THERE’S been a distinctively off odour troubling motorists and residents near Canning Bridge recently.

The pong is apparently all natural, and just a heap of seagrass decomposing on the riverbank according to Mark Cugley, director at the department of Biodiversity, Conservation and Attractions.

He says warmer weather causes the seagrass to grow rapidly, and when it dies, wind the pushes it towards the banks to decompose.

He says at this time of year the Swan River is full of seagrass and macroalgae and the unfortunate pile-up could happen anywhere along the river foreshore.