Effects of different types of microplastics on the growth and low molecular weight organic acids release of Dunaliella salina

Microplastics (MPs) have been recognized as a new type of environmental pollutant by the scientific and the public, and long-term exposure to them can have harmful effects on organisms. However, the effects of different types of MPs on the release of low molecular weight organic acids (LMWOAs) from a typical marine microalgae Dunaliella salina is extremely limited. This study investigated the effects of different types of MPs, including polyethylene (PE), polyvinyl chloride (PVC), polystyrene (PS), polyethylene terephthalate (PET) and polytetrafluoroethylene (PTFE), on the cell growth, nutrient utilization and LMWOA release of Dunaliella salina by series cultivation experiments. Results indicated that the mean inhibition rate (IR) values of MPs on Dunaliella salina were in the order of: PTFE (-2.44 %) > PET (-7.39 %) > PVC (-12.10 %) > PS (-13.94 %) > PE (-14.91 %). The removal rates of NO-N in the culture media of the PE, PVC, PS, PET, PTFE and control groups were 94.96 %, 79.47 %, 84.20 %, 85.37 %, 81.61 % and 69.45 %, respectively. Dunaliella salina could release lactic acid, acetic acid and formic acid to the culture media. The mean concentration order of the three LMWOAs in the media during the cultivation period was lactic acid > acetic acid > formic acid. The release of lactic and acetic acid was significantly affected with the additions of PS, PE and PVC in the media. The additions of various MPs also caused accumulations of the three LMWOAs in the media. The results of this study enriched the understanding of the toxicity of different MPs to Dunaliella salina.