Mussel Wash Up 3 2014 12 02

It must have been a bit of shock for the locals living in South Africa’s Plettenberg Bay when they awoke recently to find their characteristically gorgeous beaches littered with masses of mussels. It’s certainly not the first time the world has seen this phenomenon (Staten Island, Connecticut and Hua Hin beach in Thailand have all had their share of washed-up bivalves in recent years) and local scientists are offering a number of theories to explain the mussel mystery.

Although the wash-up initially sparked fears that a destructive algae bloom called a red tide may be responsible, most experts are doubtful that this is the cause. According to South African National Parks marine ecologist Kyle Smith, the event was most likely the result of a large ocean swell. “If you start to get very dense beds of mussels, a strong sea can potentially rip off large “mats” of [them],” he explains. “Apparently most of the mussels were still alive when they washed up, which strengthens this argument.”

Another theory from Professor Christopher McQuaid of Rhodes University, who identified the bivalves as Choromytilus meridionalis, a native species more common on the west coast of South Africa, is that the mussels may have been attached to ropes used in octopus aquaculture. Although he stresses that it is merely speculation, some of the mussels were found attached to some hemp rope and black plastic boxes that resemble the kind of equipment used in octopus farming facilities.

“This really is speculation, but it's a possibility, given the rope and the boxes and the fact that the mussels were all alive when they reached the shore and had obviously grown sub-tidally – the shells were remarkably clean with none of the usual epibiont organisms or shell-eroding cyanobacteria. Having said that, I have no idea if there is or ever was an octopus growing facility in Plettenberg Bay or the vicinity.”

The Earth Touch crew headed to the beach to film the miles of mussels:

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