Microplastics are love-killers for Pacific oysters!

The effects of long-term exposure to microplastics on the reproductive characteristics of the Pacific oyster (Crassostrea gigas) were studied. During their gametogenesis, oysters were exposed or not (control), for two month, to polystyrene beads (diameter 2 and 6 μm, concentration:1800 and 200 ml-1 respectively). During the reproductive period, gamete characteristics were
assessed by studying oocyte quantity and quality (flow cytometry, D-larval yield) and sperm biological features (image analysis and flow cytometry).
A significantly lower number of oocytes (38%) was collected after gonad stripping in microplastic exposed oysters as compared to control ones. Oocyte relative size of oysters exposed to microplastics was significantly lower (8%) than values observed for control. On the other hand, no significant differences were recorded between the two oyster groups for oocyte ROS production
and viability. For sperm, no significant differences were observed between the two oyster groups for the following parameters: sperm viability and morphology, mitochondrial membrane potential, ROS production and the percentage of motile spermatozoa. However, sperm movement speed from oysters exposed to microplastics was 23% lower than that from control oysters.
Furthermore, the D-larval yield estimated 48h post fertilization, decreased by 41% for larvae produced from female oysters exposed to microplastics as compared to control ones.
In the present study, we demonstrated that the exposure of ripening oysters to microplastic particles reduced their fecundity, gamete quality and fertilization success.