Effects of Different Microplastic Types and Surfactant-Microplastic Mixtures Under Fasting and Feeding Conditions: A Case Study on Daphnia magna.

This study evaluates the mortality and immobilization on Daphnia magna after 24-96 h of exposure to microplastic dispersions (PP, PE, PVC, PVC/PE), and to microplastic + surfactant solutions both under fasting and feeding conditions. The tested microplastics were analysed with μFT-IR to determine their chemical composition, purity, and dimensions. The results show that: (i) exposure under fasting conditions produces acceptable results on negative controls no later than 24 h; (ii) the dispersion of microplastics forms homo-agglomerates that are able to affect animals' motility and cause mortality and immobilization; (iii) different types of tested microplastic produce different effects on endpoints (the most toxic is PVC + surfactant); (iv) in all cases, the effects were reduced under feeding conditions (i.e. 4 times reduction of PE toxicity); (v) effects of surfactant on observed toxicity are microplastic-type dependent; (vi) the age of the animal affected the mortality and immobilization responses after exposure under both fasting and feeding conditions.