Divers are scouring the seabed off Peacehaven for signs of a tiny worm whose existence could affect plans for a £200 million sewage treatment works.

Over many years the creatures, known as ross worms, can help create natural reefs, which provide a home for other marine creatures such as crabs.

They do this by gradually building up the sand grain tubes in which they live.

They commonly occur around the coastline in low numbers as a thin crust on gravel or rocky seabeds.

In areas where conditions are favourable large numbers can build reefs up to 60cm off the seabed.

Marine ecologists from Emu Ltd are searching for the worms at Friars Bay, off Peacehaven, as part of a survey by Southern Water.

The water firm is preparing to lodge plans for a new £200 million treatment works at Lower Hoddern Farm, Peacehaven.

But before the application can be submitted various environmental and archaeological surveys must be completed.

The results will show the company if the worm is building reefs in this area so that a long sea outfall pipe, which will release the treated sewage out to sea, can be tunnelled beneath the seabed to avoid the most environmentally-sensitive locations.

The search was carried out at a depth of eight metres, with one team of divers following a 100-metre-long rope to note any relevant marine life. They used an underwater slate and pencil.

A second diving team then followed with a camera and video so that a permanent record could be taken back to the laboratory for analysis.

Damon Elliott, Southern Water's major projects manager, said: "The extensive environmental, landscape, engineering and archaeological surveys are a vital part of our investigation work.

"They will allow us to assess properly any impact the works may have and, if necessary, include appropriate mitigation measures in our final detailed proposals."

The proposed treatment works will deal with the 95 million litres of waste water generated every day by residents of Brighton and Hove, Woodingdean, Ovingdean, Rottingdean, Saltdean, Telscombe Cliffs and Peacehaven.

Southern Water chose the site at Peacehaven after looking at 66 possible sites, which were later reduced to a shortlist of eight.

This followed the rejection of Southern Water's plans to expand its existing treatment works at Portobello, near Telscombe Cliffs.

Peacehaven residents reacted angrily when their town was chosen for the works and sludge recycling centre.

Many said their town would become "Poohaven" and claimed the works could damage property prices and create nasty smells.

Southern Water says the plant is needed because Brighton and Hove is the only Sussex resort unable to meet the latest European environmental standards on sewage treatment.