July 29, 2008

Marine Life Fears After Japanese Seaweed Found Growing Off West Coast


A SPECIES of Japanese seaweed which threatens the health of our seas has been discovered off the west coast of Scotland for the first time.

The alien species, Heterosiphonia japonica, was found in May by Dr Colin Moore, of the Centre for Marine Biodiversity and Biotechnology at Heriot-Watt University. He was diving off the island of Oronsay at the mouth of Loch Sunart between the Ardnamurchan and Morvern peninsulas when he found the species which forms dense red tufts up to 30cm long.

Dr Moore said the seaweed could affect species of fish and invertebrates.

"What really concerns me is the consequences of this arrival are unknown, " he said. "This is new to Scotland, but in Norway it has densely coated the maerl beds which are a bit like coral reefs in that they are a home to a diversity of animals and plants. So the worry is that this seaweed might take over, out-compete all the other plants and we could get something like a mono-culture destroying the natural diversity of our rich marine habitat."

Mr Moore said maerl was made up of twig-like nodules of calcium carbonate produced by the pink algae which coats the surface of the nodules. It grows at about one millimetre per year, but supports an extremely high diversity of life.

On one site off the west coast, Dr Moore had recorded 185 different species living on the surface of the maerl and 174 species living between the maerl twigs.

Heterosiphonia japonica has existed in the Pacific but was first recorded in Europe as recently as 1994, when it was spotted living in oyster ponds in the Netherlands.

It has since turned up in oyster farming areas in France and Spain and over a period of about 10 years has spread over much of the Norwegian coast . Mr Moore said it was likely the alien seaweed arrived in Europe either with imported oysters or in the ballast water of ships.

"This seaweed breaks up into fragments which can live for a long time in darkness and can colonise other areas through vegetative reproduction, " he said. "Normally baby oysters are reared on land in the UK so I think it more likely it came here in ballast water. " He examined samples in a laboratory to identify the species as Heterosiphonia japonica. Since then he has been looking at its distribution and abundance and has subsequently found it elsewhere in Loch Sunart and Loch Creran in north Argyll. At some sites it has already become the dominant seaweed, coating the rocks in shallow waters down to at least 10m.

Mr Moore said: "We have only just found this seaweed so now we would like to investigate its spread and see whether any damage is being done to sensitive habitats like maerl beds. " He has worked closely with SNH on the conservation of Scottish marine habitats and species.

Dr Fiona Manson, marine advisory officer at SNH, said: "At the moment we don't know what impact it will have on marine wildlife although it is likely it will reduce the diversity of our native seaweeds by outgrowing them, as it has in other parts of Europe.

"Now it is here there is not much we can do to eradicate it but, like wireweed (Sargassum muticum), another nonnative species of seaweed that is spreading rapidly around the west coast, it's important boat users and others take care not to spread it further. "

Originally published by Newsquest Media Group.

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