The sea lettuces comprise the

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

''Ulva'', a group of edible

green alga The green algae (: green alga) are a group of chlorophyll-containing autotrophic eukaryotes consisting of the phylum Prasinodermophyta and its unnamed sister group that contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ( ...

e that is widely distributed along the coasts of the world's

ocean The ocean is the body of salt water that covers approximately 70.8% of Earth. The ocean is conventionally divided into large bodies of water, which are also referred to as ''oceans'' (the Pacific, Atlantic, Indian Ocean, Indian, Southern Ocean ...

s. The type species within the genus ''Ulva'' is ''

Ulva lactuca ''Ulva lactuca'', also known by the common name sea lettuce, is an edible green alga in the family Ulvaceae. It is the type species of the genus ''Ulva''. A synonym is ''U. fenestrata'', referring to its "windowed" or "holed" appearance. De ...

'', ''lactuca'' being

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

for "lettuce". The genus also includes the species previously classified under the genus ''Enteromorpha'', the former members of which are known under the common name green nori.

Description

Individual blades of ''Ulva'' can grow to be more than 400 mm (16 in) in size, but this occurs only when the plants are growing in sheltered areas. A macroscopic alga which is light to dark green in colour, it is attached by disc holdfast. Their structure is a leaflike flattened

thallus Thallus (: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. A thallus usually names the entir ...

Nutrition and contamination

Sea lettuce is eaten by a number of different sea animals, including

manatee Manatees (, family (biology), family Trichechidae, genus ''Trichechus'') are large, fully aquatic, mostly herbivory, herbivorous marine mammals sometimes known as sea cows. There are three accepted living species of Trichechidae, representing t ...

s and the sea slugs known as

sea hare The order Aplysiida, commonly known as sea hares ('' Aplysia'' species and related genera), are medium-sized to very large opisthobranch gastropod molluscs with a soft internal shell made of protein. These are marine gastropod molluscs in t ...

s. Many species of sea lettuce are a food source for humans in

Scandinavia Scandinavia is a subregion#Europe, subregion of northern Europe, with strong historical, cultural, and linguistic ties between its constituent peoples. ''Scandinavia'' most commonly refers to Denmark, Norway, and Sweden. It can sometimes also ...

Great Britain Great Britain is an island in the North Atlantic Ocean off the north-west coast of continental Europe, consisting of the countries England, Scotland, and Wales. With an area of , it is the largest of the British Isles, the List of European ...

Ireland Ireland (, ; ; Ulster Scots dialect, Ulster-Scots: ) is an island in the North Atlantic Ocean, in Northwestern Europe. Geopolitically, the island is divided between the Republic of Ireland (officially Names of the Irish state, named Irelan ...

China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

, and

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

(where this food is known as ''aosa''). Sea lettuce as a food for humans is eaten raw in

salad A salad is a dish consisting of mixed ingredients, frequently vegetables. They are typically served chilled or at room temperature, though some can be served warm. Condiments called '' salad dressings'', which exist in a variety of flavors, a ...

s and cooked in

soup Soup is a primarily liquid food, generally served warm or hot – though it is sometimes served chilled – made by cooking or otherwise combining meat or vegetables with Stock (food), stock, milk, or water. According to ''The Oxford Compan ...

s. It is high in

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

, soluble

dietary fiber Dietary fiber (fibre in English in the Commonwealth of Nations, Commonwealth English) or roughage is the portion of plant-derived food that cannot be completely broken down by human digestive enzymes. Dietary fibers are diverse in chemical co ...

, and a variety of

vitamin Vitamins are Organic compound, organic molecules (or a set of closely related molecules called vitamer, vitamers) that are essential to an organism in small quantities for proper metabolism, metabolic function. Nutrient#Essential nutrients, ...

s and

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...

s, especially

iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...

. However, contamination with

toxic heavy metal A toxic heavy metal is a common but misleading term for a metal-like element noted for its potential toxicity. Not all heavy metals are toxic and some toxic metals are not heavy. Elements often discussed as toxic include cadmium, mercury and ...

s at certain sites where it can be collected makes it dangerous for human consumption.

Aquarium trade

Sea lettuce species are commonly found in the saltwater aquarium trade, where the plants are valued for their high nutrient uptake and edibility. Many reef aquarium keepers use sea lettuce species in refugia or grow it as a food source for herbivorous fish. Sea lettuce is very easy to keep, tolerating a wide range of lighting and temperature conditions. In the refugium, sea lettuce can be attached to live rock or another surface, or simply left to drift in the water.

