Assessing the impact of suspended irregular microplastics on the mortality of herring and cod eggs

The increasing prevalence of microplastics in the marine environment has raised concerns about their impact on aquatic ecosystems and inspired many studies on the biological effects of the particles. However, we are still lacking knowledge about their potential effects on vulnerable early life stages of key species. To fill this gap, we investigated the physical and mechanical effects of microplastics on the eggs of Gulf herring (Clupea harengus membras) and Atlantic cod (Gadus morhua). Unlike previous studies that primarily used unweathered, spherical microplastics, our experiments employed partially degraded PE and PP microplastics collected from an oceanic garbage patch (220–1000 µm). Considering not only the presence of suspended microplastics but also their morphology, we compared the influences of sharp-edged and round-edged particles on fish embryo mortality. Our results showed no significant adverse effects of the microplastics on the mortality of herring and cod eggs, regardless of their shape. These results add to the growing body of evidence that the impact of microplastics on early life stages of fish, particularly at environmentally relevant concentrations, may be less severe than previously thought.