Leachates from pyroplastics alter the behaviour of a key ecosystem engineer

As plastic pollution is increasing rapidly, novel forms of plastic litter have been lately described. One of most recently described type of plastic litter is pyroplastic, i.e. an amorphous matrix derived from the burning of manufactured plastics. We surveyed 12 locations along northern French shores where mussel reefs are a predominant feature. We recorded pyroplastic items at six sites (average weight of 3.34g) mainly made of polyethylene. We then tested the effects of exposure to raw and beached pyroplastic leachates on adaptive behavioural traits of the mussel Mytilus edulis, a key ecosystem engineer. The ability of mussels to move and aggregate were significantly affected by pyroplastic leachates, particularly those from beached pyroplastics. Additionally, the strength of the effects was polymer-dependent, with PE having a more pronounced effects than PP. Our results provide the first evidence that pyroplastics have more severe impacts on living organisms than those triggered by non-burnt plastics.