A sandy beach in Marsaxlokk has been completely covered in empty shells over the past few days in what a marine biologist has described as a very rare phenomenon.

“Abroad, there are numerous bays which are covered in seashells but on Maltese coastlines it is quite rare and, when it does happen, it is never at the large scale we see here in Marsaxlokk,” Alan Deidun told Times of Malta.

Shells of mollusc species, like clams and cockles, have coated the whole beach, which lies at the inner part of the bay near Hunter’s Tower.

Strong south-east winds generated very large waves strong enough to either dislodge the burrowed creatures or pick up empty shells at the bottom of the seabed- Alan Deidun

Deidun said such species are usually found in shallow waters and close to harbours. He put forward three possible reasons for the invasion of shells.

One, and the most likely, is the windy weather.

“Over the last few weeks, we have experienced strong south-east winds, which generated very large waves strong enough to either dislodge the burrowed creatures or pick up empty shells at the bottom of the seabed.

“So, they get washed up on the bay,” he said, pointing out that the shells are likely to have been empty for a while and were previously at the bottom of the seabed.

A mix of colourful shells found on the beach. Photo: Jonathan Borg

Another reason for the rare sighting in Marsaxlokk could be seabed dredging.

In dredging, layers of silt and sand are removed from the seabed, usually before construction work on the bay is carried out.

“This is speculation because I don’t know whether any dredging took place recently in Marsaxlokk, however, it could be another explanation for what has happened at the bay,” Deidun said.

He was quick to dismiss another possible reason: pollution.

“Since such species are usually found in harbours known for their poor sea quality, the species are tolerant to pollution,” he said.

However, unless there was a major oil spill in recent days that killed all the species, it is unlikely the shell-filled bay is a result of pollution, he added.

“I believe the main reason is due to the strong winds but I do not ignore the idea that it could have been a combination of all three,” Deidun said.

He cautioned against throwing the shells back into the sea, saying it was best to leave them where they lay. They might attract shell collectors or fishing enthusiasts, who would look for clams or cockles still alive, to be used later on for bait.

Also, leaving the bay as it is would reduce trampling, which could affect the biodiversity of the bay.

Should there be concern over the phenomenon?

Deidun says it depends on the reason behind the washed-up shells.

“Since we do not know if it is because of dredging, pollution or the strong currents, it is hard to say,” he said.

“Of course, if we start seeing a repetition and pattern of this marine phenomenon, then, yes, it will raise eyebrows and be worth investigating.”