Ancient Greek and Roman underwater ruins scattered across the Mediterranean Sea are suffering from widespread stone decay, according to a new study that examined submerged archaeological sites in France, Italy and Cyprus.
The research, published in the Journal of Cultural Heritage, was led by Luigi Germinario of the Department of Geosciences at the University of Padova in Italy. His team studied stone remains from three ancient port sites: the Roman harbor of Anse des Laurons in France, the Roman complex of Baia in Italy, and the Hellenistic harbor of Amathus in Cyprus, a site tied to the ancient Greek world.
Divers collected 52 stone samples from the three locations during the first half of 2023. Back in the lab, researchers examined the samples under powerful microscopes and used a 3D scanning technique to measure exactly how much the stone surfaces had changed over time.
Marine life drives stone decay in ancient Greek underwater ruins
The results point to one main culprit: marine life. Sea creatures and plants that grow on and inside stone, a process scientists call “biodeterioration,” turned out to be the most common form of damage. Algae, tube worms, barnacles and sponges were found coating or boring into the ancient blocks at all three sites.
Not every organism causes equal harm, though. Barnacles did the most damage, roughening stone surfaces and increasing surface roughness by as much as six times compared with untouched rock.
Tube worms and small colonial creatures called bryozoans caused somewhat less damage. Red algae, by contrast, formed smooth crusts that closely matched the original stone surface and caused the least harm, sometimes even acting as a protective layer.
Bore holes and chemical changes deepen the underwater damage
The most serious damage came from creatures that bore holes into the stone itself, mainly sponges and worms. These organisms carved dozens of tiny tunnels into every square centimeter of some samples, with some holes measuring more than two millimeters wide, weakening the stone from within.
The study also found chemical changes linked to marine life, including a buildup of sulfur and iron compounds on limestone and marble surfaces, along with shifts in calcium content within the rock.
Despite covering three very different locations across the western, central and eastern Mediterranean, the pattern of decay turned out to be remarkably similar, the study noted. That suggests ancient Greek and Roman underwater ruins across the region face comparable risks of decay, regardless of location.
Researchers said the findings could help shape future conservation strategies, especially as climate change and warming seas continue to alter the marine ecosystems that interact with historic underwater structures.
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