient Ecosystem

Abstract

Artificial light at night (ALAN) is a widespread alteration of the natural environment that can affect the functioning of ecosystems. ALAN can change the movement patterns of freshwater animals that move into the adjacent riparian and terrestrial ecosystems, but the implications for local riparian consumers that rely on these subsidies are still unexplored. We conducted a 2-year field experiment to quantify changes of freshwater-terrestrial linkages by installing streetlights in a previously light-naïve riparian area adjacent to an agricultural drainage ditch. We compared the abundance and community composition of emerging aquatic insects, flying insects, and ground-dwelling arthropods with an unlit control site. Comparisons were made within and between years using two-way generalized least squares (GLS) model and a BACI design (BeforeAfter Control-Impact). Aquatic insect emergence, the proportion of flying insects that were aquatic in origin, and the total abundance of flying insects all increased in the ALAN-illuminated area. The abundance of several night-active ground-dwelling predators (Pachygnatha clercki, Trochosa sp., Opiliones) increased under ALAN and their activity was extended into the day. Conversely, the abundance of nocturnal ground beetles (Carabidae) decreased under ALAN. The changes in composition of riparian predator and scavenger communities suggest that the increase in aquatic-to-terrestrial subsidy flux may cascade through the riparian food web. The work is among the first studies to experimentally manipulate ALAN using a large-scale field experiment, and provides evidence that ALAN can affect processes that link adjacent ecosystems. Given the large number of streetlights that are installed along shorelines of freshwater bodies throughout the globe, the effects could be widespread and represent an underestimated source of impairment for both aquatic and riparian systems.

Effects of street lighting technologies on the success and quality of pollination in a nocturnally pollinated plant

“…), and may affect diurnal communities as well as nocturnal (Manfrin et al. ). Despite this, little attention has been paid to the potential disruptive effect that artificial light may have on ecosystem services provided by nocturnal organisms (Lewanzik and Voigt ).…”

How dark is a river? Artificial light at night in aquatic systems and the need for comprehensive night‐time light measurements

“…It is well known that many nocturnal insects are attracted by lamps and can become disoriented, exhausted, and finally an easy prey, which has been termed the “vacuum cleaner effect” (Eisenbeis, ). Aquatic insects seem to be particularly affected by ALAN as shown with streetlamps in field studies (Manfrin et al, ; Perkin, Hölker, & Tockner, ) and by studying light polarization at bridges (Szaz et al, ).…”

“…Over larger spatial scales, ALAN can induce food web distortions and influence the transfer of organic matter (here insects) between aquatic and terrestrial ecosystems (Manfrin et al, ; Meyer & Sullivan, ; Perkin et al, ). Predator–prey relationships can be influenced by ALAN as shown for pacific salmon ( Oncorhynchus clarki ) (Mazur & Beauchamp, ), bullheads ( Cottus sp.)…”

“…The presence of ALAN has also shown to alter daytime behavior of certain species. For example, nocturnal riparian spiders shift foraging activities into the day (Manfrin et al, ). Guppies ( Poecilia reticulata ) have shown higher risk taking during the day when being exposed to ALAN in contrast to the control group not exposed to ALAN (Kurvers et al, ).…”

“…Streetlights and lit structures can impose a dispersal barrier for flying insects important for aquatic systems as demonstrated with moths in field experiments (Degen et al, ). Furthermore, illuminated riverside roads form continuous “interaction edges,” where fluxes of organisms and nutrients between aquatic and terrestrial ecosystems may be altered by ALAN (Manfrin et al, , Meyer & Sullivan, ). This can lead, for example, to the fragmentation of habitats solely because of lighting effects.…”