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Groundbreaking Research Identifies Lethal Dose of Plastics for Seabirds, Sea Turtles and Marine Mammals: “It’s Much Smaller Than You Might Think”

Humpback whale calf swimming underwater in clear blue ocean water, representing marine mammals threatened by plastic pollution

“Ocean Plastics are an Existential Threat to the Diversity of Life on Our Planet”: Data Show that Nearly Half of Animals that Ingested Plastics were Red-Listed as Threatened Species

WASHINGTON — The Proceedings of the National Academy of Sciences today released a new study, “A quantitative risk assessment framework for mortality due to macroplastic ingestion in seabirds, marine mammals, and sea turtles.” Led by Ocean Conservancy researchers, the peer-reviewed paper is the most comprehensive study yet to quantify the extent to which a range of plastic types (from soft, flexible plastics like bags and food wrappers; to balloon pieces; to hard plastics ranging from fragments to whole items like beverage bottles) result in the death of seabirds, sea turtles, and marine mammals that consume them.

The study reveals that, on average, consuming less than three sugar cubes’ worth of plastics for seabirds like Atlantic puffins (which measure approximately 28 centimeters, or 11 inches, in length); just over two baseballs’ worth of plastics for sea turtles like Loggerheads (90 centimeters or 35 inches); and about a soccer ball’s worth of plastics for marine mammals like harbor porpoises (1.5 meters, or 60 inches), has a 90% likelihood of death. At the 50% mortality threshold, the volumes are even more startling: consuming less than one sugar cube’s worth of plastics kills one in two Atlantic puffins; less than half a baseball’s worth of plastics kills one in two Loggerhead turtles; and less than a sixth of a soccer ball kills one in two harbor porpoises.

“We’ve long known that ocean creatures of all shapes and sizes are eating plastics; what we set out to understand was how much is too much,” said lead author of the study Dr. Erin Murphy, Ocean Conservancy’s manager of ocean plastics research. “The lethal dose varies based on the species, the animal’s size, the type of plastic it’s consuming, and other factors, but overall it’s much smaller than you might think, which is troubling when you consider that more than a garbage truck’s worth of plastics enters the ocean every minute.”

To arrive at their findings, Ocean Conservancy scientists analyzed the results of 10,412 necropsies, or animal autopsies, conducted worldwide in which cause of death and data on plastic ingestion were known. Of the animals studied, 1,537 were seabirds representing 57 species; 1,306 were sea turtles representing all seven species of sea turtles; and 7,569 were marine mammals across 31 species.

They then modeled the relationship between the plastics in the gut and likelihood of death for each group, looking both at total pieces of plastics as well as volume of plastics. Based on data availability, they also looked at different plastic types to determine which are particularly lethal to each group. They found that rubber and hard plastics are especially deadly for seabirds, soft and hard plastics for sea turtles, and soft plastics and fishing gear for marine mammals.

“This study reminds us that plastic bags, lost fishing gear, and other larger items can be dangerous to animals big and small,” said Ocean Conservancy’s Director of Ocean Plastics Research and study co-author Dr. Britta Baechler, who co-authored a study in 2024 that showed microplastics are present in both animal and plant-based proteins eaten by humans. “One in 20 sea turtles that we studied died from ingesting plastics. I wouldn’t take those odds.”

Nearly half (47%) of all sea turtles; a third (35%) of seabirds; and 12% of marine mammals in the dataset had plastics in their digestive tracts at their time of death; overall, one in five (21.5%) of the animals recorded had ingested plastics, often of varying types. Additional findings included:

Seabirds

Of seabirds that ate plastic, 92% ate hard plastics, 9% ate soft plastics, 8% ate fishing debris, 6% ate rubber, and 5% ate foams, with many individuals eating multiple plastic types.

Seabirds are especially vulnerable to synthetic rubber: just six pieces, each smaller than a pea, are 90% likely to cause death.

Sea Turtles

Of sea turtles that ate plastic, 69% ate soft plastics, 58% ate fishing debris, 42% ate hard plastics, 7% ate foam, 4% ate synthetic rubbers, and 1% ate synthetic cloth.

