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

Changes in the abundance, concentration, and composition of the microplastics and fibers in gray seals (Halichoerus Grypus Atlantica) scat on Nantucket Island in July and November 2019 and January 2020

Researchers documented the first report of microplastics and fibers in gray seal scat from Nantucket Island, finding contamination in 100% of samples with an average of 34 particles per scat sample. The composition and abundance of microplastics varied by season, with July samples containing the most contamination and November samples dominated by smaller particles. Polyester and nylon were the most common synthetic polymers found, with seasonal changes suggesting shifts in diet or plastic inputs through the food web.

2025 Marine Pollution Bulletin 1 citations
Article Tier 2

Evaluating exposure of northern fur seals, Callorhinus ursinus, to microplastic pollution through fecal analysis

Fecal samples from 44 northern fur seals across their eastern Pacific range were analyzed for microplastics, with plastic fragments found in 55% and fibers in 41% of scats, and a mean of 16.6 fragments/scat among positive samples. The study documents microplastic exposure in a marine mammal species consumed by humans, raising questions about potential exposure during subsistence harvesting.

2018 Marine Pollution Bulletin 88 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 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

No evidence of microplastics in Antarctic fur seal scats from a hotspot of human activity in Western Antarctica

Examination of Antarctic fur seal feces from Deception Island revealed no microplastics among the fragments and fibers recovered, which were instead identified as silicate minerals and chitin from prey. The findings suggest that microplastic pollution levels in the pelagic food web of the western Antarctic Peninsula region remain very low.

2020 The Science of The Total Environment 53 citations
Article Tier 2

A review on microplastics in mammalian feces: Monitoring techniques and associated challenges

Researchers reviewed how microplastics appear in the feces of humans, dogs, cats, and marine mammals, finding PET plastic to be the most common type across species. Analyzing feces offers a non-invasive way to track how much plastic organisms are ingesting, which could help guide environmental health policies.

2025 Environmental Challenges
Article Tier 2

Monk seal faeces as a non-invasive technique to monitor the incidence of ingested microplastics and potential presence of plastic additives

Researchers used a non-invasive technique to collect and analyze monk seal fecal samples for microplastic contamination, marking the first time this approach has been used for this endangered species. They found microplastic particles in the samples along with plastic additives and biomarkers indicating dietary exposure. The method offers a practical way to monitor microplastic ingestion in protected marine mammals without disturbing the animals.

2023 Marine Pollution Bulletin 17 citations
Article Tier 2

Microplastics in grey seal (Halichoerus grypus) intestines: Are they associated with parasite aggregations?

Microplastics were found throughout the intestines of grey seals caught as bycatch off the Irish coast, but no clear link was found between microplastic presence and parasite infections. This adds to evidence that marine mammals are regularly exposed to microplastics through their diet.

2019 Marine Pollution Bulletin 68 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

Anthropogenic debris in three sympatric seal species of the Western Antarctic Peninsula

Researchers investigated microplastic contamination in three seal species inhabiting the Western Antarctic Peninsula: crabeater, leopard, and Weddell seals. The study confirmed the presence of anthropogenic debris in these Antarctic marine mammals, demonstrating that microplastic pollution has reached even remote polar ecosystems and their wildlife.

2024 The Science of The Total Environment 17 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

Assessing microplastic exposure of the Critically Endangered Mediterranean monk seal (Monachus monachus) on a remote oceanic island

Researchers assessed microplastic exposure in the critically endangered Mediterranean monk seal using scat analysis and found microplastics in 100% of samples, suggesting high pollution levels in the Madeira archipelago's coastal food web.

2022 The Science of The Total Environment 21 citations
Article Tier 2

Plastic and other anthropogenic debris in Arctic fox (Vulpes lagopus) faeces from Iceland

Researchers examined fecal samples from Arctic foxes in Iceland across multiple years and regions and found plastic debris in about 5% of samples, but concluded that while foxes encounter plastic pollution, their feces are an imperfect monitoring tool because the source of ingested plastics — marine or terrestrial — is difficult to determine.

2022 Polar Biology 7 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

Marine litter: trends and impacts in marine fauna

This review synthesizes evidence on marine litter sources, distribution, and ecological impacts, with particular focus on microplastics as a pervasive contaminant across all marine habitats. It finds that microplastics threaten marine life through ingestion, entanglement, and chemical transport, with impacts spanning trophic levels from plankton to large marine mammals.

2025 Portuguese National Funding Agency for Science, Research and Technology (RCAAP Project by FCT)
Article Tier 2

Marine debris ingestion by the South American Fur Seal from the Southwest Atlantic Ocean

Marine debris was found in 7% of South American fur seals examined from beaches in Argentina and Brazil, with plastic being the most common type. While the ingestion rate was relatively low, the findings confirm that this marine mammal species is exposed to plastic pollution throughout its range.

2017 Marine Pollution Bulletin 45 citations
Article Tier 2

An assessment of microplastics in fecal samples from polar bears (Ursus maritimus) in Canada's North

Researchers assessed the potential for plastic ingestion in polar bears from Canada by analyzing fecal samples, first validating protocols to confirm reliable microplastic recovery from bear feces. Microplastics including films, foam, and fragments were detected in polar bear feces, providing the first evidence of plastic ingestion by this Arctic apex predator.

2024 Arctic Science 6 citations
Article Tier 2

Microplastics in faeces of European shags Gulosus aristotelis in central Norway

Researchers analyzed microplastics in 36 fecal samples from European shag chicks in central Norway to quantify egested microplastics using a non-lethal sampling method. Microplastics were detected in the majority of samples, dominated by fibers, confirming that seabirds in Norwegian coastal waters are routinely ingesting plastic debris.

2024 Marine Pollution Bulletin 5 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

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

Marine Mammals and Interactions with Debris in the Northeastern Atlantic Region: Synthesis and Recommendations for Monitoring and Research

This synthesis reviews what is known about interactions between marine mammals in the northeastern Atlantic and plastic debris, including ingestion and entanglement. The authors identify data gaps and recommend standardized monitoring approaches to better understand and mitigate plastic impacts on whales, dolphins, and seals.

2023
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