Determination of microplastics in the wetlands of specific regional area and unveiling the toxic properties of predominant HDPE particle on animal and plant models

Microplastics are emerging environmental pollutants that cause a great threat to all forms of living organisms. However, the information on MPs existence in freshwater sources and its environmental implications on freshwater associated flora and fauna remain limited. Hence, the present study was designed to identify the presence of MPs in the sediments of major wetlands of Coimbatore, Tamilnadu, India and to assess the toxicity of predominantly detected MPs in animal and plant models. In this study, six different types of MPs such as filaments (FI), fragments (F), irregular filaments (IF), pellets (P), films (FM) and colored fragments (CF) were identified from the samples through Phase contrast and Scanning Electron Microscopy. Besides, high Density Polyethylene (HDPE) was identified as predominant MPs from the wetlands by micro-Raman spectroscopy analysis and hence, HDPE has been selected for further toxicity assessment studies. In toxicity study, HDPE exposure significantly affected the phenotype, survival and hatching rate, heart shape and function of the zebrafish embryos. Moreover, HDPE toxicity significantly increased the expression pattern of major stress marker genes such as P5CS, CAT, SOD and APX1 in Sorghum bicolor plant. This study spotlighted the presence of MPs in major wetlands of Coimbatore and elucidated the toxicity nature of predominant MPs pollutant HDPE in zebrafish embryos and major agriculture crop S. bicolor as the first report.