Sea turtles, which on average weigh several hundred pounds, are especially vulnerable to soft plastics, like plastic bags: just 342 pieces, each about the size of a pea, would be lethal with 90% certainty.

Mammals

Of marine mammals that ate plastic, 72% ate fishing debris, 10% ate soft plastics, 5% ate rubber, 3% ate hard plastics, 2% ate foam, and 0.7% ate synthetic cloth.

Marine mammals are especially vulnerable to fishing debris: 28 pieces, each smaller than a tennis ball, are enough to kill a sperm whale in 90% of cases.

The study also found that nearly half of the individual animals who had ingested plastics are red-listed as threatened (that is, near-threatened, vulnerable, endangered or critically endangered) by the IUCN. Notably, the study only analyzed the impacts of ingesting large plastics (greater than 5 millimeters) on these species, and did not account for all plastic impacts and interactions. For example, they excluded entanglement, sublethal impacts of ingestion that can impact overall animal health, and microplastics consumed.

“This research really drives home how ocean plastics are an existential threat to the diversity of life on our planet,” said Nicholas Mallos, vice president of Ocean Conservancy’s Ending Ocean Plastics program and a study co-author. “Eating plastics is just one way that marine life is threatened by the plastic pollution crisis. Imagine the dangers when you also consider entanglement and the everpresent threat of toxic chemicals leaching from plastics.”

Scientists estimate that more than 11 million metric tons of plastics enter the ocean every year. Much of those plastics are single-use items like those commonly found by volunteers during Ocean Conservancy’s annual International Coastal Cleanup®. Since 1986, more than 19 million volunteers have removed more than 400 million pounds of trash from beaches and waterways worldwide.

“Every year, volunteers collect massive numbers of balloons, plastic bags, straws, food wrappers, and other items that are lethal to wildlife even in small amounts, according to this research,” said Ocean Conservancy’s Senior Director of Conservation Cleanups Allison Schutes. “When you pick up just a few pieces of plastic, you are helping to protect the life of a marine animal. And when we all clean up together, we are helping to protect countless lives.”

Scientists have determined that to successfully address the plastic pollution crisis, we need to reduce plastics production, improve waste collection and recycling, and clean up what does get into the environment.

“We are thrilled to have this new research quantifying the wildlife impacts of plastic pollution,” said Ocean Conservancy’s Director of Plastics Policy Dr. Anja Brandon. “While there is no single solution to this issue, these hard numbers reaffirm that our work addressing particularly problematic items like balloons and plastic bags are truly meaningful. In the fight to protect our marine wildlife, every policy and every individual action matters.”

“Governments around the world are grappling with how to address plastic pollution, and they are looking for science-based targets to inform policy decisions,” said Dr. Chelsea Rochman, associate professor in the Department of Ecology and Evolutionary Biology at the University of Toronto, scientific advisor to Ocean Conservancy, and senior author of the study. “This research provides an important foundation for decision-makers to understand thresholds for risk to better protect biodiversity.”

Photos and b-roll of marine animals, ocean plastic pollution, and other related subjects, as well as FAQ about the study, are available here.

About the organization

For more than 50 years, Ocean Conservancy has delivered effective, evidence-based solutions for the ocean and all who depend on it. Today, we continue to unite science, people and policy to protect our ocean from the greatest challenges it faces: climate change, plastic pollution and biodiversity loss. We are a 501(C)3 headquartered in Washington, D.C. that inspires a worldwide network of partners, advocates and supporters through our comprehensive and clear-eyed approach to ocean conservation. Together, we are securing a healthy ocean and a thriving planet, forever and for everyone. For more information, visit oceanconservancy.org, or follow us on LinkedIn, Facebook, X (formerly Twitter), Bluesky or Instagram.

