Microplastics and food shortage impair the byssal attachment of thick-shelled mussel Mytilus coruscus

Microplastics (MPs) have become a ubiquitous emerging pollutant in the global marine environment. The potential toxic effects of MPs and interactions of MP pollution with other stressors such as food limitation on marine organisms' health are not yet well understood. This study investigated the effects of three-week exposure to different MPs and food shortage on the physical defense mechanisms (byssus production and properties) of Mytilus coruscus. Starvation significantly reduced the number of byssus threads, and combined exposure to MPs and food shortage suppressed the adhesion ability and condition index of mussels. The length of the byssus threads was not affected by all experimental exposures. Transcript levels of genes encoding key proteins involved in byssus formation (the mussel foot proteins mfp-1, -2, -3, -4, -5 and -6, and prepolymerized collagen proteins preCOL-D, -P and -NG) were altered by interactions between the MPs and food shortage. These findings show that insufficient food supply can exacerbate the adverse effects of MPs on mussel defense which might have implications for survival and fitness of mussels under food limited conditions (e.g. in winter) in polluted coastal habitats.