Health concerns

In August 2009, unprecedented amounts of these algae washed up on the beaches of

Brittany Brittany ( ) is a peninsula, historical country and cultural area in the north-west of modern France, covering the western part of what was known as Armorica in Roman Gaul. It became an Kingdom of Brittany, independent kingdom and then a Duch ...

France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...

, causing a major public health scare as it decomposed. The rotting leaves produced large quantities of

hydrogen sulfide Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is toxic, corrosive, and flammable. Trace amounts in ambient atmosphere have a characteristic foul odor of rotten eggs. Swedish chemist ...

, a toxic gas. In one incident near

Saint-Michel-en-Grève Saint-Michel-en-Grève (; ) is a Communes of France, commune in the Côtes-d'Armor Departments of France, department of Brittany (administrative region), Brittany in northwestern France. In 2009 huge quantities of sea lettuce seaweed (''Ulva lac ...

, a horse rider lost consciousness and his horse died after breathing the seaweed fumes; in another, a lorry driver driving a load of decomposing sea lettuce passed out, crashed, and died, with toxic fumes claimed to be the cause. Environmentalists blamed the phenomenon on excessive nitrogenous compounds washed out to sea from improper disposal of pig and poultry animal waste from industrial farms.

Species

Species in the genus ''Ulva'' include: ;Accepted species *''

Ulva acanthophora ''Ulva acanthophora'' is a species of benthic subtropical seaweed in the Ulvaceae family that can be found in California and Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country ...

'' (Kützing) Hayden, Blomster, Maggs, P.C. Silva, Stanhope & J.R. Waaland, 2003 *'' Ulva anandii'' Amjad & Shameel, 1993 *'' Ulva arasakii'' Chihara, 1969 *'' Ulva atroviridis'' Levring, 1938 *'' Ulva australis'' Areschoug, 1854 *'' Ulva beytensis'' Thivy & Sharma, 1966 *''

Ulva bifrons ''Ulva bifrons'' is a species of blackish-green coloured seaweed in the family Ulvaceae that can be found in Sezimbra, Portugal, in France and Spain, and Balearic islands The Balearic Islands are an archipelago in the western Mediterranean ...

'' Ardré, 1967 *'' Ulva brevistipita'' V.J. Chapman, 1956 *'' Ulva burmanica'' (Zeller) De Toni, 1889 *'' Ulva californica'' Wille, 1899 *'' Ulva chaetomorphoides'' (Børgesen) Hayden, Blomster, Maggs, P.C. Silva, M.J. Stanhope & J.R. Waaland, 2003 *'' Ulva clathrata'' (Roth) C. Agardh, 1811 *''

Ulva compressa Ulva (; ) is a small island in the Inner Hebrides of Scotland, off the west coast of Mull. It is separated from Mull by a narrow strait, and connected to the neighbouring island of Gometra by a bridge. Much of the island is formed from Cenozoic ...

'' Linnaeus, 1753 *'' Ulva conglobata'' Kjellman, 1897 *'' Ulva cornuta'' Lightfoot, 1777 *'' Ulva covelongensis'' V. Krishnamurthy & H. Joshi, 1969 *''

Ulva crassa ''Ulva lactuca'', also known by the common name sea lettuce, is an edible green alga in the family Ulvaceae. It is the type species of the genus ''Ulva''. A synonym is ''U. fenestrata'', referring to its "windowed" or "holed" appearance. Des ...

'' V.J. Chapman, 1956 *'' Ulva crassimembrana'' (V.J. Chapman) Hayden, Blomster, Maggs, P.C. Silva, M.J. Stanhope & J.R. Waaland, 2003 *'' Ulva curvata'' (Kützing) De Toni, 1889 *'' Ulva denticulata'' P.J.L. Dangeard, 1959 *'' Ulva diaphana'' Hudson, 1778 *''

Ulva elegans Ulva (; ) is a small island in the Inner Hebrides of Scotland, off the west coast of Mull. It is separated from Mull by a narrow strait, and connected to the neighbouring island of Gometra by a bridge. Much of the island is formed from Cenozo ...

'' Gayral, 1960 *'' Ulva enteromorpha'' Le Jolis, 1863 *'' Ulva erecta'' ( Lyngbye) Fries *''

Ulva expansa Ulva (; ) is a small island in the Inner Hebrides of Scotland, off the west coast of Isle of Mull, Mull. It is separated from Mull by a narrow strait, and connected to the neighbouring island of Gometra by a bridge. Much of the island is formed ...

