Morphometric effects of various weathered and virgin/pure microplastics on sac fry zebrafish (Danio rerio)

Microplastics (5 mm to1 nm) and plasticizers are ubiquitous worldwide in waterways, beaches, sediments, and biota. Ingestion of microplastics by various marine species and bioaccumulation of plasticizers continues to be of concern. Additionally, microplastics act as a carrier for the transport of persistent organic pollutants and some harmful microorganisms, increasing the hazard to aquatic species. Microplastics vary in composition based on their monomeric component and the specific plasticizer(s). There is a large data gap in our understanding of the biological toxicity of the different plastic polymers. The results presented here examine gross morphological alterations in sac fry zebrafish as a result of exposure to weathered microplastics and virgin/pure plastic polymers. Embryos were exposed from 3 hours post fertilization (hpf) to 96 hpf with samples of weathered microplastics from estuaries in Newark Bay, NJ, as well as commercially available virgin/pure plastics at concentrations of 1 µg/mL or 10 µg/mL. The Newark Bay microplastics were chemically identified using pyrolysis GC-MS. The three field samples were composed primarily of polyethylene (FPE), polypropylene (FPP) and polyvinyl chloride vinyl acetate mixture (FVA). Significant morphometric changes (P < 0.05) were noted between the control zebrafish and the treated groups in the embryonic zebrafish samples for the Newark Bay, weathered samples following statistical analysis of morphometric data. The commercial microplastics tested included: low density polyethylene (LDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), sodium polyacrylate (SPA), polyethylene terephthalate (PET), polyurethane (PUR), poly methyl-methacrylate (PMMA), polyethylene (co-vinyl-acetate) (PEVA), and polystyrene (co-acrylonitrile) (PSAN). Significant changes were seen in total body length in all three Newark Bay field sample microplastics, as well as virgin/pure microplastic treatment groups PET, PUR, PMMA. The pericardial sac size was found significantly altered in FPP 10 µg/mL sample plastic as well as pure microplastic treatment groups HDPE, SPA, PET, PUR, PMMA, PP, and PEVA. The interocular distance was found to be significantly changed in the pure microplastic treatment groups HDPE and PET. The pericardial sac size was the most sensitive endpoint measured followed by total body length. The least sensitive endpoint was interocular distance. These results highlight the associated toxicity with both weathered and lab standard grade microplastics exposure to treated zebrafish developing embryos. The laboratory induced cardiac and growth alterations following laboratory microplastic exposure could be examined in field populations exposed to high microplastic concentrations.