Sarah E. Nelms, Tamara S. Galloway, Brendan J. Godley, Dan S. Jarvis, Penelope K. Lindeque,
Investigating microplastic trophic transfer in marine top predators,
Environmental Pollution, 2018, ISSN 0269-7491,
Microplastics are highly bioavailable to marine organisms, either through direct ingestion, or indirectly by trophic transfer from contaminated prey. The latter has been observed for low-trophic level organisms in laboratory conditions, yet empirical evidence in high trophic-level taxa is lacking. In natura studies face difficulties when dealing with contamination and differentiating between directly andindirectly ingested microplastics.
The ethical constraints of subjectinglarge organisms, such as marine mammals, to laboratory investigations hinder the resolution of these limitations. Here, these issues were resolved by analysing sub-samples of scat from captive grey seals (Halichoerus grypus) and whole digestive tracts of the wild-caughtAtlantic mackerel (Scomberscombrus) they are fed upon. An enzymaticdigestion protocol was employed to remove excess organic material andfacilitate visual detection of synthetic particles without damagingthem. Polymer type was confirmed using Fourier-Transform Infrared (FTIR) spectroscopy.
Extensive contamination control measures were implementedthroughout. Approximately half of scat subsamples (48%; n = 15) and a third of fish (32%; n = 10) contained 1–4 microplastics. Particles weremainly black, clear, red and blue in colour. Mean lengths were 1.5 mm and 2 mm in scats and fish respectively. Ethylene propylene was the most
frequently detected polymer type in both. Our findings suggest trophic transfer represents an indirect, yet potentially major, pathway ofmicroplastic ingestion for any species whose feeding ecology involves the consumption of whole prey, including