Concerns have been raised about the decline of the common toad in Valley Ponds in Newhaven by a conservation group member.
Keith Corbett, from the Friends of Newhaven Valley Ponds, said the toad population had plummeted from more than 1,000 to just 83.
Lewes District Council stressed it was keen to work with the group but added the toads’ falling numbers was a complex issue.
Keith said: “Southern Water chose to run their surface water drainage straight into the ponds without any oil interceptor or even silt traps, and with the point of entry as that favoured by toads arriving back to spawn.
“After rain thick oil is clearly visible emerging from their first culvert, and then as oil films on through the next two ponds. Needless to say such pollution is an immediate hazard to an amphibian’s skin.”
The district council, which manages Valley Ponds on behalf of Newhaven Town Council, said: “The demise of toads is a complex issue and there are many theories including viruses, droughts, changing habitats and pollution.
“Our officers are in regular contact with colleagues at Southern Water and we join with them in providing advice and information to residents on how to dispose of oil and other materials that may cause pollution.”
Southern Water said these ponds and the surface water pipes existed before water companies were privatised in 1989.
It added the pipes carried water from roofs and roads into the ponds, topping them up with water and preventing flooding.
Southern Water said its inspector noted the ponds were teeming with life and found no sign of pollution or any problems.
Surface water pipes can be contaminated by spills of oil or fuel on roads or by people pouring substances down the drains.
A spokesman for the water company said: “It is important to note that in this instance it has not been established what, if anything, has made its way into the ponds. Silt traps and filters are not normally placed at the end of surface water pipes because they are ineffective during high volumes of water during storms – causing the system to back up and flood. Such devices are better placed before the point of entry into the sewer such as on road gullies, which are the responsibility of the local authority.”
While on site Southern Water inspected a nearby wastewater sewer which was becoming blocked with congealed cooking oil.
It said this would be cleared.
Keith said: “A leading reason for identifying this site for nature conservation was the presence of a declining yet UK Biodiversity Action Plan (BAP) species – the ‘common’ toad. Its population here had been carefully monitored each spring over a number of years; sadly, this has now revealed a reduction from over 1,000 down to but 83.”
Keith said significant losses came from road deaths from ever increasing cars, taxis, vans, and buses on the estate but added he was concerned about the pollution getting into the ponds from the Southern Water’s surface water pipes.