Evidence of Microplastic Translocation in Wild-Caught Fish and Implications for Microplastic Accumulation Dynamics in Food Webs

The
presence of microplastics within the gut of animals is well
documented. Whether microplastics bioaccumulate in organisms and biomagnify
in food webs remains unclear and relies on the ability of microplastics
to translocate to other tissues. Here, we demonstrate the widespread
presence of microplastics and other anthropogenic microparticles in
the gastrointestinal tract, fillet, and livers of seven species of
sportfish from Lake Simcoe, Ontario, Canada. Larger fish had a higher
microplastic load compared to smaller fish, but the opposite trend
was observed with translocated microplastics standardized by fish
mass (i.e., smaller fish contained more translocated particles per
gram wet weight than larger fish). Moreover, we observed no evidence
of biomagnification as there was no significant relationship between
the trophic level and total or translocated microplastics per individual.
Overall, this suggests that microplastics are translocating, but that
excretion of translocated particles or growth dilution may be occurring
rather than bioaccumulation and biomagnification. Moreover, the assemblages
of shapes and material types varied among tissues, suggesting that
particle characteristics may predict biological fate. Our findings
highlight the need for further work to understand the mechanisms of
microplastic translocation and excretion and the implications for
the dynamics of microplastics accumulation in food webs and human
exposure.