Exposure of marine mussels Mytilus spp. to polystyrene microplastics: Toxicity and influence on fluoranthene bioaccumulation.
The effects of polystyrene microbeads (micro PS; mix of 2 and 6 mm; final concentration: 32 mg L( 1) alone or in combination with fluoranthene (30 mg L( 1) on marine mussels Mytilus spp. were investigated after 7 days of exposure and 7 days of depuration under controlled laboratory conditions. Overall, fluoranthene was mostly associated to algae Chaetoceros muelleri (partition coefficient Log Kp 4.8) used as a food source for mussels during the experiment. When micro PS were added in the system, a fraction of FLU transferred from the algae to the microbeads as suggested by the higher partition coefficient of micro PS (Log Kp 6.6) which confirmed a high affinity of fluoranthene for polystyrene microparticles. However, this did not lead to a modification of fluoranthene bioaccumulation in exposed individuals, suggesting that micro PS had a minor role in transferring fluoranthene to mussels tissues in comparison with waterborne and foodborne exposures. After depuration, a higher fluoranthene concentration was detected in mussels exposed to micro PS and fluoranthene, as compared to mussels exposed to fluoranthene alone. This may be related to direct effect of micro PS on detoxification mechanisms, as suggested by a down regulation of a P glycoprotein involved in pollutant excretion, but other factors such as an impairment of the filtration activity or presence of remaining beads in the gut cannot be excluded. Micro PS alone led to an increase in hemocyte mortality and triggered substantial modulation of cellular oxidative balance: increase in reactive oxygen species production in hemocytes and enhancement of anti oxidant and glutathione related enzymes in mussel tissues. Highest histopathological damages and levels of anti oxidant markers were observed in mussels exposed to micro PS together with fluoranthene. Overall these results suggest that under the experimental conditions of our study micro PS led to direct toxic effects at tissue, cellular and molecular levels, and modulated fluoranthene kinetics and toxicity in marine mussels.
Environmental pollution