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Issue 132 - May 2026

SeaKeepers Welcomes Dr. Mark Luther as First Scientist Chairman, Marking a New Era for Ocean Research

The International SeaKeepers Society marks a historic milestone, appointing Dr. Mark Luther of the University of South Florida as its first scientist Chairman, succeeding Jay Wade and signaling a deeper scientific chapter for the yachting-led conservation organization.
Jay Wade and Dr. Mark Luther of The International SeaKeepers Society
Outgoing Chairman Jay Wade with incoming Scientist Chairman Dr. Mark Luther. Photo: SeaKeepers.

April 10, 2026. The Board of Directors of The International SeaKeepers Society has announced a leadership transition, extending its deepest gratitude to outgoing Chairman Jay Wade and welcoming Dr. Mark Luther as the organization’s first scientist Chairman, a historic milestone for the ocean conservation NGO.

During his tenure, Jay Wade provided steady, thoughtful leadership, guiding the organization through a period of growth while remaining anchored in SeaKeepers’ mission to advance oceanographic research, conservation, and marine education. A passionate advocate for the yachting and boating community, Wade championed a vision of transforming private vessels into platforms for scientific discovery, expanding the organization’s global reach and strengthening its role as a bridge between ocean science and the maritime industry.

A first scientist Chairman for SeaKeepers

Dr. Mark Luther brings decades of expertise in physical oceanography and maritime systems, alongside a lifelong connection to the water. He earned his Ph.D. in Physical Oceanography from the University of North Carolina at Chapel Hill and currently serves as Professor and Director of the Center for Maritime and Port Studies at the University of South Florida’s College of Marine Science.

With over 30 years of experience supporting oceanographic observation systems, including longstanding work with NOAA’s Tampa Bay Physical Oceanographic Real-Time System, Dr. Luther has been at the forefront of integrating science with real-world maritime operations. His leadership extends across key regional and federal committees, where he collaborates closely with the U.S. Coast Guard, port authorities, and maritime stakeholders to address environmental challenges tied to marine transportation.

A dedicated member of the SeaKeepers community, Dr. Luther has served as Chair of the organization’s Scientific Advisory Council, helping to guide and elevate its scientific initiatives. He is also an avid boater and U.S. Coast Guard-licensed captain, having spent more than four decades navigating the waters of Tampa Bay and Florida’s west coast.

“With years of dedicated service to SeaKeepers, Mark brings a deep understanding of our mission to this role. It is exciting to see him step into the position of Chairman and help guide the organization forward.”

Jay Wade, outgoing Chairman, The International SeaKeepers Society

Dr. Luther’s appointment signals an exciting new chapter for SeaKeepers, one that deepens the organization’s scientific leadership while continuing to engage the global fleet in meaningful ocean research, education, and conservation.

About The International SeaKeepers Society. The International SeaKeepers Society works with the yachting community to take part in research, conservation, and educational efforts that advance the health of the ocean. Learn more at seakeepers.org or @seakeepers on social.

Adapted from a press release issued by The International SeaKeepers Society on April 10, 2026.

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Issue 132 - May 2026

Falmouth Harbour Trials the World’s First All-Concrete Pontoon Float to Replace EPS in Marinas

Falmouth Harbour is trialling the world’s first all-concrete marina pontoon, designed by Cornwall-based ScaffFloat, as a recyclable alternative to Expanded Polystyrene floats and a step toward cutting marine microplastic pollution.

Falmouth, Cornwall, UK. Falmouth Harbour is trialling the world’s first all-concrete marina pontoon float, designed and built by the team at ScaffFloat in neighbouring Penryn, in a first step to removing all Expanded Polystyrene (EPS) floats from its leisure and commercial operations.

The Harbour has pledged to move away from EPS products in the light of mounting evidence that polystyrene microplastics in the world’s oceans inflict serious damage on the marine environment and life within it. Polystyrene, globally used for its lightness and buoyancy, is made from fossil fuels, is virtually un-decomposable, and when it breaks down into microplastics can be ingested by marine life with devastating consequences.

“The amount of broken-up polystyrene around our creeks and rivers, particularly after this year’s storms, is awful to see and very hard to clean up without damaging the delicate ecology of our shorelines. Expanded Polystyrene fragments in the marine environment pose a serious ecological concern, as seabirds, fish, turtles and other fauna mistake EPS beads for food, which can cause internal injuries or death; entering the food chain poses health risks to humans as well.”

