Ancient shellfish used for purple dye vanishes from eastern Med

Red-mouthed rock shell was one of main sources of Tyrian purple and study blames its collapse on rising sea temperatures

Peter Beaumont in Jerusalem

Monday 5 December 2016 15.24 GMT

The shellfish that was one of the main sources of Tyrian purple – one of the most storied and valuable trading products in the ancient world – has disappeared from the eastern Mediterranean coast, amid warnings of an ongoing multi-species collapse blamed on global rises in sea temperatures.

Described by Aristotle and Pliny among other ancient writers, Tyrian purple or imperial purple was a dye extracted from shellfish along the Levant coast and favoured by emperors and kings in a trade of huge value. Associated with royalty, clothes with purple in them were believed to convey high status.

A new Israeli survey of shallow water Mediterranean habitats has noted the almost total disappearance of stramonita haemastoma – the red-mouthed rock shell – which was one of the two main sources of the dyes.

In a survey for Nature’s Scientific Reports, the Israeli marine biologist Gil Rilov identified the mollusc as one of a number of species to have vanished in recent decades from shallow eastern Mediterranean coastal waters highly vulnerable to sharp temperature changes. 

Rilov said coastal waters were a “potential hotspot” for species collapse and present-day surveys had failed to find 38 of 59 mollusc species once common on Levant reefs. In addition, he said he found strong evidence for major, sustained population collapses of two urchins, one large predatory gastropod and a reef-building gastropod.

“Temperature trends indicate an exceptional warming of the coastal waters in the past three decades,” he wrote. “Though speculative at this stage, the fast rise … may have helped push these invertebrates beyond their physiological tolerance limits leading to population collapses and possible extirpations. 

“If so, these collapses may indicate the initiation of a multi-species range contraction at the Mediterranean south-eastern edge that may spread westward with additional warming.”

Among the species identified by Rilov as having almost entirely disappeared from areas in Israel and elsewhere in the region where it once existed was the red-mouthed rock shell.

Continued