Occurrence of Microplastics in Digestive Tracts of Fish with Different Modes of Ingestion in Japanese Bays and Lake Biwa

Abstract

Microplastics pollution has recently drawn worldwide attention, and may have negative effects on ecosystems. Microplastics are plastic smaller than 5 mm. This study documents microplastics larger than 100 µm in seven fish species from five Japanese bays and Lake Biwa. 197 fish individuals were examined. A total of 140 microplastics particles were found in the digestive tracts of 37.6% of all fish. All species except Sardinella zunasi had ingested microplastics in all areas. The mean number of microplastics particles was 1.89±1.41 per individual fish. Most microplastics were polypropylene （40.7%） and polyethylene （35.0%） as identified by Fourier Transform Infrared Spectrometer （FT-IR）. The median of the mean sizes of microplastics was 543 µm as measured using a microscope and digital camera. The fish species were divided into filter feeders and the others on the basis of modes of ingestion. 54.6% of 97 individuals of filter feeders had ingested microplastics, and the total number of particles was 112. The mean number of microplastics particles in filter feeders was 2.11±1.54 per individual fish. 21.0% of 100 individuals of the others group had ingested microplastics, and the total number of particles was 28. The mean number of microplastics particles in the others group was 1.33±0.80 per individual fish. These results indicated that modes of ingestion influence the fish's ingestion of microplastics. Keywords: Microplastics；Digestive tracts of Fish；Filter feeder；Japan 1 ） 京都大学大学院工学研究科 〒606-8501 京都府京都市左京区吉田本町 2 ） 京都大学大学院地球環境学堂 〒606-8501 京都府京都市左京区吉田本町 3 ） 東京農工大学農学部環境資源科学科 〒183-8509 東京都府中市幸町 3-5-8 ¶