Vicki Spooner, Environment Manager, Falmouth Harbour

Inside the Reef Float: an inert, recyclable alternative to EPS

Penryn marine company ScaffFloat Ltd has tackled the challenge of finding alternatives to traditional pontoons by inventing the “Reef Float.” Their first commercial prototype, made entirely from concrete, has been undergoing trials beneath a Falmouth Harbour pontoon. ScaffFloat developed the new product as part of a business development project that received £284,787 from the UK Government through the UK Shared Prosperity Fund as part of Cornwall’s Good Growth Programme.

The Reef Float’s buoyant core is made using ultra-low-density waterproof concrete, instead of EPS foam, and the core is then cast inside a high-strength engineered concrete skin. In the highly unlikely event that a Reef Float ever failed, the materials would simply sit inertly as stone in the marine environment, whereas a cracked-open EPS float exposes its polystyrene foam core to the marine elements.

“We replaced a failing EPS pontoon float at Falmouth Harbour with a Reef Float, where it survived all that this January’s storms could throw at it. It’s what we would expect, of course, as we’ve designed it to be strong with an ultra-long life. But it’s also completely inert in the marine environment and 100 percent recyclable, so a game-changing alternative to the EPS floats currently used all over the world.”

Toby Budd, Founder and Managing Director, ScaffFloat

Local innovation, global stage

Local MP Jayne Kirkham, checking out the new Reef Float in Falmouth, called it “exactly the kind of innovation we want to see in Cornwall: local businesses developing practical but cutting-edge solutions to global environmental challenges. Cutting polystyrene pollution from our waters while creating skilled jobs is a win for our marine environment and our economy. I’m proud to see government funding helping projects like this lead the way.”

“Falmouth Harbour has made the conscious decision to move away from EPS foam pontoons in all our operations, and it’s fantastic that our neighbours at ScaffFloat are the first company to offer a plastic-free alternative. Reef Floats are easily installed, in situ, on a rolling basis, as and when we need to replace old EPS floats, and they have a zero-cost, 100 percent recyclable end-of-life disposal. It’s another tremendous example of Cornish ingenuity, and we look forward to working with them into the future.”

Miles Carden, CEO, Falmouth Harbour

The Reef Float team has been shortlisted for the Innovation Award at Marina26 in Australia this May, with an invitation to attend and present at the biggest marina conference in the world, demonstrating what a major issue EPS has become for the marina industry and legislative authorities alike.

Australia itself lost more than 1,000 pontoons in the 2022 Queensland floods, where they broke up and created an environmental disaster known as the “White Spill,” with the ocean and beaches covered with EPS balls that were almost impossible to clear up.

Learn more. For more information on Reef Float and parent company ScaffFloat, visit scafffloat.co.uk/reeffloat. For more on Falmouth Harbour, including its wide-ranging environmental initiatives, see falmouthharbour.co.uk.

Adapted from a press release issued by Louise Midgley Communications, on behalf of ScaffFloat and Falmouth Harbour.

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Conservation Photography

Little Cayman Hope Spot Shows Early Signs of Reef Recovery After the World’s Most Extreme Coral Bleaching Event

CCMI’s 2025 Healthy Reefs Report Card shows Little Cayman’s coral cover edging back to 13.4 percent, an early but unmistakable sign that the island’s reefs are beginning to recover from the world’s most extreme coral bleaching event.

Little Cayman, Cayman Islands. Marking Earth Day 2026, the Central Caribbean Marine Institute (CCMI) released its 2025 Healthy Reefs Report Card, revealing early signs of recovery and renewed hope for Little Cayman’s reefs after the most extreme coral bleaching event on record in 2023.

The summer of 2023 was the hottest ever measured, and it brought with it one of the most extensive global coral bleaching events in modern history, decimating reefs from the Caribbean to the Indo-Pacific and casting their future in doubt. CCMI’s Healthy Reefs campaign has tracked Little Cayman’s reefs since 1998, and the 2024 surveys delivered the bleakest numbers in the program’s history: coral cover had collapsed to 9.8 percent, down from 26 percent before the marine heatwave.

