Seaweed riches

It is wonderful - I think so, anyway - that the rocky shores of Mayo and Maine, with the whole Atlantic Ocean between them, should end up growing the same kinds of seaweed, in just the same sequence, from the topmost boulders right down to the waves and far out into the kelp forest. They have their separate niches, their different ways of dealing with exposure, and of surviving, frond by frond, the great surges of the sea. This ecological regime, with local variations in species, goes right round the temperate shores of the world.

It is ridiculous that while the Japanese make culinary use of 50 kinds of seaweed, consuming almost seven kilos a head each year and employing some 80,000 people in cultivating - yes, cultivating - seaweed, most of us still think of dillisk, slouk and carrageen as curiosities of a peasant past. Millions of tonnes of what the Japanese call nori are grown in seawater tanks in glasshouses, much of it for export to Europe. Nori is Porphyra, or laver - or slouk - and grows abundantly all along the Atlantic coasts of Ireland, Britain and France.

It has taken Europe's discovery of Japanese cuisine - sushi restaurants, and so on - to bring "sea vegetables" into fashion. France has a burgeoning seaweed industry that harvests or cultivates a dozen or more species, from the sweet kelp, Laminaria saccharina, to the bright-green sea-lettuce, Ulva lactuca. But these are just a few of the 500 kinds of seaweed that grow around our own shores.

There are five small companies in Ireland harvesting and packaging wild sea vegetables for the health and snackfood markets. An even more lucrative future lies in aquaculture of seaweeds on ropes and rafts moored offshore (the plant's spores are first seeded on to lengths of string in seawater tanks on land). Mussels are already grown in this way to keep them beyond the reach of starfish. Seaweed can be hybridised from selected strains, raised to a standard quality and harvested mechanically, just like any other commercial vegetables.

Kelp species intended for French-fry snackfoods have been grown on ropes off the Isle of Man since the early 1980s. Now, in a project backed by the Marine Institute and the Irish Seaweed Industry Organisation (which is based in the Martin Ryan Marine Science Institute in UCG), the eminently chewable Palmaria palmata, otherwise dillisk, is to be grown on ropes off counties Galway and Clare, fluttering in the sunlit ocean like strings of darkred bunting.

The same research alliance has also surveyed the great biomass of "industrial" seaweeds growing down the whole west coast, from Co Donegal to Co Cork. The intertidal bladderwrack and undersea kelps produce chemicals and gels with a multitude of uses, from plant-growth extracts to body-care products, from printing textiles to making ice-cream slithery and putting the foam on beer.

The mid-shore knotted wrack, Ascophyllum nodosum, is the seaweed that grows in a thick, goldenolive fringe on sheltered inlets of the coast. The greater the shelter, the more rapid the growth, so that in the deep maze of south Connemara's shore, for example, the regeneration cycle is as little as three to four years. Ascophyllum has been the mainstay of the Irish seaweed industry for 50 years - but mostly as a basic raw material, dried and milled and exported to the alginate industry in Scotland.

AT least it can be said that Arramara Teoranta, at Kilkieran, with its State shareholding, has never abused its natural resource. Indeed, the new survey shows that the harvest could be doubled, quite sustainably, to something like 75,000 wet tonnes along 1,200 km of coastline.

The really big potential would seem to lie in the millions of tonnes of kelp - the five Laminaria species - which grow in dense beds along half the west coast and in the shelter of many of its islands, with Galway, once again, the richest area. Until the new survey, the extent of this resource had scarcely been identified, let alone harvested, except in the passive gathering of "sea rods" - the thick, fleshy stems of the kelp plants - washed up after storms and processed by Arramara.

The Norwegians harvest the living kelp (166,000 tonnes of it a year) by towing dredges through the kelp forest that drag the plants off the rock - as much as a tonne in a single sweep. The "harvested" areas do regrow, but even after four or five years the plants are only two-thirds the size they should be.

Kelp is hugely important in the inshore ecosystem. It is grazed directly by marine creatures such as sea urchins and gives physical support to a great diversity of animals and plants. It provides a nursery ground for fish and scallops, and enriches the water around it with dissolved trace elements and particles.

In this way, a bed of Laminaria hyperborea is like a forest ashore, full of birds, animals and insects. It shelters other plants and - like a windbreak wood - helps to absorb the energy of waves arriving from the west and so to reduce the impact of breakers on sandy beaches.

The new survey says nothing about how the kelps should be harvested, or how often. But it does stress their importance in the marine ecosystem of the west coast and "in maintaining its rich biodiversity and unique attractions to the ever-increasing tourism industry". Dr Michael Guiry, Prof of Botany in UCG, has been a prime mover in urging the sustainable use of seaweed resources - he has written extensively about them and helped produce the current survey* - and his presence is reassuring.

With 501 native species to choose from, there should at least be no need to take risks with alien kinds, as the French, unfortunately, have done.

In the 1980s, the Japanese wakame seaweed, Undaria pinnatifida, was cultivated off the west coast of Brittany from laboratory seeding. The sea temperatures were thought to be too low to allow reproduction. They weren't. The seaweed has already colonised one bay, and will probably make its way north to Ireland and Scotland, even Norway. It will follow the dreaded Japanese crab, teeming and omnivorous, that arrived in Brittany with half-grown Pacific oysters.

* Mapping and Assessment of the Seaweed Resources (Ascophyllum nodosum, Laminaria spp.) off the West Coast of Ireland is available from the Marine Institute, 80 Harcourt Street, Dublin 2.