The uses of seaweeds in iceland

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Fourth International Seaweed Symposium 1961 France
*(on Rhodymenia palmata) commonly referred to as Dulse


The State Electricity Authority, Geothermal Department, Reykjavik, Iceland

SEAWEEDs have been used in Iceland for over 1000 years as food, animal fodder, fuel, manure and for dyeing, medicinal purposes, the making of kelp and for various minor uses, and numerous references on this can be found in the extensive literature written in Iceland during the past eight centuries.

The following extract is intended as an introduction to those interested but not familiar with the Icelandic literature on the subject.

According to the Icelandic Sagas, Rhodymenia palmata   called "sol" in Iceland   has been known to be edible since at least the year 961.

The Icelanders' oldest lawbook written in the first half of the twelfth century mentions the right to collect s6l and in addition, the right to eat s6l when on another man's land which means that sol was also eaten fresh.

The right to collect sol was considered a great concession and licence were issued to many churches all around Iceland.

References relating to events happening in 1118 mention the collecting, of and trading with sol. From this time to the end of the nineteenth century sol was a common victual transported over long distances and sold in exchange for wool, meat, etc., to the inland farmers. Thus sol ap­parently was eaten by both poor and rich.

So1 was collected at low water,, usually in late August, when it was mature. In some places it was washed thoroughly in fresh water, dried like hay and packed in barrels or special huts where it was kept dry and compressed, sometimes for months.

The sol was often eaten daily with dried fish and butter or with milk and in bread.

Sol may be considered as having been to some extent a substitute for vegetables and a source of vitamins with the advantage of being easily preserved. So1 has always been highly valued ,in Iceland as a palatable, healthy and nourishing food and a cure for many ailments such as nausea, indigestion, seasickness, etc.


At the beginning of the twentieth century farmers near one of the two major s6l localities commonly prepared up to over a ton of dried S61 per summer, but nowadays s6l is only occasionally collected and dried.

The second best known of the edible seaweeds, Alaria esculenta (and pylaiei), was used to a considerable extent as food during the past centuries. It was steeped f6r 2 days in fresh water, chopped, cooked with water or milk and flour and eaten as a thick pudding with milk or cream. The midrib of the frond was considered to be easily digested.

Chondrus crispus and Gigartina mamillosa growing mainly on the south and south west coast were often picked along with the s6l, but eaten mainly during hard seasons. The method of preparation was somewhat similar to that for Alaria.

There is evidence that all the Laminariaceae and the Fucaceae species, have been used for human consumption in the following order of pre­ference:

Laminaria digitata (probably the frond only) and, in times of starvation, the frond of Laminaria cloustoni and lastly the Fucaceae, mainly the abund­ant Ascophyllum nodosum.
The major uses of brown and red seaweeds in Iceland have been for the~ grazing of sheep, and to a lesser extent horses and cattle. Since early times sheep have resorted to the seaweed beaches when the grassland was snow­bound or because of lack of grassland altogether, but also in order to save hay many farmers grazed their sheep on seaweeds. The sheep were ­fed entirely on seaweeds for 6 8 weeks and sometimes up to 18 weeks a­ year, and in many places the farmers relied on the cast weed. Thus seaweed grazing was considered a great advantage.

Sheep grazing on cast weed selectively choose certain species and seem to prefer species like R. palmata and Alaria. Further it is known that horses carefully pick the youngest part of the frond of L. saccharina.

But it is only in the past 10 years or so that grazing on seaweed in Iceland ­has had some attention on a scientific level. It has been found that when eating much seaweed (it may be as much as 10 kg per day per animal) during the latter half of the gestation period a certain (frequently fatal) nervous disorder or demyelination occurs in newly born and young lambs. This has been found to be similar to the well known "swayback" (enzootic ataxia) and could be prevented by giving copper supplement to the pregnant ewes, indicating a partial utilization of copper contained in the seaweed.
By using more hay, less seaweed and some copper sulphate during the gestation period, this disorder is much less widespread now than it was 30 40 years ago, when on some farms the mortality of lambs born was up to 90 per cent. At least 10,000 ewes or about I per cent of the total stock in Iceland today feeds on fresh seaweed.

As to any beneficial effects such as fattening, increase in wool production and fertility due to feeding on seaweeds we have no scientific proof. Never­theless many have faith in seaweeds for improving the health of the animals in general. On the other hand since concentrated fodder was introduced and more and better hay produced the sheep do not seem to take as much to the fresh seaweeds although this varies considerably from place to place.

