An "invasive and aggressive" species of seaweed, which has contributed to boating accidents and may severely harm native aquatic life, has been discovered for the first time along the State's coastline. Marine scientists recently found the seaweed, known as japweed, on the Co Wicklow coast, while they were searching for another type of seaweed.
Dr Stefan Kraan of the Marine Institute and the Irish Seaweed Centre, NUI Galway, along with research assistant Kelly Barrington, found the seaweed at Kilmore Quay marina, at the end of last month.
"The introduction of japweed in Irish waters can be quite problematic both economically and ecologically. It has been responsible for fouling fishing gear and boat propellers (causing boating accidents, as well as blocking intake pipes," said Dr Kraan.
The seaweed, Sargassum muticum, can "drastically alter the ecosystem of shallow coastal waters and rock pools by out-competing other species" by taking all the light and nutrients needed to sustain life. This would reduce "the overall seaweed biodiversity", he said and would have "major implications and change the underwater scenery for divers", said Dr Kraan.
The characteristics of the seaweed contribute to its potential threat. It is tough, can regenerate and, crucially, it can reproduce from only small fragments of itself. And once established, populations of the seaweed are self-sustaining.
Efforts at eradication have failed in other places where the seaweed has taken hold.
The Isle of White, for example, the site of the first European discovery of japweed in 1973, tried to eradicate it by removing thousands of tonnes of it from the sea. "To no avail," said Dr Kraan. "It is virtually impossible to remove all the bits."
Scientists believe the seaweed was introduced to the Isle of White in the 1960s by oyster farming in northern France.
The species has spread its geographical range dramatically in the last 40 years.
Endemic to Japan before 1944, the seaweed was first discovered in the Canadian Pacific in the 1950s, and has now colonised the coastlines of North America.
During the 1980s, japweed appeared in Strangford Lough in the North, but the seaweed did not cause widespread damage as it found its own ecological niche, said Dr Kraan.
The marine scientists found the japweed almost by accident. They were trying to determine the current distribution of a type of red seaweed, Asparagopsis armata.
Dr Kraan said there are several possible ways japweed may have arrived in costal waters: on boats; from Strangford Lough by floating on sea currents; carried on anchor chains; or in the ballast water of large tankers. Kilmore Quay experiences a lot of marine traffic, he said, which could be a major factor in the spread.
The seaweed may not lead, however, to economic or ecological damage. It may find a secure niche and keep to itself - like the situation that occurred at Strangford Lough. And it may have potential economic benefits, said Dr Kraan.
Extracts from similar types of seaweed have been used as ingredients in, among other things, pet food, toothpaste, paint, ice cream as well as having medical applications.
Japweed may have extracts that could be mined for these resources; it may also contain other extracts with potential applications, he said.
The future direction and spread of the seaweed in Irish waters is not yet known, said Dr Kraan, as it depends on several environmental factors which influence its biology.