Ulva lactuca#Life history

Ulva lactuca is a thin flat green alga growing from a discoid holdfast. The margin is somewhat ruffled and often torn. It may reach {{convert|18|cm|frac=4}} or more in length, though generally much less, and up to {{convert|30|cm|abbr=on}} across.{{cite web|url=http://www3.gettysburg.edu/~rcavalie/bda_i/078.html|website=Gettysburg College|title=Ulva lactuca

|access-date=December 28, 2007}} 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.{{Cite book|author=Burrows, E.M.|year=1991|title=Seaweeds of the British Isles|volume=2|publisher=Natural History Museum|place= London|isbn=978-0-565-00981-6}}

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 with one to three pyrenoids. There are other species of Ulva which are similar and not always easy to differentiate.

The sporangial and gametangial thalli are morphologically alike. The diploid adult plant produces zoospores by meiosis – making them haploid. 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.{{Cite book |author1=Abbott, I.A. |title=Marine Algae of California. |author2=Hollenberg, G.J. |publisher=Stanford University Press |year=1976 |isbn=978-0-8047-0867-8 |place=California |name-list-style=amp}}{{Cite book |author1=Mondragon, J. |title=Seaweeds of the Pacific Coast. |author2=Mondragon, J. |publisher=Sea Challengers |year=2003 |isbn=978-0-930118-29-7 |place=Monterey, California |name-list-style=amp}}"{{cite web |title=Plant Science 4 U |url=http://www.plantscience4u.com/2014/05/diplohaplontic-life-cycle-in-algae.html#.V3vOW6s7o3R |access-date=5 July 2016}}

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.{{cite web|title=Ulva lactuca Linnaeus|url=http://www.algaebase.org/search/species/detail/?species_id=c1f137497a33b2948&sk=0&from=results|website=AlgaeBase}}

Ulva lactuca is very common on rocks and on other algae in the littoral and sublittoral on shores all around the British Isles,{{Cite book|author1=Hardy, F.G. |author2=Guiry, M.D. |year=2006 |title=A Check-list and Atlas of the Seaweeds of Britain and Ireland |publisher=British Phycological Society |place=London |isbn=978-3-906166-35-3}} the coast of France,{{cite web |url=http://www.vliz.be/vmdcdata/tisbe/tisbe.php?p=taxdetails&id=145984 |title=Tisbe taxon details: Ulva lactuca Linnaeus, 1753 |publisher=Flanders Marine Institute (VLIZ)}} the Low Countries and up to Denmark.{{cite journal |author1=Geertz-Hansen, O. |author2=Sand-Jensen, K. |author3=Hansen, D. F. |author4=Christiansen, A. |date=September 1993 |title=Growth and grazing control of abundance of the marine macroalga, Ulva lactuca L. in a eutrophic Danish estuary |journal=Aquatic Botany |volume=46 |issue=2 |pages=101–109|doi=10.1016/0304-3770(93)90039-Y }} It is particularly prolific in areas where nutrients are abundant.{{cite web |url=http://www.seaweed.ie/algae/ulva.html |website=The Seaweed Site |author=Michael Guiry |title=Overview of Ulva lactuca ecology |access-date=December 28, 2007}} 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.{{cite news |author=Hirst, Michael |date=August 11, 2009 |url=http://news.bbc.co.uk/2/hi/europe/8195180.stm |title=Toxic seaweed clogs French coast |work=BBC News |access-date=August 11, 2009}}{{cite news |url=http://news.bbc.co.uk/2/hi/europe/8242649.stm |title=Seaweed suspected in French death |work=BBC News |date=September 7, 2009 |access-date=2009-09-08}} The result is that large quantities of U. lactuca are washed up on beaches, where their decay produces methane, hydrogen sulfide, and other gases.{{cite journal |author=Nedergaard, Rasmus I. |author2=Risgaard-Petersen, Nils |author3=Finster, Kai |date=August 17, 2002 |title=The importance of sulfate reduction associated with Ulva lactuca thalli during decomposition: a mesocosm experiment |journal=Journal of Experimental Marine Biology and Ecology |volume=275 |issue=1 |pages=15–29 |doi=10.1016/S0022-0981(02)00211-3|url=http://www.elsevier.com/locate/jembe |url-access=subscription }}

