Two campaigns have been launched to prevent a channel being "gouged" through an existing Falmouth marine site and to protect an at risk zone which is home to fish, molluscs and crustaceans.

The Marine Conservation Society and Falmouth Friends of the Earth are seeking public support against plans which they say would "destroy" the Fal and Helford Special Area of Conservation (SAC) by dredging a new channel for Falmouth Docks.

With the government's marine regulator the Marine Management Organisation set to give pre-application advice on the plans from Falmouth Harbour Commissioners, the two organisations started a campaign on September 23 which they say has already gained the support of thousands.

The area was awarded protected status for its exceptional biodiversity, but earlier this year Falmouth Harbour Commissioners submitted new evidence which they say shows mitigation of any ecological impacts.

Emily Williams, MCS campaign officer, said: “This decision should be about conservation, and yet the site is being jeopardised because of the interests of a few. Given the fragility and uniqueness of the wildlife found here, the MMO must be robust in all processes relating to this proposal and consider all the evidence that is made available to them. Ultimately, they must recognise that damaging activities on this scale should not be up for consideration in a protected site.”

A report commissioned by the Marine Conservation Society and produced by local scientist Dr Miles Hoskin claims that live maerl in the area, which provides vital habitat for many species, would be killed. It also raises important questions about the release of large quantities of waste materials into surrounding areas which could smother wildlife-rich habitats including prime fishing ground.

Meanwhile, the Cornwall Wildlife Trust is calling for public support for a new Marine Conservation Zone to protect aquatic wildlife in an area around 14 miles off the coast of Falmouth.

The government is set to consult on the allocation of 50 of these zones, where the seabed is protected to safeguard ecological diversity, including important spawning grounds.

The South East of Falmouth site is home to mackerel, smelt, monkfish and gurnard, as well as small spotted catsharks, and is currently identified as being at high risk of damage and deterioration.

The trust has produced a report, The case for more Marine Conservation Zones, which will be handed to environment minister, Therese Coffey ahead of the public consultation next year.

Dr Nick Tregenza, trustee for Cornwall Wildlife Trust, said: "This is the much needed next step to complete an effective network of protected areas at sea. If the government lives up to its stated commitments such a network would put us at the forefront of worldwide marine conservation. "Designating these additional 48 wild havens as Marine Conservation Zones will go some way to guaranteeing a future for the extraordinarily diverse natural landscapes that exist beneath the waves off our coast."

And Ruth Williams, the group's marine conservation manager, added: "We know that the public support an ecologically strong network of protected areas at sea and we want the government to be as ambitious as possible in order to restore decades of decline in the health of our seas and enable recovery in future."

For more information and to support the Cornwall Wildlife Trust's campaign on MCZs, go to wildlifetrusts.org/MCZs

To join the campaign to protect Falmouth's SAC go to www.mcsuk.org/savefalbay