'' (Setchell) Setchell & N.L. Gardner, 1920 *'' Ulva fasciata'' Delile, 1813 *'' Ulva flexuosa'' Wulfen, 1803 *'' Ulva geminoidea'' V.J. Chapman, 1956 *'' Ulva gigantea'' (Kützing) Bliding, 1969 *'' Ulva grandis'' Saifullah & Nizamuddin, 1977 *'' Ulva hookeriana'' (Kützing) Hayden, Blomster, Maggs, P.C. Silva, M.J. Stanhope & J.R. Waaland *'' Ulva hopkirkii'' (M'Calla ex Harvey) P. Crouan & H. Crouan *'' Ulva howensis'' (A.H.S. Lucas) Kraft, 2007 *'' Ulva indica'' Roth, 1806 *''

Ulva intestinalis ''Ulva intestinalis'' is a green alga in the family Ulvaceae, known by the common names sea lettuce, green bait weed, gutweed, and grass kelp. Until they were reclassified by genetic work completed in the early 2000s, the tubular members of the ...

Linnaeus Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...

, 1753 *'' Ulva intestinaloides'' (R.P.T. Koeman & Hoek) Hayden, Blomster, Maggs, P.C. Silva, M.J. Stanhope & J.R. Waaland, 2003 *'' Ulva javanica'' N.L. Burman, 1768 *'' Ulva kylinii'' (Bliding) Hayden, Blomster, Maggs, P.C. Silva, M.J. Stanhope & J.R. Waaland, 2003 *''

, 1753 *'' Ulva laetevirens'' J.E. Areschoug, 1854 *''

Ulva laingii ''Ulva laingii'' is a species of seaweed in the family Ulvaceae that can be found in Australia and New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island ...

'' V.J. Chapman, 1956 *'' Ulva linearis'' P.J.L. Dangeard, 1957 *''

Ulva linza Ulva (; ) is a small island in the Inner Hebrides of Scotland, off the west coast of Isle of Mull, Mull. It is separated from Mull by a narrow strait, and connected to the neighbouring island of Gometra by a bridge. Much of the island is formed ...

, 1753 *'' Ulva lippii'' Lamouroux *'' Ulva litoralis'' Suhr ex Kützing *'' Ulva littorea'' Suhr *'' Ulva lobata'' (Kützing) Harvey, 1855 *'' Ulva maeotica'' (Proshkina-Lavrenko) P.M.Tsarenko, 2011 *'' Ulva marginata'' (J. Agardh) Le Jolis *'' Ulva micrococca'' (Kützing) Gobi *'' Ulva mutabilis'' Föyn, 1958 *'' Ulva neapolitana'' Bliding, 1960 *'' Ulva nematoidea'' Bory de Saint-Vincent, 1828 *'' Ulva ohnoi'' Hiraoka & Shimada, 2004 *'' Ulva olivascens'' P.J.L. Dangeard *'' Ulva pacifica'' Endlicher *'' Ulva papenfussii'' Pham-Hoang Hô, 1969 *'' Ulva parva'' V.J. Chapman, 1956 *'' Ulva paschima'' Bast *'' Ulva patengensis'' Salam & Khan, 1981 *'' Ulva percursa'' (C. Agardh) C. Agardh *'' Ulva pertusa'' Kjellman, 1897 *'' Ulva phyllosa'' (V.J. Chapman) Papenfuss *'' Ulva polyclada'' Kraft, 2007 *'' Ulva popenguinensis'' P.J.L. Dangeard, 1958 *'' Ulva porrifolia'' (S.G. Gmelin) J.F. Gmelin *'' Ulva profunda'' W.R. Taylor, 1928 *''

Ulva prolifera ''Ulva prolifera'' (previously ''Enteromorpha prolifera''), also known as the branched string lettuce, is a species of seaweed algae in the family Ulvaceae that can be found worldwide. Description ''U. prolifera'' is visually filamentous and ...

'' O.F.Müller, 1778 *'' Ulva pseudocurvata'' Koeman & Hoek, 1981 *'' Ulva pseudolinza'' (R.P.T. Koeman & Hoek) Hayden, Blomster, Maggs, P.C. Silva, M.J. Stanhope & J.R. Waaland, 2003 *'' Ulva pulchra'' Jaasund, 1976 *'' Ulva quilonensis'' Sindhu & Panikkar, 1995 *'' Ulva radiata'' (J. Agardh) Hayden, Blomster, Maggs, P.C. Silva, M.J. Stanhope & J.R. Waaland, 2003 *''

Ulva ralfsii Ulva (; ) is a small island in the Inner Hebrides of Scotland, off the west coast of Isle of Mull, Mull. It is separated from Mull by a narrow strait, and connected to the neighbouring island of Gometra by a bridge. Much of the island is formed ...