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,{{cite web |access-date=2009-08-11 |url=http://news.bbc.co.uk/2/hi/europe/8195180.stm |title=Toxic seaweed clogs French coast |publisher=BBC |date=2009-08-11 |author=Hirst, Michael}}{{cite web |access-date=2009-08-11 |url=https://www.telegraph.co.uk/travel/travelnews/6005673/Almost-100-places-in-Brittany-have-toxic-seaweed.html |title=Almost 100 places in Brittany have toxic seaweed |publisher=Telegraph.co.uk |date=2009-08-11 |author=Samuel, Henry}} 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 pigs and poultry. In an earlier separate incident at the same beach in July 2009, a truck driver had died near his vehicle after hauling three truckloads of sea lettuce without protective gear during the annual cleanup. Although initially recorded as a heart attack, the death of the truck driver prompted French authorities to exhume his remains for an autopsy. It was later determined to be cardiac arrest resulting from pulmonary edema, which is an indication of possible hydrogen sulfide poisoning.{{cite book|last1=Lymbery|first1=Philip|title=Farmageddon: The True Cost of Cheap Meat|date=2014|publisher=Bloomsbury Publishing|isbn=9781408846421|page=179}} Environmentalists claimed that dead animals found on the algae-clogged beaches (including 31 wild boars in July 2011) were a result of toxic fumes.{{cite news|last1=Chrisafis|first1=Angelique|title=Brittany beaches hit by toxic algae|url=https://www.theguardian.com/environment/2011/jul/27/brittany-beaches-toxic-algae-boars|access-date=31 December 2015|work=The Guardian|issue=27 July 2011}}{{cite magazine|last1=McKenna|first1=Maryn|title=Attack of the Deadly Slime: Farm Effluent Ruins French Beaches|url=https://www.wired.com/2011/07/green-slime-beaches/|magazine=Wired|access-date=31 December 2015|date=26 July 2011}}

U. lactuca is locally used in Scotland in soups and salads.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}}{{cite web|url=http://www.mbari.org/staff/conn/botany/greens/anna/frontpages/recipes.htm|website=Monterey Bay Aquarium Research Institute|title=Ulva Recipes|access-date=December 28, 2007|url-status=dead|archiveurl=https://web.archive.org/web/20080102053143/http://www.mbari.org/staff/conn/botany/greens/anna/frontpages/recipes.htm|archivedate=January 2, 2008}} In Hawaiʻi, U. lactuca is also called limu pālahala and eaten in different ways: mixed with other algae, salted and served with raw fish, boiled in water and served as a soup, or served with chili pepper, onions, soy sauce and sugar.{{Cite book|last=Aiona.|first=Abbott, Isabella|url=http://worldcat.org/oclc/34798092|title=Limu : an ethnobotanical study of some Hawaiian seaweeds|date=1996|publisher=National Tropical Botanical Garden|oclc=34798092}} Additionally, U. lactuca has traditional uses in Hawaiʻi as fertilizer and as adornment for hula. When U. lactuca is used for hula it is called limu pāpahapaha.

{{Reflist|2}}

• Hayden, H.S., Blomster, J., Maggs, C.A., Silva, P.C., Stanhope, M.J. and Waaland, J.R. (2003) [http://www.biosciences.bham.ac.uk/labs/callowj/ent/Hayden_Blomster_Maggs.pdf "Linnaeus was right all along: Ulva and Enteromorpha are not distinct genera"] European Journal of Phycology 38: pp. 277–294, {{doi|10.1080/1364253031000136321}}

• [http://www.algaebase.org/search/species/detail/?species_id=39&sk=0&from=results Ulva lactuca], AlgaeBase entry
• [https://web.archive.org/web/20060911143925/http://omp.gso.uri.edu//doee/biota/algae/chloro/ulva.htm Ulva lactuca], University of Rhode Island

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Category:Edible seaweeds

Category:Ulvaceae

Category:Algae of Australia

Category:Plants described in 1753

Category:Taxa named by Carl Linnaeus