Foam builds up on Durban beaches. Picture: Duncan Guy

Durban - Dirty-looking seas this week had people on the Dolphin Coast wondering whether the ocean was mucky with human-made pollution.

Coupled with dirty water were large numbers of dead cuttlefish that had beached.

However, it is speculated that it had more to do with the heavy seas and cold water temperatures than pollution.

Ezemvelo KZN marine coastal manager Lionel van Schoor told The Independent on Saturday that it could be compared with what happens in a marine fish tank where water is pushed through a column, taking with it the toxins that develop.

“A scum is formed on top of the tank and it’s exactly the same as the foam that washes up on the beach.”

In the sea, sediments and rubbish in the water come up as a result of easterly winds that push cold water up from the depths.

These meet south winds that bring warm water as a result of slowing down the Agulhas Current.

Van Schoor said that it was not unusual for dead cuttlefish to wash up at this time of year, although this year the number was far higher than usual.

Carcasses were often ravaged because, while in the sea, they provided food for other fish which nibbled on them.

SA Association for Marine Biological Research senior scientist Sean Fennessy added it was possible nutrients from the colder depths had caused an algae bloom when they entered warmer, shallower water.

He said that it would take some time before data had been collected from along the coastline, and processed, and a more conclusive explanation would be forthcoming.

However, he cast doubts on pollution being a factor because only one fish species – the cuttlefish – had been found dead in great numbers on the beaches.