Papers

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Article Tier 2

Occurrence of Microplastics in Harbour Seals (Phoca vitulina) and Grey Seals (Halichoerus grypus) from German Waters

The gastrointestinal tracts of 63 harbour and grey seals from German North Sea and Baltic Sea waters were examined for microplastics, with 540 suspected particles identified in intestinal samples and 228 in stomach samples, predominantly fibers and fragments. No significant correlations were found between microplastic presence and parasite infestation or inflammatory responses, though fragments showed evidence of retention in the gut.

2022 Animals 12 citations
Article Tier 2

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

Researchers analyzed fecal samples from grey seals in the North Sea and found 71 microplastic particles — mostly fibers and fragments — confirming that wild marine mammals in European waters are ingesting microplastics through their prey. Marine mammals at the top of the food chain can accumulate microplastics from the fish they eat.

2021 Research Square (Research Square) 3 citations
Article Tier 2

Microplastics in marine mammals stranded around the British coast: ubiquitous but transitory?

Researchers examined whole digestive tracts of 50 stranded marine mammals from 10 UK species and found microplastics in every animal (mean 5.5 particles). The low numbers and predominance in stomachs versus intestines suggest particles are largely transitory rather than accumulating permanently in marine mammal guts.

2025 Figshare
Article Tier 2

Microplastics in marine mammals stranded around the British coast: ubiquitous but transitory?

Researchers examined the entire digestive tracts of 50 stranded marine mammals from 10 species around the British coast and found microplastics in every single animal. However, the relatively low particle counts suggest that microplastics may pass through the gut rather than accumulate permanently. The findings indicate that microplastic ingestion is ubiquitous among marine mammals, though the long-term health consequences remain unclear.

2019 Scientific Reports 367 citations
Article Tier 2

Ingestion of microplastics and occurrence of parasite association in Mediterranean anchovy and sardine

Scientists quantified microplastic ingestion in European sardines and anchovies from the Northwestern Mediterranean, finding 58–60% occurrence rates and noting that parasite infection was negatively associated with microplastic presence, suggesting shared ecological or physiological factors.

2020 Marine Pollution Bulletin 91 citations
Article Tier 2

Using a non‐invasive technique to identify suspected microplastics in grey seals ( Halichoerus grypus ) living in the western North Sea

Faecal samples from living wild grey seals in the western North Sea were analyzed for suspected microplastics, representing the first non-invasive record of microplastic exposure in this wild pinniped population. The study demonstrates that faecal analysis can provide indirect evidence of microplastic ingestion in free-ranging marine mammals without requiring capture or euthanasia.

2022 Veterinary Record 10 citations
Article Tier 2

Investigating microplastic trophic transfer in marine top predators

Researchers investigated trophic transfer of microplastics in grey seals by analyzing digestive tracts of wild-caught Atlantic mackerel (fed to captive seals) alongside seal scat. Microplastics were detected in both prey fish and seal scat, providing empirical in natura evidence for trophic transfer in a marine top predator.

2025 Figshare
Article Tier 2

Handle with Care—Microplastic Particles in Intestine Samples of Seals from German Waters

Researchers found microplastic particles — mostly fragments and fibers — in the intestines and feces of harbor seals and grey seals in German North Sea and Baltic Sea waters. This confirms microplastics have reached marine mammal top predators, raising concerns about contamination throughout the food chain.

2020 Sustainability 17 citations
Article Tier 2

Incidence of marine debris in cetaceans stranded and bycaught in Ireland: Recent findings and a review of historical knowledge

This study examined stranded and bycaught cetaceans in Ireland and found plastic debris — including microplastics — in a substantial portion of the animals, with ingestion increasing over the sampling period. The findings highlight that marine mammals in Atlantic waters face growing exposure to plastic pollution.

2017 Environmental Pollution 214 citations
Article Tier 2

Opportunistic detection of anthropogenic micro debris in harbor seal (Phoca vitulina vitulina) and gray seal (Halichoerus grypus atlantica) fecal samples from haul-outs in southeastern Massachusetts, USA.

This study opportunistically detected anthropogenic micro debris including cellophane and synthetic rubber in the fecal samples of harbor and gray seals in Massachusetts, finding plastic fragments in a small percentage of individuals. The findings confirm that these marine mammals are ingesting human-made debris, likely through contaminated prey, and suggest that seal fecal analysis is a practical monitoring approach.

2019 Marine pollution bulletin
Article Tier 2

Investigating microplastic trophic transfer in marine top predators

Researchers investigated whether microplastics can transfer through the food chain by analyzing the scat of captive grey seals and the wild mackerel they were fed. They found microplastics in about half of the seal scat samples and a third of the fish, with similar particle types in both. The study suggests that trophic transfer is a plausible route for microplastics to move up marine food chains to top predators.

2018 Environmental Pollution 978 citations
Systematic Review Tier 1

Marine mammals and microplastics: A systematic review and call for standardisation

Microplastics were found in the gastrointestinal tracts of marine mammals in all but one of 30 studies reviewed, with 0-88 particles per animal, and were detected in pinniped scat in 8 of 10 studies, though considerable methodological inconsistencies make cross-study comparisons difficult.

