seaweed

seaweed, name commonly used for the multicellular marine algae. Simpler forms, consisting of one cell (e.g., the diatom) or of a few cells, are not generally called seaweeds; these tiny plants help to make up plankton. The more highly developed types of seaweed usually have a basal disk, called a holdfast, and a frond of varying length and shape, which often resembles a plant in having stemlike and leaflike parts.

Types of Seaweed

The simplest of the seaweeds are among the cyanobacteria, formerly called the blue-green algae, and green algae (division Chlorophyta), found nearest the shore in shallow waters and usually growing as threadlike filaments, irregular sheets, or branching fronds. The brown algae (division Phaeophyta), in which brown pigment masks the green of the chlorophyll, are the most numerous of the seaweeds of temperate and polar regions. They grow at depths of 50 to 75 ft (15-23 m). The red seaweeds (division Rhodophyta), many of them delicate and fernlike, are found at the greatest depths (up to 879 ft/268 m); their red pigment enables them to absorb the blue and violet light present at those depths.

Reproduction in Seaweeds

Seaweeds reproduce in a variety of ways. Lower types reproduce asexually. More advanced kinds produce motile zoospores that swim off, anchor themselves, and grow into new individuals, or they reproduce sexually by forming sex cells (gametes) that, after fusing, follow the same pattern. Sometimes pieces of a seaweed break off and form new plants; in a few species there is a cycle of asexual and sexual reproduction foreshadowing the alternation of generations characteristic of plants.

Common Species and Their Uses

The largest of the green algae, Ulva (sea lettuce), grows to a ribbon or sheet 3 ft (91 cm) long. It provides food for many sea creatures, and its broad surface releases a large amount of oxygen. Fucus, called rockweed or bladderwrack, is a tough, leathery brown alga (though it often looks olive-green) that clings to rocks and has flattened, branched fronds buoyed by air bladders at the tips.

Seaweeds, especially species of the red algae Porphyra (nori) and Chondrus, form an important part of the diet and are farmed for food in China and Japan; other species (often called laver) are eaten in the British Isles and Iceland. Commercial agar (vegetable gelatin) is obtained from species of red algae and is the most valuable seaweed product. Irish moss or carrageen (Chondrus crispus), a red alga, is one of the few seaweeds used commercially in the United States. After being bleached in the sun the fronds contain a high proportion of gelatin, which is used for cooking, textile sizing, making cosmetics, and other purposes. In Japan it is made into a shampoo to impart gloss to the hair.

The kelps generally include the many large brown seaweeds and are among the most familiar forms found on North American coasts. Some have fronds up to 200 ft (61 m) long, e.g., the Pacific coast Nereocystis and Macrocystis, found also off the Cape of Good Hope. Common Atlantic species include Laminaria and Agarum (devil's apron). The kelps are a source of salts of iodine and potassium and, to a lesser extent, other minerals. When the seaweed is burned, the soluble mineral compounds are removed from the ashes (also called kelp) by washing. They are used chiefly as chemical reagents and for dietary deficiencies in people and in livestock. Kelp is also a commercial source of potash, fertilizer, and medicines made from its vitamin and mineral content. Kelps are especially abundant in Japan, and various foods known as kombu are made from them.

The brown algae of the genus Sargassum are called gulfweed. They inhabit warm ocean regions and are commonly found floating in large patches in the Sargasso Sea and in the Gulf Stream. Gulfweed was observed by Columbus. Although it was formerly thought to cover the whole Sargasso Sea, making navigation impossible, it has since been found to occur only in drifts. Numerous berrylike air sacs keep the branching plant afloat. The thick masses of gulfweed provide the environment for a distinctive and specialized group of marine forms, many of which are not found elsewhere.

Any of certain species of red, green, and brown marine algae that generally are anchored to the sea bottom or to a solid structure by rootlike holdfasts that perform the sole function of attachment and do not extract nutrients as do the roots of higher plants. The most obvious seaweeds are brown algae; mosslike carpets of red algae are seen at low tides. Seaweeds are often dense in shallow water. Brown algae commonly found as seaweeds include kelp, which include the largest algae, and sargassum. Some seaweeds have hollow, gas-filled floats that keep their fronds at the surface of the water. Ulva species, commonly called sea lettuce, are among the relatively few green algae that are seaweeds. Seaweeds are used as food, and brown algae are used in fertilizers. The red alga Gelidium is used to make the gelatin-like product called agar.

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Laver is an edible seaweed that has a high mineral salt content, particularly iodine and iron. It is used for making laverbread, a traditional Welsh dish. Laver is common around the west coast of Britain and east coast of Ireland along the Irish Sea. Laver is unique among seaweeds because it is only one cell thick. It is smooth and fine, often clinging to rocks. The principal variety is purple laver (Porphyra laciniata/Porphyra umbilicalis). This tends to be a brownish colour, but boils down to a dark green pulp when prepared. The high iodine content gives the seaweed a distinctive flavour in common with olives and oysters.

Ulva lactuca, also known as Sea lettuce, is occasionally eaten as green laver, which is regarded as inferior to the purple laver.

Laver is sometimes also known as "sloke".

Cultivation

Laver cultivation as food is thought to be very ancient, though the first mention was in Camden’s Britannica in the early 17th century. It is plucked from the rocks and given a preliminary rinse in clear water. The collected laver is repeatedly washed to remove sand and boiled for hours until it becomes a stiff green mush. In this state the laver can be preserved for about a week. Typically during the 18th century the mush was packed into a crock and sold as "Potted laver".

Cultivation of laver is typically associated with Wales, and is still gathered off the Pembroke coast, although similar farming methods are used in west coast of Scotland.

Laver can be eaten cold as a salad with lamb or mutton. A simple preparation is to heat the laver and to add butter and the juice of a lemon or Seville orange. Laver can be heated and served with boiled bacon. It is used to make the Welsh dish known as laverbread, which can be eaten with or without oatmeal.

Laverbread

Laverbread (Bara Lawr) is a traditional Welsh delicacy made from laver. Laver is often associated with Penclawdd and its cockles, being used traditionally in the Welsh diet and is still eaten widely across Wales in the form of laverbread. The seaweed is boiled for several hours then minced or pureed: the gelatinous paste that results can then be sold as it is or rolled in oatmeal.

Laverbread is traditionally eaten fried with bacon and cockles for breakfast. It can also be used to make a sauce to accompany lamb, crab, monkfish, etc, and to make laver soup (Welsh: Cawl Lafwr). Richard Burton has been attributed as describing laverbread as "Welshman's caviar".

Swansea Market has several stalls selling only laverbread and cockles from the nearby Gower peninsula. The source of the seaweed used to make laverbread was historically the Gower coastline. There are still small producers of Gower laverbread, though it is now mainly along the Pembroke coast.

In addition to Wales, laverbread is eaten across the Bristol Channel in North Devon, especially around the Exmoor coast around Lynmouth and Combe Martin.

Laver is highly nutritious because of its high proportions of protein, iron, and especially iodine. It also contains high levels of vitamins B2, A, D and C.

See also

• Nori - a similar tasting Porphyra common in Japanese cuisine
• Gim (Korean food) - similar style food in Korean cuisine
• Aonori

References

Notes

Bibliography

• Lamb, Leeks and Laverbread, Gilli Davies, Grafton (16 Mar 1989), ISBN 0586201394

External links

• Seaweeds and their Value in Foodstuffs, W. A. P. BLACK, Institute of Seaweed Research, 1952