THESE pictures show “foul-smelling”, brown foam in the sea off Brighton beach.

A concerned photographer said the murky water was “swirling around” near one of the groynes, with swimmers avoiding the area.

He described the water has having a “foul-smelling stench”.

The Argus: Algae in the sea off Brighton beach Algae in the sea off Brighton beach

Last week, Brighton and Hove City Council dispelled concerns that a similar looking brown-foam in Southwick was algae and not sewage.

A council spokesman said it is common for marine algae to be “mistaken for sewage”.

He said: “This is marine algae in a stage of rapid growth.

The Argus: Similar foam was spotted in SouthwickSimilar foam was spotted in Southwick

“It is composed of microscopic plant and animal plankton, not raw sewage. This is a natural process.

“After the spring equinox, when daylight hours and sunlight increase, the plant (and animal) plankton in the water column respond.

“The plant plankton photosynthesise and proliferate, the animal plankton responds in turn as the plant plankton is a food source.

“Eventually, the algae bloom dies off once the oxygen and nutrient levels in the water have been depleted.

“The various colours seen relate to the algae in various stages of growth. If there is an unpleasant smell, it is due to the algae having died and entered the stage of decomposition - think rotting vegetables.

“If the sunny conditions combine with southerly winds, the algae is ‘whipped up’ onto the surface and blown onto the coastline. This is what is seen and is sometimes mistaken for sewage.”

The Environment Agency has released information to help beach goers determine the difference between algae and sewage.

The advice states: “Marine algae can affect our coastline and shores, especially after windy conditions following warm weather, and is often mistaken for sewage.

“If you notice foam on the water’s surface or on the beach this is likely to be the result of algae dying off and breaking down. It is very unlikely to be sewage.”

It said the sewage discharges was unlikely to form as foam or scum on the surface of the water.

A spokesman for the agency said: “If you are concerned that what you see is not algae and is some other kind of pollution, please phone the Environment Agency’s free 24-hour emergency hotline on 0800 80 70 60.”