This year’s data tells a different story. The 2025 surveys, summarized in the new Report Card, show coral cover edging back up to 13.4 percent. The shift is not yet statistically significant, but the direction is unmistakable: recovery in Little Cayman has begun.

A site-by-site picture

Zoom in from the island-wide average and the recovery looks more layered. Twenty percent of surveyed sites posted a significant increase in coral cover between 2024 and 2025. One site, Coral City, held the line entirely through the bleaching, exhibiting no significant loss. In total, 30 percent of sites have either maintained pre-bleaching coral levels or demonstrated significant recovery this year. The remaining 70 percent show either minor, non-significant recovery or no recovery at all.

Reef recovery is rarely visible on a 12 to 24 month horizon. Corals are slow-growing animals, and even after a disturbance ends, biologists typically expect at least three years before measurable rebound, and a minimum of seven years (sometimes nearly thirty) for a reef to return to pre-bleaching baselines. Against that timeline, what CCMI is recording in 2025 is striking: the resilience built into Little Cayman, with strong protections and minimal local disturbance, appears to be doing exactly what reef science predicts it should do.

Fish populations holding the line

While coral cover is still climbing back, fish populations have continued to thrive. CCMI has documented consistent increases in fish density since 2016, with a dramatic jump in density and biomass in 2024 that held through 2025. That matters more than it might sound: herbivorous fish keep macro-algae in check, and when algae is left unchecked it can smother corals and block new recruits from settling. A healthy reef-fish community is, in many ways, what makes coral recovery possible at all.

A Hope Spot earning its name

Little Cayman is a Mission Blue Hope Spot, a designation that frames the island as a small-but-mighty example of what marine protection can look like when conservation is prioritized. Under the pressures the ocean is now under, that framing reads less like marketing copy and more like a working hypothesis the reef is steadily proving out.

The island has form here. Little Cayman’s Nassau grouper spawning aggregation rebounded from roughly 1,000 individuals to nearly 9,000 over a decade, one of the most cited recovery stories in the Caribbean. The early coral signal in the 2025 Report Card could become another chapter in that record.

The nursery, and three resilient genotypes

CCMI’s coral nursery was hit hard during the 2023 bleaching, losing close to 90 percent of its stock. Genetic work in the aftermath identified three staghorn coral genotypes that survived nearly 20 degree-heating weeks. Since 2023, those three genotypes have rebuilt the nursery from just 17 fragments to nearly 300 as of March 2026. CCMI’s nursery likely represents one of the last remaining populations of the critically endangered staghorn coral, Acropora cervicornis, in Little Cayman.

Why this matters beyond Little Cayman

Hope Spots like Little Cayman do not just protect their own waters. They function as larval source populations, exporting recruits along ocean currents to less resilient reefs downstream. In a warming ocean where many sites have lost their capacity to bounce back unaided, these pockets of resilience are increasingly the difference between regional collapse and regional recovery.

The 2025 numbers do not erase what 2023 took. Coral cover is still well below pre-heatwave levels, and the recovery is partial, uneven, and fragile. But for the first time since the bleaching, the trendline is pointing in the right direction. As CCMI puts it, research and science-based actions are critical right now to understand the ecological processes driving this resilience and to translate that understanding into management and protection.

Acknowledgments

CCMI thanks this year’s Healthy Reefs sponsors: Wheaton Precious Metals International, Foster’s Supermarket, Cayman Water, and Ugland Properties; and the Restoration program sponsors who made the work possible: The Ernest Kleinwort Charitable Trust, Artex Cayman Islands, Walkers, and Marfire.

Read the full 2025 Healthy Reefs Report Card at tinyurl.com/CCMI-25HRR and learn more about the Healthy Reefs campaign at reefresearch.org/our-work/research/healthy-reefs/.

Adapted from a press release issued by the Central Caribbean Marine Institute (CCMI), April 22, 2026. Photo credit: CCMI.

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