Below is a press release about the Methods in Ecology and Evolution article ‘What goes in, must come out: Combining scat‐based molecular diet analysis and quantification of ingested microplastics in a marine top predator‘ taken from Plymouth Marine Laboratory.

Wild grey seals. By Philip Newman, Natural Resources Wales

A brand new method has been developed by scientists at Plymouth Marine Laboratory (PML) and the University of Exeter, in collaboration with Abertay University and Greenpeace Research Laboratories, to investigate links between top predator diets and the amount of microplastic they consume through their prey. It offers potential insights into the exposure of animals in the ocean and on land to microplastics.

An estimated 9.6-25.4 million tonnes of plastic will enter the sea annually by 2025.  Microplastics in particular have been found on the highest mountains and in the deepest seas. New techniques are needed to trace, investigate and analyse this growing concern.

The development of this new non-invasive method was funded by the Natural Environment Research Council (NERC). It combines two existing techniques to analyse wild grey seal (Halichoerus grypus) scats for prey species in the seals’ diet and the presence of microplastics. The scat samples were collected by staff of the Wildlife Trust of South and West Wales (Edward Stubbings, Birgitta Bueche, Sarah Purdon, Sarah Parmor, Sylwia Zbijewska and Nathan Wilkie).

Microplastics pose a growing concern in oceans and other habitats. (©5Gyres, Oregon State University)
Microplastics pose a growing concern in oceans and other habitats. (©5Gyres, Oregon State University)

The first part of the method uses metabarcoding: a molecular technique that uses the DNA present in the scat to identify which prey species have been eaten by the seal. The second part then isolates the microplastics. This allows researchers to assess the quantity of the microplastics and record characteristics, such as shape and colour. With this information, they can get a better understanding of their sources.

By looking at both of these factors together, the method allows scientists to see whether the levels of microplastic exposure in these top predator species are related to the type of prey they’re eating. This is particularly useful because top predators tend to consume microplastics through ‘trophic transfer’ (by eating prey that have already consumed microplastics themselves, which then pass to the predator).

This method could be applied to any top predator. ©Kevin Pluck
This method could be applied to any top predator. ©Kevin Pluck

In organisms lower down the food chain, microplastics can cause effects including intestinal damage, energy depletion and reduced reproduction. They can also act as a carrier for harmful chemical contaminants. By understanding top predator diets, scientists can examine disruptions to food web interactions and potential threats to species and habitats. The method could be used to investigate where the microplastics are coming from, how they’re travelling through the ecosystem and where they’re ending up. This will help researchers to study their fate and effects.

This new technique is not just applicable to top predators in the marine environment. Because the method relies on collected scat, it could be applied to predators in freshwater ecosystems or on land as well. It can be used to build our understanding of the ways that microplastics are impacting every environment on Earth.

Lead author, Dr Sarah Nelms, who completed her PhD with PML and the University of Exeter, said: “Trophic transfer is an indirect, but potentially major, route of microplastic ingestion for top predators. Accessing information on their diet is crucial if we are to understand the extent to which these important animals are exposed to plastic pollution. We hope our new method can unlock this, as yet, understudied area of microplastics research.”

©Miguel Martinez
©Miguel Martinez

Dr Penelope Lindeque, Head of the Marine Plastics Research group at PML, said: “Metabarcoding is a powerful technique which can be used to determine what an animal has eaten by looking at the DNA of the ingested prey in the scat of the predator. This paper has, for the first time, further developed this powerful technology to identify not only what prey a predator has eaten, but also what small pieces of plastic. Unfortunately, as microplastics are now so prevalent in our environment, such novel techniques are needed to help determine the impact of the microplastics and ultimately influence their prevention.”

Read full article:
Nelms SE, Parry HE, Bennett KA, Galloway TS, Godley BJ, Santillo D, and Lindeque PK. What goes in, must come out: Combining scat‐based molecular diet analysis and quantification of ingested microplastics in a marine top predator. Methods in Ecology and Evolution2019;00:1–11.

Media contact:
Bridie Kennerley or Kelly-Marie Davidson, PML Press Team, Email: /