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Those plastic bottles that are so readily available at convenience stores, groceries, conferences, and sports venues are a real problem: they kill marine creatures.
A recent study published in Proceedings of the National Academy of Sciences concludes that plastic ingestion has been documented in nearly 1,300 marine species, including every seabird family, marine mammal family, and sea turtle species. Researchers analyzed data from more than 10,000 autopsies from marine creatures killed by ingesting plastic; they calculated amounts consistent with a 90% likelihood of death.
Acute mortality,…
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Those plastic bottles that are so readily available at convenience stores, groceries, conferences, and sports venues are a real problem: they kill marine creatures.
A recent study published in Proceedings of the National Academy of Sciences concludes that plastic ingestion has been documented in nearly 1,300 marine species, including every seabird family, marine mammal family, and sea turtle species. Researchers analyzed data from more than 10,000 autopsies from marine creatures killed by ingesting plastic; they calculated amounts consistent with a 90% likelihood of death.
Acute mortality, due to obstruction, perforation, or torsion of the gastrointestinal (GI) tract, has been confirmed via necropsy in all three species.
What is the relationship among the GI load (pieces and volume/animal length) of different plastic types—hard, soft, rubber, or fishing debris—and likelihood of plastic-induced mortality? When modeling plastic together, a 90% chance of mortality was associated with:
- 23 pieces (0.098 cm3/cm) in seabirds;
- 29 pieces (39.89 cm3/cm) in marine mammals: and,
- 405 pieces (5.52 cm3/cm) in sea turtles (377 for juveniles).
The plastic types that posed the greatest risks were rubber for seabirds, soft plastics and fishing debris for marine mammals, and hard and soft plastics for sea turtles. (The study did not include data on microplastics, which are smaller pieces invisible to the naked eye.)
See It with Your Own Eyes
Everyday beach walkers in my condo community scour the incoming tide and wrack line for litter. The amount of debris they pick up can depend on the direction of the current or a recent storm at sea. Tourist season, which runs from January through April in Florida, definitely increases human-made objects that wash up on the shore, most of which are plastic-based. It’s an ongoing battle to fight the plastic crisis—not just in our community but around the world.
How much plastic did the marine creatures in the recent study actually consume? When modeling all plastic types together, a 90% chance of mortality was predicted if:
- a seabird consumed 23 pieces of plastic (or 0.098 cm3/cm body length);
- a marine mammal consumed 29 pieces (or 39.89 cm3/cm body length);
- a sea turtle consumed 405 pieces (or 5.52 cm3/cm CCL); and,
- a juvenile sea turtle (<35 cm CCL) consumed 377 pieces.
The amount of plastic predicted to cause death varied dramatically by taxon. This was primarily driven by the size of the animal and the size of plastic pieces they consume.
When considering all plastic types together, seabirds had the lowest thresholds—they had the least tolerance for pieces or volume/length. The piece-based thresholds for marine mammals fell between seabirds and sea turtles. However, on average, marine mammals consumed much larger pieces of plastic (77), so volume-based mortality thresholds in marine mammals were the highest.
Sea turtles contained the highest frequencies and loads of plastic, as their foraging ecology and habitat use influence plastic ingestion. Nearly 50% of sea turtles included in the dataset had ingested plastic, compared to 35% of seabirds and 12% of marine mammals. They had the highest mortality thresholds by pieces but the mean piece size was small (0.22 cm3).
Among sea turtles, ingested plastic was the reported cause of death in 4.4% of all necropsied individuals—almost all post-hatchlings and juveniles—compared with 1.6% of all necropsied seabirds and 0.7% of all marine mammals. Ingestion rates by plastic type varies across the life stage, with post-hatchling sea turtles consuming more hard plastics and adult sea turtles consuming more fishing debris and soft plastics (e.g., film).
Lessons We Take Away from the Marine Mortality Rates due to Plastics
Plastics are widely used around the world due to ease of manufacturing, low cost, stable chemical properties, and good water resistance. Habitual plastic daily use in all economic sectors has a serious cost to the environment. Ubiquitous plastic consumption requires significant and immediate action, since the exponential increase in plastic production and use has outpaced society’s ability to properly manage this increasingly complex material.
In addition to recommendations for future research for colleagues in the science world, there were several important implications for advancing plastic pollution reduction policies.
**Type of plastics marine organisms consume: **Knowing the effects of widespread plastic use can inform policymakers and regulators about possible plastic distribution thresholds to mitigate environmental concerns like marine creature mortality. Importantly, the study authors say that, with risk thresholds being set by decision makers, they can be adapted to fit the values, goals, or needs of the regions and communities in which they are implemented.
Yes, we live in a western world in which it is often assumed that some level of pollution is inevitable; we not always voice concerns when ill-informed leaders suggest a little plastic pollution is okay–no harm really occurs, does it?For example, the US does not support global production caps or bans on certain plastic products or chemical additives to them–the fossil fuel lobby is too strong. The US State Department is intent, instead, on improving waste collection, management, product design, and recycling. Yet these are the very people who can provide important regulatory levers for reducing marine pollution.
**Likelihood of mortality based on GI load: **The most disheartening truth about plastics is that they don’t disintegrate, like other manufactured materials that we have come to accept as part of our daily lives. Every piece of plastic that has ever been produced still exists in our environment today. The world produces nearly a half-billion tons of plastic each year, more than twice the amount produced two decades ago. Eating plastic can be deadly to marine life in a number of ways. Hard pieces can puncture or tear the internal organs of an animal and kill it. The buildup of plastic fragments or large pieces can block food. And even if neither of these things happen, eating enough plastics can starve animals by filling their guts but not providing nutrients.
**Ecological benefits of interventions that target important foraging areas (e.g., coastal cleanups): **Every time we sponsor a local beach cleanup, or bring a speaker in to our community to talk about the importance of joining in to stop litter, we are helping to prevent additional marine mortality. We can start by saying that we want to live in a pristine environment. Later, as the cleanup efforts become a habit, we can educate about how our cleanups protect the marine ecosystem, wildlife, and the overall environment. Beach cleanups are essential in combating the growing problem of marine pollution and its detrimental effects on marine life and coastal communities.
**Identification of problematic materials (e.g., balloon release bans or plastic bag bans): **In June, scientists published a study that looked at Ocean Conservancy data from tens of thousands of shoreline cleanups on river, lake, and ocean beaches. It found less litter in areas that enacted plastic bag bans. Plastic bag bans and fees have emerged as popular policy solutions to address this problem—over 100 countries have already passed regulations to minimize plastic ban use.
Final Thoughts
The future for plastic pollution doesn’t have to be on a downward trajectory. Existing technology and knowledge can correct the bulk of the plastic pollution problem. And so can you! Buy in bulk. Bring your own reusable water bottle everywhere you go. Talk to each other about the deadly impacts of plastic pollution on our environment, especially marine creatures.
References
- “A quantitative risk assessment framework for mortality due to macroplastic ingestion in seabirds, marine mammals, and sea turtles.” Erin L. Murphy, Britta R. Baechler, Lauren Roman , and Chelsea M. Rochman. *Proceedings of the National Academy of Sciences. *November 2025.
- “Groundbreaking research identifies lethal dose of plastics for seabirds, sea turtles, and marine mammals: ‘It’s much smaller than you might think.’” Ocean Conservancy. November 2025.
- “How much plastic can kill a tea Turtle? A new study has answers.” Sachi Kitajima Mulkey. New York Times. November 2025.
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