A seaweed survey conducted off the north Norfolk coast has uncovered a purple sponge never before seen in the United Kingdom.

Surveying the North Sea at a number of locations between Northumberland and Essex over a period of 10 days earlier this month, experts also found seaweed species new to the east coast of England, including the 'reflexed grape weed' or red seaweed.

An unidentified sea-slug which is new to Norfolk was also found, while the unknown purple sponge was discovered during dives off East Runton, near Cromer.

In total The Seaweed East survey found 131 types of seaweed, including four non-native species, while starlet sea anemones, which are listed as a conservation priority in the UK, were seen along the Suffolk and Norfolk coast.

The Wildlife Trusts helped fund and coordinate Seaweed East in conjunction with Seasearch, a volunteer organisation for divers to get involved with surveying the marine wildlife they encounter in the UK.

The project focused on seaweed but the team of surveyors – which included marine biologists, volunteer divers, a botanist and a wild food expert – used the opportunity to look at other species in the relatively unexplored waters.

Joan Edwards, head of living seas for the Wildlife Trusts, said: 'This survey has thrown up some important finds.

'Although the main objective was to survey seaweed, the team took advantage of being in a relatively unexplored environment to survey other species, resulting in the sponge discovery off Norfolk.

'The samples and results are still awaiting full analysis. We have no doubt that once this is done they'll form a crucial part of our knowledge base around what's living in the North Sea off the east coast of England.'

The information gathered from the research – along with a Wildlife Trusts scheme to analyse nature on the shoreline – could be used in the future to help identify areas of special importance for marine life above and below the sea surface.