It seems like we discover a new negative consequence of plastic pollution every other week. Here's the latest. According to an article form Nationofchange.org, a marine ecologist named Ignacio Gestoso first discovered strange crust-like formations on the shoreline of the Portuguese island of Madeira in 2016. Over a three year period, this plasticrust grew to cover almost 10 precent of the rocks' surface. Chemical analysis revealed that the crust was polyethylene. Polyethylene is a very common plastic used in many common single-use plastic items.
“[The crusts] likely originated by the crash of large pieces of plastic against the rocky shore, resulting in plastic crusting the rock in a similar way algae or lichens do,” Gestoso told Gizmodo Earther in another article covering the topic. The initial concern is that the plasticrust is gradually replacing the natural biological crusts that barnacles and snails adhere to and feed from. It will take time to study these effects, but it is unlikely positive one given plastic pollution's effect on sea life and other creatures.
The findings were published in the journal of Science of The Total Environment where the authors explained this never before seen plastic pollution phenomena.