Artificial Light can affect the diet composition in riparian insects and spiders

Artificial light can affect trophic interactions between aquatic and terrestrial ecosystems. This is clear from an article published in the journal OIKOS under the title “Dietary changes in predators and scavengers in a nocturnally illuminated riparian ecosystem”. In this article is shown that artificial illumination along rivers can change the diet of insects and spiders living in the riparian area by changing quantity and quality of their natural “food”.

Aquatic and terrestrial systems are connected through a flux of material and energy. Aquatic insects represent an important path of this connection as they are an important source of “food” for many predators in the riparian area. Artificial light can affect this path altering the quantity and quality of the aquatic insects that emerge from the water and attracting them towards the sources of illumination.

In this study, stable isotope analysis of carbon (δ13C) was used to understand if the increased amount of aquatic insects, due to artificial illumination, changes the diet composition of terrestrial insects and spiders that feed on them.

The results of the analysis confirmed the study hypothesis: artificial illumination is changing the diet composition of riparian insects and spiders. This new discovery highlights the fact that artificial illumination can cascade through the food chain potentially affecting trophic relationships within and across ecosystems. Also, this study points out the need of further research as artificial illumination might affect directly human activities. This can be the case of agroecosystems, where spiders, changing their natural diet, might release from predation many pest species (e.g. aphids), leading to an uncontrolled increment of these populations.

The authorship of the cited article is by Manfrin Alessandro, David Lehmann, van Grunsven Roy H., Larsen Stefano, Syväranta Jari, Wharton Geraldene, Voigt Christian C., Monaghan Michael T., and Hölker Franz.