Jerusalem, 24 December, 2025 (TPS-IL) — Israeli and Cypriot scientists have uncovered significant human-made pollution inside coastal sea caves in the Mediterranean, revealing a previously undocumented environmental threat to fragile marine ecosystems and endangered species. The findings, shared exclusively with The Press Service of Israel, mark the first systematic documentation of debris inside these caves, which serve as critical shelter and breeding sites for wildlife, including the endangered Mediterranean monk seal.
“What’s new is that for the first time we now have documentation of these caves,” Prof. Dror Angel of the University of Haifa, one of the study’s authors, told TPS-IL. “No one knew about it before. There was no record of it. And this is endangering an already endangered species.”
The study, a collaboration between the University of Haifa and the Cyprus Marine and Maritime Institute (CMMI), examined 23 sea caves along the Cypriot coast. Cyprus has more sea caves, and monk seals are known to occupy many of them.
Researchers recorded more than 24,000 pieces of debris weighing roughly 176 kilograms. Plastics accounted for about two-thirds of the waste, much of it fragmented polystyrene and degraded plastic that had accumulated over the years. The findings were published in the peer-reviewed Marine Pollution Bulletin.
Unlike open beaches or seabeds, sea caves function as natural traps. Ocean currents push debris deep into narrow chambers, where it becomes lodged and rarely exits. In some caves, pollution density reached nearly 100 items per square meter, the research found, levels significantly higher than those typically recorded in exposed marine environments.
Of particular concern is the discovery of “plastitar” — a hardened mix of plastic and tar — coating cave walls and floors, Angel told TPS-IL. This material forms when oil residues from ships combine with plastic debris, creating persistent contamination that is difficult to remove, he explained.
Angel added that sea caves have become essential habitats for the Mediterranean monk seal (Monachus monachus), one of the world’s rarest marine mammals. As human activity has intensified along coastlines, seals have increasingly retreated to caves to give birth and raise pups. The study found that some of the highest concentrations of debris were located in the deepest sections of caves, areas most commonly used for pupping and resting.
Although no direct seal deaths linked to cave debris have yet been documented, the study notes that microplastics have already been detected in monk seals and other marine species elsewhere in the Mediterranean, raising concerns about long-term health impacts.
Researchers say the findings expose a major blind spot in marine pollution monitoring, which has largely overlooked enclosed habitats like sea caves. By documenting the scale and sources of contamination, the study may provide a foundation for targeted conservation measures.
“It means that now that we know what pollutes these caves, usually oil and debris from ships, we can regulate it,” Angel told TPS-IL. “Perhaps even create laws against it.”
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