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Microplastic ingestion and diet composition of humpback whales from the Northeast Pacific Ocean
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Scientists studying humpback whale poop found these ocean giants swallow over 400,000 microplastic particles a day while feeding on krill near Vancouver Island, yet this only adds up to a tiny fraction of their body weight, and most of the particles were harmless cellulose fibers (a plant-based material), not harmful plastics. While the whales themselves seem to face low risk, this research matters because it shows just how deeply microplastics have infiltrated ocean food chains, the same food chains that produce the seafood many of us eat.
The rapid recovery of humpback whale populations in the North Pacific, following decades of intense commercial whaling, represents a conservation success story. However, the future population growth and stability of this enigmatic species is now threatened by a growing list of anthropogenic stressors, including plastic pollution. My thesis aimed to quantify the level of microplastic (MP) ingestion among humpback whales foraging near the Juan de Fuca Strait, via opportunistically collected fecal samples. A total of 20 humpback whale fecal samples were collected during the summer of 2024, yielding an average of 24.4 ± 16.4 MP/g (dry weight), the majority of which were regenerated cellulose fibres. Stable isotope analysis and whole genome sequencing indicated that the sampled whales were primarily feeding on krill, enabling estimation of consumption rates which, combined with fecal MP concentrations, resulted in an average ingestion of 418,227 MP particles per day (95% CI: 402,191 - 436,172). This corresponds to an ingested mass of 0.37 g of MP per day (95% CI: 0.36 - 0.39), representing approximately 1.3×10^−6 % of the body mass of a 30 tonne humpback whale. Given the low estimated mass of ingested MP and scarce toxicological effects of regenerated cellulose, the risk to whales in this study appears relatively low. However, this finding is context-specific, and smaller particle classes such as nanoplastics, which were not assessed here, may have different bioavailability and toxicological implications. Nevertheless, these findings provide insight into the toxicological landscape of coastal food webs and can help inform future species risk assessments in Canadian Pacific waters.
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Researchers documented the first confirmed presence of microplastics in the gastrointestinal tract of a baleen whale (humpback whale), finding multiple polymer types including polyethylene, polypropylene, and PET in particle sizes from 1 mm to 17 cm, reflecting both the diversity of marine plastic pollution and the unselective filter-feeding strategy of these large marine mammals.
Cetaceans and microplastics: First report of microplastic ingestion by a coastal delphinid, Sousa chinensis
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Researchers reported the first documented case of microplastic ingestion by the Indo-Pacific humpback dolphin (Sousa chinensis), finding microplastics in the intestinal contents of both adult and calf individuals. The findings indicate that both prey consumption and unintentional ingestion are likely exposure pathways for microplastic accumulation in this coastal cetacean species.
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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.
Research digests by email
When a large batch of papers lands in the Atlas, we read through it and send a short write-up of what stood out.