18th December

Undaria: the latest invasive seaweed species to reach Ireland

Dr Stefan Kraan, Ocean Harvest Technology

With seaweed being heralded as the superfood of the 21st century, many Irish people will be familiar with Wakame (Undaria pinnatifida), the edible brown seaweed - or sea vegetable – with a subtly sweet, nutty flavour, popular in Asian cusine, as an ingredient in healthy snack foods and a tasty additive for soups and salads.

12.3 OHT Undaria

Undaria growing in Kilmore Quay, Co Wexford

A member of the kelp family of seaweeds, Wakame is a native of the Pacific where it has been wild harvested for generations and more recently has been cultivated in large quantities for human consumption.

 

 

In Japan, Korea and China, thousands of hectares of coastline are devoted to farming Wakame, and tens of thousands of people are engaged in some form of seaweed aquaculture. According to the FAO, well over two million tonnes of Wakame - worth more than one billion dollars – are harvested annually.

In northwest Europe, our kelp Alaria esculenta - for which I have coined the name ‘Atlantic Wakame’, is similar to its Asian cousin in taste and nutritional value. Market demand for Atlantic Wakame is however much smaller.

Nevertheless, with the uses and applications of seaweed on the increase in Europe, cultivation will be the key to control quality and quantity. The European market for seaweeds is destined to grow considerably as its benefits as nutritious and healthy becomes more widely known and appreciated.

How did Asian Wakame get to Europe?

In 1971, Wakame was accidentally introduced with oyster spat from Japan to the Étang de Thau - the largest of a string of lagoons (étangs) stretching along the French coast from the Rhône River to the foothills of the Pyrenees and the border to Spain in the Languedoc-Roussillon. Wakame was subsequently introduced to the French Atlantic coast in 1983 when an attempt was made to cultivate it commercially for the export market.

At the time it was assumed that Wakame could not reproduce under the conditions of the French Atlantic coast. Shortly after its introduction however, the seaweed ‘escaped’ from the farm and began colonising areas of bays and harbours in Brittany where it soon became a local nuisance, clogging marinas, navigation channels and blocking the intake pipes to power stations.

By 1990, Asian Wakame was growing in Spain; by 1994 it had been recorded in the UK; by 1999 in Belgium and The Netherlands, and by 2008 it was found in Portugal. In 2012 it was spotted for the first time in Belfast Lough, currently the most northerly population of it to be seen in Europe.

Arrival in the Republic of Ireland

Between 2000 and 2003, large-scale surveys along Ireland’s southeast coast and spot checks at Clogherhead ; Howth Marina and Kilmore Quay, Co. Wexford, failed to find any Asian Wakame. As these ports handle large volumes of traffic between Ireland, England and France, they became prime candidates for early colonisation of Wakame.

We did however find another invasive brown seaweed species for the first time in Ireland ― the wire weed, or Sargassum muticum ― in 2001. In June of this year, Wakame was found growing on the pontoons at the marina in Kilmore Quay. The fact that this colony consisted of several fertile plants was a clear indication that a steady population has been present in this area for several years at least.

Ecological impact/implication

In France and Spain in the mid ‘90s, several farms were developed and succeeded to produce up to 100 tonnes dry weight of product. It was concluded that farming Wakame did not have any adverse ecological impact on native seaweeds in these countries, even when different species occurred together in some areas. Nevertheless, as with other native seaweed species, Wakame will probably continue to be a major fouling algae in harbour areas.

Asian Wakame contains the bioactive substance, fucoidan ― a class of naturally-occurring carbohydrates classified as sulphated polysaccharides. Several peer-reviewed studies have already reported the benefits of fucoidans in the treatment of cancers, ranging from anti tumoral, anti-proliferation, to immune stimulation and other health benefits.

Besides its nutritional value as a sea vegetable therefore, Wakame is becoming the focus of interest from the functional food perspective.

Now that Wakame has been resident in Ireland for several years, the question must be asked should we start cultivating it commercially and to exploit its high value as a food and its potential bioactives for health applications?

In view of the fact that Wakame in Europe has not impacted negatively on species biodiversity or on the environment in general and with a highly developed market for it in Asia and a growing market in Europe, the answer is obvious.

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