2020 Environmental Pollution 235 citations
Article Tier 2

Assessing microplastic distribution within infaunal benthic communities in a coastal embayment

Researchers assessed microplastic contamination in benthic infauna from 20 subtidal stations in Galway Bay, Ireland, finding an average of 0.79 particles per individual with fibers as the dominant type. Results were comparable to North Sea subtidal fauna studies, suggesting consistent microplastic uptake patterns across European coastal benthic communities.

2021 The Science of The Total Environment 34 citations
Article Tier 2

A Quantitative Analysis of Microplastics in the Gastrointestinal Tracts of Odontocetes in the Southeast Region of the United States

Researchers quantified microplastic accumulation in the gastrointestinal tracts of toothed whales from the southeastern United States. The study found microplastics present in all examined specimens, indicating that these marine mammals are routinely ingesting microplastic particles from their ocean environment.

2024 Environmental Toxicology and Chemistry 3 citations
Article Tier 2

Association of zoonotic protozoan parasites with microplastics in seawater and implications for human and wildlife health

Researchers found that zoonotic protozoan parasites, including Cryptosporidium and Giardia, can associate with microplastics in seawater, suggesting that microplastics may serve as vectors for these pathogens. The study raises concerns that ingestion of parasite-laden microplastics by marine animals, including those consumed by humans, could pose risks to both wildlife and human health.

2022 Scientific Reports 66 citations
Article Tier 2

No accumulation of microplastics detected in western Canadian ringed seals (Pusa hispida)

Researchers examined stomach contents of ten ringed seals (Pusa hispida) harvested from the Inuvialuit Settlement Region in the western Canadian Arctic and detected no microplastic particles of 80 micrometers or larger, suggesting limited microplastic accumulation in this species despite the Arctic acting as a potential sink for anthropogenic debris.

2023 Marine Pollution Bulletin 5 citations
Article Tier 2

Ingestion of microplastics by fish and other prey organisms of cetaceans, exemplified for two large baleen whale species

Researchers reviewed microplastic contamination in the prey species of minke and sei whales, finding microplastics were widespread in krill, fish, and other whale food. Since cetaceans consume large quantities of these prey, they are likely ingesting significant amounts of microplastics indirectly through their diet.

2019 Marine Pollution Bulletin 58 citations
Article Tier 2

Documentation of Microplastics in Tissues of Wild Coastal Animals

Researchers investigated microplastic contamination in organs and tissues of fish, seabirds, and marine and terrestrial mammals from a polluted coastal area near Bergen, Norway. They found microplastics in the gastrointestinal tracts and other organs of multiple species, with polymer types and concentrations varying across animals. The study provides important baseline data on microplastic accumulation in wild coastal species relevant to human food chains.

2021 Frontiers in Environmental Science 71 citations
Article Tier 2

Preliminary Study on Microplastic Contamination in Black Sea Cetaceans: Gastrointestinal Analysis of Phocoena phocoena relicta and Tursiops truncatus ponticus

Researchers conducted a preliminary study of microplastic contamination in the gastrointestinal tracts of Black Sea harbor porpoises and bottlenose dolphins, documenting microplastic presence and characterizing particle types and polymer compositions.

2024 Animals 6 citations
Article Tier 2

Understanding the occurrence and fate of microplastics in coastal Arctic ecosystems: The case of surface waters, sediments and walrus (Odobenus rosmarus)

This holistic study examined microplastics in Arctic surface waters, sediments, and walrus tissues in coastal Svalbard, detecting plastics across all compartments and documenting for the first time microplastic occurrence in walrus gastrointestinal tracts.

2021 The Science of The Total Environment 68 citations
Article Tier 2

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

By combining molecular diet analysis from seal scat with quantification of ingested microplastics, researchers found that a marine top predator was regularly ingesting plastic particles, with exposure likely mediated through prey species that had themselves ingested plastics. The study demonstrates trophic transfer of microplastics through a food chain to a marine mammal predator.

2019 Methods in Ecology and Evolution 64 citations
Article Tier 2

Tissue-specific microplastic burden in cetacean non-digestive organs

Researchers analyzed microplastic accumulation in non-digestive tissues of nearshore and offshore cetacean species and found widespread contamination, with detection rates exceeding 75% across organs including heart, liver, and lung. The characteristics of microplastics varied more between tissue types than between species, suggesting that organ physiology influences particle accumulation patterns. The study emphasizes the importance of examining multiple tissues to understand the full extent of microplastic pollution in marine mammals.

2025 Environmental Research 1 citations
Article Tier 2

No microplastics detected in the first assessment of Atlantic walrus stomachs from Nunavut, Canada

Examination of stomach contents from 36 Atlantic walruses harvested across five Inuit communities in Nunavut, Canada, found no microplastics at or above an 80 µm detection threshold — a surprising result given that walruses feed on benthic invertebrates in sediment known to accumulate microplastics elsewhere. The study represents the first global assessment of microplastic ingestion in walruses and suggests that at least some Arctic megafauna may not be significantly retaining microplastics, possibly due to digestive anatomy or regional pollution levels. The findings provide a useful baseline for tracking future changes as plastic pollution in the Canadian Arctic increases.

2023 Arctic Science 7 citations
Article Tier 2

Occurrence of microplastics in commercial fish from a natural estuarine environment

Researchers examined the gastrointestinal tracts of commercial fish caught from a natural estuarine environment and found microplastics in a significant proportion of individuals, documenting both occurrence rates and particle characteristics.

2018 Marine Pollution Bulletin 586 citations