A massive sea anemone bed has been discovered during a cutting edge survey of the seafloor environment around Kapiti Island.

"It is hundreds of metres long by tens of metres wide," said Jonathan Gardner, a professor of marine biology at Victoria University.

"We didn't know it was there [in the Rauoterangi Channel] and no one has mentioned it before.

"It must be a hugely productive area."

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Victoria University, NIWA, Department of Conservation and Land Information New Zealand joined forces for the mapping project which was conducted last year and covered 97 square kilometres around the island including the Kapiti Marine Reserve.

The marine environment was nationally important with lots of important ecological features which "we wanted to capture", Mr Gardner said.

Spearheading the unique project was NIWA's new state of the art multibeam mapping unit which fires pulses to the seafloor with the return signal providing valuable info about water depth, seafloor types and habitats, and more.

"The quality and amount of information that it can get is just amazing," Mr Gardner said.

As well as the unit, divers with video cameras were deployed, and various samples taken. Another highlight was finding lots of red algae plants which lived unattached to the seabed.

"These are nationally important and we found big areas of them around Kapiti.

"We knew they were there but we've now got a much better sense of how much is there."

Survey work now involved linking the geology with the biology.

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"We're creating a series of different layers to tell us about the geology, the plants, the animals and so forth."

Some of the survey outcomes could help with current and future management of the area, promote awareness of its richness, and give better knowledge to boaties about hazards, and more.

"We will be setting up a website and making as much of the info available as possible," Mr Gardner said.

"There are all sorts of potential uses and if the community can think of any more uses we're happy to hear from them."

Ben Knight is part of the newly formed Guardians of the Kapiti Marine Reserve, which is a discussion group on Facebook.

He said the mapping would show "Kapiti is a unique, rich and diverse undersea environment with a variety of undersea terrains ranging from sandy/muddy flats and gravel beds rich in shellfish, worms and other invertebrate life to spectacular pinnacles and reefs that are bathed in blue oceanic water over the summer months and receive annual visits from marine life far and wide including kingfish, mako and great white sharks and sun fish".

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COLOURFUL: The Kapiti marine environment is home to various creatures. Photo: Ben Knight
COLOURFUL: The Kapiti marine environment is home to various creatures. Photo: Ben Knight

It would "back up what we are saying" that the reserve "is nationally significant and should be properly protected through a well resourced monitoring and education programme", he said.

It would "support any future proposal for a recreational fishing reserve for the sea area surrounding Kapiti Island from the southern end of the Pukerua Bay reserve north to Otaki and out to the 100m mark".

It would also identify areas of major biodiversity value around the island and allow a more targeted approach to fisheries management at the local level such as that being undertaken by the Marlborough District Council which has recently announced a ban on certain fishing methods such as trawling/dredging in areas of the sounds where there are sites of high biodiversity and natural value.

"There are certain areas around Kapiti Island that may warrant similar protection," he said.

"For example, there is a protected black coral tree in a spot that is popular with local fisherman.

"The mapping project would allow the area this coral is in to be identified and protected from anchoring and other fishing related damage.

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"There are also areas where the mapping data could show, for example, that set netting is damaging a certain type of marine environment due to excessive bycatch or the loss of the net through entanglement leading to the problem known as ghost fishing where the net continues to destroy sea life for years after being lost.

"The bottom line is that if we can use the mapping data to support a more sophisticated approach to fisheries management then that has to be a good thing.

"We expect the findings of the mapping project will add further weight of evidence to our argument that Kapiti Marine Reserve and surrounding sea area is a truly special and unique part of our country that we need to better protect and manage now and for the future," he said.