'' (Harvey) Le Jolis, 1863 *'' Ulva ranunculata'' Kraft & A.J.K. Millar, 2000 *'' Ulva reticulata'' Forsskål, 1775 *'' Ulva rhacodes'' (Holmes) Papenfuss, 1960 *''

Ulva rigida ''Ulva rigida'' is a species of green algae in the family Ulvaceae. The species prefers eutrophic Eutrophication is a general term describing a process in which nutrients accumulate in a body of water, resulting in an increased growth of or ...

'' C. Agardh, 1823 *'' Ulva rotundata'' Bliding, 1968 *'' Ulva saifullahii'' Amjad & Shameel, 1993 *'' Ulva serrata'' A.P.de Candolle *''

Ulva simplex Ulva (; ) is a small island in the Inner Hebrides of Scotland, off the west coast of Mull. It is separated from Mull by a narrow strait, and connected to the neighbouring island of Gometra by a bridge. Much of the island is formed from Cenozoi ...

'' (K.L. Vinogradova) Hayden, Blomster, Maggs, P.C. Silva, M.J. Stanhope & J.R. Waaland, 2003 *'' Ulva sorensenii'' V.J. Chapman, 1956 *'' Ulva spinulosa'' Okamura & Segawa, 1936 *'' Ulva stenophylla'' Setchell & N.L. Gardner, 1920 *''

Ulva sublittoralis Ulva (; ) is a small island in the Inner Hebrides of Scotland, off the west coast of Mull. It is separated from Mull by a narrow strait, and connected to the neighbouring island of Gometra by a bridge. Much of the island is formed from Cenozoic ...

'' Segawa, 1938 *'' Ulva subulata'' (Wulfen) Naccari *'' Ulva taeniata'' (Setchell) Setchell & N.L. Gardner, 1920 *''

Ulva tanneri Ulva (; ) is a small island in the Inner Hebrides of Scotland, off the west coast of Isle of Mull, Mull. It is separated from Mull by a narrow strait, and connected to the neighbouring island of Gometra by a bridge. Much of the island is formed ...

'' H.S. Hayden & J.R. Waaland, 2003 *''

Ulva tenera Ulva (; ) is a small island in the Inner Hebrides of Scotland, off the west coast of Mull. It is separated from Mull by a narrow strait, and connected to the neighbouring island of Gometra by a bridge. Much of the island is formed from Cenozoic ...

'' Kornmann & Sahling *'' Ulva torta'' (Mertens) Trevisan, 1841 *'' Ulva tuberosa'' Palisot de Beauvois *'' Ulva uncialis'' (Kützing) Montagne, 1850 *'' Ulva uncinata'' Mohr *'' Ulva uncinata'' Mertens *'' Ulva usneoides'' Bonnemaison *'' Ulva utricularis'' (Roth) C. Agardh *'' Ulva utriculosa'' C. Agardh *'' Ulva uvoides Bory'' de Saint-Vincent *'' Ulva ventricosa'' A.P.de Candolle ;

Nomina dubia In binomial nomenclature, a ''nomen dubium'' (Latin for "doubtful name", plural ''nomina dubia'') is a scientific name that is of unknown or doubtful application. Zoology In case of a ''nomen dubium,'' it may be impossible to determine whether a ...

*'' Ulva costata'' Wollny, 1881 *''

Ulva repens Ulva (; ) is a small island in the Inner Hebrides of Scotland, off the west coast of Mull. It is separated from Mull by a narrow strait, and connected to the neighbouring island of Gometra by a bridge. Much of the island is formed from Cenozoi ...

'' Clemente, 1807 *'' Ulva tetragona'' A.P.de Candolle, 1807 A newly discovered Indian endemic species of ''Ulva'' with tubular thallus indistinguishable from ''Ulva intestinalis'' has been formally established in 2014 as '' Ulva paschima'' Bast. Ten new species have been discovered in New Caledonia: ''Ulva arbuscula'', ''Ulva planiramosa'', ''Ulva batuffolosa'', ''Ulva tentaculosa'', ''Ulva finissima'', ''Ulva pluriramosa'', ''Ulva scolopendra'' and ''Ulva spumosa''. Lagourgue, L ''et al'' 2022 The new species of ''Ulva'' (Ulvophyceae, Chlorophyta) discovered in New Caledonia genetic and morphological and diversity, and bloom potential. ''British Phycological Society'' 57;458 - 478.

References

External links

Marine botany: Ulva
*
Toxic seaweed clogs French coast Caledonia: morphological diversity, and bloom potential.t (BBC)
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Other References

* {{Authority control Ulvaceae Edible seaweeds Edible algae Taxa named by Carl Linnaeus