Filtration, assimilation and elimination of microplastics by freshwater bivalves

Abstract

The bivalve Anodontites trapesialis, a filter feeder, was assessed as a potential sentinel organism for freshwater microplastic contamination in the South American Pantanal region. There are few studies on microplastic and on the use of bivalves to detect them in waters and sediments of this region. Bivalves were placed in 4 ​L aquariums with 0.3 ​g of polyethylene microparticles varying in size between 55 and 110 ​μm. At increasing exposure times (3 ​h–192 ​h), individuals were collected to assess amounts of filtered, assimilated and eliminated microplastics. Microplastics assimilated in the bivalve tissues, were estimated from histological cuts under polarized light, while in the eliminated feces and pseudofeces, they were counted under a stereomicroscope and polymer type was confirmed by Raman spectrometry. A strong and significant positive correlation was found between filtered microplastics and exposure times. The probability of finding them after 24 ​h of exposure was 78% in gill tissues, and 90% in the eliminated material. The analysis of the particles eliminated from A. trapesialis allows a quick and effective assessment of the presence of microplastics in the ecosystem, avoiding sacrificing the organisms.