Microplastic fragments and microbeads in digestive tracts of planktivorous fish from urban coastal waters

Abstract

We investigated microplastics in the digestive tracts of 64 Japanese anchovy (Engraulis japonicus) sampled in Tokyo Bay. Plastic was detected in 49 out of 64 fish (77%), with 2.3 pieces on average and up to 15 pieces per individual. All of the plastics were identified by Fourier transform infrared spectroscopy. Most were polyethylene (52.0%) or polypropylene (43.3%). Most of the plastics were fragments (86.0%), but 7.3% were beads, some of which were microbeads, similar to those found in facial cleansers. Eighty percent of the plastics ranged in size from 150 μm to 1000 μm, smaller than the reported size range of floating microplastics on the sea surface, possibly because the subsurface foraging behavior of the anchovy reflected the different size distribution of plastics between surface waters and subsurface waters. Engraulis spp. are important food for many humans and other organisms around the world. Our observations further confirm that microplastics have infiltrated the marine ecosystem, and that humans may be exposed to them. Because microplastics retain hazardous chemicals, increase in fish chemical exposure by the ingested plastics is of concern. Such exposure should be studied and compared with that in the natural diet.

Figure 1. Sampling location in Tokyo Bay.

Sixty-four Japanese anchovy (Engraulis japonicus) were caught on 23 August 2015. Map created using QGIS and data provided by the Geospatial Information Authority of Japan.

Figure 2. Spectra of FT-IR analysis and photographs of plastic fragments.

All suspected plastics were identified by FT-IR and photographed. Two examples are shown.

Figure 3. Types of plastics recovered from digestive tracts of Japanese anchovy (Engraulis japonicus).

(a) Percentage by shape. (b) Percentage by polymer.

Figure 4. Photographs of microbeads ingested by Japanese anchovy (Engraulis japonicus).

Scale bar represents 500 μm. All photographs were taken in reflected light, but in the case of d, only photographs taken with transmitted light are available.

Figure 5. Size distribution of plastics in Japanese anchovy (Engraulis japonicus).

Figure 6. Photographs of polyethylene microbeads in four brands of facial cleansers.

(a) Brand M1, irregular shapes. (b) Brand M2, blue and transparent spheres and irregular shapes. (c) Brand R1, irregular shapes. (d) Brand S1, transparent spheres.