Both dried R. palmata and dried and cooked Alaria have for centuries been used for cattle, sheep and horses. This was considered a good milk producing and fattening fodder.

Around the year 1900 fresh Laminariaceae were successfully preserved by ensiling and reported to give a wholesome and palatable fodder for sheep.

Fresh Alaria was also dried after washing in the rain and put in between la yers of hay and thus given to cattle and sheep with encouraging results.

In 1939 41, production of Ascophyllum meal was attempted for the first time in Iceland in a specially,designed drying plant using geothermal heat.

Production of seaweed meal was again started in 1960 as a result of recent experimental work on the drying of Ascophyllum nodosum, and the present time the product is sold as supplementary fodder on the home market.
In the past two years some experiments have been made on the effect of seaweed meal on fertility of sheep compared to that of herring meal, mineral supplements and the plain basic ration. The results show that fertility of sheep is improved, when using seaweed meal as the only supplement to a basic ration of hay alone, but in some cases inferior to herring meal although superior to a conventional admixture of mineral salts.
Where peat was scarce dried seaweeds have been used as fuel up to the beginning of this century. The main species used was A. nodosum cast or cut. Other Fucaceae and stipes of L. cloustoni and L. digitata have also been used. When cut, A. nodosum was either carried,  tugged in nets or let drift ashore, dried and stored in covered stacks for the winter months.




Between 1775 and 1854 various experiment were carried out on the burning of Laminaria species for the making of kelp and, in one case, preparation of iodine and Glauber's salt.

The only lasting production of kelp, however, was done between 1903 and 1908 near Reykjavik. The method used was to blow hot exhaust gas from a coal furnace through the fresh stipes. Experiments were also done successfully by preserving the seaweed under compression.

Cast weeds are still collected by gardeners in Iceland for use as manure. The older method of preparation was to let the cast weed decompose in heaps but preferably it had to be soaked in boiling water.

In the past two years seaweed meal has found use as a fertilizer for grass, trees and vegetables. Also some preliminary observations have been made on the use of seaweed meal as a soil conditioner.

Seaweed extract has recently been introduced in Iceland and used with promising results as supplementary fertilizer for tomatoes, flowers and vegetables in greenhouses.
According to references from the eighteenth century some seaweeds such as A. nodosum were used for dyeing home spun cloth. Other species were used as medicine against heart ailments and indigestion, on wounds, to protect plants against frost, as fillings in cushions, for cleaning, as lampwicks, and various other smaller uses.

There is thus evidence that 3 red seaweeds and 13 brown seaweeds have been used in Iceland.

The most outstanding botanical work ever done on the botany of seaweeds around Iceland was by the late Dr. H. Jo'nsson around 1900 who found and classified 200 seaweed species in Icelandic water. Of these 76 species belong to the red seaweeds and 67 species to the brown seaweeds. Since then hardly anything has been done in this field.


In order to evaluate the food value of the principal edible seaweeds, several analyses were done in 1903 8. These indicated the following order of value as foodstuff: Porphyra umbilicalis, R. palmata, L. saccharina, L. digitata, Gigartina mamillosa, A. esculenta, and then the Fucaceae.

It may be noticed that A. esculenta and G. mamillosa are listed here as being inferior to the two Laminaria species, otherwise these results coin­cide with the centuries' long experience.

In 1938 9 investigations were carried out on the possibilities for the exporting of dried and bleached C. crispus and G. mamillosa found on the west and south west coast. Although the results were rather favourable these species still remain unutilized.

In the past 15 years intermittent work has been carried out on cast weed, L. digitata, L. saccharina and A. nodosum. In 1946 7 investigations were carried out on the occurence, composition, quality and magnitude of cast seaweeds on the south and south west coast. These investigations were made with the possible production of alginates in mind, and included analyses of L. digitata and L. saccharina from near Reykjavik with respect to alginic acid and ash content. The conclusion was that it would not be­feasible to build an alginate factory using this cast weed as raw material

In the following years it was realized that geothermal heat, although of localized nature, could play a basic role in the utilization of the Laminari­aceae assuming the necessity for the drying of these species.

In 1950 a survey was therefore carried out on rich Laminaria beds near Reykjanes in the north of Breidafj6rdur where an ample source of geo­thermal heat is available. Based on the results of this survey, cost estimations for a sodium alginate factory as well as a small sulphuric acid plant, were made in the following years. By experiment it has also been found techni­cally possible to extract alginates using a mixture of ammonia and ammonium carbonate, or ammonia alone under pressure.

