Ulva lactuca

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Ulva lactuca
Ulva lactuca.jpeg
Scientific classification
Kingdom: Plantae
Phylum: Chlorophyta
Class: Ulvophyceae
Order: Ulvales
Family: Ulvaceae
Genus: Ulva
Species: U. lactuca
Binomial name
Ulva lactuca
Linnaeus, 1753

Ulva lactuca Linnaeus, a green alga in the division Chlorophyta, is the type species of the genus Ulva, also known by the common name sea lettuce.


Ulva lactuca is a thin flat green alga growing from a discoid holdfast. The margin is somewhat ruffled and often torn. It may reach 18 centimetres (7.1 in) or more in length, though generally much less, and up to 30 centimetres (12 in) across.[1] The membrane is two cells thick, soft and translucent, and grows attached, without a stipe, to rocks or other algae by a small disc-shaped holdfast.[2]

Green to dark green in colour, this species in the Chlorophyta is formed of two layers of cells irregularly arranged, as seen in cross-section. The chloroplast is cup-shaped in some references but as a parietal plate in others[2] with one to three pyrenoids. There are other species of Ulva which are similar and not always easy to differentiate.


The distribution is worldwide: Europe, North America (west and east coasts), Central America, Caribbean Islands, South America, Africa, Indian Ocean Islands, South-west Asia, China, Pacific Islands, Australia and New Zealand.[2][1]


Ulva lactuca is very common on rocks and on other algae in the littoral and sublittoral on shores all around the British Isles,[3] the coast of France,[4] the Low Countries[4] and up to Denmark.[5] It is particularly prolific in areas where nutrients are abundant.[6] This has been the case off the coast of Brittany where a high level of nitrates, from the intensive farming there, washes out to sea.[7][8] The result is that large quantities of Ulva lactuca are washed up on beaches, where their decay produces methane, hydrogen sulphide, and other gases.[7][9]

Certain environmental conditions can lead to the algae spreading over large areas. In August 2009, unprecedented levels of the algae washed up on the beaches of Brittany, France,[10][11] causing a major public health scare as it decomposed. The rotting thalli produced large quantities of hydrogen sulfide, a toxic gas which, like hydrogen cyanide, inhibits cytochrome c oxidase, inhibiting cellular respiration and resulting in critical cellular hypoxia. In one incident near Saint-Michel-en-Grève, a horse rider lost consciousness and his horse died after breathing the seaweed fumes. Environmentalists blamed the phenomenon on excessive use of fertilizers and the excretion of nitrates by pig and poultry farmers.[10] In a separate incident at the same beach, a truck driver and several schoolchildren died after taking part in the cleanup without protection.[citation needed]

Life history[edit]

The sporangial and gametangial thalli are morphologically alike. The diploid adult plant produces haploid zoospores by meiosis, these settle and grow to form haploid male and female plants similar to the diploid plants. When these haploid plants release gametes they unite to produce the zygote which germinates, and grows to produce the diploid plant.[12][13][14]


From Sowerby's English botany, 1790-1814, by James Sowerby

U. lactuca is locally used in Scotland in soups and salads.[15] [16]


  1. ^ "Ulva lactuca". Gettysburg College. Retrieved December 28, 2007. 
  2. ^ a b c Burrows, E.M. (1991). "Seaweeds of the British Isles" 2. London: Natural History Museum. ISBN 0-565-00981-8. 
  3. ^ Hardy, F.G.; Guiry, M.D. (2006). "A Check-list and Atlas of the Seaweeds of Britain and Ireland". London: British Phycological Society. ISBN 3-906166-35-X. 
  4. ^ a b "Tisbe taxon details: Ulva lactuca Linnaeus, 1753". Flanders Marine Institute (VLIZ). 
  5. ^ Geertz-Hansen, O.; Sand-Jensen, K.; Hansen, D. F.; Christiansen, A. (September 1993). "Growth and grazing control of abundance of the marine macroalga, Ulva lactuca L. in a eutrophic Danish estuary". Aquatic Botany 46 (2): 101–109. 
  6. ^ Michael Guiry. "Overview of Ulva lactuca ecology". The Seaweed Site. Retrieved December 28, 2007. 
  7. ^ a b Hirst, Michael (August 11, 2009). "Toxic seaweed clogs French coast". BBC News. Retrieved August 11, 2009. 
  8. ^ "Seaweed suspected in French death". BBC News. September 7, 2009. Retrieved 2009-09-08. 
  9. ^ Nedergaard, Rasmus I.; Risgaard-Petersen, Nils; Finster, Kai (August 17, 2002). "The importance of sulfate reduction associated with Ulva lactuca thalli during decomposition: a mesocosm experiment". Journal of Experimental Marine Biology and Ecology 275 (1): 15–29. doi:10.1016/S0022-0981(02)00211-3. 
  10. ^ a b Hirst, Michael (2009-08-11). "Toxic seaweed clogs French coast". BBC. Retrieved 2009-08-11. 
  11. ^ Samuel, Henry (2009-08-11). "Almost 100 places in Brittany have toxic seaweed". Telegraph.co.uk. Retrieved 2009-08-11. 
  12. ^ Abbott, I.A. and Hollenberg, G.J. (1976). "Marine Algae of California.". California: Stanford University Press. ISBN 0-8047-0867-3. 
  13. ^ Mondragon, J. and Mondragon, J. (2003). "Seaweeds of the Pacific Coast.". Monterey, California: Sea Challengers. ISBN 0-930118-29-4. 
  14. ^ ""Life-history diagram for Ulva lactuca". MBARI. Retrieved June 13, 2007. 
  15. ^ Indergaad, M and Minsaas, J. 1991 in Guiry, M.D. and Blunden, G. 1991. Seaweed Resources in Europe: Uses and Potential. John Wiley & Sons ISBN 0 471 92947 6
  16. ^ "Ulva Recipes". Monterey Bay Aquarium Research Institute. Retrieved December 28, 2007. 

Further reading[edit]

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