Tufts of gutweed in Gullmarsfjorden at Sämstad 1

The sea lettuces comprise the

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

''Ulva'', a group of edible green algae that is widely distributed along the coasts of the world's

ocean The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the wo ...

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. Des ...

'', ''lactuca'' being

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

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 (plural: 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. Many of these organisms ...

Nutrition and contamination

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

manatee Manatees (family Trichechidae, genus ''Trichechus'') are large, fully aquatic, mostly herbivorous marine mammals sometimes known as sea cows. There are three accepted living species of Trichechidae, representing three of the four living speci ...

s and the sea slugs known as

sea hare The clade Anaspidea, 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 the ...

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

Scandinavia Scandinavia; Sámi languages: /. ( ) is a subregion in Northern Europe, with strong historical, cultural, and linguistic ties between its constituent peoples. In English usage, ''Scandinavia'' most commonly refers to Denmark, Norway, and Swe ...

Great Britain Great Britain is an island in the North Atlantic Ocean off the northwest coast of continental Europe. With an area of , it is the largest of the British Isles, the largest European island and the ninth-largest island in the world. It i ...

Ireland Ireland ( ; ga, Éire ; Ulster Scots dialect, Ulster-Scots: ) is an island in the Atlantic Ocean, North Atlantic Ocean, in Northwestern Europe, north-western Europe. It is separated from Great Britain to its east by the North Channel (Grea ...

, China, and Japan (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, mostly natural ingredients with at least one raw ingredient. They are typically served at room temperature or chilled, though some can be served warm. Condiments and salad dressings, which exist in a va ...

s and cooked in soups. It is high in

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...

, soluble dietary fiber, and a variety of

vitamin A vitamin is an organic molecule (or a set of molecules closely related chemically, i.e. vitamers) that is an essential micronutrient that an organism needs in small quantities for the proper functioning of its metabolism. Essential nutrie ...

s and

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...

s, especially

iron Iron () is a chemical element with Symbol (chemistry), symbol Fe (from la, Wikt:ferrum, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 element, group 8 of the periodic table. It is, Abundanc ...

. However, contamination with

toxic heavy metal A toxic heavy metal is any relatively dense metal or metalloid that is noted for its potential toxicity, especially in environmental contexts. The term has particular application to cadmium, mercury and lead, all of which appear in the World ...

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 (; french: link=no, Bretagne ; br, Breizh, or ; Gallo: ''Bertaèyn'' ) is a peninsula, historical country and cultural area in the west of modern France, covering the western part of what was known as Armorica during the period ...

France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of overseas regions and territories in the Americas and the Atlantic, Pacific and Indian Oceans. Its metropolitan area ...

, causing a major public health scare as it decomposed. The rotting leaves produced large quantities of hydrogen sulfide, a toxic gas. In one incident near

Saint-Michel-en-Grève Saint-Michel-en-Grève (; ) is a commune in the Côtes-d'Armor department of Brittany in northwestern France. In 2009 huge quantities of sea lettuce seaweed (''Ulva lactuca'') washed up on the beach at Saint Michel. Poisonous gases resulting fro ...

, 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 (Spanish language, Spanish: México), officially the United Mexican States, is a List of sovereign s ...

'' (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 ( es, Islas Baleares ; or ca, Illes Balears ...

'' 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'' Linnaeus, 1753 *'' Ulva conglobata'' Kjellman, 1897 *'' Ulva cornuta'' Lightfoot, 1777 *'' Ulva covelongensis'' V. Krishnamurthy & H. Joshi, 1969 *'' Ulva crassa'' 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 Ulva (; gd, Ulbha) 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 fr ...

'' Hudson, 1778 *'' Ulva elegans'' Gayral, 1960 *'' Ulva enteromorpha'' Le Jolis, 1863 *'' Ulva erecta'' ( Lyngbye) Fries *'' Ulva expansa'' (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 Ulva (; gd, Ulbha) 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 fr ...

'' (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''

Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his ennoblement in 1761 as Carl von Linné Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomial nomenclature, the ...

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

, 1753 *'' Ulva lippii'' Lamouroux *'' Ulva litoralis'' Suhr ex Kützing *'' Ulva littorea'' Suhr *'' Ulva lobata'' (Kützing) Harvey, 1855 *'' 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'' 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'' (Harvey) Le Jolis, 1863 *'' Ulva ranunculata'' Kraft & A.J.K. Millar, 2000 *'' Ulva reticulata'' Forsskål, 1775 *'' Ulva rhacodes'' (Holmes) Papenfuss, 1960 *'' Ulva rigida'' C. Agardh, 1823 *'' Ulva rotundata'' Bliding, 1968 *'' Ulva saifullahii'' Amjad & Shameel, 1993 *'' Ulva serrata'' A.P.de Candolle *'' Ulva simplex'' (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'' Segawa, 1938 *'' Ulva subulata'' (Wulfen) Naccari *'' Ulva taeniata'' (Setchell) Setchell & N.L. Gardner, 1920 *'' Ulva tanneri'' H.S. Hayden & J.R. Waaland, 2003 *'' Ulva tenera'' 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 *'' Ulva costata'' Wollny, 1881 *'' Ulva repens'' 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

nissima,

External links

Marine botany: Ulva
*
Toxic seaweed clogs French coas Caledonia: morphological diversity, and blooom potential.t (BBC)
{{Authority control Ulvaceae Edible seaweeds Edible algae Taxa named by Carl Linnaeus