Hidden plastic graveyard uncovered in the deep Mediterranean Sea

Plastic may not always float where we expect it. The ocean’s surface might look clean in some places, but far beneath the waves, a different story is unfolding.

In the southeastern Mediterranean, the deep seafloor is turning into a massive storage ground for plastic packaging, especially bags. A new study shows how this waste ends up thousands of feet below the surface, and the answer isn’t as simple as trash just “sinking.”

Plastic in the deep sea

Plastic debris has entered every corner of the ocean, but previously, most of the research has concentrated on floating plastic or beach trash. That changed with this latest study, which took a closer look at what is occurring on the ocean floor.

Scientists discovered that the Levant Basin – a deep section of the eastern Mediterranean off the coasts of Israel, Egypt, and Turkey – is among the world’s most contaminated deep-sea areas.

“We used trawls to survey the seafloor and we mainly found plastic bags and packaging that dominate the debris,” said Xing-Yu Li from the University of Haifa, the study’s lead author.

This raised a question: how does something so light – something meant to float – end up nearly a mile underwater?

A forensic approach to trash

To answer that, the team decided to treat each plastic item like a crime scene. Every piece of debris was carefully examined using a method called multi-marker analysis.

This approach looks at everything about the plastic – size, shape, color, material, surface features, and even what kinds of things are stuck to it, like tar or marine organisms.

“In the multi-marker approach anything that is found on a piece of plastic is an evidence,” said Xing-yu. “We extracted as many evidence as possible from every piece of waste, more than many previous studies, to build a fuller, more detailed view of the bottom waste.”

Instead of just counting how much trash was found, this method helped researchers understand how it got there, why it sank, and where it might have come from.

Why some plastic doesn’t sink

Most of the plastics found were polyethylene – the same material used in grocery bags. Normally, this kind of plastic floats. But when additives like calcium carbonate (CaCO₃) are mixed in during manufacturing, the plastic becomes heavier.

Those with CaCO₃ sank closer to the shore. Others, without these additives, drifted farther out before eventually settling on the seafloor.

The study also revealed that the deep basin at over 3,000 feet deep acts like a trap. Pressure and fine sediments help keep the plastic down.

Biofilms, which are slimy layers formed by microbes, usually help weigh plastics down too, but they don’t grow well in this part of the sea. Instead, things like tar, sand, and tiny shells helped plastics stay put.

The scientists noted that these plastic films – while thin and lightweight – are ending up where they can do the most long-term damage.

Even more troubling, the team found that some of this plastic could become buoyant again if disturbed, but because of how the deep sea works, that rarely happens. Once the plastic settles, it stays.

Where the trash is coming from

The plastic pollution isn’t only from local beaches. According to the research, land-based sources from Egypt, Israel, and Turkey are a big part of the problem.

Shipping also plays a role, especially in deeper waters. Surprisingly, fishing was not a major contributor – possibly due to strict Israeli regulations.

For years, scientists noticed high levels of plastic at the seafloor, but they didn’t fully understand why.

“For years in our monitoring reports we have reported a high concentration of plastic debris in this area. It was an unsolved mystery as we know that plastic debris should remain floating on the sea surface. Now we have a deep understanding of how it happens,” said Dr. Yael Segal from Israel Oceanographic and Limnological Research (IOLR).

“The Eastern Mediterranean is the most polluted area in the world, and we must take action for the sake of the next generation.”

Long-term risks to marine life

Plastic packaging is cheap, easy to produce, and used globally – but it doesn’t go away. It breaks into smaller pieces and can remain in the environment for hundreds of years.

Deep-sea habitats are already fragile, and adding plastic into the mix could disrupt food webs, introduce toxins, and harm species that haven’t even been fully studied yet.

“As the head of the national monitoring program, I see firsthand how plastic pollution is impacting the entire sea environment: beaches, water, sea bottom, and even local turtle populations,” said Dr. Segal.

Professor Revital Bookman said that the discovery is fascinating in the worst possible way.

“The eastern Mediterranean is quietly turning into a deep-sea landfill. Plastics that we use for only a few minutes are ending up trapped for centuries, threatening deep marine ecosystems we barely understand,” noted Professor Bookman.

What needs to happen next

According to the researchers, this study changes how we should think about ocean pollution. Plastic doesn’t just float around until it hits a beach. It travels far, interacts with other pollutants like tar, and ends up in hidden places.

“This previously overlooked dynamic necessitates a broader perspective on pollution processes in marine environments,” said Professor Bookman.

“Without systematic deep-sea accounting, we risk underestimating the true environmental footprint of plastic pollution and misallocating mitigation efforts by neglecting offshore and deep-sea sinks.”

To deal with this, the experts call for coordinated efforts across the region. Countries that share the sea need to work together on monitoring, cleanup, and prevention.

Without a shared strategy, plastics will continue piling up, silently choking one of the planet’s most mysterious ecosystems.

The full study was published in the journal Marine Pollution Bulletin.

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