How artifical light at night affects the incrusting community and the dynamics of predation on urbanized coastal habitats?
The benefits of artificial light were noticed immediately, but it's possible damages only began to be discussed over 100 years after being created. The effects of this artificial light at night (ALAN) on terrestrial communities are well known and consolidated, however, in the marine environment, there is still much to know, especially with the expansion of constructions in coastal areas with widespread usage of such lights and a wider and diffuse effect when compared to the terrestrial environment. Considering that, we did three experiments to characterize the coastal artificial lights and their effects on infralittoral fouling communities, specifically on recruitment, consolidated communities, the development and predation on fouling communities, and on the predator community. It was identified that ALAN affects much farther than the installation location in the five cities evaluated in the State of São Paulo, including an increase in the night sky brightness. The artificial lights caused a decrease in the recruitment of some groups such as ascidians of the Didemnidae family and some hydrozoans while favoring an increase in the area covered by a few sponge species in consolidated communities from shallower regions on the marina’s platforms. This effect reducing the differences between fouling communities along the depth gradient. During the development of the communities, ALAN favored an increase in cover area by the bryozoans Savignella lafontii, Crisia sp., and the ascidian Botrylloides niger, while reducing the coverage area of the bryozoans Schizoporella errata, Hippopodina sp. and the ascidian Didemnum perlucidum, changing the community structure, but not the indetity of species. ALAN also did not interfere with the predation intensity, maybe due to the strong generalist predation or predator species composition. This way, ALAN presented effects over important processes, such as recruitment and the abundance of some species, which will affect the structure of the fouling communities in the subtropical South hemisphere, corroborating previously seen effects for temperate regions, and showing a necessity for management plans to minimize the effects of ALAN over coastal ecosystems.