What goes in, must come out: Combining scat‐based molecular diet analysis and quantification of ingested microplastics in a marine top predator

Abstract

Microplastics (plastic particles <5 mm in size) are highly available for ingestion by a wide range of organisms, either through direct consumption or indirectly, via trophic transfer, from prey to predator. The latter is a poorly understood, but potentially major, route of microplastic ingestion for marine top predators. We developed a novel and effective methodology pipeline to investigate dietary exposure of wild top predators (grey seals; Halichoerus grypus) to microplastics, by combining scat‐based molecular techniques with a microplastic isolation method. We employed DNA metabarcoding, a rapid method of biodiversity assessment, to garner detailed information on prey composition from scats, and investigated the potential relationship between diet and microplastic burden. Outcomes of the method development process and results of both diet composition from metabarcoding analysis and detection of microplastics are presented. Importantly, the pipeline performed well and initial results suggest the frequency of microplastics detected in seal scats may be related to the type of prey consumed. Our non‐invasive, data‐rich approach maximizes time and resource–efficiency, while minimizing costs and sample volumes required for analysis. This pipeline could be used to underpin a much‐needed increase in understanding of the relationship between diet composition and rates of microplastic ingestion in high trophic level species.

In situ and low-cost monitoring of particles falling from freshwater animals: from microplastics to parasites

“…This novel approach is cheap and mobile, and can be used in other type of environmental studies (e.g. faeces-based molecular diet analyses and ingested microplastic quantification) ( Nelms et al ., 2019 ) using fishes and other aquatic animals (e.g. crayfish and other macroinvertebrates, amphibians).…”

Effects of pollution on marine organisms

“…Multiple papers explored the ability of marine mammals scat to provide information on the prevalence of microplastic ingestion in marine mammals. Nelms, Parry, et al (2019) published noninvasive methods using molecular techniques to analyze scat for diet composition and isolation methods to quantify microplastics in scat samples. Nelms, Barnett, et al (2019) measured microplastics in digestive tracts of 50 marine mammals (representing 10 species) stranded in the United Kingdom, and detected particles in all 50 individuals.…”

Investigating Microplastic Presence Amongst Grey Seals (Halichoerus Grypus) of the North Sea

“…Whether originally manufactured as microscopic in size (for instance, bres), or formed through the degradation of larger items of plastic debris 9 , microplastics have accumulated in our oceans for over 40 years 10 and now pervade even some of the most remote environments 5,11 . As such, these synthetic particles are believed to be ubiquitous within marine ecosystems worldwide 7,9,12 . Consequently, better understanding of the potential ecological rami cations of microplastic pollution is a globally recognised high-priority research area in Marine Biology 13 .…”

“…Although several papers report the presence of microplastics amongst marine mammals 5,17,19,[30][31][32] , research typically relies on necropsies performed on stranded or by-caught individuals 33 -providing few occasions to study anthropogenic contaminants 32 and with relatively small sample sizes from individuals that have died, and may have been feeding abnormally pre-mortem 12 . Alternatively, scat analysis offers the opportunity to obtain data on microplastic exposure in live, wild and free-ranging pinnipeds through a non-invasive and humane manner 18,21 .…”

“…Alternatively, scat analysis offers the opportunity to obtain data on microplastic exposure in live, wild and free-ranging pinnipeds through a non-invasive and humane manner 18,21 . This could permit the analysis of larger sample sizes, which may provide more representative estimates of microplastic pollution amongst wider populations 12 . Nonetheless, scat-based microplastic investigations on wild pinnipeds are sparse and none exist for grey seals inhabiting the North Sea.…”