We keep finding plastic in the sea for a simple reason: what’s already out there keeps fragmenting. Beach cleans help, but they don’t touch the backlog offshore. A new 2025 study shows how that backlog feeds the surface for decades and where to focus action.
What the 2025 study actually did
Researchers coupled three moving parts: how big, buoyant plastic breaks down at the surface; the size threshold where fragments are small enough to be picked up by “marine snow” (organic particles that sink); and the repeated settle–detach–resettle cycles that ferry those fragments into the deep sea. In model runs for a typical 10 mm polyethylene piece over 100 years, only the very small microplastics (≈25–75 µm) were efficiently exported and about 10% of the original plastic mass still remained at the surface after a century, continuing to feed new fragments.
Image from the recent study - https://royalsocietypublishing.org/doi/10.1098/rsta.2024.0445
Marine snow explained
Marine snow acts like Velcro for the tiny stuff. Lab and modelling work show that fragments roughly ≤160 µm are the most likely to get picked up by marine snow, and the very smallest pieces, typically <100 µm are the ones that actually make it to the seafloor. That’s why big, floaty plastics have to weather down before nature can move them out of the surface layer.
The “missing plastic” puzzle, explained
For years we’ve measured far less plastic at the surface than we’d expect from global inputs. Two clues help square the circle:
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Deep-sea sediments are a major sink - with microplastics far more abundant on the seabed than in surface waters.
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Fragmentation + marine snow steadily export tiny particles downward while leaving a long-lived tail of floating debris at the top.
What this means for solutions
Prevention comes first. If we only skim the surface, we’ll never catch the long tail of fragmentation that keeps seeding new microplastics. Skimming the open ocean alone will not stop the steady trickle of plastics fragmenting at source. The most effective approach is:
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Design for less and for return. Lightweighting, refills and verified recycled content reduce tomorrow’s legacy load
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Collect at source. Better kerbside systems, deposit return for bottles, and traps in drains and rivers keep items out of the sea
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Remove where it matters most. Prioritise rivers, estuaries and near-shore zones before debris spreads or breaks down
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Back evidence you can verify. Choose packaging with clear provenance, credible recycling streams
KURE’s stance on packaging (and why it matters)
KURE packages with Prevented Ocean Plastic™ and partners with PCX Markets, backing traceable collection of ocean-bound plastic and responsible material flows. Create value for recovered material and support measurable, verifiable impact that aligns with what the science is telling us: Cut new plastic at the source and deal with what’s already out there in a transparent, accountable way.