In 1956 7 cost estimations were made for the drying of L. digitata. In order to find whether L. digitata meal suitable for alginate extraction, could be economically produced in Iceland by using geothermal heat, the harvesting and artifical drying of L. digitata has been studied since 1957. Tests on harvesting of L. digitata have also been performed in Breida­fj6rdur with two types of equipment.

Furthermore preliminary work has been coi4pleted in an experimental air through circulation dryer and the optimum conditions found for the drying of L. digitata from a place close to Reykjavik and also from Breida 


fjordur. The seaweed was dried in a fixed bed in up to four layers in an airstream of about 70C.

Results of measurements of the viscosity of sodium alginate from the artificially dried weed compared to that of weed dried at room temperature, show that the viscosity of the first mentioned was only slightly affected under the experimental conditions.

The seasonal variations in the chemical constituents of L. digitata taken close to Reykjavik were also studied in 1959 60 with respect to alginic: acid, mannitol, laminarin, combined fucose, ash and protein.

As to the originally proposed production of sodium alginate, doubt remains whether such production is feasible in Iceland, but results of the above mentioned work seem to justify further work on artificial drying of L. digitata from the previously mentioned localities, with the aim of establishing a drying plant there for the production of L. digitata meal to be sold as raw material for high grade alginates.

It must be emphasized here that the drying of L. digitata in Iceland must be based on the use of geothermal heat as the source of energy. This would also apply to a possible production of Ascophyllum meal, whether used as foodstuff or as a raw material for chemicals.

'ARSRIT, F. 1. 1938 and 1939. Annual Reports of Fish. Ass. of Iceland.

BISKUPA S6GUR (Bishops' Sagas), vol. 1, p. 526, Copenhagen 1858.

EGILL'S SAGA p. 243. Ed. Reykjavik 1892.

GRAGAS (The Icelanders' Oldest Lawbook), vol. 1, 2, p. 94, Ed. Copenhagen 1852.

GudJonsson, S. V. Manneldi og heilsufar i fornold (Food and state of health in ancient times), p. 155. Reykjavik 1949.

HALLDORSSON, B. Grasnyt/ar (Usefulness of plants). Copenhagen 1783.

HALLSSON, S.V. Harvesting experiments on L. digitata and L. saccharina in Breidafj6rdur, Report to the State Electricity Authority (Unpublished).

HALLSSON, S. V. Experiments on the mechanical drying of L. digitata. Report to the State Electricity Authority (Unpublished).

HALLSSON, S. V. and GUDMUNDSSON, S. R. Seasonal variation in the chemical con 

stituents of L. digitata from near Reykjavik. Report to the State Electricity Authority (Unpublished).

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E. Booth: The Icelandic sheep are probably suffering from a sudden change of diet which probably is too sudden for the rumen flora to adjust itself to the change. The north Ronaldshay sheep (ca. 2000) feed on seaweed for 9 10 months of the year and "swayback" has not been reported from this island. It should also be noted that sheep are taking large quantities of copper. (Ascophyllum nodosum contains 65 ppm Cu) it has already been shown that feeding stuffs with this quantity of. copper sulphate are toxic to sheep and we must the~pfore conclude that the copper in seaweed is present in a form which is much less toxic than copper sulphate.

ANSWER: I have not tried to explain why the animals did not utilize the copper. I am only pointing out how it could be prevented, and surely by giving more hay during


the latter half of the gestation period the disease can be prevented. Certainly, the sheep do not utilize the copper as the difference in the amount of copper in the blood and liver of the sick animals suggests.

W. A. P. BLACK: Sheep in Iceland and Orkney appear to select the same species of algae (mainly Rhodymenia palmata) and it is true to say there is a mortality rate in Orkney also if the sheep are not taken off the seaweed about 6 weeks before lambing and fed on hay.

A. JENSEN: I should like to point out that there is a difference in the species of algae eaten by the sheep in Iceland and on North Ronaldshay. In the latter case, the animals eat mostly Laminarla species, while in Iceland Alaria and Rhody­menia are preferred. This difference in diets may explain at least partly the differences in effects noticed at the two places.

S. V. HALLSSON: I would like to add this: I have been told by an Icelandic farmer that lambs born in early spring were not as affected by demyelination as those born later, which could mean that the mothers of the first mentioned eat fresher drift weed whereas the mothers of the late born lambs may eat drift weed that has been lying on the shore for some time.

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