A meeting at the Poly in Falmouth on Thursday saw scientists, environmentalists and fishermen discuss why they believe the dredging operation in Falmouth Harbour “poses a threat to the marine environment in Falmouth Bay and the Carrick Roads”.

Organised by Falmouth Friends of the Earth, the meeting heard from Dr Jean-Luc Solandt of the Marine Conservation Society, whose grandfather served as harbourmaster in Falmouth, that beds of rare, coral-like maerl are vital to the area’s marine eco-system and that they were “highly vulnerable to impacts from the dredge both within and beyond the immediate dredging path”.

Dr Solandt said: “The law as it applies to the Special Area of Conservation is clear. There has to be proof that there will be no deterioration in the condition of the maerl. The Marine Conservation Society cannot believe that this will be the case given the huge quantities of silt that will be released into the water column and spread around the site from this proposal. ”

Mylor-based fisherman Dave Thomas, who co-founded the Falmouth Bay and Harbour Action Group to oppose the dredge, said that over a million tonnes of spoil from the dredge would “simply be dumped offshore in Falmouth Bay, where a much smaller dump in 2001 – a mere 47,000 tonnes – wiped out the mackerel and whiting fishery for several years”.

“The fishing didn’t really recover till 2009,” said Mr Thomas, “So you can just imagine what 1.1 million tonnes of this stuff is going to do.”

Mr Thomas said that silt, some of it contaminated with highly toxic substances such as TBT from anti-fouling paint, would inevitably spread over a very wide area of the seabed.

Marine biologist Dr Miles Hoskin claimed the estimated multi-million pound cost of the dredge would be carried by Cornwall’s council tax payers over many years, with the final cost much higher, as the money would need to be borrowed by Cornwall Council from the Treasury and then paid back with interest.

He also argued that such spending appeared to be in breach of EU regulations that rule out government subsidies for private companies.

Tom Scott of Falmouth Friends of the Earth said: “Proponents of the dredge – not least Chancellor George Osborne – have framed the argument as people who care about jobs on the one hand and people who care about insignificant algae on the other. But it’s a false contrast.

“We need to be looking at developing the local economy and creating jobs in ways that do not damage the natural environment that’s so important not just to fishing and tourism, but to the future of Falmouth and Cornwall as a whole.”

A spokesman for Falmouth Harbour Commissioners said: “The issue of sediment movement has been extensively modelled and is something the Marine Management Organisation will examine closely as part of its independent and detailed deliberations into whether or not to grant consent to dredge. The Port of Falmouth Development Initiative partners are considering potential uses for spoil to reduce the amount that would be deposited offshore from any dredge, and we have offered to meet representatives of the fishing industry to explain this.”