Scientists sound the alarm after making disturbing discovery deep in Mediterranean Sea: 'It was an unsolved mystery'

Ocean plastic is a widely known problem, typically viewed through the lens of floating debris and microplastics.

However, Earth.com covered a novel study examining plastic pollution on the seafloor.

What's happening?

Decades before the term "microplastics" was coined in 2004, the public was aware that plastic debris caused fatal entanglements among marine wildlife, such as seagulls.

Plastic debris in the ocean is unfortunately prolific, measured in particles per cubic meter of ocean water for research purposes. Plastic is often inherently buoyant, and the amount of it at or near the surface is significant.

A study from the December 2025 edition of Marine Pollution Bulletin was recently published online, and in it, researchers scoured the depths of the oxygen-rich southeastern Mediterranean Sea.

The study's authors noted that while the seafloor is known to be strewn with plastic debris, the sources and trajectories behind the pollution remained "poorly defined."

In a series of trawls, the team gathered samples of seafloor plastic, viewing them "like a crime scene." Lead author Xing-Yu Li said this involved a "multi-marker" approach, but not of the Crayola variety.

"In the multi-marker approach, anything that is found on a piece of plastic is [a piece of] evidence. 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," Xing-Yu explained.

Xing Yu said that the bulk of debris originated with "plastic bags and packaging," and the authors identified "shipping" as a broader contributor than commercial fishing, which surprised them.

Researchers determined that polyethylene was the most commonly found plastic on the seafloor, and additives such as calcium carbonate (CaCO₃) influenced how and when the debris floated, sank, and settled on the seafloor.

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Why are these findings important?

In the two decades since microplastics were identified in the context of marine pollution, researchers have worked to quantify their impact on humans, wildlife, and their habitats.

Although the full impact of microplastics on human health hasn't been quantified, what we do know points to a pervasive risk. 

Moreover, microplastics aren't just concentrated in the ocean or its deepest trenches. 

Samples have been recovered from soils everywhere, and microplastics have even made their way to areas with little to no habitation, such as Antarctica.

The new research provides insight into how plastic debris travels — which, in turn, can inform ways to reduce microplastic pollution at its source. 

Dr. Yael Segal of the Israel Oceanographic and Limnological Research (IOLR) said that until recently, the source of the high concentration of plastic debris on the basin floor was unknown.

"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," Segal explained.

What's being done about it?

Research like the new study is crucial for informing broad strategies to address the global problem of ocean plastic.

Individually, using less plastic whenever possible reduces both direct exposure to plastic particles and the accumulation of excess waste.

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