es9b06187_si_001.pdf (1.18 MB)
Microplastic Impacts on Microalgae Growth: Effects of Size and Humic Acid
journal contribution
posted on 2020-01-14, 13:11 authored by Ge Liu, Ruifen Jiang, Jing You, Derek C. G. Muir, Eddy Y. ZengResearch
has already demonstrated the toxic effects of microplastics
(MPs) on different biota. However, the underlying toxic mechanism
of MPs remains to be elucidated, especially the effect of particle
size and the presence of dissolved organic matter in water. This study
investigated the impact on Scenedesmus obliquus exposed in five types of polystyrene particle suspensions with different
sizes and surface charges, in the presence and absence of humic acid
(HA). Results indicated that the 50% growth inhibition rate of S. obliquus showed no significant difference between
the five types of MPs, but the toxic mechanism varied with particle
size. Larger size MPs caused adverse effects by blocking the light
transport and affecting photosynthesis, while smaller ones destroyed
the cell wall by adsorbing onto the algae surface. Also, the addition
of HA significantly alleviated the toxicity of smaller size MPs, but
not of the larger ones. Scanning electron microscopy images and the
reactive oxygen species assay demonstrated that the HA could form
a corona on the surface of MPs, reduce the affinity to microalgae,
and minimize the adverse effect. Together, these findings identified
important factors in determining the toxicity of MPs, providing valuable
data for risk assessment of MPs.