Impact of Leachates from Microplastics and Novel Plastic Forms on Mussel Adaptive Behaviour and Self-OrganisationBiogenic Reefs

Katy Nicastro^1,2, Laurent Seuront¹, Nicolas Spilmont¹, Pierre William Froneman³, Gerardo Zardi^4,1,2

¹LOG, France - ²Rhodes University, South Africa - ³Cape Town University, South Africa - ⁴BOREA, France

Self-organised spatial patterns are increasingly recognised for their critical role in ecosystem functioning. These patterns enhance an ecosystem’s capacity to respond to disturbances, thereby increasing its resilience to environmental stress. Meanwhile, plastic pollution has emerged as a major threat to coastal reefs. With the rapid increase in plastic pollution, novel forms of plastic litter have recently been documented.
We investigated the effects of leachates from pyroplastics and microplastics on the adaptive behavioural traits of Mytilus edulis, a key ecosystem engineer. The findings reveal: (i) pyroplastic leachates, especially from beached pyroplastics, significantly impaired the mussels’ ability to move and aggregate; (ii) microplastic leachates from pristine areas hindered small-scale self-organisation, while those from polluted areas completely inhibited it; and (iii) both types of leachates reduced byssal thread production compared to control conditions.
These disruptions to mussel behaviour and self-organising processes could potentially decrease the ecosystem’s capacity to resist tipping points and undermine restoration efforts in disturbed ecosystems. The impairment of these adaptive traits may compromise the mussels’ ability to form stable beds, which are crucial for enhancing ecosystem resilience and functioning.