Dr Andrew Brownlow and Nick Davison from the Scottish Marine Animal Stranding Scheme (SMASS), part of SRUC, provided the Scottish samples for the study.
Dr Brownlow said it was a “concerning indication of the state of our oceans”, adding: “While the burden of microplastics was small, in both size and number, and there was no indication that they were causing any direct harm to the animal, we still don't know enough about the effects of ingested microplastics to be confident they are totally benign.
“Given the apparently almost ubiquitous nature of microplastics in our ocean life, this is an area we really need to understand in more detail. This study is an important step in that direction.”
The study saw researchers from the University of Exeter and Plymouth Marine Laboratory (PML) examine 50 animals from ten species of dolphins, seals and whales – and found microplastics (less than 5mm) in them all.
Most of the particles (84 per cent) were synthetic fibres – which can come from sources including clothes, fishing nets and toothbrushes – while the rest were fragments, whose possible sources include food packaging and plastic bottles.
“It’s shocking – but not surprising – that every animal had ingested microplastics,” said lead author Sarah Nelms, of the University of Exeter and PML.
“The number of particles in each animal was relatively low (average of 5.5 particles per animal), suggesting they eventually pass through the digestive system, or are regurgitated. We don’t yet know what effects the microplastics, or the chemicals on and in them, might have on marine mammals. More research is needed to better understand the potential impacts on animal health.”
Though the animals in the study died of a variety of causes, those that died due to infectious diseases had a slightly higher number of particles than those that died of injuries or other causes.
“We can’t draw any firm conclusions on the potential biological significance of this observation,” said Professor Brendan Godley, of the Centre for Ecology and Conservation on the University of Exeter’s Penryn Campus in Cornwall.
“We are at the very early stages of understanding this ubiquitous pollutant. We now have a benchmark that future studies can be compared with. Marine mammals are ideal sentinels of our impacts on the marine environment, as they are generally long lived and many feed high up in the food chain. Our findings are not good news.”
In total, 26 species of marine mammal are known to inhabit or pass through British waters.
The species in this study were: Atlantic white-sided dolphin, bottlenose dolphin, common dolphin, grey seal, harbour porpoise, harbour seal, pygmy sperm whale, Risso’s dolphin, striped dolphin and white-beaked dolphin.
The study, supported by Greenpeace, used samples provided by SMASS, Cornwall Wildlife Trust’s Marine Stranding’s Network and ZSL’s (Zoological Society of London) Cetacean Strandings Investigation Programme (CSIP).
The paper, published in the journal Scientific Reports, is entitled: “Microplastics in marine mammals stranded around the British coast: ubiquitous but transitory?”